Hemispatial Neglect: When half the world disappears

Written by: Aya Ahmed Abdel Tawwab

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Doesn’t it seem peculiar saying about loss of perception of the surrounding half of the world? If

it does, how can you then imagine the unusual reality of those who develop Hemispatial neglect?

This unusual reality comes from the inability of patients with neglect syndrome to respond to

events occurring in exactly one half of their world, resulting in their weird behaviors that reflect

their deficit in processing and interaction with data from this half as if it is “neglected” by them.

Nature and Symptoms of the Syndrome:

Hemispatial neglect is a neurological condition follows a damage in definite parts of the brain

hemispheres. Patients with neglect shows symptoms of lateralized inattention and failing to report

information about scenes from one side of their center of gaze. The manifestations of neglect

syndrome can be so bizarre that they are hard to believe if not directly observed. Milder cases are

less observable. However, symptoms can develop in sever cases to reach complete ignorance -not

just inattention- for one side, and acting as if half the universe no longer exists.

This may be more understandable if you know that patients with neglect may shave

only one side of their face, brush the teeth on only one side of their mouse, eat from only one side of the plate and initiate movement to just one side. If patients are asked to point to the midline of their body, they point too far to only one side. Knowing that the left and right brain hemispheres recognize inputs from

contralateral(opposite)parts of the environment-the right hemisphere recognize inputs from left

side and vice versa-; it is reasonable that the neglected side to the neglect patients is the side

contralateral to the side of the damaged brain region. Although damage can happen to either side

of the brain, it is usually the left side of world that disappears in the neglect syndrome! The reason

of that is not fully understood yet, but one hypothesis explaining that is that brain regions related

to neglect syndrome are mostly lie in the right brain hemisphere, so that damage of any of them

causes the left side to be unrecognized.

In addition to neglecting objects on their left side, some patients show symptoms of(anosognosia),

a condition by which they deny their neurological deficit. For example, they may deny the fact that they don’t use their left hand or that they only eat from the right side of the plate!

Causes and anatomy:

Neglect syndrome results from lesion of definite brain regions accompanied to a disorder in the

middle cerebral artery territory due to a stroke or other causes as neurodegenerative disease. Often

the resulting lesion centers on the inferior parietal cortex but damage to the brain involves a number

of brain regions involved in attention, perception and memory. Research has identified nine brain

regions which are commonly associated with neglect syndrome including: right posterior middle

temporal gyrus, right inferior parietal lobule, etc. You needn’t focus on these such disturbing

concepts, instead, you should understand that the position of these nine brain regions relative to the right hemisphere reinforces the fact that neglect is relatively common following right

hemispheric damage. The severity of neglect syndrome increases as more as the brain damage

spreads to affect brain regions of major processing functions.

In case of neglect syndrome, the brain acts as a computer system that receives inputs without processing them. For instance, patients can see everything but they aren’t perceiving everything; because brain regions involved in perception of visual information are damaged. This may be better understood if we compared ‘neglect syndrome’ to ‘Hemianopia’. Both disorders lead patients to miss information on the left. Patients with hemianopia miss information on the left; because they cannot see it; due to a cut in the visual field so that visual information doesn’t transfer from the retina to the occipital lope. While patients with neglect miss information due to an attentional deficit; they see, but they don’t perceive the visual information. Appearance of neglect syndrome can be an indicator on the presence of a range of comorbid conditions. That is why neglect is important in providing early detection for such diseases. In other words, if you don’t care a lot about the disappearance of your left side, you certainly would care about the more dangerous diseases associated with this disappearance caused by neglect.

Assessments:

Diagnosis of neglect is relatively simple. Two main tests are carried in order to asses not only the

presence but the severity of the syndrome.

The first test is the behavioral inattention test (BIT), contains six pen-and-paper and nine

behavioral assessments aim at discovering the

view of the world as seen by a neglect patient.

The less clearer the seen view is the severer

the neglect is. One of the pen-and-paper

assessments is the ‘line cancellation test’. In

such assessment, patients are given a paper with lines scattered across it and a pen and asked to

mark each of the lines. Patients with neglect ignore all lines on the left side of the paper.

The second test is Catherin Bergo Scale (CBS), that provides more detailed image of how neglect

affects the daily living. It consists of ten items related to everyday functioning including grooming,

dressing, navigation, moving and eating.

Treatments:

There are a number of potential treatments for neglect ranging from compensatory and training

strategies to those targeting the underlying deficit.

The compensatory strategies are less effective and are said to treat the piece not the whole. It

depends on finding ways to bring the patients attention to the left. Prism adaption is one of the

most common applied compensatory strategies that aim at initiating leftwards movement and trying to increase cognition for the left side. In this strategy, patients are asked to point to visual

targets while wearing special lenses that shift their vision to the right.

However, recent treatments target the affected brain regions. For example, some studies are

carried to test whether dopaminergic drugs can treat neglect by reducing inattention. Although

many treatments for neglect hold promise, at present they are experimental and not widely

available. For decreasing the possibility of developing neglect, it is essential to immediately

monitor and control the presence of any other neurological conditions that would simulate the

appearance of neglect.

To sum up:

Neglect syndrome is a serious condition that requires increased awareness among health

practitioners and needs more understand for causes and symptoms. Not only the prevalence and

debilitating nature of neglect are what create the need for awareness, but also the fact that

neglect syndrome is associated with a range of comorbid conditions including some

neurodegenerative disease, strokes and hemiplegia. This enhances the role of hemispatial neglect

in alerting clinical staff to likely presence of other serious diseases; for which early detection is a

good way to avoid long term risks for such diseases. Neglect syndrome arises due different causes,

all centric about partial or complete damage to some of main brain regions involved in processing

sensory information-information received from sensory organs as mouth, nose and eyes-. This

damage results in improper functioning brain regions that provide incomplete image for the

surrounding world, so that patients affected by neglect will behave strangely because there is a

missed part of the world, they are neither feeling nor interacting with.