Bruce I. Tranmer

Spontaneous Thrombosis of an Unruptured Anterior Communicating Artery Aneurysm An Unusual Cause of Ischemic Stroke

BACKGROUND Stroke caused by spontaneous thrombosis of an unruptured intracranial aneurysm is a rare event. CASE DESCRIPTION A 66-year-old woman experienced a transient ischemic attack and cerebral infarctions due to spontaneous thrombosis of an unruptured anterior communicating artery aneurysm. Extension of thrombus into both anterior cerebral arteries and the left middle cerebral artery, resulting in ischemic infarction in all three vascular territories, was diagnosed by CT scanning, MRI, and cerebral angiography and confirmed at autopsy. CONCLUSIONS This case illustrates a rare complication of an unruptured saccular aneurysm with neuroimaging and pathological correlation. Morphological and hemodynamic factors that may have precipitated aneurysm thrombosis are discussed with reference to experimental models.

Intra-aortic balloon counterpulsation: a treatment for ischaemic stroke?

Intra-aortic balloon counterpulsation (IABC) augments cardiac output (CO) and pulse pressure (PP) allowing patients with low output heart failure to be supported for a period of time. Augmentation of CO and PP may also be beneficial to the patient with acute cerebral ischaemia. In this paper we investigated the possibility of using IABC to increase local cerebral blood flow (CBF) in ischaemic brain. In 12 anaesthetized mongrel dogs, a canine stroke model was produced by occluding the left internal carotid and middle cerebral arteries with aneurysm clips. Six dogs were then treated with IABC for 2 h, and 6 other dogs acted as controls (no IABC). Haemodynamic data were measured continuously and CBF (microsphere technique) and CO measurements were performed pre- and post-occlusion, and then twice during the treatment period. In the IABC-treated animals, PP increased from 32 +/- 5.9 to 39 +/- 7.8 mmHg (p less than 0.01) but CO and local CBF in the ischaemic brain did not change significantly during IABC. However, in 4 dogs with significant increases in CO due to IABC [1.7 +/- 0.3 to 2.8 +/- 0.7 l/min (p less than 0.05)], local CBF in ischaemic brain also increased significantly from 22 +/- 12 to 26 +/- 11 cc/100 g/min (p less than 0.05). In the control animals, CO and local CBF did not change significantly during the observation period. These data suggest that augmentation of CO and PP by IABC results in an increase in local CBF in ischaemic brain. IABC may be an effective treatment for ischaemic stroke in those patients with compromised cardiac performance whose cardiac output and pulse pressure can be augmented by IABC.

Increased cerebral blood flow in idiopathic pseudotumour cerebri.

Cerebral blood flow was studied in nine patients with idiopathic pseudotumour and one patient with cortical vein thrombosis in Denver, Colorado using the 133Xe inhalation method. Globally elevated blood flows were found in all of the idiopathic pseudotumour patients averaging 149% of control values generated in the same setting. The patient with the cortical vein thrombosis demonstrated normal global flows. Possible pathophysiological mechanisms for these findings are discussed.

Postischemic therapy with MK-801 (dizocilpine) in a primate model of transient focal brain ischemia

