Abstracts

Rationale: Standard polysomnography (PSG) typically utilizes 2-4 channels of EEG, which is inadequate to evaluate epileptiform activity. Though technical capability has long existed for more intensive EEG recording, few sleep laboratories have utilized this technique. We sought to determine the utility of combining PSG with 18-channel EEG. Methods: We reviewed combined PSG-EEG studies, performed between 10/1/2005 and 3/1/2007, evaluating demographics, referral source, indications, and results. Data were recorded on a Nihon-Kohden system. Automatic spike-seizure detection utilized the Persyst software, in addition to visual inspection.Results: In this period, we performed 102 PSG-EEG studies. Patient’s mean age was 42.2 (range 16-81, 49 women). Indications included: 1) Known epilepsy (treated medically and/or surgically), with possible subclinical nocturnal seizures vs. primary sleep disorder as reason for fatigue or sleepiness (28 patients). 15 were diagnosed with obstructive sleep apnea (OSA), 2 with periodic limb movements of sleep (PLMS), 8 with both OSA and PLMS, and 3 had normal PSGs. Regarding EEG, 1 had probable subclinical electrographic seizures recorded and 6 others had interictal epileptiform discharges; 5 of these patients had coexisting sleep disorders. 2) Unusual nocturnal behaviors (30 patients). 1 had REM Behavior Disorder, and 2 patients had interictal epileptiform discharges (1 with OSA). In the remaining 27 patients without discharges, epilepsy was considered less likely after the study. Of this group, 13 had OSA, 5 had PLMS, and 4 had both. 3) Unexplained daytime alterations of awareness that could be attributed to either extreme sleepiness or complex partial seizure (25 patients). 14 had OSA, 2 had PLMS, 5 had both, and 1 had epileptiform discharges. 4) Insufficient history documenting indication for the combined study (19 patients). 10 were performed for CPAP titration in patients with known OSA, while 9 had an epilepsy diagnosis. Of these, 3 had OSA, 1 had PLMS, 3 had both (2 with epileptiform discharges), and 2 were normal. In summary, among 102 studies, 81 documented sleep disorders, 4 showed epileptiform discharges, 8 revealed both sleep disorders and epileptiform EEGs, and 9 had neither. Conclusions: Of 102 combined PSG-EEG studies, 91% supported the diagnosis of a sleep disorder, epilepsy, or both. Patients who can benefit include: 1) those with known epilepsy who may also have a sleep disorder, 2) those with undiagnosed nocturnal events, and 3) those with unusual daytime alterations of awareness and no definitive diagnosis.