Recent advances

on

Prism Adaptation in

Unilateral Neglect

Introduction

• Unilateral neglect (UN) is a common behavioral syndrome

in patients following stroke.

• It is defined as “a failure to report, respond, or orient to

novel or meaningful stimuli presented to the contra-lesional

hemispace that cannot be attributed to sensory or motor

impairments.”

Stroke 1999;30:1196-1202

• The reported incidence of UN varies widely from 10-82%

following right-hemisphere stroke & from 15-65% following

left-hemisphere stroke.

Phys Ther 2003;83:732-40

• Hemispatial neglect is more severe & frequent after the right

than the left hemisphere injury due to specialization of many

attentional functions to the right hemisphere.

• UN can occur as a result of lesions at different anatomical

sites.

• It can occur with a lesion in any of the following areas:

posterior parietal cortex, frontal lobe, cingulate gyrus,

striatum & thalamus.

• Recent research has shown that attention is mediated by a

network of these anatomic areas working together.

Phys Ther 2001;81:1572-80

• UN usually recovers spontaneously (3 months post stroke)

but can be persistent in about 10% of patients.

J clin neurol 2006;2:12-28

Eura Medicophys 2007;43:255-69

• Patients with UN need a much longer hospital stay, have a

higher level of residual disability & need much more

assistance in ADL than those without UN.

Disabil Rehabil 2009; 31: 630–7

Types of unilateral neglect

2 classification systems

Modality in which behavior is elicited

Distribution of abnormal behavior

Neuropsychological Rehabilitation 1994;4:133-39

• In terms of modality in which behavior is elicited

i. Sensory neglect

ii. Motor neglect

iii. Representational neglect

• In terms of distribution of behavior

i. Personal

ii. Spatial

• Sensory neglect: defined as being unaware of sensory

stimuli on the side of the body or space opposite the brain

lesion.

− It can be visual, auditory & tactile (somatosensory).− Also referred to as “inattention” or “input neglect.”

• Motor neglect: defined as failure to generate a movement

response to a stimulus even though the person is aware of

the stimulus.

− It can manifest as hypometria, hypokinesia or bradykinesia.− Also referred to as “output neglect” & “intentional neglect.”

• Representational neglect: It is when a person ignores the

contra- lesional half of internally generated images.

− Internally generated images are mental representations or

visualizations of a task, action or environment.

− Also referred to as “imagery neglect.”

• Personal neglect: defined as lack of exploration or

awareness of the side of the body opposite the brain

lesion.

− Eg: failure to dress one half of the body, combing only one

side of head etc.

• Spatial neglect: defined as failure to acknowledge stimuli

on the contralesional side of space.

− Further divided into peripersonal & extra-personal neglect.

− Peri-personal neglect refers to neglect behaviors occurring

within reaching space (near space). Eg: failure to eat food

from one half of plate.

− Extra-personal neglect refers to neglect behaviors

occurring in far space. Eg: contacting obstacles such as

doorway when walking.

Phys Ther 2003;83:732-40

Assessment of unilateral neglect

• Traditionally, the assessment of UN in the clinical setting

has involved the use of “pen-and-paper” tests such as

line bisection test

cancellation tasks

Copying & drawing test

Behavioral inattention test(BIT).

• These tests are popular in clinical settings because they

are simple & quick to administer.

Phys Ther 2003;83:732-40

Star cancellation test

Line cancellation test

Line bisection test

• Some tests are available to measure the functional

impact/behavioral aspect of unilateral neglect:

Semi structured scale for functional evaluation of Hemi-

inattention:

Comprises 2 subscales, one each for personal &

extrapersonal neglect.

The Catherine Bergego Scale (CBS):

Is a checklist(10 items) for therapists to assess the

presence & severity of UN in a range of daily activities.

Scored on a 4 point scale by observation.

