The body image or body schema is a person’s subjective representation against which the integrity of his body is judged and the movement and positioning of its parts assessed. Specific abnormalities of the body image arise in neurological disorders. These abnormalities include the awareness of a phantom limb after amputation, unilateral lack of awareness or neglect(usually following stroke), hemisomatognosia (the person feels, incorrectly, that a limb is missing), and anosognosia (lack of awareness
of loss of function often of hemiplegia). These abnormalities are described in textbooks of neurology and in the textbook of neuropsychiatry by Lishman (1998).
Distorted awareness of size and shape of the body occurs occasionally in healthy people when they are tired or falling asleep. The experience, which
includes feelings that a limb is enlarging, becoming smaller, or otherwise being distorted, occurs also in migraine, as part of the aura of epilepsy, and after taking LSD. Changes of shape and size of body parts are described by some schizophrenic patients. Except for some schizophrenics, the person is aware that the experience is unreal. Coenestopathic states are localized distortions of body awareness, for example, the nose feels as if it is made of cotton wool.
A general distortion of the body image occurs in anorexia nervosa: the patient is convinced that he is fat when in fact he is underweight, sometimes to the point of emaciation.
The reduplication phenomenon is the experience that the body has doubled, or that part of the body has done so, for example, that there are two left arms. The experience is reported very occasionally in migraine, temporal lobe epilepsy, and schizophrenia.