Unilateral Apraxic Agraphia without Ideomotor Apraxia from a callosal lesion in a patient with Marchiafava-Bignami disease.

Apraxic agraphia can be caused by left hemispheric cerebral lesions in the area that contains the spatial representations of the movements required to write, from a lesion in, or connections to, the frontal premotor cortex that converts these spatial representations to motor programs (Exner's area).  A right-handed woman with Marchiafava Bignami disease and lesions of the genu and splenium of her corpus callosum had apraxic agraphia without ideomotor apraxia of her left. A disconnection of Exner's area in the left hemisphere from the right hemisphere's premotor and motor areas may have led to her inability to write with her left hand.