APMR 2003; 84: 51-7

Management of unilateral neglect

DOI:10.1016/j.neubiorev.2006.03.001

Rest Neurol Neurosci 2006; 24:409-18

Eura Medicophys 2007;43:255-69

Ann N Y Acad Sci 2008;1142:21-43

Treatment

Top down Approach

Bottum up Approach

Top Down Therapies

• Therapies based on this approach require taking an active

role in implementing newly learned cognitive strategies to

compensate for spatial bias.

• It is a classical approach to neglect rehabilitation in the early

post stroke period.

• An obvious prerequisite for such training is that patients

retain awareness of deficits.

• It involves the patient in simple actions followed by

performance of increasingly complex tasks that emphasize

visual exploration & attention to stimuli within the neglected

field.

Methods used:

Visual scanning training: VST involves a behavioral

compensatory mechanism. From a practical point of view,

the training program is progressive & based on the

principles of ‘‘anchoring, pacing, density and feedback.’’

Example: Visual anchors, visual scanning systems etc.

Limb activation technique: In this technique, the patient is

required to initiate movements with his/her left paretic limb

in the left part of the space.

• This in turn was considered to activate corresponding areas

of extra-personal space.

Mental imagery training: The purpose is to reduce left-sided

representational neglect by enhancing or training mental

imagery.

• Visual & movement imagery exercises are used. Example:

Use of an elongated stick.

Feedback training: Specific feedback training procedures

were developed involving a top-down mechanism to

compensate for neglect behavior.

• For instance, use of video records (Soderback et al 1992),

mirror therapy (Ramachandran et al 1999), guided

interviews (Tham et al 2001).

Sustained Attention training (SAT): By stimulating arousal

through external alerting stimuli in the general arousal

system, it was hoped to enhance the impaired spatial

attention system.

• This specific training was developed by Robertson et al in

1995 & it followed several sequential stages.

• In the first, the patient carries out a particular task & spatial

errors are pointed out.

• In the 2nd stage, the patient is required to carry out the task

again but this time the trainer knocks loudly & unpredictably

on the desk on average every 20–40 s & employs the words

‘‘attend!’’ in a loud voice.

• In the final stage, it is hoped that the patient can be trained

to ‘‘self-alert’’.

According to evidences…

All these approaches require the patients to voluntary

initiate and maintain attention to the left side and many

patients find it difficult to apply in everyday life.

Neuropsychologia 2003;41:886-93

Bottom up therapies

• These methods are more passive in nature & require less

active patient participation.

• Such strategies aim to reconfigure or enhance processing

of external stimuli, potentially through rectification of biased

spatial representations.

• Methods used:

Sensory stimulations: The idea was enhancing automatic

orientation toward the left space, without the requirement of

language mediated attentive learning.

• Vestibular stimulation, optokinetic stimulation (OPK), neck

muscle vibration (NMV), trunk rotation (TR) proved to

alleviate most of the classic symptoms of left neglect.

• These stimulations work by affecting the activity of cortical

networks responsible for calibrating spatial coordinate’s

frames.

OPK + NMV OPK Drum

Eye patching and Hemi-spatial glasses: Hemi-spatial

glasses consist of a standard eyeglass frame with the

ipsilesional (right) hemifields of both lenses blocked out by a

light-deflecting lens or an opaque patch.

• Full-eye patches completely eliminate visual input into the

covered, ipsilesional (right) eye.

Hemispatial glasses

Pharmacologic therapy: Finally, pharmacological agents

have been tried to ameliorate visuo-spatial neglect.

• Dopamine-agonists & Noradrenergic agonist (Guanfacine)

have been shown to ameliorate some of the classical signs

of visuo-spatial neglect such as line bisection, letter

cancellation & reading.

According to evidences…

Only a single application of these techniques were used

or the amelioration lasted for only a few minutes(10-15).

Brain 2002;125:608-23

• It was therefore a challenge to develop a strategy to

combine the advantages of the 2 approaches & to propose

a technique that, bypassing the awareness level, could

also promote long-lasting effects.

• Hence, recent research has indicated that prism

adaptation training may be of benefit to patients with

neglect.

