Pacific University Optometry Continuing Education Unilateral Spatial Inattention and Neglect Laukkanen

Unilateral spatial inattention, also known as spatial neglect, is a condition typically associated with brain injury. Patients with this condition have reduced awareness of one hemifield, usually on the side contralateral to the lesion or injury. Unilateral spatial inattention/ neglect (USI/N) is commonly the result of traumatic or acquired brain injury (e.g., a stroke) and can be quite variable in its presentation and severity. USI/N typically requires an extensive battery of tests to confirm its presence or absence and thus is often not identified by care providers. This lack of recognition can leave USI/N patients underserved with respect to their visual needs.

In this course, we will review some of the common definitions, causes, classifications, rates of occurrence, and manifestations of USI/N. We will also review some of the more common procedures used to detect and diagnose and treat the condition, and will discuss the clinical prognosis for USI/N patients.

Remember when Joe Smith came into your office last week? He was fairly normal looking, although if you really looked closely, his hair was slightly messy on the left side and his beard wasn’t quite as well kept on the left side. He seemed to have a slight head turn with a gaze slightly to the right of center. This gaze shift was so slight that you hardly even noticed it and didn’t really give it a second thought.

You also barely noticed that as he walked down the hallway to the exam room he tended to walk a little closer to the left wall, and even caught a door knob, in passing, with his coat on the left side. During the case history his wife happened to mention that he has been hugging the center line of the road when he drives, and has almost crossed into the oncoming traffic a couple of times recently. She also noted that it seems to startle him when a car passes him on the left side and that he hasn’t been using his left turn signal or left side mirror as much as he used to. One other thing Mrs. Smith mentioned (she liked to talk) was that he had recently been leaving a little bit of food on the left side of his plate, even though he used to always clear his plate completely.

Mr. Smith admitted to feeling slightly “unsteady” recently, although he couldn’t quite put his finger on what it was and thought maybe it was just an “aging thing.”

While checking his acuities, Mr. Smith seemed to consistently miss the beginning VA letter on every line, but your projector makes the letters not quite as clear on the sides so you didn’t think much of it. Mr. Smith also didn’t follow the bead quite as far to the left when you were evaluating his extraocular muscles. However, when you ran the Frequency Doubling Technology perimetry screener on Mr. Smith, there was no field loss noted. At the end of the exam, you told Mr. Smith that you were changing his glasses prescription slightly and that his eyes were healthy - and that was the end of that.

Maybe, but things might have been different and you might have been able to make a big difference in Mr. Smith’s life if you had realized that all of the symptoms mentioned above could have been associated with USI/N. Even though none of his other health care providers had picked it up, you were in a position to detect the condition and if you had put all of this together and sent Mr. Smith for an MRI, a recent minor stroke in the posterior parietal lobe might have been diagnosed.

Although USI/N can occur in mild forms, in its complete manifestation USI/N is a phenomenon in which an entire hemifield (generally the left) is ignored, and the “patient fails to report, respond or orient to novel or meaningful stimuli presented to the side opposite of the brain lesion.”(1) The patient acts as if a hemianopia were present, however he or she is unaware of the defect.

USI/N may be present after various types of unilateral brain damage. It can be seen after traumatic brain injury (TBI) or acquired brain injury (ABI). The most common cause of TBI is motor vehicle accidents. Other causes include assault, accidents in the home or workplace, and sports injuries.(2)

ABIs can be caused by cerebrovascular accidents (CVAs) such as stroke. USI/N is seen more commonly after stroke, particularly when the middle cerebral artery is involved.(3,4) USI/N can occur after left brain damage (LBD), but it is typically more frequent, more severe, and longer lasting after right brain damage (RBD).(3,5)

Unilateral spatial inattention/neglect can occur following a lesion to any of the following areas: posterior parietal cortex, frontal lobe, cingulate gyrus, thalamus, and striatum.(6) These areas are located throughout the brain, but they all play important roles in attention.

USI/N is most frequently seen after insult to the right inferior parietal lobe, also identified as the posterior parietal lobe. This area of the brain seems to play a large role in representation of personal space or body image, and external space.(3) More specifically, research suggests that the posterior parietal area is responsible for spatial localization, directing attention during voluntary and tactile tasks, and for visual awareness.(7) It is believed that the area receives and integrates incoming sensory input and produces a spatial representation of the world relative to the self.(7) The posterior parietal lobe integrates converging information from visual, auditory and vestibular areas and has extensive interconnections with the premotor cortex, the frontal eye fields, the superior colliculus, and the paralimbic areas (the strongest connections being with the cingulate gyrus).(6)

Researchers tend to associate deficits with a lesion in just one area, but Mesulam (8-10) believes this to be a mistake in the case of USI/N. He believes that USI/N behaviors are not a product of one specific area of the brain but are due to failures within the many interconnections between parts of the brain.

Estimates of USI/N occurrence rates vary greatly in the literature. Stone, et al., (11) reported that over 80% of patients demonstrate USI/N following a right cerebrovascular accident, whereas Denes, et al., (12) reported only a 17% occurrence rate following a right CVA.

There is agreement in the literature, however, about the fact that USI/N is more likely to occur following lesions in the right hemisphere (potentially causing left spatial inattention) versus the left hemisphere (potentially causing right spatial inattention). Allegri (13) found that between 31% and 46% of right hemisphere stroke patients exhibited USI/N whereas only 2% to 12% of left hemisphere stroke patients showed evidence of USI/N. As measured during neuropsychological testing, left USI/N is commonly more severe than right USI/N (12), and larger lesions increase the severity of USI/N.(6)

USI/N appears to occur more frequently following stroke than following a TBI, (3) however exact numbers comparing the incidence of USI/N in stroke patients versus TBI patients are difficult to find.

