Obstructive Sleep Apnea-hypopnea Syndrome (osahs) Is Characterized by Repeated Episodes of Upper Airway Obstruction during Sleep,

1515 OBSTRUCTIVE SLEEP APNEA-HYPOPNEA SYNDROME (OSAHS) IS CHARACTERIZED BY REPEATED EPISODES OF UPPER AIRWAY OBSTRUCTION DURING SLEEP, with disturbances in arterial blood gases and increasing inspiratory effort until the upper airway obstruction discontinues due to arousal. OSAHS has a relatively high prevalence and occurs in 5% of the adult population.1 OSAHS may cause daytime sleepiness, reduce work performance, increase the risk of a traffic accident, and diminish quality of life.2 Neurocognitive problems, such as, deficits in memory, attention, and visuoconstructive abilities, are frequently found in patients with OSAHS.3 The pathophysiology of these deficits remains controversial, though the main contributory factors are presumed to be sleep fragmentation and intermittent nocturnal hypoxemia during sleep apneas. A deterioration of cognitive performance has been significantly correlated with the degree of nocturnal hypoxemia4 and with the severity of nocturnal breathing irregularities.5 The visual inspection of a 99mTc-(d,l)-hexamethylpropyleneamine-oxime (HMPAO) single photon emission tomography (SPECT) study during repeated obstructive apneas has shown marked frontal hyperperfusion in 5 patients and left parietal hypoperfusion by the analysis of 32 regions of interests.6 Routine transcranial Doppler is a technique primarily used for measuring relative changes in cerebral blood flow. It has been reported that, during obstructive sleep apneas, profound changes in cerebral blood flow occur7 and that apnea-induced hypoxemia combined with reduced cerebral perfusion may predispose patients with OSAHS to nocturnal cerebral ischemia.8 Because patients with OSAHS frequently report neurocognitive problems as well as excessive daytime sleepiness,1-5 we postulated that these daytime symptoms are associated with rCBF changes during the daytime awake state as a consequence of increased hemodynamic changes during night sleep due to frequent sleep apneas. CBF changes during wakefulness have not been previously studied in patients with OSAHS. Statistical parametric mapping (SPM) is a proven and effective method for the voxel-by-voxel analysis of functional images.9 The advantage of this approach lies in its promise of fully automated neurophysiologic imaging analysis throughout the whole brain using various statistical approaches. rCBF has been considered to be a marker of neuronal activity, and SPM analysis for detecting rCBF changes has allowed the exploration of regional cerebral hemodynamics with a good localizing power.10 The aim of this study was to investigate the effect of frequent nocturnal obstructive sleep apneas on rCBF during the waking state in patients with OSAHS. To achieve it, we performed 99mTcethylcysteinate dimer (ECD) brain SPECT in severe patients with OSAHS and healthy volunteers during the waking state and then analyzed rCBF differences between the 2 groups. Reduced Cerebral Blood Flow During Wakefulness In Obstructive Sleep ApneaHypopnea Syndrome