ABSTRACT:Cerebral blood flow (CBF) and central conduction time (CCT) were recorded from 58 subarachnoid hemorrhage patients and from 49 age-matched controls. CBF was calculated following Xenon inhalation and CCT was determined from somatosensory evoked potentials (SSEP's) following median nerve stimulation. Each patient had a CT scan on the day of admission which was graded from I-IV. CBF, CCT and neurological grade (Hunt and Hess classification) were concomitantly recorded 1, 4, 7 and 14 days after subarachnoid hemorrhage. Mean CBF was highest in patients with neurological grades I and II (48.6 ± 12.3 and 48.1 ± 10.3 ml/lOOgm/min respectively) and lowest in patients with neurological grade IV (37.3 ± 9.6 ml/lOOgm/min). Patients in neurological grade I or II had mean CBF and CCT measurements that were significantly different from those obtained from patients in neurological grade IV (P < 0.05). Neurological grade and CT scan grade correlated with CBF (P < 0.0001) better than CCT (P = 0.015). Unexpectedly low CBF's from patients in neurological grades II and III (< 37 and < 31 ml/lOOgm/min respectively) failed to significantly prolong CCT suggesting CCT is unable to detect marginal ischemia. A significant correlation between CBF and CCT occurred only when CBF was < 30 ml/lOOgm/min (R = 0.75, P = 0.05). It appears that prolonged CCT is associated with a drop in CBF only when CBF drops below a certain threshold.
Measurement of Somatosensory Evoked Potentials in Aneurysmal Subarachnoid Hemorrhage
