Asymmetric Tonic Seizures Research Articles

Asymmetric tonic seizures with bilateral parietal lesions resembling frontal lobe epilepsy

ABSTRACT We performed long‐term video/ EEG monitoring and a single photon emission computed tomographic (SPECT) study to clarify generating mechanism of bilateral tonic motor seizures resembling seizures generated by the supplementary motor area (SMA), in patients with bilateral parietal lesions. We describe 2 patients (age 24 and 32 years), with bilateral parietal lesions. Clinically, seizures were preceded by lightning sensation in the body, followed by asymmetric tonic posturing of both hands and thrashing movements of the feet, lasting for less than 1 min. Ictal rhythmic (7‐15 Hz) activity at the vertex was observed on the EEG in 1 patient. Interictal SPECT in 2 patients showed decreased blood flow in both parietal areas, consistent with bilateral parietal abnormalities on T2‐ and T1‐weighted MRIs. Ictal SPECT in 1 patient showed increased blood flow in the right parietal and frontopolar areas. The present 2 patients had clinically asymmetric tonic seizures, most likely resulting from spreading of the ictal activity from the parietal lesions via the superior longitudinal fasciculus to the SMA. Bilateral, homologous lesions in the parietal area might cause disinhibition on the unilateral epileptogenic side.

Epileptic negative myoclonus and brief asymmetric tonic seizures. A supplementary sensorimotor area involvement for both negative and positive motor phenomena

ABSTRACT Epileptic negative myoclonus (ENM) is an epileptic motor dysfunction characterised by brief lapses of postural tone provoked by paroxysmal cortical discharges. We report the electrophysiological and video‐polygraphic findings in a patient presenting with the unusual association of ENM and brief asymmetric tonic‐postural seizures of cryptogenetic origin. Focal EMG silent periods in the left deltoid muscle (mean duration 81.2 ± 16.4 ms), time‐locked with vertex spikes were present. The time lag between spikes and ENM was 33.1 ± 4.6 ms. We suggest the involvement of mesial frontal areas in the genesis of both negative and positive motor phenomena.

Hemimegalencephaly and intractable epilepsy: benefits of hemispherectomy.

We observed 4 children with hemimegalencephaly, (3 boys, 1 girl aged 3-7 years). One child had a linear sebaceous nevus. All patients had a similar clinical, EEG, and neuroradiologic pattern. All patients had macrocrania, hemiparesis, hemianopsia, and psychomotor retardation of variable degree. All cases had an epileptic syndrome with onset during the first days or the first months of life. The seizures were consistently similar: partial motor seizures, generally hemiclonic and asymmetric brief tonic seizures, in series, involving predominantly one side of the body, contralateral to the cerebral damage. The EEG was initially characterized by a hemihypsarrhythmia and afterward, over the malformed hemisphere, by a rather high-frequency background activity associated with almost continuous transients of spikes, sharp waves, and spike and waves that progressively involved the contralateral hemisphere. Hemispherectomy was performed in two children with sudden and complete recovery from seizures and improvement in psychomotor development. Macroscopic examination was consistent with the computed tomography (CT) scan and magnetic resonance imaging (MRI) showing pachygyria and poorly represented white matter. Histologic examination showed the characteristic absence of cortical neuronal layering, and the presence of giant neurons, neuronal heterotopias, and gliosis. For hemispherectomy to be successful, we believe prolonged EEG monitoring is needed to verify that no seizures are originating in the normal hemisphere.