Brief communication Sawtooth wave density analysis during REM sleep in temporal lobe epilepsy patients Francisco Vega-Bermudez a,b, * , Sara Szczepanski b , Beth Malow c , Susumu Sato a a EEG Section, NINDS, NIH, Bethesda, MD, USA b Zanvyl-Krieger Mind Brain Institute, Johns Hopkins University, Baltimore, MD, USA c Department of Neurology, Vanderbilt University, Nashville, TN, USA Received 5 August 2004; received in revised form 7 February 2005; accepted 7 February 2005 Abstract Background and purpose: This study analyzes sawtooth waves (STW), a characteristic feature of rapid eye movement (REM) sleep, in temporal lobe epilepsy patients in order to test the hypothesis of STW dysfunction in this population. Methods: Polysomnographic records from 16 patients with temporal lobe epilepsy and 11 controls were scored for density (STW/h of REM sleep), duration (STW duration in s), and frequency of STW (waves/second within each STW complex). These measures were compared between both groups. Results: STW measures were significantly different in control vs. epilepsy patients; respectively, density was 60.8 vs. 20.9 waves/h (P!0.005), average duration was 6.5 vs. 5.4 s (P!0.005 cycles 1–4), and frequency was 2.75 vs. 2.61 Hz (P!0.0005 across all cycles). Conclusions: Our measurements show a change in the density, duration and frequency of STW in patients with temporal lobe epilepsy compared to controls. Other parameters of REM sleep appear to be similar in both groups. These findings suggest a cortical influence on REM sleep either directly or through limbic–hypothalamic–brainstem connections. q 2005 Elsevier B.V. All rights reserved. Keywords: Sawtooth waves; REM sleep; Temporal lobe epilepsy; Polysomnography 1. Introduction Rapid eye movement (REM) sleep is associated with a number of physiologic phenomena, including loss of muscle tone, rapid eye movements, low-voltage, mixed frequency electroencephalogram (EEG) and sawtooth waves (STW). STW are described as 20–100 mV, 2–5 Hz surface positive waves widely distributed but of maximal amplitude at Cz, commonly seen before a burst of REMs [1]. They have been well characterized in normal subjects [2,3], but their precise origin is unknown. However, an animal model suggested a relationship to ponto-geniculo-occipital (PGO) spikes [4]. Neurological conditions affecting the brainstem like post-polio syndrome [5], or the cortex in hemispheric stroke [6], show abnormalities of STW. Thus, we hypoth- esize that other neurological conditions could also lead to abnormalities in REM sleep. We examined temporal lobe epilepsy since these patients show abnormalities of sleep [7]. In this study, we examined the question whether REM sleep and specifically STW, a feature of REM sleep, is affected in patients with temporal lobe epilepsy. 2. Methods 2.1. Subjects Eleven normal subjects, five males and six females with no history of significant illness or drug use and a normal neurological exam, participated in the study. Each subject gave written consent according to the NIH Clinical Center Institutional Review Board guidelines. Each subject par- ticipated in two consecutive nights of recording. Due to technical problems with two studies, 20 night recordings Sleep Medicine 6 (2005) 367–370 www.elsevier.com/locate/sleep 1389-9457/$ - see front matter q 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.sleep.2005.02.005 * Corresponding author. Address: The Mind/Brain Institute, Johns Hopkins University, 3400 N. Charles Street, 338 Krieger Hall, Baltimore, MD 21218, USA. Tel.: C1 410 516 8640. E-mail address: fvega@jhu.edu (F. Vega-Bermudez).