Asymptomatic middle cerebral artery stenosis diagnosed by magnetic resonance angiography

We reviewed 1440 MRA studies to identify patients with middle cerebral artery stenosis (MCAS). We identified 99 cases, and after reviewing the clinical records, classified 28 as asymptomatic MCAS (AMCAS), a prevalence of 2%. Suspected stroke was the most frequent indication for MRA. Follow-up was available for 21, mean 46.7 months (range 2.4-75.6 months). One stroke occurred in the AMCAS territory (5%), other strokes in five patients (24%). There were five deaths in patients with MCAS; age > 69 (P = 0.045) was the only associated risk factor. This study suggests that patients in whom MRA is performed and shows AMCAS may be at increased risk of strokes in any vascular distribution or of death.

Functional evaluation of arteriovenous malformations

Detailed knowledge of the angioarchitecture of arteriovenous malformations (AVMs) is necessary in determining the optimal timing and method of treatment of these challenging lesions. Many techniques are available for studying the functionality of surrounding cortical structures of AVMs. These include the use of positron emission tomography, functional magnetic resonance imaging, magnetoencephalography, and direct provocative testing of cortical function. The use of these methods to determine flow dynamics and tissue perfusion is also reviewed. These techniques are discussed in the present study, and their judicious utilization will enhance the safety of AVM therapy.

Benefits of perfusion MR imaging relative to diffusion MR imaging in the diagnosis and treatment of hyperacute stroke

BACKGROUND AND PURPOSE

The development of thrombolytic agents for use with compromised cerebral blood flow has made it critical to quickly identify those patients to best treat. We hypothesized that combined diffusion and perfusion MR imaging adds vital diagnostic value for patients for whom the greatest potential benefits exist and far exceeds the diagnostic value of diffusion MR imaging alone.

METHODS

The cases of patients with neurologic symptoms of acute ischemic stroke who underwent ultra-fast emergent MR imaging within 6 hours were reviewed. In all cases, automatic processing yielded isotropic diffusion images and perfusion time-to-peak maps. Images with large vessel distribution ischemia and with mismatched perfusion abnormalities were correlated with patient records. All follow-up images were reviewed and compared with outcomes resulting from hyperacute therapies.

RESULTS

For 16 (26%) of 62 patients, hypoperfusion was the best MR imaging evidence of disease distribution, and for 15 of the 16, hypoperfusion (not abnormal diffusion) comprised the only imaging evidence for disease involving large vessels. For seven patients, diffusion imaging findings were entirely normal, and for nine, diffusion imaging delineated abnormal signal in either small vessel distributions or in a notably smaller cortical branch in one case. In all cases, perfusion maps were predictive of eventual lesions, as confirmed by angiography, CT, or subsequent MR imaging.

CONCLUSION

If only diffusion MR imaging is used in assessing patients with hyperacute stroke, nearly one quarter of the cases may be incorrectly categorized with respect to the distribution of ischemic at-risk tissue. Addition of perfusion information further enables better categorizing of vascular distribution to allow the best selection among therapeutic options and to improve patient outcomes.

Intraoperative magnetic resonance image guidance in neurosurgery

Recently, there has been a burgeoning interest in the use of image-guided navigation to improve the safety and effectiveness of neurosurgical procedures. The intraoperative use of magnetic resonance imaging (MRI) provides the most accurate guidance available. This report discusses the hardware and software improvements that have made intraoperative MRI a reality and describes the use of this technology for neurosurgical intraoperative guidance.

The dominant role of increased intrasellar pressure in the pathogenesis of hypopituitarism, hyperprolactinemia, and headaches in patients with pituitary adenomas