One reason for discrepancies in the rate of USI/N occurrence found in the literature could be the method of testing used to determine whether USI/N was present or not. Hier, et al., (14) studied the same group of patients and found a diagnosis rate of 46% based on behavioral observations of USI/N and an 88% diagnosis rate based on the paper and pencil Figure Copying Test. Another study (15) found a difference in diagnosis rates of between 49% on a letter cancellation test and 30% using Albert’s Test, which is a line cancellation procedure.

Another reason for the wide range of reported diagnosis rates could relate to selection criteria used in different studies and exclusion of patients who could not complete certain tasks required for some studies. An additional thing to keep in mind when comparing incidence rate data is the wide range in sample sizes used in different studies; many studies only recruited very small samples. For example, one study that Bowen, et al., (5) considered found a USI/N occurrence rate of 100% in RBD patients, but only 9 RBD patients were involved in the study.

USI/N can be very debilitating for patients. There are many different manifestations of the condition and possibly even different forms of USI/N. There is also a wide range in severity seen in USI/N patients. In a severe case, the patient could lie in bed with eyes and head rotated toward the side ipsilateral to the lesion, unable to attend to the contralateral side even when spoken to from that side.(3) In other cases, such as the one described in the introduction to this course, only mild symptoms are manifest.

Many varying problems can occur in day-to-day living skills for USI/N patients. For example, he or she might be not pick up food from the side of the plate contralateral to the lesion, or might not brush hair, apply makeup, or shave on the side of the face contralateral to the lesion.

Even if USI/N begins to resolve, it can still be a very disabling condition. For example, if patients go out on a busy street many possible dangers exist if they are unaware of objects, people, or traffic on their left side.

Patients with USI/N can vary in the degree of awareness of their defect. Suchoff (7) proposes that a continuum exists ranging from no neglect (basic hemianopia with total awareness of the field cut) to complete neglect (USI/N with complete unawareness of the field cut). Patients can fall anywhere along this continuum.

It is believed that patients with USI/N experience a shift in their perception of “straight ahead” or their egocentric localization so that the subjective perception of straight ahead does not correspond to the patient's objective midline. This creates a “spatial mismatch between their subjective and objective visual spaces.”(7) Karnath provided the first scientific demonstration of this phenomenon and found that the midline shift can be 15-degrees or more.(7)

Patients with large midline shifts tend to report feeling “unsteady,” “out of synch with the world,” and “not grounded.”(7) Symptoms associated with midline shift syndrome can include the following:

Extinction is a phenomenon seen with many mild USI/N patients (or a step in the USI/N recovery process, or possibly even a sub-type of USI/N). It is a condition in which patients are capable of distinguishing a contralesional stimulus when it is presented alone but are unable to detect the same stimulus when competing stimuli are simultaneously present in the patient’s ipsilesional (and presumably intact) field.(16) This behavior is referred to as extinction because the competing ipsilesional stimulus appears to extinguish perception of the contralesional stimulus.(16) Extinction often becomes apparent when double stimulus presentation confrontational fields are done with the patient.

Swan (6) has identified three different categories of unilateral spatial inattention. They are:

The category of memory and representational deficits describes a condition in which USI/N extends to visual memory and imagery of space in patients’ minds. Bisiach, et al., (17,18) described the condition in two patients with lesions in the right temporo-parietal region, and consequently left USI/N. They were asked to describe, from memory, a familiar square containing a cathedral, palaces, and shops. The patients were asked to imagine themselves facing the cathedral.

Both patients accurately described the right side of the square, but left out many things on the left side. They were then asked to imagine themselves facing away from the cathedral, and this time they were able to accurately describe what was previously on their left. But, they omitted landmarks on the other side of the square that they had recalled perfectly when oriented the other direction.(17,18)

This study suggests that memories of extra-personal space are stored in relation to one’s own self-location in that space. This study shows that USI/N is not limited to motor and sensory deficits and that it extends to behavioral aspects of brain function.(6)

Motor neglect is not a deficiency of the motor pathway; instead it refers to an inability or failure to move in space contralateral to the damaged hemisphere.(6) Motor neglect can manifest with respect to any part of an individual’s body.

Swan references a study by Watson, et al., (19) in which five monkeys were trained to open a door to their right after left leg stimulation and to open a door to their left following right leg stimulation. The monkeys were then surgically given unilateral lesions in the frontal arcuate gyrus or the intralaminar nucleus of the thalamus and the mesencephalic reticular formation. Lesions were placed in either the right or left hemisphere of the monkeys’ brains.

Following surgery the monkeys demonstrated USI/N. None of the monkeys were afflicted with limb weakness. The monkeys were then retested on the door-opening task and showed mistakes when the stimulus was presented to the ipsilesional limb (failure to open the door on the side contralateral to the brain lesion). However, when the stimulus was applied to the contralesional limb, no mistakes were made. This demonstrated that the monkeys were able to make motor responses following a sensory stimulus, but with decreased motor responses in contralateral space after sensory stimulation of the ipsilesional limb.

Sensory neglect is a decreased or lack of awareness of sensory stimulation in contralesional space, which occurs in spite of intact primary sensory cortical areas and sensory pathways. (6) This corresponds to the observation that following right hemisphere lesions, patients with USI/N fail to attend to left hemispace (the field beginning at the body’s midline and extending laterally to individual's the left). Swan (6) states that over time these observations have led to the following conclusion: “in an individual with no known neurological pathology or impairments, the right hemisphere of the brain attends to both the right and left hemispace while the left hemisphere attends primarily to the right hemispace. Following a right hemisphere lesion, attention is directed primarily to the right hemispace, resulting in a neglect of the left hemispace. A lesion of the left hemisphere does not usually result in USN [unilateral spatial neglect] because the intact right hemisphere can direct attention to both hemispaces.”

