John R. Little

Symptomatic Chiari malformation in adults: a new classification based on magnetic resonance imaging with clinical and prognostic significance.

Thirty-five consecutive adults with Chiari malformation and progressive symptoms underwent surgical treatment at a single institution over a 3-year period. All patients underwent magnetic resonance imaging scan before and after surgery. Images of the craniovertebral junction confirmed tonsillar herniation in all cases and allowed the definition of two anatomically distinct categories of the Chiari malformation in this age group. Twenty of the 35 patients had concomitant syringomyelia and were classified as Type A. The remaining 15 patients had evidence of frank herniation of the brain stem below the foramen magnum without evidence of syringomyelia and were labeled Type B. Type A patients had a predominant central cord symptomatology; Type B patients exhibited signs and symptoms of brain stem or cerebellar compression. The principal surgical procedure consisted of decompression of the foramen magnum, opening of the fourth ventricular outlet, and plugging of the obex. Significant improvement in preoperative symptoms and signs was observed in 9 of the 20 patients (45%) with syringomyelia (Type A), as compared to 13 of the 15 patients (87%) without syringomyelia (Type B). Postoperative reduction in syrinx volume was observed in 11 of the 20 patients with syringomyelia, including all 9 patients with excellent results. Magnetic resonance imaging has allowed a classification of the adult Chiari malformation in adults based on objective anatomic criteria, with clinical and prognostic relevance. The presence of syringomyelia implies a less favorable response to surgical intervention.

Postoperative hemorrhage: a survey of 4992 intracranial procedures

A series of 4992 intracranial procedures performed over an 11-year period was evaluated for the occurrence of postoperative hemorrhage. Forty patients (0.8%) experienced postoperative hemorrhage. Twenty-four hemorrhages were intracerebral (60%), 11 were epidural (28%), 3 were subdural (7.5%), and 2 were intrasellar (5.0%). Hematomas in 33 patients occurred at the operative site, and 7 occurred remote from the operative site. Intracranial tumor was the reason for operation in 56% of the patients developing a clot, and meningioma was the most common tumor associated with this complication. The use of the sitting position was not associated with an increased incidence of postoperative hemorrhage. Disturbances of coagulation and hypertension seemed to be potential precipitating factors. Postoperative hemorrhage was recognized within 12 hours of operation in 35% of the patients. An altered level of consciousness was the most frequent clinical finding, present in all patients. There was no clear relationship between the time of recognition and the final clinical outcome. Parenchymal clots carried the worst prognosis, accounting for 8 of the 11 deaths and all 7 patients with poor neurological outcome.

Basilar and distal vertebral artery stenosis: long-term follow-up.

Forty-four patients with greater than or equal to 50% stenosis of a distal vertebral artery (VA) and/or basilar artery (BA) were followed up for an average of 6.1 years. Angiography was performed for definite vertebrobasilar (VB) transient ischemic attacks (TIA) in 19 (43%), for VB infarcts in 13 (30%) and for non localizing symptoms in 12 (27%). Stenosis in the BA with or without VA involvement was present in 28 patients (64%), while 16 patients (36%) had occlusive disease in one or both distal VA sparing the BA. In follow up, 7 patients (16%) had definite VB TIA and 3 patients had possible VB TIA. Eight patients (18%) sustained a stroke, 5 of which were in the VB territory. The observed stroke rate was 17 times the expected rate for a matched normal population. Eight patients died during follow up, three patients due to stroke (2 brainstem infarctions, one intraventricular hemorrhage). The observed 5 year survival rate was 78% compared to 90% in a matched normal population. In comparing this data with our previous study of 93 patients with proximal VA occlusive disease, distal VB occlusive disease appears to carry a higher risk for brainstem ischemia.

Cerebral circulation during arteriovenous malformation operation

The circulatory changes in the cortex around a cerebral arteriovenous malformation (AVM) were studied in 18 patients. The AVMs had rapid circulation times with early draining veins on angiography. Local cortical blood flow (lCoBF) was measured with cortically applied thermister/Peltier stack arrays. The AVMs had a more pronounced effect on lCoBF at a 2- to 4-cm distance from the AVM margin than in the adjacent cortex. Mean preexcision lCoBF was 62.9 +/- 6.7 (SE) ml/100 g/minute (i.e., similar to normal controls) near the AVM margin and 43.0 +/- 4.2 ml/100 g/minute far (i.e., greater than 2 cm) from the AVM. CO2 reactivity (COR) before excision was 1.1 +/- 0.3 ml/100 g/minute/torr of CO2 (i.e., similar to normal controls) at near sites and 0.6 +/- 0.3 ml/100 g/minute/torr of CO2 at far sites. The mean postexcision near lCoBF remained stable at 55.8 +/- 5.1 ml/100 g/minute at near sites, but the far lCoBF significantly increased (P less than 0.05) to 57.2 +/- 6.8 ml/100 g/minute. The cortical feeding artery pressure was substantially below the normal cortical artery pressure in 50% of the cases studied. Pressure in these arteries normalized after occlusion and AVM excision, resulting in a rapid increase in cortical artery perfusion pressure. Draining red vein pressure, which was elevated before AVM excision, also dropped after excision, contributing to the increase in perfusion pressure. Two patients who developed the normal perfusion pressure breakthrough syndrome (PBS) after operation had low lCoBF and disturbed COR before AVM excision and marked increase of lCoBF after excision.(ABSTRACT TRUNCATED AT 250 WORDS)

Altered cerebral autoregulation and CO2 reactivity after aneurysmal subarachnoid hemorrhage.

