Autotopagnosia, also called somatotopagnosia, is a rare, neurological disorder. The “main symptom is an inability to point, on verbal command, to human body parts, either one's own or those on another person (or doll or picture of a human). Patients with this disorder vary with regard to the exact symptomology they display,” according to Jenni A. Ogden, PhD in her book Fractured Minds: A Case-Study Approach to Clinical Neuropsychology.
Different hypotheses exist on the cause of autotopagnosia. Ogden notes that there are three hypotheses: the first hypothesis believes that the disorder is the result of a language-related problem, which can be caused with a lesion of the posterior left hemisphere; the second suggests that the disorder has a visuospatial aspect, correlating to a lesion in the parietal lobe; and the third hypothesis notes that autotopagnosia “is the result of a disruption of a discrete body image that is mediated by systems in the region of the left parietal lobe,” according to Ogden.
The difficulty with pinpointing the correct hypothesis is that autotopagnosia is that the disorder can be caused by more than one problem.
In Fractured Minds, Ogden notes a case study, Julian, who has autotopagnosia, along with other disorders, like apraxia, agraphia and right-left confusion. The patient could name any body part that the examiner pointed to, either on his body or a model; however, when the examiner named a body part and asked the patient to point to it, he had severe problems doing so.
During the examinations, Ogden notes that Julian would not look below the waist for the body part in question, and that he realized his inability to locate certain body parts. The patient continued to show problems even when he did not need to understand the body part names. Through computed tomography (CT) scan, the doctor found that the patient had a large mass in the left parietal region of the brain.