Stein has proposed a different system for categorizing USI/N.(20) He believes that there are two general categories. The first involves somatic dysfunctions and includes impaired tactile perception and denial of the existence of the contralesional side of the body. These are dysfunctions in personal space.

The second category involves dysfunctions of visual motor control, visual localization, and impaired visual representation of the outside world. These are dysfunctions in extra-personal space. He further subdivides this category into dysfunctions in peri-personal space.(20)

Suchoff and Ciuffreda (3) believe that initially the most obvious manifestations of USI/N occur in personal space and then proceed to dysfunctions in peri-personal space. They give examples of dysfunctions seen in each of the above categories. Personal space USI/N behaviors can include:

Extra-personal space behaviors can include an unawareness or inattention to one side of the external world.

USI/N has many different manifestations and categories. It can have very negative implications for daily living affecting personal, peri-personal, and extra-personal spaces. To assist in understanding the effects of USI/N, we have created a graphical representation of the Suchoff and Ciuffreda model.

There is a wide range of tests that can be used to help detect USI/N. The most popular are “pen and paper” tests, which include line bisection, cancellation, copying, and drawing tasks.(21)

One of the more popular test batteries is the Behavioral Inattention Test (BIT). It consists of six pencil-and-paper tests (line crossing, letter and star cancellation, figure and shape copying, line bisection and representational drawing), and nine ‘behavioral’ tests.(22)

When considering the accuracy of USI/N tests, factors such as test sensitivity and specificity should be kept in mind. Misdiagnosis is minimized by using a test with high sensitivity and high specificity because it will generate fewer false negatives and less false-positives.

The Line Bisection Test, which is part of the BIT battery, is a common USI/N assessment tool. It simply requires the patient to determine the mid-point of a horizontal line. The line is presented on a piece of paper centered with respect to the patient’s midline. The patient is asked to mark or indicate the exact middle of the line.(23) The test is scored by measuring the deviation from the patient's perceived midpoint to the true center of the line. A deviation toward the ipsilateral side of the lesion is usually indicative of USI/N. For example, a patient with a right parietal lobe lesion would bisect the line more toward the right of the center. The deviation from the true midpoint of the line can depend on the extent or severity of the patient's USI/N.

One of the problems associated with the line bisection test is that there are many different versions of it and the different versions are not standardized.(24) Some investigators also feel that other factors, such as hemianopia, might influence the results of this test. One study found that the line bisection test missed 40% of USI/N patients.(25) However, test-retest reliability was found to be 0.97 using an intra-class correlation coefficient (ICC). This indicates good reliability for the test. (26, 27)

Cancellation tests involve visual search skills and possibly figure-ground perceptional skills also. In a cancellation test, the patient searches a page of print for specific stimuli (e.g., letters) and crosses them out as they are found.(23) Patients with USI/N have a tendency to miss stimuli contralateral to the side of the brain lesion. These tests are considered to be among the most sensitive pen and paper tests available.(28) Sensitivity is increased with a high number of targets and distracter items.(29)

There are a variety of different cancellation tests available for clinical use. Examples include the Line Crossing test, Bells test, and the Star Cancellation test.(23) A subtest of the BIT battery, the Star Cancellation test has been shown to be the most sensitive part of the battery.(21) The test consists of a page printed with 56 small stars, 52 large stars, 13 letters, and 10 short words. The goal of this test is to have the patient locate and cross out all of the small stars.(21)

The Star Cancellation test has good potential for high sensitivity because of the presence of distracter items as well as the high target density. Bailey, et al., (26) found an intra-class correlation coefficient of 0.89, indicating good repeatability. This was corroborated by another study, which found that the Star Cancellation test had a diagnostic sensitivity of 80% and a diagnostic specificity of 91%.(30)

The Line Crossing Test, also part of the BIT battery, is sometimes confused with the line bisection test, but it is a different assessment tool. The Line Crossing test is composed of a page printed with uniform black lines in random orientations.(21) Patients are asked simply to cross out every black line on the page. Those with USI/N should make more omissions on the side contralateral to the lesion. However, one study found a sensitivity of only 23% for the Line Crossing test.(21)

The Indented Paragraph test is another commonly administered part of the BIT battery. A paragraph is printed on a page with the left-most word indented on each line by a different number of spaces. The patient reads the paragraph aloud, and the examiner notes any omissions or additions as well as how long it takes to complete the task. In one study the sensitivity of this test was found to be 77%.(21)

The Baking Tray Test can also be used to detect USI/N. For this test, the patient is asked to place "buns," which are actually wooden cubes, as evenly and symmetrically as possible on a wooden board "baking tray." Subjects with USI/N generally skew the distribution of buns in an ipsilesional direction. Bailey, et al., (26) found the test-retest reliability to be 0.87 for patients with USI/N (this indicates good reliability).

The Clock Test is another part of the BIT battery that can be used as a test for representational inattention.(22) There are different versions of the test, but all share the common theme of requiring that a clock face be drawn from memory. For patients with USI/N, the numbers on the clock are typically drawn or skewed towards the side of the circle ipsilateral to the brain lesion.

Many studies have been done to assess the effectiveness of different tests for the detection of USI/N. These studies have primarily relied upon stroke patients because there is a higher USI/N prevalence in this population than there is in the traumatic brain injury population. Consequently, the majority of studies have been limited to elderly patients because this population has a higher occurrence of strokes.(26)

Marsh and Kersel’s (21) investigation of test reliability and validity compared four different tests: Star Cancellation, Line Bisection, Indented Paragraph, and Line Crossing. They found that the Star Cancellation test was the most sensitive test of the four and that the Line Bisection and the Line Crossing were the least sensitive with 31% and 23% detection rates for USI/N, respectively. The Indented Paragraph test had a sensitivity of 77%, and the Star Cancellation test was found to have a sensitivity of 100%. Interestingly, they found a significant correlation between the Star Cancellation test and the results of an activities of daily living (AOL) assessment.