Mild hyperprolactinemia frequently accompanies the hypopituitarism seen in patients with pituitary macroadenomas that do not secrete PRL. Recent data suggested that the hypopituitarism and mild hyperprolactinemia in this setting are largely due to compression of pituitary stalk and portal vessels. Headaches (HAs) are frequently seen in patients with large adenomas and at times in those with microadenomas. Because the walls of the sella turcica are relatively rigid, we postulate that tumor growth within the sella increases intrasellar pressure (ISP), which in turn impairs portal blood flow, resulting in mild hyperprolactinemia and hypopituitarism. We also postulate that increased mean ISP (MISP) contributes to the development of HAs. Normal MISP is not known but is unlikely to exceed normal intracranial pressure of less than 10-15 mm Hg. We determined MISP in 49 patients who had transsphenoidal surgery for pituitary adenomas. MISP was measured using a commonly available intracranial monitoring kit where a fiberoptic transducer was inserted through a 2-mm dural incision at the time of adenomectomy. Patients with deficient FSH, LH, ACTH, or TSH secretion were considered hypopituitary. Data on serum PRL levels were included for analysis only in patients whose adenomas had negative immunostaining for the hormone. MISP measurements ranged from 7-56 mm Hg, with a mean (+/-SD) of 28.8 +/- 13.5 and a median of 26 mm Hg. The pressure measurements were higher in patients with hypopituitarism than in those with normal pituitary function (P = 4.6013 x 10(-6)). Patients presenting with HAs had higher MISP than those who did not (P = 5.44 x 10(-7)), regardless of their pituitary function or tumor sizes. PRL levels correlated positively with MISP values (r = 0.715, P < 0.0001). Tumor size did not correlate with MISP or PRL levels. The findings of increased MISP in hypopituitary patients and the documented correlation with PRL levels, suggest that ISP is a major mechanism involved in the pathogenesis of hypopituitarism and hyperprolactinemia. Similarly, the increased MISP in patients with HAs, irrespective of tumor size or pituitary function, suggest that increased ISP is a major mechanism involved in the pathogenesis of this symptom. The data support the hypothesis that in patients with pituitary adenomas increased ISP is a major mechanism contributing to the development of hyperprolactinemia, hypopituitarism, and HAs. Increased ISP in these patients leads to compression of the portal vessels and the associated interruption of the delivery of hypothalamic hormones to the anterior pituitary. This would explain the reversibility of pituitary function observed in most patients after adenomectomy. However, increased ISP may also lead to decreased blood supply, resulting in ischemic necrosis in some regions of the pituitary. The latter could limit potential recovery of pituitary function after adenomectomy.

Emergency management of ischemic stroke

The accurate diagnosis of acute ischemic stroke is possible using clinical skills and diagnostic tools that are familiar to all neurosurgeons. Avoidance of immediate complications relies on the fundamentals of critical care. Effective treatment for ischemic stroke is available in the form of intravenous thrombolysis, but many stroke patients are denied this therapy because of the narrow window of opportunity for safe administration. Intra-arterial delivery may extend this benefit to a greater number of patients and may eventually prove more effective than intravenous treatment. Surgical treatment in a small number of ischemic stroke patients can be lifesaving and may afford reasonable functional recovery. This article discusses typical clinical presentations and differential diagnosis, diagnostic imaging for ischemic stroke, and possible treatments.

Predictors of clinical improvement, angiographic recanalization, and intracranial hemorrhage after intra-arterial thrombolysis for acute ischemic stroke

BACKGROUND AND PURPOSE

We sought to evaluate predictors of clinical outcome, angiographic success, and adverse effects after intra-arterial administration of urokinase for acute ischemic stroke.

METHODS

We designed a Brain Attack program at University Hospitals of Cleveland for diagnosis and treatment of patients presenting within 6 hours of onset of neurological deficit. Patients with ischemia referable to the carotid circulation were treated with intra-arterial urokinase. Angiographic recanalization was assessed at the end of medication infusion. Intracerebral hemorrhage was investigated immediately after and 24 hours after treatment. Stroke severity was determined, followed by long-term outcome.

RESULTS

Fifty-four patients were treated. There was improvement of >/=4 points on the National Institutes of Health Stroke Scale from presentation to 24 hours after onset in 43% of the treated patients, and this was related to the severity of the initial deficit. Forty-eight percent of patients had a Barthel Index score of 95 to 100 at 90 days, and total mortality was 24%. Cranial CT scans revealed intracerebral hemorrhage in 17% of patients in the first 24 hours, and these patients had more severe deficits at presentation. Eighty-seven percent of patients received intravenous heparin after thrombolysis, and 9% of them developed a hemorrhage into infarction. Angiographic recanalization was the rule in complete occlusions of the horizontal portion of the middle cerebral artery, but distal carotid occlusions responded less well to thrombolysis.

CONCLUSIONS

The intra-arterial route for thrombolysis allows for greater diagnostic precision and achievement of a higher concentration of the thrombolytic agent in the vicinity of the clot. Disadvantages of this therapy lie in the cost and delay. Severity of stroke and site of angiographic occlusion may be important predictors of successful treatment.

Hyperacute stroke: ultrafast MR imaging to triage patients prior to therapy

PURPOSE

To test diffusion- and perfusion-weighted MR imaging techniques within the extreme time constraints of stroke evaluation before therapy, and then, with MR imaging, stratify patients into those without ischemia, those with noncortical ischemia, and those with cortical ischemia.

MATERIALS AND METHODS

T2-weighted turbo gradient- and spin-echo images and echo-planar diffusion- and perfusion-weighted images were obtained. Trace diffusion-weighted images and time-to-peak perfusion maps were automatically postprocessed and immediately available for interpretation.