Arch Phys Med Rehabil 2006;87:1668-72.

What is Prism Adaptation?

• Prism Adaptation(PA) is a simple way of producing low-level,

automatic modifications of visuo-motor correspondences.

• It was introduced by Rossetti et al. in 1998 after studying the

effects in unilateral neglect patients.

Rest Neurol Neurosci 2006;24: 409–18

• PA treatment involves a period of reaching for targets while

wearing glasses fitted with prismatic or Fresnel lenses.

Arch Phys Med Rehabil 2006;87:1668-72

Principles of Prism Adaptation

• When someone first looks through wedge prisms that

optically displace the visual field, e.g.10° in the rightward

direction, he/she may have little feeling that anything is out of

the ordinary, until he/she experiences extraordinary difficulty

in perceptual-motor tasks (i.e. direct effects of prism

exposure). For eg, pointing toward a visual target produces

an error to the right of the target position.

• First, a relatively abrupt reduction of the lateral error can be

observed due to a strategic component of adaptation.

• Then, a more gradual reduction of the terminal error is

observed, returning to pre-exposure levels as the person

makes repeated attempts at target pointing.

• The strategic component is at work only over a short period

of time, the true adaptation to the prismatic displacement (or

realignment) develops more gradually.

• When the prisms are removed the person experiences

unforeseen errors in the opposite direction, to the left of the

target.

• This negative after-effect of prism exposure demonstrates

persistence of the adaptation acquired during exposure.

• Vision of the starting hand position is usually occluded to

ensure the optimal development of the adaptation.

• A pointing task without visual feedback (open loop) is

performed before & after the adaptation procedure to

evaluate the development of a visuo-manual adaptation to

the visual shift.

Anatomo-functional hypothesis

• The literature is somewhat controversial about the neural

structures involved in prism adaptation.

• Altogether, anatomical & behavioral data suggest that the

clinical effect of prism adaptation on neglect relies on a

network of brain areas where the visual error-signal

generated by right prisms is initially processed in the left

occipital cortex.

• The information is then transferred to the right cerebellum.

• Here the visuo-motor realignment (true adaptation) takes place

in congruence with the rightward deviation of prisms.

• The clinical effect could be mediated through the modulation of

cerebral areas in the left hemisphere via a bottom-up signal

generated by the cerebellum.

• The temporal cortex, frontal cortex & the PPC have been

shown to be targets of output from the cerebellum via a

neuronal loop also implicating the dentate nucleus and sub-

cortical structures, such as the thalamus & the globus pallidus.

• The clinical effect might therefore be mediated by the

recruitment of pathways in the left hemisphere that

are functionally homologous to those involved in

spatial cognition in the damaged hemisphere.

Current Opinion in Neurology 2006, 19:1-8

Recent Studies

SEARCH STRATEGY

Databases searched:

- Pubmed, Science direct, Cebp, Google scholar, Free

medical journals, Sagepub, Medline, Cinahl, Pedro.

Selection criteria:

- Full text articles from 2006- 2010.

Keywords used:

- Prism adaptation, unilateral neglect, hemispatial neglect,

Rehabilitation of unilateral neglect.

Use of Fresnel Prism Glasses to Treat Stroke

Patients With Hemispatial Neglect (2b)

Sheila Keane, Caoilfionn Turner, Catherine

Sherrington, John R. Beard.

Arch Phys Med Rehabil 2006;87:1668-72

• Objective: To explore the functional effects of prism

adaptation training on patients with hemispatial neglect after

stroke.

• Participants: 4 subjects with hemispatial neglect.

• Method: 15° deviating Fresnel lenses to a pair of night vision

m(yellow tinted) clip-on sunglasses.

- PA training sessions consisted of 30 repetitions of reaching

for visual targets while wearing the glasses, and each

session took about 10 minutes to complete.

- A screen obscured the patient’s view of the trajectory of their

hand for the first half of the reach, but they could msee their

hand as it approached the target object.