The interclass correlation coefficient, as well as other statistical tests, has been used in many studies to assess USI/N diagnoses.(27) Based on these studies, it is apparent that having a greater number of tests in the testing battery increases its sensitivity for detection of USI/N.(28) However, often patient cooperation and resources are limited making it difficult to use a testing battery consisting of a large number of different tests.(22) When this is the case, the Star Cancellation test is a very valuable screening test. There is good literature support for the notion that on its own the Star Cancellation test is one of the more sensitive tests for the detection of USI/N.(21,22,31) To make the test more sensitive, observation of which side the patient begins the test can be helpful. This observation is simple and does not lengthen the testing time but provides a useful clue to whether or not USI/N is present.

The figure below summarizes the most common tests available for the detection ands assessment of USI/N.

It is sometimes necessary to differentiate the effects of a USI/N from those associated with a visual hemianopia. Hemianopia is a sensory loss in which the damaged neural elements are in the postchiasmal visual pathway up to and including the primary visual cortex. USI/N, on the other hand, is a perceptual deficit in which there is no problem with the neural components necessary for sight.(32)

One way to differentiate USI/N from hemianopia is with line bisection tasks. Patients with USI/N typically transect the line off to the side contralateral to their field defect, whereas patients with only hemianopia typically do the opposite and transect the line in the direction of their scotoma.(32)

Another way to differentiate USI/N from a hemianopia is by noting the difference in visual scan paths used when the patient views a stimulus. Patients with USI/N have more abnormal scans and fewer glances into their neglected field as compared to patients with hemianopia.(32)

Visual acuity testing is another good way to differentiate hemianopia from USI/N.(3) Commonly, the hemianopic patient will initially omit letters on one side of the chart; but once this omission is pointed out, will turn his or her head to scan into the missing field and call out all the letters. USI/N patients in contrast, also omit letters but will continue to omit the letters even after the omission is pointed out.(3)

Another important, yet simple, method of differentiation involves observing a patient walk down a hallway.(3) Those without hemianopia or USI/N will generally walk straight down the hallway without favoring one side or the other. Patients with hemianopia (right side lesion) will tend to swerve off toward the left in the hallway plus generally show a head turn toward that side (or show awareness of the defect by scanning into the left field). However, a USI/N patient with a right side lesion will tend to swerve toward the right side of the hallway and generally will not show a head turn or scan into the neglected field, demonstrating a lack of awareness of the loss.

Another simple way to differentiate hemianopia from USI/N involves asking the patient if it appears that “one side of the world is missing” or if he or she “frequently bumps into things on one side.” Patients with a hemianopia will generally answer "yes" to these questions whereas patients with USI/N will typically answer "no," thus demonstrating denial of the condition.(3)

Useful questions to ask patients and their significant others, family members, or caregiver are:

Patients with USI/N typically deny most of these behaviors, but their caretakers will disagree.(3)

It is important to be aware that hemianopia and unilateral spatial inattention may not be distinct and mutually exclusive diagnoses. Depending on the site of the lesion, either hemianopia, USI/N or a combination of the conditions may be present to varying degrees.

To treat or not to treat?

There is some controversy in the literature regarding the best treatment for patients with USI/N. Some researchers suggest that rehabilitation for USI/N patients is unnecessary due to the high rate of spontaneous recovery.(16) However, studies have shown that early intervention results in faster progress with therapy for brain injury patients.(33) It has been shown that delay in admitting patients to a rehabilitation program of more than 35 days after injury resulted in these patients requiring twice than much treatment as patients who were admitted soon after the injury. There is a potential cost savings benefit of $40,000 per patient on average for acute hospital care through the prevention of secondary complications or improved neurological outcomes alone if patients were admitted soon after injury.(33)

Behavioral rehabilitation versus compensation methods of treatment

There are two distinct management approaches to treatment of USI/N patients: behavioral rehabilitation and compensation. Behavioral rehabilitation methods involve training attention in the neglected hemispace and scanning training. This type of training tends to be more successful with patients who have at least some awareness of their field defect. Patients with severe USI/N tend to not respond well to this type of training because they are being asked to perceive a part of space that is nonexistent to them.(3)

Behavioral Rehabilitation Methods

Using behavioral rehabilitation methods, the patient is encouraged to become aware of and look into the affected field. If open eye movements are difficult for the patient, he or she can first be trained to scan into the affected hemifield with eyes closed.(34)

Some of the techniques used for training are similar to paper and pencil USI/N tests. Patients are asked to circle or cross out certain words on a newspaper page with the goal of increasing attention and awareness in the unattended area.(3) Another technique involves reading with red tape or highlighted areas used on the left side of the page to draw attention to the neglected side.(3) It is also helpful with some left USI/N patients to have them turn or tilt the book so that they have to read in an "uphill" direction.

Movement and scanning techniques

To do this type of training, a patient is encouraged to walk around the room in the direction of the unattended side. Movement in the direction of the neglected field helps sensitize the patient that this area does in fact exist even when the hemifield is unattended.(34) Another technique involves asking the patient to make a head or eye movement towards the left side every time the left foot is picked up while walking.

Margolis Eye Throwing Technique

Margolis has popularized a training method called the Margolis Eye Throwing Technique. First, the patient is taught to rapidly scan from the most extreme lateral position of the affected field over to the unaffected field.(35) Next, the patient learns how to “throw” his or her eyes as far into the extreme lateral position on the affected side as physically possible.

To begin training, the technique is done with the eyes closed and then later with the eyes open. To help transfer eye throwing to real world environments (outside of the clinic), Margolis recommends that the patient wear a programmable pager set to vibrate every few seconds. This reminds the patient to make a large scanning movement. Eventually, the pager will become unnecessary because the patient learns to spontaneously scan into the affected field without the reminder.

