Cerebral Commissurotomy: Magnetic Resonance Imaging in the Long Term
Joseph E. Bogen, Los Angeles, CA; and William G. Bradley and Keith Kortman, Pasadena, CA

The role of the cerebral commissures was clarified, and hemispheric specialization was confirmed and elaborated by investigations, leading to the award of the Nobel Prize for Physiology in 1981 to R.W. Sperry in patients whose corpora callosa were sectioned as a treatment for seizure disorders intractable to medical treatment and unsuitable for other surgical therapy. In contrast, few of the components of the hemisphere disconnection syndrome appear following surgical section, which spares a significant fraction of the splenium. The increasing use of callosotomy, both deliberately partial and putatively complete, as a treatment for seizure disorder or to afford access to midline lesions, coupled with a wide variety of neuropsychological testing methods, has led to a profusion of opinions often in conflict. Since some resolution of these issues might be affored by MRI, patients who participated in the aforementioned studies have recently cooperated in an imaging project that included MRI. The status of massa intermedia (not CT-determinable) has been shown, as have a variety of extracallosal lesions, some unexpected. Findings include confirmation of extent of section, subcortical gliosis deep to parasagittal retraction sites, and some evidence for early cortical atrophy.