• A treatment program consisting of 5 sessions of prism

adaptation training over 12 to 17 days, in addition to their

standard rehabilitation treatment.

• Outcome measures: The FIM instrument, Catherine

Bergego Scale (CBS), subjective straight ahead pointing,

Albert’s mline cancellation, letter cancellation, & line

bisection.

- Ambulatory patients also performed the Timed Up & Go test.

- All measures were applied immediately before & after each

treatment session.

• Results: Immediate effects of prism adaptation training

included improvements in both subjective straight ahead

pointing & in the Albert’s line cancellation task.

- Letter cancellation, line bisection, FIM & CBS scores

improved in all subjects. Improvements in a functional task

were also observed immediately following PA treatment.

- Obstacle avoidance while walking improved after PA training

in 2 ambulatory subjects.

• Conclusion: PA training shows promise as a new treatment

to supplement current strategies for the clinical management

of hemispatial neglect after stroke.

Neglect treatment by prism adaptation: What

recovers and for how long (2b)

Andrea Serino, Silvia Bonifazi, Laura Pierfederici, Elisabetta Ladavas

Neuropsych Rehabil 2007; 17: 657-87

• Objective: 1) to assess the duration of the treatment’s

beneficial effects particularly 6 months after treatment.

2) to investigate whether the treatment effects were

generalised to different visuo-spatial functions, different

portions of the space & different sensory modalities.

• Participants: 21 neglect patients(3 months after stroke).

• Method: Prism Adaptation was given to the patients for 10

daily sessions over a period of 2 weeks.

• Outcome measures: BIT, Bell cancellation test, Fluff test,

room description test, reading test, clinical test for tactile

extinction, scale for proprioceptive sensibility & the

Motricity index for mobility

- These measures were applied 5 times: screening, before

treatment, one week, 1, 3 & 6 months after treatment.

• Results: A consistent neglect amelioration that lasted up to

6 months after the end of the treatment with PA was seen.

This improvement was seen in all the tests except for the

proprioceptive sensibility test & in Motricity index.

• Conclusion: Rehabilitative intervention in neglect patients

based on PA can induce beneficial effects involving different

domains & last up to 6 months after the end of treatment

Acute neglect rehabilitation using repetitive prism

adaptation: A randomized placebo-controlled

trial(1b) G.M.S. Nys, E.H.F. de Haan, A. Kunneman, P.L.M.

de Kort, H.C. Dijkerman

Rest Neurol Neurosci 2008; 26: 1-12

• Objective: To examine the effects of prism adaptation on

neglect in acute stroke rehabilitation unit.

• Participants: 16 acute stroke patients(within 4 wks).

• Method: A single-blind randomized controlled design resulting

in 6 neglect patients who received placebo treatment & 10

neglect patients who received the experimental prism

treatment.

- All patients received the first treatment one day after the

screening.

- EG was given PA with prism glasses inducing 10° shift to the

right & CG with 0° shift.

- Subjects had to do 100 pointing movements towards visual

targets placed randomly either to left or right(50 each).

- Visual feedback of starting point of hand was occluded for

optimal adaptation.

- Treatment was given 4 days in a row, 30 minutes of each

session for both the groups.

• Outcome measures: Schenkenberg Line Bisection test,

Scene Copying task, Letter cancellation test from the BIT.

- These measures were applied immediately before & after

each treatment session.

- The entire BIT & the Barthel index was applied one month

post treatment.

• Results: The pre & post treatment scores of all tests except

figure copying showed improvement in the EG than the CG

indicating faster recovery in the EG following PA.

• There was neither a main effect of group(conventional+

ecological tasks) indicating no long lasting effect of the

experimental treatment one month post treatment.

• Conclusion: Four consecutive prism sessions produced

beneficial effects in patients with acute neglect.

Long-term effects of prism adaptation on

chronic neglect after stroke (2b)

Hideki Shiraishi, Yuriko Yamakawa, Ayaka Itou,

Toshiaki Muraki, Takashi Asada

NeuroRehabil 2008; 23: 137–151

• Objective: to determine the long-term effect of prism

adaptation with activity performance instead of pointing

performance on chronic neglect patients.