The purpose of this study was to develop a primate model for assessing EEG, behavior and histology, and to test the effect of NMDA receptor blockade in transient focal ischemia. Squirrel monkeys (Saimiri sciureus) under halothane anesthesia were subjected to 110 min of transient focal ischemia (n = 15) by temporary clip occlusion of the MCA. An eight-lead EEG was recorded. Neurobehavioral testing was done in a subgroup of animals (n = 6). Brain temperature (37.5 degrees C) was monitored and controlled to avoid hypothermia or intergroup temperature differences, and blood pressure was regulated to 60 mmHg. The entire brain was subserially sectioned, and 52 standardized coronal sections encompassing the infarct were examined histologically 2 wk after the ischemia. Animals were randomized to receive either (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) 1 mg/kg of maleate salt or carrier solution, 20 min and again at 12 h after the onset of ischemia. Cingulate and retrosplenial cortex were examined for NMDA-antagonist-induced neuronal necrosis. No reduction, or trend toward reduction of neurobehavioral deficit was seen with MK-801. MCA occulsion reduced EEG power over the ischemic hemisphere. MK-801 appeared to cause brain activation, and globally increased power at several frequencies. MK-801 did not reduce infarction in either neocortex (p > 0.05) or striatum (p > 0.05). No selective neuronal necrosis was seen in the cingulate or retrosplenial cortex. We conclude that MK-801 given 20 min after the onset of transient ischemia offers no significant neuroprotective effect against either neurobehavioral deficit or ischemic infarction in this model of transient focal ischemia. Further experiments in unanesthetized animals are necessary to determine if MK-801-induced necrosis exists in the gyrencephalic brain, but the enhancement of primate brain electrical activity by MK-801 suggests that brain activation occurs in primates as it does in rodents.

Role of hypervolemic hemodilution in focal cerebral ischemia of rats

This study was designed to better define a protocol for hypervolemic hemodilution in acute cerebral ischemia and investigate the mechanism of action of this therapy. Anesthetized rats (n = 40) were subjected to 6 h of middle cerebral artery (MCA) occlusion. At 45 min after MCA occlusion, each rat received one of the following treatment modalities: (1) control, (2) isovolemic hemodilution, (3) hypervolemic nonhemodilution (whole blood), (4) hypervolemic hemodilution (normal saline), and (5) hypervolemic hemodilution (hetastarch). Local cerebral blood flow (CBF) was determined with hydrogen clearance technique, and cardiac output was assessed by measuring the descending aorta blood flow (DAF). Infarction volume was estimated by 2,3,5-triphenyltetrazolium chloride staining method. Hetastarch infusion increased both DAF and local CBF more than the other treatments, by 98% and by 89%, respectively. Hetastarch also reduced infarction volume the most to 71 +/- 19 mm3 (p < 0.01 versus control 117 +/- 32 mm3). A significant correlation between percent (%) changes in local CBF and % changes in DAF existed in ischemic brain regions, and the hetastarch infusion improved local CBF more prominently in profoundly ischemic regions in contrast to isovolemic hemodilution. These data demonstrated the superiority of hypervolemic hemodilution with hetastarch as compared to other similar treatment modalities for acute cerebral ischemia, and indicate that cardiac output augmentation may be more responsible than decreased blood viscosity for the beneficial effect of hypervolemic hemodilution on local CBF in profoundly ischemic regions, as such ischemic brain tissue can severely lose its regulatory control of CBF to alterations in cardiac output.

Pretreatment of transient focal cerebral ischemia in rats with the calcium antagonist AT877.

Background and Purpose The efficacy of pretreatment with the recently developed intracellular calcium antagonist AT877 against transient focal cerebral ischemia was investigated in rats subjected to middle cerebral artery occlusion and reperfusion using the endovascular suture method. Methods Halothane-induced moderate hypotension (60 mm Hg) was used during 100 minutes of temporary middle cerebral artery occlusion. In the treated animals (n=10), an intravenous infusion of AT877 (0.03 mg/kg per minute) was initiated 30 minutes before the ischemic event and continued during the ischemic period. The control rats (n=10) received physiological saline in a similar fashion. Local cerebral blood flow was measured by the hydrogen clearance technique. Neurological examinations were performed daily during the 48-hour observation period, and infarct size was assessed by triphenyltetrazolium chloride staining. Results A continuous infusion of AT877 significantly improved local cerebral blood flow during ischemia. The treated animals showed a better neurological outcome after a 24-hour observation period, and a significant reduction in ischemic brain injury resulted in both the neocortex (149±20 versus 41 ± 14 mm3, P<.01) and the striatum (80±5 versus 46±8 mm3, P<.05). The size of the neocortical infarct was reduced, with increasing mean ischemic cerebral blood flow in the control and treated animals (r=.923, P=.0001). Conclusions AT877 pretreatment was effective in preventing brain injury during transient focal cerebral ischemia and improving neurological status. This beneficial effect seems to be mediated, in part, by its primary action of increasing cerebral blood flow.

