Acceleration of cerebral blood flow velocity in a patient with sleep apnea and intracranial arterial stenosis.

Sleep apnea (SA) syndromes of different etiologies are known to induce complications including cardiovascular diseases and stroke. However, the exact mechanisms involved in cerebral ischemia remain obscure. We measured the cerebral blood flow velocities (CBFV) by means of transcranial Doppler sonography in an 81-year-old patient who presented with an acute ischemic stroke caused by an intracranial middle cerebral artery (MCA) stenosis in the presence of SA syndrome. During apnea episodes simultaneous recordings revealed reduced intra-arterial oxygen but increased carbon dioxide saturation. This resulted in an increased CBFV (220 to 320 cm/s) and suggested intermittent hemodynamic relevance of a structurally only moderate MCA stenosis. Intracranial artery stenosis can become hemodynamically significant due to episodic hypercapnia in patients with SA. This may cause ischemic infarction in the periphery of the related cerebral vascular territories.