• Participants: 7 patients with chronic unilateral spatial

neglect(12-84 months).

• Method: Prism glasses that made objects move 15° to the

right from the actual positions were used.

- Each subject wore the prismatic glasses for an average of 50

minutes.

- First 10-15 min, the subject was instructed to toss rings

using the non-paralytic arm.

- Next 10–15 min, the subject was instructed to perform a

pegboard exercise.

- Remaining 20–30 min, the subjects were instructed to

perform activities such as a ball throwing game or a dart

game using their right upper limb.

- The duration of intervention using the prismatic glasses

lasted for up to 8 weeks(4.2 times per week).

• Outcome measures: Changes in eye movement using an

eye mark recorder system, intentional spatial bias in terms of

COG in standing position using a tactile sensor scan system,

regional cerebral blood flow was measured using SPECT &

Barthel index(applied pre treatment & after 8 wks).

• Results: Eye movements significantly improved on the

neglected side (p < 0.01), COG significantly moved to the left

and forward & rCBF showed a significant increase at the

parietal cortex, pericalleosal area of the left hemisphere(<

0.05).

• Conclusion: Prismatic glasses could improve eye

movement on the neglected side & correct intentional spatial

bias.

- It might be a valuable method for the activation of the

important areas of the brain in neglect patients.

Effectiveness of Prism Adaptation in Neglect

Rehabilitation: A Controlled Trial Study

Andrea Serino, Moreno Barbiani, Maria Luisa

Rinaldesi, Elisabetta Ladavas

Stroke 2009;40:1392-8

• Objective: to investigate the effectiveness on neglect

recovery of a 2-week treatment based on prism adaptation

(PA) in comparison to an analogous visuomotor training

performed without prisms, ie., neutral pointing (NP).

• Participants: 20 neglect patients after right hemispheric

stroke.

• Method: Patients were divided into 2 matched groups, one

was submitted to PA & the other to NP.

- PA treatment consisted of 10 daily sessions over a period of

2 weeksm with sessions lasting approximately 30 minutes

each.

- Patients were required to repeatedly point at a visual target

with their right index finger while wearing prismatic lenses,

with 10° rightward shift(90 times, 30 each towards left, right &

centre).

- During the adaptation procedure, patients could see only the

final part of their movement, ie., their index finger.

- NP treatment was administered using exactly the same

procedures, over the same amount of time except the

patients in the NP group performed their pointing exercises

while wearing neutral goggles.

• Outcome measures: Neglect was assessed before and

after each treatment & 1 month after the end of the PA

treatment.

- BIT battery, cancellation tasks & reading test were applied.

• Results: Visuospatial abilities improved after both PA & NP

treatment; however, the improvement was significantly higher

in the patients in the PA group(<0.001) than in the patients in

the NP group(<0.004).

- Long-lasting beneficial effects of PA were confirmed 1 month

from the end of treatment.

• Conclusion: The leftward recalibration of sensorimotor

reference frames induced by PA is effective to obtain proper

neglect recovery, although visuomotor training based on

pointing might partially improve neglect symptoms.

A single blinded randomised controlled pilot trial of

prism adaptation for improving self-care in stroke

patients with neglect (2b)

Ailie J. Turton; Kelly O'Leary; Judith Gabb; Rebecca

Woodward; Iain D. Gilchrist

Neuropsychol Rehabil 2010; 20: 180 -96

• Objective: to determine the feasibility of delivering prism

adaptation treatment in a clinically valid sample & to assess

its impact on self-care.

• Participants: 34 right hemispheric stroke patients.

• Method: Patients were randomized into either prism

adaptation (using 10 dioptre, 6 degree prisms, n=16) or

sham treatment (using plain glasses, n=18) groups.

• The participant, positioned directly in front of a box

containing a touch screen was required to use the index

finger to touch a bold vertical line (width 15 mm), which

appeared either directly in the centre or 100 mm to the left or

right of centre on the screen randomly(30 trials).