Epstein–barr virus-associated primary b-cell lymphoproliferative disorder of the cerebellum in an immune competent man

Background. The role of the Epstein‐Barr virus (EBV) in lymphoproliferative lesions has been widely accepted. Most of these lesions occur in patients who have deficiencies in their immune status. Lymphomatoid granulomatosis (LG) is a lymphoproliferative disorder originally characterized as an angiocentric, necrotizing, pleomorphic infiltrate of mononuclear cells. The etiology of LG is unknown. It was originally hypothesized that LG may represent an unusual lymphoid response to an infective organism, possibly EBV.

Interrupted Arterial Occlusion Reduces Ischemic Damage in a Focal Cerebral Ischemia Model of Rats

It is generally thought by neurosurgeons that when temporary clipping of a major cerebral vessel is necessary during aneurysm surgery, repeated short periods of cerebral ischemia are safer for the brain than a single long episode. This study was performed to investigate whether repetitive short episodes of cerebral ischemia would alter the resulting brain injury as compared with a single long period of ischemia in a rat model for focal cerebral ischemia. Middle cerebral artery occlusion and reperfusion were performed by the intraluminal thread technique. The experimental design consisted of a single 90-minute occlusion period in the continuous ischemia group versus three 30-minute occlusion periods with 15-minute reperfusion periods in the repetitive group. Local cerebral blood flow was measured by the hydrogen clearance technique. During the ischemic period, local cerebral blood flow values significantly decreased in both the continuous and the repetitive groups. Cerebral blood flow restoration was demonstrated after each episode of reperfusion in both groups. The neurological status scores 2 hours after surgery in the rats subjected to repetitive insults were significantly better compared with those in the rats of the continuous ischemia group. However, the scores on Days 1, 3, and 7 did not show a significantly better difference. The animals were killed 7 days after the induction of ischemia for the measurement of the infarction area under the microscope. The total area of infarction was significantly reduced (4.05 +/- 4.56 versus 47.2 +/- 37.3 mm2, P < 0.001) by interruption of the ischemic time period.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperdynamic therapy for focal cerebral ischemia of rats: Use of colloidal volume expansion and dobutamine

The effects of hyperdynamic therapy with colloidal volume expansion and pharmacological augmentation of cardiac function with dobutamine on local cerebral blood flow (CBF) and the size of ischemic injury were investigated in rats subjected to 6 h of middle cerebral artery (MCA) occlusion. At 45 min after MCA occlusion, each rat was randomly assigned to one of the following treatment groups: (1) control; (2) hetastarch infusion (HES); and (3) hetastarch plus dobutamine (12 micrograms/kg/min) infusion (HES/DOB). In both the HES and HES/DOB groups, cardiac output and local CBF in ischemic brain markedly increased after treatment and infarction volumes were significantly reduced as compared to the control group. There were, however, no significant differences between both groups apart from a dobutamine-induced tachycardia. Colloidal volume expansion augmented cardiac output, increased CBF in ischemic brain, and substantially modified the extent of ischemic injury. However, the addition of dobutamine did not bring about adjunctive beneficial effects of cardiac performance, CBF, or the degree of ischemic brain damage in the rat focal ischemic model.

An unusual case of temporal encephalocele

An unusual case of temporal encephalocele is presented in this report. A large temporal mass was detected prenatally by ultrasound and following delivery by caesarian section. It was determined to be a large temporal encephalocele with extensive invasion into the subtemporal, facial and cervical regions. This case is presented because of the unique pathology of this congenital malformation and the extensive surgery that was required. The management and the clinical and radiological features are discussed.