&NA; Disruption of local cortical blood flow (CBF) autoregulation and CO2 reactivity, or vasoparalysis, has been documented in humans after aneurysmal subarachnoid hemorrhage (SAH). Generally, the degree of vasoparalysis is related to the patients clinical grade. Using intraoperative measurement of local CBF, we evaluated pressure autoregulation and CO2 reactivity in patients after SAH. Fourteen patients with SAH and 10 patients with asymptomatic aneurysm underwent craniotomy for clipping of their aneurysms. During operation, local CBF was recorded with thermal conductivity probes placed on the middle frontal gyrus, 4 to 6 cm from the nearest point of retraction. Before retractor placement, CBF was measured with the PCO2 at 25 and 35 mm Hg and the mean arterial blood pressure (MABP) between 70 and 80 mm Hg. After aneurysm clipping, flows were again measured. With the PCO2 at 25 mm Hg, the MABP was raised from 65 to 85 mm Hg. The PCO2 was then allowed to rise to 35 mm Hg, after which the MABP was lowered from 85 to 65 mm Hg. Six patients underwent operation within the 1st week after SAH (Grade I, n = 3; Grade II, n = 3). The remainder (n = 8) were operated on 9 days to 3 months after SAH. After aneurysm clipping, significant CBF changes (P < 0.001) with PCO2 alteration occurred in control patients and those operated on more than 7 days after SAH. There was no significant change in CBF in patients operated on within 7 days after SAH. Changes in CBF reactivity to alteration of MABP were significantly larger in early operation patients than in other groups (P < 0.008). Pressure autoregulation and CO2 reactivity are significantly disturbed in good grade patients after early operation.

Evolving focal cerebral ischemia in cats: spatial correlation of nuclear magnetic resonance imaging, cerebral blood flow, tetrazolium staining, and histopathology.

The spatial correlation of nuclear magnetic resonance imaging (NMRI) and cerebral blood flow (CBF) may improve our ability to identify ischemic brain lesions and may provide further insight into the pathophysiology of early cerebral ischemia. Eleven pentobarbital-anesthetized adult cats underwent exposure of the common carotid arteries bilaterally and the right middle cerebral artery through a transorbital approach. Baseline NMRI images were obtained with a single spin-echo, multislice technique using a 0.6-T field, 0.4-cm slice thickness, and a surface coil. Focal ischemia was produced with right middle cerebral artery occlusion and potentiated with bilateral common carotid artery ligation. Sequential NMRI studies were then performed at 1, 2, 4, 6, and 12 hours or until CBF was determined in the same cats using [14C]iodoantipyrine at either 2 (n = 2), 4 (n = 2), 6 (n = 2), or 12 (n = 1) hours after the time of occlusion. This protocol allowed temporal and spatial correlation of NMRI and CBF. Alternate 5-mm brain slices were incubated with 1% 2,3,5-triphenyltetrazolium chloride (TTC) for 45 minutes at 37-41 degrees C and frozen in liquid Freon for later autoradiographic CBF determination. Four cats were studied only with NMRI and TTC (not CBF). The correlation between areas of increased NMRI signal intensity observed in T2-weighted images (repetition time 2,000 msec, echo time 120 msec), vital staining with TTC, low CBF, and routine histology was evaluated. During the early phase (less than 6 hours), T2-weighted NMRI changes were localized to the central ischemic gray matter areas, as defined in the later CBF images, with no involvement of the white matter. By the twelfth hour the NMRI changes involved the entire ischemic area including gray and white matter. The initial visible changes seen on T2-weighted NMRI are suggestive of cellular edema, and the later changes are characteristic of vasogenic edema. The spread of NMRI changes compared with the ischemic area determined from autoradiographic CBF is consistent with the previously described biphasic evolution of ischemic injury. These data suggest that T2-weighted NMRI could be used clinically to delineate areas of acute ischemic stroke.

Vertebral artery stenosis: long-term follow-up.

