Modifications in morphology of epileptic seizures after callosotomy

The callosotomy on drug-resistant epileptic seizures may abolish or reduce their frequency and may modified the morphology of different kind of seizures. Our series is composed of 36 patients. Drop-attacks and complex partial seizures (CP) were present in all patients, generalized tonic-clonic seizures (GTC) in 16 (44.4%) and simple partial seizures (SP) and myoclonic attacks (MY) in 6 patients each. We found two kinds of modifications: a) lateralization of hypotonia which becomes hemisomatic, with lateral bending to the hypotonic side; b) different way of falling, due not only to the lateralization of hypotonia but also to the gradual impairment of muscle tone. Modifications in CP mainly concerned automatisms, which disappeared in 39.1% of patients, while 34.8% of them had a significant reduction in automatisms; this reduction consisted in simplification of automatic movements and in shorter duration of seizures.

EEG Patterns after callosotomy

In 36 patients with drug-resistant epilepsy submitted to anterior callosotomy (27 cases), to two-stage total callosotomy (8 cases) and to posterior callosotomy (1 case) the EEG variations concerning background activity, focal activity and sharp-waves (SW) bisynchronous activity were evaluated. EEG modifications observed after callosotomy are the following: background rhythm tends to be better organised as spectral analysis demonstrated, this finding usually coincide with reduction of bisynchronous discharges. It appears that improvement in background activity cannot be correlated with outcome, but it seems to be to some extent since at the same time cognitive functions also seem to improve; however, this last aspect need to be checked in much larger series. The number and location of EEG foci do not change, but they appear to be more active; this is likely to depend only on the concomitant reduction of bisynchronous activity. No correlation seems to exist between the number and the location of foci, which are generally multiple. Lateralization of bisynchronous discharges as well as the reduction of their frequency and duration were observed. However, the clinical course is quite different: in some patients we have achieved good clinical responses in others postoperative results were poor. Lateralization of bisynchronous discharges is never absolute, on the grounds that in prolonged recordings bisynchronous discharges are nearly always present. Bisynchronous discharges in some cases are alternatively predominant in both hemispheres even within minutes or seconds. It was observed that after certain time, generally some months, lateralized discharges tend to generalize again, confirming that corpus callosum is replaced in discharge diffusion by other structures (brain-stem, diencephalon).

Mutism in 36 patients who underwent callosotomy for drug-resistant epilepsy

Thirty-six drug-resistant epileptic patients submitted to callosotomy were studied. Anterior callosotomy was performed in 27 patients, total two-stage callosotomy was performed in 8 patients and 1 patient had only posterior callosotomy. We found mutism in 10 patients (2 after complete callosotomy and 8 after anterior section). The patients did not speak, but the comprehension was present: they were able to carry out orders and to write. Their attitude to the environment was characterized by complete indifference. The mutism was always transient, lasting from 4 to 25 days (mean 7 days). Regression of mutism was always complete. We think that this complication should be chiefly attributed mainly to surgical manipulation, even if it is impossible to completely exclude a multi-factorial etiology.