Headlamp Scanning

Headlamp scanning is another technique suggested by Margolis that can be used to teach scanning. With this training method, patient wears a headlamp and plays flashlight tag with the therapist who moves the illuminated spot from a flashlight around on the wall as the patient tries to superimpose his or her headlamp spot with the lighted spot from the therapist's flashlight. Initially this activity makes the patient turn his or her head to find the target, but as he or she improves, the patient also learns to visually cross the midline with his or her eyes and scan into the affected field.

Prism

Although the use of prism is generally considered more of a compensation method than a training technique, it can also be used as a behavioral rehabilitation method. A good starting point is 2 to 4 diopters of prism placed with the bases oriented opposite to the affected side. The effects of the prisms on head turn, reaching, walking, posture are explored. Afterwards, the minimum amount of prism power required to change the patient’s behavior is prescribed for one-hour sessions two to three times per day interspersed with one to two hours of no prism wear.

Vis-à-vis technique and eye movements

Another training activity that can be used to increase awareness of the affected side requires the use of polarized glasses by both the clinician and patient. The clinician asks the patient to pay attention to things on the unseen side. To stimulate patient awareness of the affected side, the clinician asks questions. For example, “Can you see both of my eyes?” or “Look to my ear, can you still see my eyes?”

In another exercise the clinician asks the patient to close his or her eyes and look over into the neglected area/field. The patient is then asked to open his or her eyes and the clinician notes where the patient is actually looking.(34) In a similar exercise, the patient is asked to quickly look as far over to the affected side as he or she can. The clinician then asks the patient to pay attention to how it feels to have the eyes over in extreme gaze toward the affected side.(34)

Targets and tools for training

The targets used for teaching scanning can make a key difference in the success or failure of the procedure. It is helpful to use flashing or strobing targets, possibly with sound, and to begin training with large targets, then moving to smaller ones. Some clinicians prefer to use a scan board mounted either on a wall or a table-top to teach scanning.(34) The board can have letters, numbers, or symbols, which are modified and matched to the patient’s cognitive ability. Many clinicians like to use a chalkboard for the same purpose.(34)

Game play, such as crossword puzzles or card games, provide motivational as well as beneficial training for patients with USI/N. Initially, visual game stimuli are presented near the patient's midline and thereafter progressively shifted into the affected field.

Mirror technique

A direct feedback technique suggested by Margolis requires the patient wear a vertical stripe along his or her midline (e.g., a piece of tape) and walk towards a full-length mirror.(35) A vertical stripe is also placed on the center of the mirror, and the patient is asked to match the vertical stripe on his or her midline with the vertical stripe on the mirror as he or she walks towards it. This increases the patient’s awareness of mismatch between his or her perceived visual world and the actual world around him or her.

Poker card wall scan

Poker card wall scan is yet another training technique introduced by Margolis. Fifty-two standard playing cards are randomly placed on a wall. The patient also has a matching deck of cards, which are revealed as the patient turns them over one card at a time. After each card is turned, the patient scans the wall with eyes only (no head movements are allowed) for its match. The card's locations on the wall can be changed to avoid memorization, and this activity can also be timed to monitor the patient's progress.

Computer programs

Computer-based programs, which are sometimes used for diagnosis of USI/N, can also be helpful in treatment. Two commonly used programs are: Reaction Time Measure of Visual Field (REACT) and the Single and Double Simultaneous Stimulation Test (SDSST).

With the REACT program, the patient presses a button each time he or she perceives a stimulus presented at a random location on the computer screen. The stimuli are presented in a butterfly-shaped pattern of 16 trials, and the rate of stimulus presentation increases in increments of 0.01 sec. This allows the examiner to compare reaction times in different fields and to compare relative improvement in response speeds from one trial to another.(3)

For the SDSST program, minus and equal signs are presented as stimuli. Either single or double displays of these stimuli are randomly presented during 45 trials involving the lateral edges of the computer screen. The patient presses response keys when the stimuli are detected. The computer tallies responses for peripheral awareness, sensitivity, and accuracy.(3)

There are many other useful computer programs available that were not specifically designed with USI/N patients in mind, but are very helpful in training USI/N patients. The following is a list of programs along with specific activities that could be used for training USI/N. (36)

VISION BUILDER: (available from the Optometric Extension Program)
- -Peripheral Vision
- -Saccades
- -Tennis
- -Track Letters
- -Reaction Time (have the patient fixate the right hand side of the monitor for left USI/N
PTS2 (Perceptual Therapy System-2): (available from Bernell Corp, http://www.bernell.com/
- -Visual Sequential Processing (random placement mode)
- -Visual Motor Integration
- -Parafoveal Stimulation
- -Visual Closure
HTS (Home Therapy System, available from Bernell Corp)
- -Saccades
- -Pursuits
CAVT (Computer Assisted Vision Therapy Track and Read Module, available from Bernell Corp)
- -Eye Rotation Therapy
- -Random Eye Movements
- -Span of Recognition
- -Same or Different
- -Letter Locator
- -Search Find and Track

These and other computer training programs can be modified by incorporating a headrest so that after the patient detects the stimulus on the affected side, he or she can’t move his or her head to look at it. In order to play, the patient is forced to move his or her eyes into the affected field. Ideally, either the headrest or the monitor location can eventually be set so that the patient’s nose does not point directly at the middle of the screen but rather at the edge of the screen on the affected side. The training sequence is designed to build up to stimuli being presented mostly on the affected side.(36)

Advantages of computer training include:

Most patients often enjoy and are motivated by computer training,
It is easy to alter the program so as to match the patient’s skill level and response speed with respect to target size, color, complexity, and speed of presentation,
Computer training is relatively low cost,
Training can easily done at home with minimal supervision (assuming that the patient has computer access), and
Therapy compliance and progress can easily be monitored and verified by the doctor or therapist. (36)

