Hemispatial neglect · Grey Matter

Hemispatial neglect is a failure to notice, attend to or act on one side of space, almost always the left after damage to the right hemisphere, although the eyes and the sense of touch on that side still work.

Hemispatial neglect. Hemispatial neglect is a failure to notice, attend to or act on one side of space, almost always the left after damage to the right hemisphere, although the eyes and the sense of touch on that side still work.

A patient may eat only the food on the right half of the plate, shave or make up only the right side of the face, draw a clock with all the numbers crowded on the right, and bump into doorframes on the left. The defect is in attention and the representation of space more than in vision: patients with neglect may also leave out the left side of a scene they imagine or remember. They are often unaware of the problem. The classic lesion is in the right inferior parietal lobe and the temporoparietal junction, with damage to the frontal cortex and the white matter between them also able to cause it.

It is asymmetric because the hemispheres are. The right hemisphere directs attention to both sides of space, the left mainly to the right; after a left lesion the right hemisphere still covers both sides, while after a right lesion nothing covers the left.

It differs from homonymous hemianopia. A patient with hemianopia knows the half-field is missing and turns the head to compensate; a patient with neglect does not look for what is not attended to, although the two can occur together.

It is a strong predictor of poor recovery after stroke, since it disrupts rehabilitation of everything else.

Questions: Why does damage to the right parietal lobe make people ignore the left side, while left damage rarely does the reverse? Attention to space is lateralised: the right parietal and frontal network attends to both sides of space, while the left attends mainly to the right side. After a left lesion the intact right hemisphere still covers both sides, so neglect of the right is rare and mild. After a right lesion, especially of the inferior parietal lobe and temporoparietal junction, only the left hemisphere is left, and it has little interest in the left side, so the patient eats half the plate and draws half the clock.