- The participant was able to see only the terminal part of each

pointing movement to allow visuomotor adaptation.

- Participants in the control group received the same pointing

procedure but instead of prisms they wore flat plain glass in

the trial frames.

- The pointing procedure was delivered once a day, each

working day, for 2 weeks alongside the routine rehabilitation

programme.

• Outcome measures: Primary outcome measure was the

Catherine Bergego Scale(CBS).

- The conventional pencil and paper tests from the BIT were

used.

- Secondary outcome measures used were Motricity Index,

adapted version of the Nottingham Sensory Assessment,

Barthel assessment of activities of daily living.

- Outcomes were measured before treatment, after 4 days of

treatment in 2 weeks & after 8 weeks.

• Results: Over the treatment days only the prism treated

group showed increased leftward bias in open loop pointing

to targets on a touch screen.

- However, despite the group level changes in pointing

behaviour no overall effect of the treatment on self-care or

BIT were found.

• Conclusion: The prism adaptation treatment is deliverable in

a stroke rehabilitation service.

Strength in numbers: combining neck vibration

and prism adaptation produces additive

therapeutic effects in unilateral neglect (1b)

Saevarsson S, Kristjansson A, Halsband U

Neuropsychol Rehabil 2010; 20: 704-24

• Objective: to investigate possible benefits of using NV & PA

in combination (NVPA), compared to when NV is used in

isolation.

• Participants: 12 patients with chronic neglect.

• Method: The patients were randomly assigned to 2

experiments by coin-toss with 6 patients in each group.

- A 600 Hz neck vibration apparatus and 10° right shifted prism lenses were used.

- NV was applied for 20 minutes on the left posterior neck

muscle of the patient.

- Both groups of patients underwent NV while seated in front

of an adaptation box. The NVPA group underwent PA

treatment simultaneously to the NV.

- Patients in NVPA group were asked to perform rapid pointing

movements approximately 4 times/min while wearing 10°

right shifted prism glasses.

• Outcome measures: Visual search performance, standard

neglect tests & open loop tests were applied pre & post

treatment for both the groups.

• Results: Both groups showed improved performance on the

computerized visual search task following their treatment.

- The NVPA group showed improvement on standard neglect

tests following treatment while the NV group did not.

• Conclusion: The current findings may have some important

implications regarding them therapeutic nature of both NV &

PA, which count among the most promising rehabilitation

procedures for unilateral neglect.

- Using two treatments in combination is more effective than

using either on its own.

Levels of Evidence

1a- SR (with homogeneity)of RCTs.

1b- Individual RCT (with narrow Confidence Interval)

1c- All or none

2a- SR (with homogeneity) of cohort studies.

2b- Individual cohort study (including low quality RCT).

3a- SR (with homogeneity) of case-control studies

3b- Individual Case-Control Study.

4- Case-series (and poor quality cohort and case control studies.

5- Expert opinion without explicit critical appraisal, or based on

physiology, bench research or first principles.

Implications for Practice

• PA treatment is well tolerable, safe & inexpensive to

administer in clinical settings.

• PA treatment has a stronger impact on peripersonal neglect

but also has potential to be useful in personal & extra-

personal spatial domains.

• PA treatment has a beneficial effect on functional mobility &

activities of daily living in stroke patients with spatial neglect

i.e., within 2 months of stroke.

• PA training is effective in treating sensory neglect(tactile &

visual) in chronic stroke patients.

• PA treatment even without pointing performance can help to

improve some manifestations of neglect in the chronic phase

of stroke.

Implications for Research

• High quality randomized control trials are needed to clarify

the functional effects of PA.

• The effect of prism adaptation training on contraversive

pushing needs further exploration.

• Studies are required to know the effects of PA combined with

other treatment strategies in the early phase of stroke.

• Systematic investigations are needed to determine both

the optimum prism strength, frequency of treatment

sessions and adaptation method.

Thank You