Sensory manipulation and stimulation techniques

Several researchers have found a reduction in USI/N symptoms following manipulation of sensory information transmitted to the brain relative to the position of the head in space.(6) Some studies have incorporated vestibular stimulation via caloric irrigation and found a temporary remission of USI/N symptoms.(6) Other studies have used galvanic stimulation of the vestibular nerves and also found a temporary reduction in USI/N symptoms, which seemed to last for about a day.(6)

Karnath, et al., (37) found a temporary reduction in USI/N by vibrating the left posterior neck muscles and also by lengthening the left posterior neck muscles by rotating the trunk 15-degrees to the left. This temporary reduction was presumed to be due to changed proprioceptive input from the neck muscles. Some clinicians also advocate the use of vibrators placed on patients’ contralesional posterior neck muscles.

Another technique, which can easily be done in the office, involves simply adding vestibular input on the same side as the USI/N and combining this with scanning techniques. Stimulation should progress from the clinician providing the stimulation (i.e., rotating the patient’s chair to the left) to the patient providing the stimulation for him- or herself. It is also good to add proprioceptive cues, such as finger pointing. Simple things like squeezing a ball in the neglected field can also be helpful.(34)

Bell Technique

With the bell training technique (38), the patient is asked to look straight ahead at a target on a table (e.g. a coin). The therapist would then ring a bell in the unperceived field (thus providing auditory and visual localization cues), and ask the patient to find the bell and touch it simultaneously with both hands. Next, after looking back to the coin, the patient would be asked to find the bell using only his or her eyes, thus teaching scanning. The patient would then be asked to look at and touch the bell using only the hand on the affected side.

As training progresses, the patient would be asked to repeatedly look back and forth between the bell and the coin. Next, the patient looks only at the coin, and touches the bell location from memory using only one finger (the bell would not be ringing for this stage of training). The patient is then encouraged to look and compare the bell location to where his or her finger touched and the process is repeated until he or she consistently touches the bell. This training could be done with many different bell locations in the affected hemifield.

Training would progress to two simultaneous stimuli in the unperceived field (e.g., a bell and a cube). The patient would be asked what they saw, asked to touch the bell, and then to touch the cube. The therapist always asks the patient qualitative questions about the two objects, such as, “Which one is larger?” or “Which one is closer?” This procedure could be repeated and expanded by modifying the targets and stimuli (e.g., by working with multiple stimuli and reaching into the neglected field with both hands).

Compensation Methods

Yoked Prism

Compensation methods for treating USI/N are designed to eliminate or diminish the visual field defects by modifying the visual input. The most common method involves the use of horizontally-oriented yoked prisms with the bases oriented contralesionally (i.e., bases toward the "bad" side). One variation uses partial (or half-field) yoked prisms - typically Fresnel prisms placed on one half of each spectacle lens. The typical starting power for compensatory, contralesional prisms is 7 to 25 prism diopters. Commonly, power is determined by the minimum amount of prism that increases the patient's field awareness. These half-lens prisms are placed with axes 2 mm lateral to the pupil on each spectacle lens and are worn full-time in most cases. The power is decreased and the placement of the prisms is moved to a more temporal placement as the patient adopts the desired scanning behaviors into the affected field.

This compensatory technique used by some practitioners requires the base of each prism to be oriented in the direction of the field loss. Thus, less eye movement is needed by the USI/N patient to view targets in the compromised area. The problem, however, is that patients need to actively look into the prismatic areas of their lenses in order for there to be any therapeutic benefit. Compensatory prism is not particularly effective for USI/N patients because they are unaware of their field loss and unattended hemifield.(3)

Other practitioners prefer to place the bases of the prisms ipsilesionally with the bases in the direction opposite to the field loss (as discussed above in the behavioral rehabilitation section). With this method, the patient’s visual world is shifted leftward (RBD) towards the affected hemifield with the goal of coaxing the eyes to go to the left of the midline. Often an immediate improvement in measured fields is produced; however the initial improvement frequently disappears following removal of the prisms. With time, the improvement seems to become more permanent.

Full-field, ground-in yoked prisms seem to be more effective than half-field prisms because they do not require the patient to actively look into only the portion of the lens with the prism for there to be a benefit.(3) The effect of full-field prisms is that the entire visual field is shifted towards the apex of each prism. This theoretically helps the patient to become more aware of people and objects present in the compromised field.

A problem with shifting the patient's entire field is that some of the intact peripheral intact field is also lost.(3) However, in some cases this method of treatment is reported to be quite successful. Rossi, et al., (39) used base left yoked prisms on right brain damaged USI/N patients and found that after four weeks of wearing the prisms, the patients showed significant improvement on visual perception tests.

Mirrors

Mirrors have also been used as a therapeutic device to draw attention to the impaired field.(3) Mirrors can be either mounted or clipped to the nasal side of the spectacle lens on the same side as the field defect. The mirror is tilted to reflect the missing field. However, as with the partial yoked prisms discussed above, these require that the patient actively look into the mirror in order to see the missing field. Significant problems associated with mirrors include the reversed image of the field seen by the patient, and the cosmetic issue of having a visually unappealing appliance mounted on one's spectacles.(3)

Ramachandran, et al., (40) placed a mirror in the right plane of patients with left USI/N. Patients were then asked to reach for an object in the left field that was visible in the mirror, some patients were able to locate the object, whereas others mislocated with the mirror image of the object. Ramachandran, et al., named this behavior “mirror agnosia.”(40)

Patching

Several researchers have explored using an eye patch to help USI/N patients. Research has shown that for a person with an intact nervous system, retinal input is strongest to the contralateral superior colliculus.(6) Visual stimuli transmitted to the right superior colliculus produces leftward saccades, and visual stimuli transmitted to the left superior colliculus generate rightward saccades.(6)

When the right eye of a left USI/N patient is covered with a patch, the visual stimuli from the left eye most likely follows the stronger pathway to the right superior colliculus and results in a leftward saccade. This should theoretically shift the patient’s attention to the compromised left field.(41) It has been theorized that the eye patch affects perception and attention by shifting the patient’s attention to the left.

