Dystonic posturing in seizures of mesial temporal origin: electroclinical and metabolic patterns.

OBJECTIVE

To test the hypothesis that extratemporal neuronal networks are involved in dystonic posturing (DP) observed in mesial temporal epilepsy (MTLE).

METHODS

The authors analyzed electroclinical findings in 36 patients with MTLE with or without DP. Three DP types were defined (types I, II, III) corresponding to a gradual increase in duration and complexity. Interictal [18F]fluorodeoxyglucose-PET in different groups and subgroups was compared with control subjects using statistical parametric mapping software (SPM99).

RESULTS

DP was found in 20 patients (55%), contralateral to the epileptogenic focus in 95%. Patients with DP had longer seizure duration, higher frequency of head deviation, salivation, motor manifestations, secondary generalization, severe clouding of consciousness, and prolonged postictal confusion when compared with patients without DP. Ictal discharge patterns during DP consisted of fast rhythmic activity spreading to frontal or suprasylvian areas, whereas slow rhythmic activity restricted to the temporal areas occurred in the absence of DP. In patients with DP, widespread temporal and extratemporal hypometabolism including the putamen was found. Hypometabolism was restricted to the anteromesial part of the temporal lobe and anterior insula in patients without DP. Putaminal hypometabolism was found in all DP types, but different extratemporal cortical involvements were found in DP subgroups: insula and inferior frontal gyrus in type I, inferior and superior frontal gyri and anterior cingulate gyrus in type II, and parietal areas in type III.

CONCLUSION

Dystonic posturing may result from involvement of both putaminal and extratemporal cortical areas. Moreover, different frontal or parietal networks may be involved according to the duration or complexity of dystonic posturing.