Yuhei Yoshimoto

Cerebral aneurysms unrelated to arterial bifurcations

SummaryThe majority of saccular cerebral aneurysms arise at arterial branchings; those arising elsewhere are rare. Among 557 saccular cerebral aneurysms surgically treated between 1983 and 1994, 29 (5.2%) were unrelated to arterial divisions. These cases were retrospectively analysed. The ages of the subjects ranged from 6 to 80 years (mean 57); 17 (59%) were female, and 12 (41%) male. Twenty-four (83%) presented with subarachnoid haemorrhage. Seventeen (59%) had a history of hypertension, and ten (34%) had multiple cerebral aneurysms. The most common site was the internal carotid artery (45%), followed by the middle cerebral artery (28%), the vertebrobasilar arteries (17%), and the anterior cerebral artery (10%). The aneurysms were classified in relation to arterial curvature into three groups: dorsal curvature (41%), ventral curvature (10%) and non-curvature (49%). During surgery, sclerotic changes were noted in the arterial wall adjacent to the aneurysms in 14 patients (48%). Five cases (17%) had small thin walled (blisterlike) aneurysms, four of which ruptured during surgery resulting in poor clinical outcomes. We suggest that arteriosclerotic changes in the arterial wall, carotid siphon, and/or local haemodynamic forces are important factors in the development of this type of aneurysms. At surgery, one should bear in mind the possibility of sclerotic or blister-like aneurysms which require special attention to deal with them.

Intraparenchymal and intrasylvian haematomas secondary to ruptured middle cerebral artery aneurysms : prognostic factors and therapeutic considerations

The aim of this study was to investigate prognostic factors and the most appropriate treatment for patients with ruptured middle cerebral artery (MCA) aneurysms in relation to haematoma distribution. Ninety-two patients with ruptured MCA aneurysms, who underwent surgery during the last 11 years from 1986 to 1996, were assigned to one of the three groups according to the haematoma distribution. Group A comprised 17 patients who had an intraparenchymal haematoma (IPH) larger than 30 mm (maximum diameter) with or without subarachnoid haemorrhage (SAH), group B comprised 24 patients having a dense intra-Sylvian fissure haematoma (ISH) larger than 30 mm (maximum diameter) and group C consisted of 52 patients having only diffuse SAH without a localized dense haematoma. The clinical course and factors affecting the outcome of the patients in each group were investigated. Patients in groups A and B had a more severe clinical grade on admission than those in group C. As a result, patients in these two groups had a poorer outcome. In group C, independent life was achieved for 98% of the patients. In group A, the clinical grade on admission and the diameter of the haematoma were significantly correlated with outcome. Initial brain damage due to IPHs seemed to be the main cause of disability, while only 7% developed delayed ischaemic neurological deficits (DIND). In group B, 54% of patients suffered from subsequent brain oedema and DIND occurred in 50%. These factors were related to a poor outcome. The MCA aneurysms tend to have localized dense haematomas, as well as diffuse SAH; the former seems to affect more on the course and outcome of the patients. Accurate assessment of the bleeding patterns in patients with ruptured MCA aneurysms will be useful in helping us predict the clinical course and the most appropriate treatment for these individuals.

Publication bias in neurosurgery: lessons from series of unruptured aneurysms.

Summary. Background: Bias favouring publication of research with “positive” results over studies with “negative” results is widely suspected. The present investigation addressed this problem in the field of neurosurgery through a review of recent literature concerning outcome of surgery for unruptured intracranial aneurysms. Methods and findings: A Medline search was performed seeking case series of surgical treatment for unruptured intracranial aneurysms that analyzed 50 or more patients. Ten type I studies (retrospective studies from a single institution; 1457 patients) met these entry criteria. In general, type I studies reported excellent surgical outcome, with mean combined mortality and morbidity of 7.8% (95% confidence interval (CI), 6.4% to 9.2%). We found 4 multicenter or community-based studies (type II studies; 5401 patients). Mean combined mortality and morbidity in the type II studies was 20.3% (95% CI, 19.2% to 21.4%), much higher than in type I studies. Relative risk was 2.6 (95% CI, 2.2 to 3.1) for patients in type II studies compared with those in type I studies. Two meta-analyses (type III studies) described combined mortality and morbidity of 5.0% and 12.7%, essentially corresponding to results of type I studies. Interpretation: Publication bias is present in the neurosurgical literature. Studies with an excellent surgical outcome are more likely to be published than those with an average outcome. Conclusions of literature reviews or meta-analyses based on published work therefore may be misleading. The solution to the problem would be community-based prospective registration of all patients who underwent surgery, providing a sampling frame free from publication bias.