RESULTS

Forty-one patients with acute stroke symptoms underwent imaging within 6 hours of symptom onset; 35 were eligible for the therapy protocol. The mean time from entering the emergency department to beginning MR imaging was 45 minutes; the mean total MR imaging time was less than 15 minutes. Immediate image analysis directly affected individual clinical management. Four patients showed evidence of no infarct; seven, of lacunar infarct; and 24, of acute cortical infarct. Sixteen patients underwent angiography, thirteen had large-vessel occlusion, eleven were treated intraarterially, and in seven, recanalization was achieved.

CONCLUSION

Echo-planar diffusion- and perfusion-weighted MR imaging for acute stroke is feasible and applicable before therapy decisions. Ultrafast MR imaging permitted immediate triage of 35 patients with symptoms of hyperacute stroke and thus helped avoid the risks from angiography and thrombolytic agents in some or spurred the judicious use of more aggressive intervention in others.

Temporary vascular occlusion during cerebral aneurysm surgery

Temporary artery occlusion is an effective way to reduce the detrimental effects of intraoperative aneurysm rupture and to facilitate aneurysm dissection. The major risk incurred is of cerebral infarction. Dilemmas in the use of this technique include the amount of time that arterial flow may be interrupted safely and whether or not there is benefit to intermittent reperfusion. Protocol for the use of temporary occlusion is described.

Brain attack: emergency treatment of ischemic stroke

Thrombolysis has been demonstrated to be an effective treatment for ischemic stroke. The major obstacles to more widespread use of this therapy are lack of awareness that the treatment is possible and the short (less than three hours) therapeutic window. Indiscriminant use of this therapy can lead to an unacceptably high rate of intracerebral hemorrhage. Early recognition of the onset of stroke. Immediate transfer to a suitably equipped treatment facility and careful screening of a computed tomographic scan of the head for signs of early infarction are necessary for the safe administration of intravenous thrombolysis.

Thrombolysis for acute ischemic stroke

The use of thrombolytic agents to restore cerebral blood flow is one of the most notable advances in the treatment of ischemic stroke. This article reviews thrombolytic therapy, its limitations, and the techniques by which thrombolytic agents can be delivered.

Brain attack. The emergent management of hypertensive hemorrhage

Intracerebral hemorrhage (ICH) accounts for one half of stroke-related deaths, with hypertensive hemorrhage being the primary etiology. The evolution of minimally invasive devices for removal of ICHs, and the earlier delivery of patients for medical attention may have a great impact on the management of hypertensive hemorrhage.

Mortality rates, hospital length of stay, and the cost of treating subarachnoid hemorrhage in older patients: institutional and geographical differences

The risk of disability and death and the cost of medical care are particularly high for patients with aneurysmal subarachnoid hemorrhage (SAH) who are 65 years of age or older. A retrospective analysis of 47,408 Medicare patients treated over an 8-year period was performed to determine whether a relationship exists between the mortality rate and surgical volume for older patients with SAH. The mortality rate, length of stay in the hospital, and cost of treatment for patients with SAH in California and New York state were also compared. The mortality rate was 14.3% for patients with SAH who were 65 years old or older and who were treated surgically in hospitals in which an average of five or more craniotomies were performed per year; in hospitals averaging between one and five craniotomies annually the mortality rate was 18.4%; and in those averaging less than one such operation per year the rate was 20.5% (trend p = 0.01). There was no difference in the mortality rate for patients in California versus the rate for those in New York. Surgically and medically treated patients, respectively, left the hospital an average of 6.7 and 5.1 days sooner in California than in New York. The unadjusted average reimbursement from Medicare to hospitals for surgically treated patients averaged $1468 more in New York than in California (p < 0.0001), but was equivalent for medically treated patients in the two states. The mortality rate in older patients who are treated surgically for SAH may be inversely correlated with the annual number of craniotomies performed for SAH in patients 65 years of age or older at a given institution. Hospital stays for patients with SAH are significantly shorter in California than in New York.

Cyclosporin A delays mitochondrial depolarization induced by N-methyl-D-aspartate in cortical neurons: evidence of the mitochondrial permeability transition

N-Methyl-D-aspartate causes a rapid increase in intracellular Ca2+ leading to collapse of the mitochondrial membrane potential and eventually cell death in cortical neurons. The aim of this study was to investigate the mechanism responsible for mitochondrial depolarization using laser scanning confocal microscopy of single cultured rate cortical neurons. To monitor mitochondrial membrane potential, neuronal mitochondria were labeled with tetramethylrhodamine methyl ester, a cationic fluorophore that accumulates in polarized mitochondria. In neurons cultured on poly-D-lysine-coated coverslips, N-methyl-D-aspartate caused mitochondrial depolarization in 88% of cells in 30 min. Cyclosporin A, an inhibitor of the mitochondrial permeability transition, delayed depolarization in a dose-dependent manner (0.2-1 microM). In neurons cultured on an astrocyte feeder layer, N-methyl-D-aspartate also caused mitochondrial depolarization. Cyclosporin A again delayed mitochondrial depolarization, although higher concentrations were needed. These data show for the first time that mitochondrial depolarization induced by N-methyl-D-aspartate may be due to the induction of the mitochondrial permeability transition.

