Sporadic nocturnal frontal lobe epilepsy: A consecutive series of 8 cases

Abstract

Objective: To present findings on a series of cases of sporadic nocturnal frontal lobe epilepsy (NFLE), a form of NFLE that is infrequently reported, in contrast to familial (autosomal dominant) NFLE. Both forms of NFLE need to be distinguished from parasomnias, nocturnal temporal lobe epilepsy, and other nocturnal disorders.

Methods: Eight consecutive cases of sporadic NFLE were evaluated at a sleep clinic in Taiwan. All patients had clinical evaluations, daytime waking and sleeping EEGs, brain MRIs, and overnight video-polysomnography (vPSG) with seizure montage.

Results: Gender was equal (four males, four females); mean age was 18.4 yrs (range, 7-41 yrs). Age of NFLE onset was by puberty. Premorbid history was negative for any neurologic, medical or psychiatric disorder. NFLE subtypes: nocturnal paroxysmal dystonia, n=6; paroxysmal arousals, n=2. MRI brain scan abnormalities with clinical correlates were found in one patient. Daytime awake EEGs were negative for ictal/interictal activity in all patients, but two patients had daytime sleep EEGs with interictal epileptiform EEG activity. During vPSG studies, three of eight patients with NFLE seizure events had concurrent epileptiform EEG activity, and two patients had interictal epileptiform EEG activity during their vPSG studies. No case had a spontaneous remission. Anticonvulsant therapy was highly effective in all eight cases (>75% reduction in seizure frequency).

Discussion: These cases confirm that sporadic NFLE closely resembles familial NFLE, and comprises a set of distinct clinical manifestations, with variable intensity, and variable scalp EEG epileptiform abnormalities across sleep and wakefulness, which have previously been identified in Caucasian patients from Europe and North America.

Keywords: Anticonvulsant therapy; Nocturnal frontal lobe epilepsy (sporadic, familial); Nocturnal paroxysmal dystonia; Nocturnal temporal lobe epilepsy; Paroxysmal arousals; Video-polysomnography.

Fig. 1

Nocturnal PSG (30s epoch) during stage 2 sleep and the emergence of tachypnea following the four limb dystonic posturing. Black solid arrow indicates the event onset time (11:05:03 p.m.), and the event duration persists for 36 sec. EEG montage (channels 12–19) shows with a run of sharp waves during the event episode. The electrooculogram (channel 7–8) indicates no rapid eye movement. The electrocardiogram (channel 11) shows an increase in heart rate during the episode attack. Channels 20–23 represent the nasal/oral airflow, chest respiratory effort, abdomen respiratory effort and O₂ saturation, which do not show any sleep apnea or oxygen desaturation, but an increase in respiratory rate beginning with the onset of the episode attack.

Fig. 2

Nocturnal PSG (10s epoch) during N2 sleep and the emergence of epileptiform EEG discharge. EEG montage (channels 12–19) shows a run of spike-and-waves during an interictal period. The electrooculogram (channels 7–8) indicates no rapid eye movements. The electrocardiogram (channel 11) is unremarkable during the interictal epileptiform EEG discharge. Channels 20–23 represent the nasal/oral airflow, chest respiratory effort, abdomen respiratory effort and O₂ saturation, which do not show any sleep apnea, oxygen desaturation, or tachypnea.