Beyond standard polysomnography: Advantages and indications for use of extended 10–20 EEG montage during laboratory sleep study evaluations

PURPOSE Standard polysomnography (PSG) typically utilizes 4-6 channels of electroencephalography (EEG), which is inadequate to evaluate focal epileptiform activity. Though technical capability has long existed for more extensive EEG recording, few sleep laboratories have utilized this technique. The objective of this study was to determine the utility of combining PSG with 18-channel EEG in select patients with paroxysmal nocturnal events or other symptoms concerning for sleep disorders, nocturnal seizures or both. METHODS Consecutive combined PSG-EEG studies (n=237) were performed between 10/1/2005 and 8/1/2009. Demographics, referral source, indications, and results were reviewed and analyzed. RESULTS Of the 237 consecutive combined PSG-EEG studies performed, 93% revealed the presence of a primary sleep disorder, 38% were shown to have abnormal EEGs, and 37% had both. Among the 221 subjects (93%) shown to have sleep disorders, the majority of these cases were obstructive sleep apnea (OSA) 89%, followed by periodic limp movements of sleep (PLMS) 22% and rapid eye movement behavior disorder (RBD) 6%. Significantly more patients with known epilepsy were diagnosed with OSA then were patients without a seizure history. CONCLUSIONS Combined PSG-EEG, utilizing 18-channel EEG, is an under-utilized technique which can assist in diagnosing paroxysmal nocturnal events, and differentiate between the presence of a primary sleep disorder, seizure activity, or both. Our study further illustrates the importance of considering sleep disorders in epilepsy patients.