J Neurosurg 59:514-519, 1983 Mutism as a consequence of callosotomy NElL M. SUSSMAN, M.D., RUBEN C. Gun, PH.D., RAQUEL E. Gun, M.D., PH.D., AND MICHAEL J. O'CONNOR, M.D. Departments of Neurology and Neurosurgery, The Graduate Hospital and the University of Pennsylvania, Philadelphia, Pennsylvania v" Transient mutism has been reported following commissurotomy and callosotomy. The cause for this mutism is unknown. A case of mutism following callosotomy is presented, and the preoperative and postoperative data on neurological, physiological, and psychological functioning are discussed. The data suggest that the mutism is not caused by general intellectual deterioration, cortical lesion, or peripheral damage affecting speech production. The syndrome may result from severing interhemispheric connections in cases where both hemispheres are required for speech production. KEY WORDS ~ callosotomy 9 mutism 9 speech 9 hemispheric disconnection epilepsy 9 corpus callosum C OMMISSUROTOMY and callosotomy have been used in the treatment of medically intractable epilepsy that is not amenable to focal surgical excision.7.11,21,37.40Sunderland36 found in monkeys that the interhemispheric fibers are arranged anteriorly to posteriorly; the frontal lobes are connected via the rostrum and genu; the midtemporal, posterior tem- poral, and parietal lobe fibers pass through the body; and the occipital lobe fibers pass through the splenium. The mesial and anterior portions of the temporal lobes are connected via another pathway, the anterior com- missure. There are fewer than 100 reported cases of calloso- t o m y for seizure control.l-7'11'12'21"31'33'37'39'4~ This proce- dure is palliative and produces few obvious intellectual deficits. 1-6'31'33In addition to the "disconnection syn- drome, ''16'34 memory quotients have been reported to be lower in postcommissurotomy patients than might be expected on the basis of intelligence quotients (IQ's). 41 A major consequence of this procedure is transient mutism. 12 Bogen 1~ reports that "in almost every case there was a time in which the patient was mute." Wilson, et a/.,39'a~ mutism in three of their first 12 cases. We present the pre- and postoperative data in a patient who suffered mutism following callosotomy. These data may be pertinent to an explanation of this phenomenon. Case Report This 20-year-old right-handed man had an 1 l-year history of seizures. He was the product of a normal pregnancy and a forceps delivery. He had delayed de- velopmental milestones and was placed in special edu- cation classes from 6 years of age onward. His full-scale IQ at 7 years old was 73, with a verbal subscore of 9 1 and a performance subscore of 58. Observed seizures began at 9 years old, with three to four episodes per week. One year later, he was noted to have one to two generalized tonic-clonic seizures per month, as well as episodes described as jerking of his head backward with momentary loss of awareness (10 to 15 per month). At the age of 12 years, he also experienced 15 epileptic drop attacks per month, re- quiting him to wear a helmet constantly. At 15 years of age he entered an institution for disabled children and had a normal physical and neurological examina- tion, apart from a mild to moderate intellectual im- pairment. A seizure log was maintained for 3 months preoperatively by his school caretakers and revealed 94 atonic and tonic-clonic seizures. Numerous electroen- cephalographic (EEG) examinations showed diffuse ab- normalities without a clear focus. He was admitted to our institution in August, 1980, for corpus callosotomy. Examination. Neurological examination disclosed a cheerful cooperative boy with decreased attention 514 J. Neurosurg. / Volume 59 / September, 1983