Stephen C. Rossiter

Correlations between cerebral arterial velocities, blood flow, and delayed ischemia after subarachnoid hemorrhage.

Elevated middle cerebral erythrocyte velocities and tissue hypoperfusion have been correlated with delayed ischemia after subarachnoid hemorrhage, but few studies have compared serial arterial velocities with cerebral blood flow and neurological deficits. Methods Serial measurements of middle cerebral velocities, using transcranial Doppler ultrasonogra-phy, were performed in 34 patients after subarachnoid hemorrhage and correlated with cerebral blood flow, measured in 20 of the 34 using single-photon emission computed tomography with technetium-99m hexamethylpropylene amine oxime and neurological evidence of delayed ischemia. Results In 16 patients without delayed ischemia, eight had evidence of vasospasm (>120 cm/sec), but only one of seven had hypoperfusion, suggesting that vasospasm might be more common than hypoperfusion in this group (p=0.1). In 10 patients with delayed ischemia and a lateralizing deficit, both asymmetrical middle cerebral vasospasm (eight of nine with vasospasm) and hypoperfusion (six of six studied) were concordant with the clinically ischemic hemisphere (p<0.05). Vasospasm occurred with nonlateralized delayed ischemia in seven of eight patients and with hypoperfusion in five of six, affecting the anterior cerebral territory in three. Conclusions Concordant vasospasm and hypoperfusion were most often present in patients with delayed ischemia and lateralizing neurological deficits. Discordant results reflect inherent limitations and the different levels of the circulation monitored by the two techniques.

A single-photon emission computed tomography study of hypoperfusion after subarachnoid hemorrhage.

We used single-photon emission computed tomography with technetium-99m hexamethylpropylene amine oxime in 18 studies on 13 patients with subarachnoid hemorrhage to determine whether any changes in cerebral blood flow could be correlated with clinical or computed tomographic evidence of delayed ischemia. Among the seven patients without focal neurologic deficits, regional cerebral hypoperfusion was demonstrated in only one who died. Among the 10 patients with aneurysmal subarachnoid hemorrhage, one died before surgery, and six developed postoperative delayed ischemic deficits, of whom two died. Among the patients with angiographically documented aneurysms, regional hypoperfusion correlated with the presence and severity of delayed neurologic deficits, whereas correlative computed tomographic scans showed either early infarction or no relevant abnormality. This technique facilitates early diagnosis of cerebral tissue hypoperfusion due to vasospasm after subarachnoid hemorrhage.

Cerebral hypoperfusion in stroke prognosis and brain recovery.

Background and Purpose The value of acute cerebral blood flow measurements in stroke prognosis is controversial. No previous study has determined whether acute perfusion deficits independently add to a validated clinical prognostic score. We aimed to compare the value of acute hypoperfusion deficits with a quantitative clinical score in stroke prognosis and to correlate the changes in perfusion with brain recovery. Methods Volumetric analysis of regional hypoperfusion was performed in 38 patients with middle cerebral infarction within 72 hours of onset by use of single photon emission computed tomography and 99mTc hexamethylpropylene amine oxime. Stroke severity was assessed by the Canadian Neurological Score and Barthel Index. Allens prognostic score was determined acutely in all patients. Clinical outcome was evaluated in 36 of 38 patients, of whom 18 had repeat blood flow studies. Results Acute hypoperfusion correlated with both the outcome Barthel Index (P < .001, r=-.61) and Canadian Neurological Score (P < .001, r=-.64). Allens score correlated better with both the outcome Barthel Index (P < .001, r=.80) and Canadian Neurological Score (P < .001, r=.81). Acute hypoperfusion deficits, after allowing for Allens score, independently predicted neurological but not functional outcome. Despite overall neurological improvement, mean hypoperfusion increased on the repeat blood flow studies (P<.05). Conclusions Volumetric analysis of acute regional hypoperfusion within 72 hours of onset predicts stroke outcome after 3 months, but Allens score is a better prognostic method. Neurological recovery is not associated with chronic infarct reperfusion. (Stroke. 1993;24:1691-1696.)

Magnetic resonance imaging and late-onset epilepsy.

Summary: The value of magnetic resonance imaging (MRI) in investigation of patients with late‐onset epilepsy has not been studied systematically. We evaluated prospectively the usefulness of MRI in 50 patients with late‐onset epilepsy in whom a computed tomography (CT) scan was normal (32), did not allow a definitive diagnosis to be made (12), or showed irrelevant lesions (6). Patients were assessed clinically and had an EEG, and CT and MRI scans were reported by one neuroradiologist blinded to clinical and laboratory data. Of the 32 patients with a normal CT scan, MRI was normal in 20, showed irrelevant ischemic lesions in 8, and showed the cause of seizures in 4 patients. Of the 12 patients with nondiagnostic CT, MRI clarified the diagnosis in 5 and was normal in 2 patients. In 6 patients, both scans showed irrelevant ischemic lesions, and in 1 patient MRI showed a relevant additional lesion. The incidence of MRI‐detected white matter ischemic lesions was no greater than in an age‐ and sex‐matched group of subjects without seizures. MRI was diagnostic in 32% of the patients with partial seizures and/or focal EEG findings, as compared with 0% of patients without focal features (p < 0.01). We conclude that MRI is useful in investigation of patients with late‐onset epilepsy with focal features.

Dynamic CT brain scanning in the haemodynamic evaluation of cerebral arterial occlusive disease

SummaryDynamic cerebral CT scanning (DCT) was used to quantitatively analyse the haemodynamic effects of extracranial and intracranial arterial occlusive lesions in 17 patients with TIAs or minor cerebral infarcts. Using DCT and gamma variate curve fitting, mean transit times were determined for the terminal internal carotid arteries, middle cerebral arteries and middle cerebral-supplied Sylvian cortex at the level of the Circle of Willis. Six patients were studied sequentially, four before and after transcranial bypass surgery. No arterial or tissue delays were found in patients without haemodynamic arterial lesions or cortical infarcts. Seven of nine patients with haemodynamic, extracranial carotid lesions showed ipsilateral delays in arterial or tissue transit times. Tissue delays usually correlated with CT or clinical evidence of infarction. Improved haemodynamics in patients re-studied correlated with the effects of surgery or clinical recovery. DCT has several important limitations but has the potential to provide additional haemodynamic information about the cerebral circulation in selected patients with cerebral arterial occlusive disease.

Analysis of dynamic computed tomography scan brain images.

Dynamic computed tomography (DCT) of the brain can be used to study the transit time of first passage of a bolus injection of intravenous contrast medium. Comparison of cerebral perfusion with corresponding sites in the left and right cerebral hemispheres is of diagnostic interest because a real difference may be indicative of differential damage. A method for estimating the mean transit time and approximating its standard error, by assuming a gamma function for the response curve and an appropriate error structure, is presented. Expressed as log-linear regression, estimation is achieved by maximum likelihood using a statistical package such as GLIM or SPSSX. Statistical comparison of the mean transit time to or between corresponding sites can be made; issues of model fit and biologic interpretation need to be considered as an integral part of statistical inference. These methods enable users of CT equipment (without specific software for estimation of mean transit time) to use any log-linear routine for diagnostic purposes. An example of the fit procedure and interpretation in the light of clinical evidence is given.