Ninety-six patients with ⩾50% unilateral vertebral artery (VA) stenosis were followed up for an average of 4.6 years. In 89 patients (93%) at least one VA origin was involved, while the intracranial VA was affected in 3 patients (3%). Seventy-four patients (77%) had 2=50% stenosis of at least one internal carotid artery, of whom 52 underwent carotid endarterectomy. None of the patients had definite vertebro- basilar transient ischemic attacks (VB TIA). Nineteen patients (19.8%) experienced nonlocalizing symp- toms possibly compatible with VB TIA, none of whom had a stroke. Twenty-three patients (24%) had strokes. The only two patients (2%) who sustained a brainstem infarction had fatal strokes and both were known to have basilar artery stenosis in addition to their VA stenosis. The observed stroke rate was 8.5 times the expected infarction rate for a normal population. Forty patients died during follow up. The observed 5-year survival rate was 60% compared to 87% in a matched normal population. Eight deaths (20% of all deaths) were caused by stroke and 21 deaths (52.5% of all deaths) were cardiac related. VA stenosis is most frequently located at the VA origin (93%), and is associated with a low incidence of brainstem infarction. Stroke Vol 15, No 2, 1984

Intracranial Meningiomas in the Aged: Surgical Outcome in the Era of Computed Tomography

Seventy-five patients older than 60 years of age underwent surgical resection of intracranial meningiomas during a 10-year period at a single institution. All patients had a computed tomographic scan preoperatively, and all were followed for at least 3 months postoperatively. There were 50 patients 61 to 70 years of age (Group A), and 25 patients older than 70 years (Group B). Sixteen patients (21%) were asymptomatic, and no patient was severely disabled preoperatively. Operative morbidity and mortality and outcome at 3 months were assessed and correlated with age, preoperative neurological status, and tumor size and location. Operative mortality was 6.6% (6% in Group A; 8% in Group B). Perioperative morbidity (including medical and surgical complications and worsening in neurological status) was 48% (46% in Group A; 52% in Group B). Neurological status 3 months after surgery was improved by at least one grade as compared to before surgery in 40% of patients (38% in Group A; 44% in Group B), unchanged in 29% (34% in Group A; 20% in Group B), and worsened in 31% (28% in Group A; 36% in Group B). While nearly half of the patients were asymptomatic 3 months after surgery, 11 patients (15%) had died or remained seriously disabled. Outcome at 3 months correlated significantly with low neurological grade preoperatively and with a tumor location over the cortical convexity. There was no significant correlation with age or tumor size. We conclude that resection of intracranial meningiomas is associated with significant morbidity and mortality in the elderly.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiological monitoring during basilar aneurysm operation.

Intraoperative brain stem auditory evoked potential (BAEP) and somatosensory evoked potential (SEP) monitoring was evaluated in 16 patients each undergoing intracranial operation for basilar artery aneurysm. The 16 patients had 18 posterior circulation aneurysms, including 2 patients with 2 aneurysms. Fourteen aneurysms arose from the rostral basilar artery, 2 arose from the midbasilar artery, 1 arose from the vertebrobasilar junction, and 1 arose from the proximal segment of the posterior cerebral artery. Five aneurysms were classified as giant (i.e., greater than 25 mm), and 5 aneurysms were large (i.e., 15 to 25 mm). Ten patients had BAEP and SEP monitoring, 4 had BAEP monitoring only, and 2 had SEP monitoring only. Two patients showed significant abnormalities during operation, including 1 patient with transient changes in the BAEP when the lower pons and the 8th cranial nerve were retracted. Another patient had progressive increases in latency and decreases in amplitude and subsequent loss of the SEP cortical components during a period of intermittent temporary rostral basilar artery occlusion. Wave P13 was also lost during that period. The cortical components as well as Wave P13 returned after circulation was restored. The BAEPs were unchanged in the same patient during the period of temporary basilar artery occlusion. Fourteen patients had no significant abnormalities. There were no consistent changes during the various stages of operation. BAEP and SEP monitoring failed to identify ischemic events in 4 patients with neurological findings of brain stem ischemia immediately after operation (i.e., 25% false-negative studies).(ABSTRACT TRUNCATED AT 250 WORDS)

Patch angioplasty in carotid endarterectomy. Advantages, concerns, and controversies.

There is much controversy in the literature regarding the precise role of patch angioplasty in carotid endarterectomy. Our report summarizes the theoretical and experimental considerations, including the hemodynamic effects and biologic behavior of the graft, associated with this technique. We present a detailed review of the literature regarding the clinical efficacy of patch angioplasty in carotid endarterectomy, including the early results, the late results, and the incidence and nature of carotid restenosis. We address concerns about the use of patch angioplasty, including the duration of cross-clamping, potential problems with the graft and suture-line disruption, and graft atherogenesis. We conclude that most recent literature indicates that patch angioplasty decreases acute complications (notably carotid occlusion) after carotid endarterectomy and prevents or delays carotid restenosis. As pressure increases to achieve a minimal rate of perioperative morbidity, many surgeons are expected to adopt patch angioplasty in more of their cases. However, in the absence of conclusive results from a prospective randomized study, opinion will continue to be divided regarding the routine versus the selective use of patch grafting in carotid endarterectomy. We present criteria for randomized trials of this technique.