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A Cukiert, JA Burattini, PP Mariani, CM Cukiert, C Baise-Zung, M Argentoni-Baldochi, CR Forster, VA Mello.
Epilepsy Surgery Program, Hospital Brigadeiro, São Paulo SP, Brazil.
Rationale: Callosotomy is a good palliative surgical option in patients with secondary generalized epilepsy, especially of the Lennox-Gastaut or Lennox-like type. On the other hand, the outcome after callosal section has been poorly described in patients with primary generalized epilepsy. Primary generalized epilepsy is usually considered a benign form of epilepsy and is usually treated with low dose anticonvulsant (such as valproate) dosages. Unfortunately, some patients with primary generalized epilepsy belong to the refractory side of the biological continuum represented by this disease. We present the outcome after callosotomy in patients with refractory primary generalized epilepsy.
Material: Eleven patients with primary generalized epilepsy were studied. Age ranged from 17 to 43 years (mean=27 years). Two patients were classified as having juvenile myoclonic epilepsy and 9 as having childhood absence epilepsy. All patients had daily absence seizures and tonic-clonic seizures (mean frequency = 1 seizure / week) despite adequate medical therapy which included high dose valproate, lamotrigine and phenobarbital. The patients diagnosed as having juvenile myoclonic epilepsy did not had myoclonic jerks by the time of operation. MRI was normal or showed mild diffuse atrophy in all patients. Interictal EEG showed bilateral and synchronous spike (n=7) or polispike (n=4) and wave discharges (2.5 to 3.5 Hz) prevailing over the frontal regions. In 6 patients, fragmentation of this EEG pattern could be seen after high dose valproate therapy. Preoperative general IQ ranged from 75 to 110 (mean = 87). All patients were submitted to 90% callosal section under general anesthesia. Follow-up time ranged from 9 months to 7 years (mean= 32 months).
Results: All patients presented with an acute callosal disconnection syndrome characterized by apathy, urinary incontinence and hemineglect that lasted for 2-3 weeks. At least a 85% reduction in seizure frequency was obtained in all patients, and 1 patient became seizure free. Post-operative EEG showed bilateral synchrony rupture in all patients during wakefulness; in 9 patients bilateral synchrony was rebuilt during slow wave sleep. MRI documented uneventful surgical procedures. One-year postoperative neuropsychological testing was available for 7 patients. There was a mean increase of 11 points in general IQ, basically related to increased attention.
Discussion: The clinical, neurophysiological and neuropsychological data obtained in this patient population is very similar to those obtained in a series of patients with secondary generalized epilepsy. Genetic etiological factors are usually considered in primary generalized epilepsy and lesional factors in secondary generalized epilepsy. Our results suggest that although etiology might vary, these two types of epilepsy might share some pathophysiologic mechanisms, which should include an important role for the corpus callosum and subcortical modulation of the epileptic activity.