Beis, et al., (41) considered the effects of different patching methods for treatment of RBD stroke patients with left USI/N by using photo-oculography results, the overall score on the FIM (Functional Independence Measure), and letter cancellation test results. Patients were divided into a control group, a group with a monocular patch over the right eye, and a group with a biocular patch covering the right hemifield. The patches were worn for 12-hours a day for three months. Results of the study showed significant improvement produced by the right field biocular patches versus the control group. However, no significant differences were found between the right monocular patch group and the control group calling into question therapeutic use of monocular patching for USI/N patients.(41)

Sinemet®

Results from one study suggested that administration of carbidopa L-dopa (Sinemet®) to USI/N patients reduces symptoms as measured by improved scores on the Behavioral Inattention Test.(42) This study involved only four USI/N patients, so further research will be needed to determine if this is indeed an effective treatment for USI/N patients.

1. Baker, J. Limb Activation Treatment ‘A Rehabilitation Treatment Tool for Neglect. http://drjoshuabaker.co.uk/treatneglect/research.htm Accessed July 13, 2004.
2. Falk NS, Aksionoff EB. The primary care optometric evaluation of the traumatic brain injury patient. J Am Optom Assoc 1992;63:547-553.
3. Ciuffreda K, Suchoff I. A Primer for the Optometric Management of Unilateral Spatial Inattention. Optometry 2004;75:305-317.
4. Dombovy ML, Aggarwal U. Stroke rehabilitation. In: Grabois M, Garrison SJ, Hart KA, et al., eds. Physical medicine and rehabilitation: the complete approach. Malden, Mass.: Blackwell Scientific Publications, 2000:1331.
5. Bowen A, McKenna K, Tallis R. Reasons for variability in the reported rate of occurrence of unilateral spatial neglect after stroke. Stroke 1999;30:1196-1202.
6. Swan L. Unilateral Spatial Neglect. Physical Therapy 2001;81:1572-1580.
7. Suchoff I, Ciuffreda K, Kapoor N. Visual and Vestibular Consequences of Acquired Brain Injury. Optometric Extension Program 2001:131-142.
8. Mesulam MM. Spatial attention and neglect: parietal, frontal and cingulated contributions to the mental representation and attentional targeting of salient extrapersonal events. Phil Trans R Soc Lond B 1999;354:1325-1346.
9. Mesulam MM. A cortical network for directed attention and unilateral neglect. Ann Neurol 1981;10:309-325.
10. Mesulam MM. Large-scale neurocognitive networks and distributed processing for attention, language and memory. Ann Neurol 1990;28:597-613.
11. Stone, SP, et al. The incidence of neglect phenomenon and related disorders in patients with acute right or left hemisphere stroke. Age Ageing 1993;22:46.
12. Denes G, Semenza C, Stoppa E, Lis A. Unilateral spatial neglect and recovery from hemiplegia: a follow-up study. Brain 1982;105(pt3):543-552.
13. Allegri RF. Attention and neglect: neurological basis, assessment and disorders. (Paper in Spanish, information from abstract on PubMed). Rev Neurol 2000;20:491-4.
14. Hier DB, Mondlock J, Caplan LR. Behavioral Abnormalities after right hemisphere stroke. Neurology 1983;33:337-344.
15. Massironi M, Antonucci G, Pizzamiglio L, et al. The Wundt-Jastrow illusion in the study of spatial hemi-inattention. Neuropsychologia 1988;26:161–166.
16. Robertson LC, Schendel KL. Using reaction time to assess patients with unilateral neglect and extinction. Journal of Clinical and Experimental Neuropsychology 2002;24:941-950.
17. Bisiach E, Luzzatti C. Unilateral neglect of representational space. Cortex 1978;14:129-133.
18. Bisiach E, Capitani E, Luzzatti C, et al. Brain and conscious representation of outside reality. Neuropsychologia 1981;19:543-551.
19. Watson RT, Miller BD, Heilman KM. Nonsensory neglect. Ann Neurol 1978;3:505-508.
20. Stein JF. Representation of egocentric space in the posterior parietal cortex. Q J Exp Physiol 1989;74:583-606.
21. Marsh N.V. and Kersel D.A. Screening Tests for Visual Neglect Following Stroke. Neuropsychological Rehabilitation 1993;3(3):245-257.
22. Bailey MJ, Riddoch MJ, Crome P, Evaluation of a test battery for hemineglect in elderly stroke patients for use by therapists in clinical practice. NeuroRehabilitation 2000;14:139-150.
23. Plummer P, Morris ME, Dunai J. Assessment of unilateral neglect. Physical Therapy 2003;83(8):732-740.
24. Wilson BA, Cockburn J, Halligan PW. Behavioural Inattention Test. Titchfield, Hants, England: Thames Valley Test Company Ltd, 1987.
25. Ferber S and Karnath HO. How to Assess Spatial Neglect – Line Bisection or Cancellation Tasks? Journal of Clinical and Experimental Neuropsychology 2001;23(5):599-607.
26. Bailey MJ, Riddoch MJ, Crome P. Test-retest stability of three tests for unilateral visual neglect in patients with stroke: Star Cancellation, Line Bisection, and the Baking Tray Task. Neuropsychological Rehabilitation 2004;14(4):403.
27. Muison B. Intraclass Correlation Coefficient. Available at: http://mcs.une.edu.au/~rmurison/gest325/cnotes/node125.html. Accessed November 2, 2005.
28. Azouvi P, Samuel C, Louis-Dreyfus A, Bernati T, et al. Sensitivity of clinical and behavioural tests of spatial neglect after right hemisphere stroke. J. Neurol. Neurosurg. Psychiatry 2002;73:160-166.
29. Parton A, Husain M. Spatial Neglect. ACNR 2004;4(4):17-18.
30. Jehkonen M, Ahonen JP, Dastidar P, Koivisto AM et al. How to detect visual neglect in acute stroke. The Lancet 1998;351:727.
31. Stone SP, Wilson B, Wroot A, et al. The assessment of visuo-spatial neglect after acute stroke. Journal of Neurology, Neurosurgery, and Psychiatry 1991;54:345-350.
32. Sutter, PS. Rehabilitation and management of visual dysfunction following traumatic brain injury. CRC Press LLC 2004.
33. Cope DN, Hall K. Head injury rehab: benefits of early intervention. Arch Phys Med Rehabil 63:433-437, 1982.
34. Rummel, E. Vision therapy can correct deficiencies from hemianopsia. ADVANCE for Directors in Rehabilitation 14:49.
35. Margolis NW, Suter PS, (In press) To See or Not to See In the Periphery? That is the question! Journal of Behavioral Optometry.
36. Laukkanen, H.,“Specific Treatments for ABI” Opt 743, Neurorehabilitative Optometry lecture, Pacific University College of Optometry, 2006.
37. Karnath HO, Christ K, Hartje W. Decrease of contralateral neglect by neck muscle vibration and spatial orientation of trunk midline. Brain 1993;116:383-396.
38. Laukkanen, H., Opt 743 "Neurorehabilitative Optometry". Pacific University College of Optometry, November 2005.
39. Rossi PW, Kheyfets S, Reding MJ. Fresnel prisms improve visual perception in stroke patients with homonymous hemianopsia or unilateral visual neglect. Neurology 1990;40:1597-1599.
40. Ramachandran VS, Altschuler EL, Stone L, et al. Can mirrors alleviate visual hemineglect? Med Hypotheses 1999;52:303-305.
41. Beis JM, Andre JM, Baumgarten A, Challier B. Eye patching in unilateral spatial neglect: efficacy of two methods. Arch Phys Med Rehabil 1999;80:71-76.
42. Mukand JA, Guilmette TJ, Allen DG, Brown LK, Brown SL, Tober KL, VanDyck WR. Dopaminergic therapy with carbidoa L-dopa for left neglect after stroke: A case series. Arch Phys Med Rehabil 2001;82:1279-1282.
43. Cassidy TP, Lewis S, Gray CS. Recovery from visuospatial neglect in stroke patients. J Neurol Neurosurg Psychiatry 1998;64:555-557.
44. Sunderland A, Wade DT, Langton-Hewer R. The natural history of visual neglect after stroke: indications from two methods of assessment. J Int Disabil Stud 1987;9:55–59.
45. Doricchi F, Guariglia P, Figliozzi F, et al. Causes of cross-over in unilateral neglect: between-group comparisons, within-patient dissociations and eye movements. Brain 2005;128(Pt 6):1386-406.
46. Wang Q, Sonoda S, Hanamura M, Okazaki H, Saitoh E. Line bisection and rebisection: the cross-over effect of space location. Neurorehabil Neural Repair 2005 Jun;19(2):84-92.
47. Malhotra P, Jager HR, Parton A, et al. Spatial working memory capacity in unilateral neglect. Brain 2005;128(Pt 2):424-35.
48. Malhotra P, Mannan S, Driver J, Husain M. Impaired spatial working memory: one component of the visual neglect syndrome? Cortex 2004;40(4-5):667-76.
49. Maravita A, McNeil J, Malhotra P, et al. Prism adaptation can improve contralesional tactile perception in neglect. Neurology 2003;60(11):1829-31.
50. Morris AP, Kritikos A, Berberovic N, et al. Prism adaptation and spatial attention: a study of visual search in normals and patients with unilateral neglect. Cortex 2004;40:703-21.

