Ever seen someone who seems not to know what is happening on their left side? Perhaps the person is blind in one eye? No. This is not a case of partial blindness. If you close your left eye, you can still see much of what is happening in your left field. Apart from that, humans have the ability to sense of perceive what is happening around them without having to really look.
Anyone displaying the above characteristic might be suffering from what is known as Hemi-spatial or Spatial Neglect. Spatial neglect is a common post stroke syndrome that commonly affects the right part the brain. When this happens, one hemisphere of the brain gets damaged and despite normal vision, results in the complete neglect of the left side causing patients to only be aware of what is happening on their right side. After a stroke or brain injury that causes damage to the right sides of the brains, many survivors are left with this attention deficiency and they may not be aware of it.
An estimated 25% of right sided strokes or right sided cerebrovascular accidents victims are left with some form of spatial neglect. Studies have shown a range of between 13 to 80 percent depending on the type of assessment used. Regardless of the exact range, we know that a patient with spatial neglect is more likely to have other forms of cognitive deficiency than a person who doesn’t.
Spatial neglect is more common with damage to the right side of the brain which causes a left neglect. Damage to the left side of the brain can also occur, which will cause a right neglect, but this is not so common. A lot of people with left spatial neglect also suffer from a form of language disorder called aphasia.
Understanding Spatial Neglect
The cerebral cortex of the brain is made up of four regions called lobes: The Frontal Lobe, The Parietal Lobe, The Temporal Lobe and The Occipital Lobe.
The Frontal lobe is the part of the brain that controls our cognitive skills and personality. Some of its functions are:
- Behavior, personality and emotions
- Planning, reasoning and problem solving
- Speech, reading and writing
- Body movement and motor functions
- Intelligence, awareness, concentration
The parietal lobe controls spatial orientation and navigation. Some of its functions are:
- Interpret languages and words
- Sensory functions: touch, pain, temperature
- Interprets visions, hearing and perception
- Spatial intelligence
The temporal lobe processes sound and includes the hippocampus and the amygdala, which control memory and emotions. Some of its functions are:
- Memory and hearing
- Understanding languages
- Organization and balance
The occipital lobe processes vision and light near the back of the skull.
- Interprets vision, color, light and movement
It is the parietal lobe that controls our spatial intelligence. This is what prevents us from walking into a wall when we walk down a passageway, or why we can see and recognize an item even when it is placed in a different orientation. Spatial neglect mostly happens after an injury to the right parietal lobe. When this happens, the injury to the right side of the brain causes a reduction in the amount of neural activities crossing over to the left hemisphere via the corpus collusum. This results in the person’s left side is completely being ignored, hence the term neglect.
There are a number of strange symptoms associated with a person suffering from spatial neglect:
- Shaving or applying makeup to the right side of the face
- Running into walls or doors frames to their left
- Will not know when they are being addressed from the left side
- Dressing completely on the right side but failing to dress their left side
- Patients with spatial neglect may deny ownership of their left leg, arm or limb, claiming it belongs to someone else
- Difficulty maintaining a normal bed posture, almost always lying on their right side
- When addressed from the left, patients may reply to their right, away from where the person they are addressing is
- Patients with spatial neglect tend not to attend to the left side of their body, whether in dressing or toiletry.
What can be done?
It is important to note that even though vision is unaffected, spatial neglect also compromises the senses in the left part of the body, such as smell, pain, hearing and touch.
Treatment of spatial neglect focuses on re-engaging the right part of the brain using long term spatial orientation therapy.
Different forms of spatial neglect treatment have been tested with different results of success. Some of these treatments include the use of prism, where a prism lens is worn to redirect the vision of the patient to help redirect his or her vision to the left side. Another form of treatment used is called constrained movement. This is where the right or more used limb is constrained in a sling forcing the patient to use the other limb. Eye patches are also used. Placed over the ‘good’ eye, this serves the same function as constrained movement where the patient is encouraged to see more through the left eye. Other treatment strategies include: video feedback training, magnetic stimulation, muscle stimulation, alertness training and sensory stimulation. The problem is that all of these techniques although with some degree of success are quite slow in giving the desired result.
A Final Word
Spatial neglect causes the cleanest form of consciousness disruption known to man. Patients can process information on the ‘bad’ side and react to it in simple or complex ways without even knowing or being conscious of it.
Damage to the brain hemisphere can cause spatial neglect but the most severe cases are caused by damage to a specific region. This is the area between the temporal lobe and the parietal lobe called the temporoparietal junction or TPJ. This junction is connected to our social functions, cognitive controls, memory and attention networks and is one of the least understood yet important nexus of information in the human brain.