Macrosomatagnosia is a
somatosensory agnosia; that is, it's a loss of or problem with the perception of your own body. Specifically, it's the perception that some part of your body is noticeably too large, like a
hand the size of a
dinner plate. Symptoms are not
visual; your hand doesn't
look any larger than it should. Instead, the problem is in the way the hand
feels -- the
feedback it sends back to your
brain about its location and motion. This
agnosia can also take the form (probably caused by slightly different
neural foci involved) of body parts feeling
smaller than normal, in which case it's called
microsomatagnosia.
Macrosomatagnosia, and its smaller but just-as-evil twin, are only rarely (i.e. I couldn't find any reference to the occurrence in literature) caused by damage to the somatosensory area of the brain. Instead they are often precursors to a coming epileptic seizure, and accompany the aura that some epileptics see. Since seizure events are primarily found in the temporal lobe of the brain, it is thought that macrosomatagnosia is as well, even though the somatosensory cortex is located on the anterior parietal lobe.
Somebody in my neurology class asked the professor if a variation on macrosomatagnosia might be responsible for anorexia, in that it might cause one's whole body to feel too large. The professor said that she doubted it, as anorexia was thought to be based on ideation and mood more than on perception. I kind of wonder if the SSRI's (which help in 70% of anorexia cases) have any effect in the temporal lobe. If they didn't, then they couldn't possibly cause a cessation of macrosomatagnosiac symptoms.