Encircling method of trigeminal nerve decompression for neuralgia caused by tortuous vertebrobasilar artery: technical note

BACKGROUND Surgical treatment of trigeminal neuralgia caused by dolichoectatic vertebrobasilar artery presents a difficult problem because of the immobility and the stiffness of the atherosclerotic vessel walls. METHODS AND RESULTS A patient with trigeminal neuralgia was treated by a new method of vascular decompression. Preoperative studies demonstrated a dolichoectatic vertebrobasilar artery, and compression of the trigeminal nerve by the artery was confirmed during surgery. The fifth nerve was mobilized away from the artery using a ring-shaped piece of silicone rubber. Postoperatively, the facial pain completely resolved without complication. CONCLUSIONS Trigeminal neuralgia due to nerve compression by tortuous vertebrobasilar artery was successfully treated by an encircling method of vascular decompression.

A prospective study on the effects of early surgery on vasospasm after subarachnoid hemorrhage.

BACKGROUND To test the hypothesis that early surgery prevents vasospasm, a prospective analysis used strictly selected cases of anterior communicating artery aneurysms with symmetric distribution of subarachnoid hemorrhage. METHODS Seven patients underwent early surgery (9-29 hours after ictus) through a standard pterional approach. Subarachnoid blood clots surrounding the ipsilateral major cerebral arteries were meticulously irrigated and suctioned. Comparison was made between the hemispheres with surgical intervention and those without, in terms of incidence of delayed ischemic neurologic deficits and cerebral infarction on computed tomographic scans, degree of angiographic vasospasm, and cerebral blood flow (CBF). RESULT The degree of angiographic vasospasm, quantified by measuring the alterations in the ratio of the diameters of the intracranial arteries (C1, M1) to the extracranial internal carotid artery (C5), did not differ significantly between the surgical and nonsurgical sides. The mean CBF was also comparable between both sides in the chronic spasm phase (Day 6-9) as well as in the early postoperative period (Day 1-3). A significant reduction of CBF was observed during the early postoperative period in the basal frontal lobe of the surgical side. This CBF reduction seems to correspond to brain retraction. CONCLUSIONS The results suggest that the effect of clot removal may be offset by the negative aspect of early surgery, and early surgery per se seems to have little effect on the course of the chronic vasospasm.

Significance of pupillary reactivity in poor-grade aneurysm patients as a prognostic factor and an indication for active treatment

Sixty-eight patients with subarachnoid haemorrhage (SAH) who were admitted in a comatose state were studied to determine the factors influencing mortality and to seek criteria for case management. Overall, the functional recovery (good recovery or moderate disability) rate was 33%, with a mortality rate of 50%. Bilaterally unreactive pupils on admission was a powerful predictor of death (p < 0.0001): outcome of these patients was poor regardless of any treatment modalities with a mortality rate of 91% (20/22). Initial poor motor response (abnormal flexion, extension, or nil) was also significantly related with death (p < 0.05). However, motor response was a less powerful predictor than pupillary reactivity. Motor response often altered spontaneously during the 12 h after admission, whereas pupillary reactivity tended to be stable. Initial reactive pupils were shown to be an indicator of spontaneous improvement of motor response. These findings indicate that pupillary reactivity may be a reliable predictor of outcome in poor-grade SAH patients.