Nonconvulsive status epilepticus of frontal origin.

Objectives: To determine the electroclinical characteristics and causative factors of nonconvulsive status epilepticus (NCSE) of frontal origin.

Methods: The authors conducted a 5-year prospective study.

Results: Ten patients were studied (seven men, three women; mean age, 56.4 years). Six patients did not have previous epilepsy. The mean diagnostic delay was 48 hours (range, 3 to 96 hours). Two types of frontal NCSE were identified. In type 1 (n = 7), mood disturbances with affective disinhibition or affective indifference were associated with subtle impairment of cognitive functions without overt confusion. EEG showed a unilateral frontal ictal pattern and normal background activity. In type 2 (n = 3), impaired consciousness was associated with bilateral, asymmetric frontal EEG discharges occurring on an abnormal background. Ictal and postictal 99mTc hexamethyl propylene amine oxime (HMPAO) SPECT was performed in five patients and showed unilateral or bilateral frontal HMPAO uptake that aided localization, especially in type 2 NCSE of frontal origin. Etiologies included a focal frontal lesion in six patients (three of which were tumors), neurosyphilis, and nonketotic hyperglycemia. Eight patients did not respond to initial IV benzodiazepine (BZ), but IV phenytoin controlled six patients successfully. The immediate outcome was favorable in all patients. There was no long-term recurrence of SE in seven patients.

Conclusions: NCSE of frontal origin is a heterogeneous syndrome. Some cases are best described as simple partial NCSE, others as complex partial SE, and there are forms that overlap with absence SE. Emergency EEG and neuropsychological assessment are diagnostic, and SPECT may be useful. Many patients may not respond to IV BZ.