Lateralizing Value of Interictal Spikes on Overnight Sleep-EEG Studies in Temporal Lobe Epilepsy

Purpose: To determine the lateralizing value of interictal epileptiform discharges (IEDs) recorded during overnight sleep-EEG studies in temporal lobe epilepsy. Because IEDs are more prevalent in non-rapid eye movement (NREM) sleep than in wakefulness, overnight sleep-EEG recordings may contribute additional lateralizing information to the epilepsy surgery evaluation beyond daytime EEGs. Methods: Twenty-four subjects with medically refractory temporal lobe epilepsy underwent continuous overnight sleep-EEG recordings. Subjects were seizure free ≤24 h before study and receiving stable doses of medication. The IED foci recorded on overnight studies were compared with daytime EEGs, interictal samples, and ictal recordings during long-term monitoring, brain magnetic resonance images (MRIs), and surgical outcome. Results: (a) In all 24 subjects, including 13 without IEDs on daytime EEGs, temporal IEDs were present during NREM sleep and were exclusively or predominantly (<95%) unilateral in 15 and bitemporal in nine. (b) Unilateral NREM IEDs were concordant with surface or depth ictal-onset regions in 14 subjects, even if MRIs were normal (three subjects) or surface ictal-onset regions were bilateral (five subjects). Eleven of 12 subjects with unilateral concordant NREM IEDs who have undergone surgery are seizure free. (c) Bitemporal IEDs were associated with postoperative seizures in all subjects with normal MRIs or widespread MRI abnormalities. However, all subjects with bitemporal IEDs and MRI hippocampal abnormalities concordant with ictal-onset regions had good to excellent surgical outcomes. Conclusions: When combined with other investigations, IEDs recorded on overnight studies add prognostic data to the epilepsy surgery evaluation not provided by daytime EEGs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66154/1/j.1528-1157.1999.tb02044.x.pd

Interictal Spiking Increases with Sleep Depth in Temporal Lobe Epilepsy

Purpose : To test the hypothesis that deepening sleep activates focal interictal epileptiform discharges (IEDs), we performed EEG-polysomnography in 21 subjects with medically refractory temporal lobe epilepsy. Methods: At the time of study, subjects were seizure-free for 224 h and were taking stable doses of antiepileptic medications (AEDs). Sleep depth was measured by log delta power (LDP). Visual sleep scoring and visual detection of IEDs also were performed. Logistic-regression analyses of IED occurrence in relation to LDP were carried out for two groups of subjects, nine with frequent IEDs (group 1) and 12 with rare IEDs (group 2). Results: The LDP differentiated visually scored non-rapid eye movement (NREM) sleep stages (p = 0.0001). The IEDs were most frequent in NREM stages 3/4 and least frequent in REM sleep. Within NREM sleep, in both groups, IEDs were more frequent at higher levels of LDP (p < 0.05). In group 1, after accounting for the level of LDP, IEDs were more frequent (a) on the ascending limb of LDP and with more rapid increases in LDP (p = 0.007), (b) in NREM than in REM sleep (p = 0.002), and (c) closer to sleep onset (p < 0.0001). Fewer than 1% of IEDs occurred within 10 s of an EEG arousal. Conclusions: Processes underlying the deepening of NREM sleep, including progressive hyperpolarization in thalamocortical projection neurons, may contribute to IED activation in partial epilepsy. Time from sleep onset and NREM versus REM sleep also influence IED occurrence.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65422/1/j.1528-1157.1998.tb01329.x.pd

Focal Cerebral Magnetic Resonance Changes Associated with Partial Status Epilepticus

We report 2 patients with transient abnormalities on magnetic resonance imaging (MRI) associated with partial status epilepticus (SE). A man with a 4-month history of partial seizures had complex partial SE for 9 days, with left temporal maximum on ictal EEG. Left temporal lobe T 2 signal was increased on MRI during SE, but cerebral MRI was normal 9 weeks later. A woman with “cryptogenic” temporal lobe epilepsy for 16 years had complex partial SE for 1 week, with right temporal maximum on ictal EEG. T 2 Signal was increased over the entire right temporal lobe, extending into the insula, without mass effect, on MRI 1 month after SE ended. Repeat MRI 1 month later showed marked decrease in volume of increased T 2 intensity, without gadolinium enhancement, but with mild mass effect over the right anteroinferomesial temporal areas. A gemistocytic astrocytoma was resected. Focal cerebral MRI abnormalities consistent with cerebral edema may be due to partial SE but also may indicate underlying glioma, even in long-standing partial epilepsy. Focal structural imaging changes consistent with neoplasm should be followed to full resolution after partial SE.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65221/1/j.1528-1157.1994.tb02909.x.pd

Interictal spiking during wakefulness and sleep and the localization of foci in temporal lobe epilepsy.

We examined variations in interictal spiking during sleep and wakefulness to assess differences in reliability for localizing epileptic foci. Forty patients were studied prospectively. Spikes were assessed for rates, field, and appearance of new foci. Final localization was determined by surgery, electrocorticography, and seizure onset. Comparison of interictal EEG foci with final localization was made. In 39 patients, slow-wave sleep activated spiking compared with wakefulness. Most patients showed maximal spiking in sleep stages 3 or 4. Restriction of field in rapid eye movement (REM) sleep and wakefulness, and extension of field in slow-wave sleep occurred. New foci appeared in non-rapid eye movement sleep in 53% of patients. Similar but not identical spiking rates, foci, and field distributions were seen in wakefulness and REM sleep. All REM foci were unilateral. Our findings suggest that localization of the primary epileptogenic area is more reliable in REM sleep than in wakefulness, and in wakefulness more than in slow-wave sleep