CALLOSAL LESIONS AND INTERHEMISPHERIC DIS CONNECTION SYNDROMES AFTER HEAD-INJURY

We review the different kinds of injury to the corpus callosum in clos ed head trauma, as well as their different mechanisms. Most frequent l esions are either diffuse and at the microscopic level, secondary to d isruption of axons at the time of the trauma, or focal and at macrosco pic level, also due to torsion or shearing strains on the corpus callo sum. They are associated with diffuse axonal injury of hemispheric and brainstem white matter. Focal macroscopic lesions, sometimes extensiv e, are encountered in 16-40% of autopsies after fatal head injury. Lik ewise, MRI allows nowadays to show them in 22-49% of nonfatal head inj uries. Such lesions can produce an interhemispheric disconnection synd rome. However, clinical observation of an interhemispheric disconnecti on after head trauma has been only rarely reported in the literature, as it is showed by a brief overview of those cases, which suggests tha t this pathology is probably often overlooked. Focal damage to the cor pus callosum seems to be a marker of severe injury, with often long-la sting coma and sometimes tansitory vegetative state or mutism. Extensi on of posterior callosal lesions towards adjacent midline structures, such as the fornix, could contribute to the important memory impairmen t which is particularly frequently associated with posttraumatic inter hemispheric disconnection syndromes.