Figure Caption: The parietal lobe of the left hemisphere. Lesion of the parietal lobes commonly results in body schema disturbances.

Body Schema Disturbance: Lesions of the Parietal lobes may produce characteristic disturbances of the cognitive model representing knowledge about the arrangement of body parts and their spatial relationship to objects in the environment. Many aspects of this model are implicit and patients with disturbance of the body schema are often unaware of their impairment.

Finger Agnosia

This is a specific form of body schema disturbance in which the patients cannot identify their own fingers or those of another person. It may present as a disturbance involving identification of fingers on one or both hands. This suggests that breakdown of primary tactile and proprioceptive information and lesion of central areas representing the body schema may both result in the syndrome. Sometimes aphasia results in difficulty identifying fingers because the patient must name them. Since naming may be defective, the patient may appear to have finger agnosia.

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Right-Left Disorientation

Here the patient has difficulty recognizing the right or left sides of the body, both his own and that of the examiner facing him. Lesions of the left parietal lobe commonly result in right-left disorientation. The correct naming of body parts as being on the right or left is essentially a language task and aphasic patients have great difficulty with it. However, patients who have right hemisphere lesions, left-sided visual neglect and spatial disorders may have difficulty locating the right and left side of objects or themselves. Consequently they may misapply the right and left labels.

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Assessment

Autopagnosia
Deficits in body awareness are assessed by having the patient point to their own body parts and those on others (e.g. "Show me your left hand".), or by asking the patient to perform simple actions with parts of the body (e.g. "Touch your right ear with your left hand"). Assessment should be made of both common and difficult body parts, and should include responses to both command and imitation.

Finger Agnosia
Awareness of tactile perception is accomplished by having the patient close their eyes and indicate which of their fingers has just been touched. The examiner can number the fingers from 1 to 5 and have the patient call out a number corresponding to the finger which was touched, or the patient can point to the corresponding finger with the opposite hand.