NOTE: Gaggan Basra, O.D., contributed to the preparation of this course.

Contact this author:

Hannu Laukkanen, OD, MEd

Pacific University College of Optometry

2043 College Way

Forest Grove OR 97116

laukkanh@pacificu.edu

Pacific University College of Optometry provides On-Line CE courses as a service to optometrists. The college does not endorse or recommend any products, equipment, or services that might be discussed in the courses. Courses are prepared by individuals believed to be experts in their areas of specialization who are compensated for their efforts. The College relies on their expertise to produce accurate and timely courses.

Questions or concerns about courses should be directed to the individual authors and/or the Continuing Education Department at the College of Optometry at kundart@pacificu.edu.

	Hemianopia indicated by perimetric testing	Hemianopia indicated by single stimulus confrontation testing	Patient is aware of defect	Patient demonstrates USI/N behaviors	Extinction present with double stimulus presentation confrontation testing	Performance on the Line Bisection Test
Category 1: Hemianopia without USI/N	Yes	Yes	Yes	No	No	Contra-lesional displacement of bisection
Category 2: Hemianopia with USI/N	Yes	Yes	No	Yes	No	*Depends on side of hemianopia and USI/N
Category 3: Incomplete Hemianopia with USI/N	Relative decrease in sensitivity shown in left field	No	No	Inconsistently	Yes--left field	*Depends on side of hemianopia and USI/N - inconsistent results expected
Category 4: USI/N without Hemianopia	No	No	No	Yes	Yes--left field	Ipsilateral displacement of bisection

ASSESSMENT AND MANAGEMENT OF NEUROLOGIC UNILATERAL SPATIAL INATTENTION/NEGLECT SYNDROME