Temporary vessel occlusion during intracranial aneurysm repair

Any method that decreases the risk of intraoperative rupture should improve outcome if complications associated with its use do not negate positive effect. If application time is limited and a form of cerebral protection and appropriate monitoring of cerebral function are used, temporary clip application may meet these requirements. The efficacy of temporary occlusion as an adjunct to aneurysm clipping may be limited by technical considerations with respect to regional anatomy, aneurysm size, and aneurysm consistency. In areas of limited access, positioning proximal clips may not be feasible. The use of endovascular techniques of balloon occlusion may provide proximal control in these situations (9, 106). The decision to use total circulatory arrest and profound hypothermia, as opposed to temporary clip application, remains largely a matter of the surgeon's judgment. The role of proximal parent vessel ligation must also be considered in the decision-making process regarding the treatment of giant or technically difficult aneurysms (114). Further refinements in cerebral monitoring that can accurately reflect intracellular processes in all territories affected by the application of temporary clips or balloon occlusion and development of more effective forms of cerebral protection may permit safer use of this technique. An adequately controlled clinical trial of temporary occlusion with or without putative "cerebral protection" is needed to confirm the efficacy of this technique.

Good clinical outcome in a patient with a large CT scan hypodensity treated with intra-arterial urokinase after an embolic stroke

Hypodense regions demonstrated by CT within 6 hours of the onset of stroke may reflect irreversibly damaged tissue, and some have suggested that patients with such findings should be spared the risks of thrombolytic therapy since they are unable to benefit from it. We report here a patient with a low-density area demonstrated by CT less than 6 hours after onset of symptoms who improved dramatically after successful intra-arterial thrombolysis.

Dynamics of prolactin secretion in patients with hypopituitarism and pituitary macroadenomas

Mild hyperprolactinemia frequently accompanies the hypopituitarism seen in patients with pituitary macroadenomas that do not secrete PRL. We postulated that hypopituitarism in this setting, is primarily caused by compression of the portal vessels and/or pituitary stalk. If this were the case, the dynamics of PRL secretion in this instance would be similar to those in patients with stalk section, dopamine deficiency, or hypothalamic disease. Furthermore, as hypopituitarism in this setting is largely reversible, we postulate that PRL dynamics should also normalize after adenomectomy as a result of the resumption of hypothalamic regulation of pituitary hormone secretion. To test these hypotheses, we examined PRL responsiveness to TRH and the dopamine antagonist, perphenazine (PZ), in patients with pituitary macroadenomas who had hypopituitarism and others with intact pituitary function (controls). Dynamic studies were performed before and 2-3 months after total or subtotal adenomectomy, and the results were correlated with alterations in other pituitary function. In addition, plasma ACTH, cortisol, and PRL levels were measured hours to days after surgery to investigate immediate alterations in pituitary function following surgical decompression. Before surgery, hypopituitary patients had higher serum PRL level than controls (25.5 +/- 12 vs. 11 +/- 3 micrograms/L; P < 0.001). Preoperative dynamic testing of PRL secretion in hypopituitary patients demonstrated an increase in PRL levels after TRH, but not after PZ, administration. In contrast, PRL levels increased appropriately when either stimulus was given to controls. Hours after adenomectomy, PRL levels decreased by 50% in hypopituitary patients (P < 0.0001) and remained so until discharge. In contrast, controls had a transient increase in serum PRL levels after adenomectomy. After surgery, 25 of 43 previously hypopituitary patients recovered part or all pituitary function. Serum PRL levels in the latter subgroup became normal and increased appropriately after stimulation with either TRH or PZ. In contrast, patients who did not recover pituitary function had lower PRL levels that increased minimally after TRH or PZ. The mild increase in serum PRL levels in hypopituitary patients and the discordant responses to stimulation with TRH and PZ suggest dopamine deficiency as a cause of hyperprolactinemia. The drop in serum PRL levels immediately after surgery, at a time when other pituitary hormones (e.g. ACTH), were documented to rise suggests restoration of hypothalamic control over pituitary hormone secretion. The pattern of PRL responses to stimulation in patients recovering function postoperatively was similar to that in controls, although the incremental rise was subnormal.(ABSTRACT TRUNCATED AT 400 WORDS)

Cerebral arterial aneurysm formation and rupture in 20,767 elderly patients: hypertension and other risk factors

Cerebral arterial aneurysms are common in the general population and their rupture is a catastrophic event. Considerable uncertainty remains concerning the conditions that predispose individuals to aneurysm formation or rupture. The role of systemic hypertension in aneurysm formation and rupture has been especially controversial. Demographic variables have rarely been addressed because of the small sample sizes in previous studies. The authors describe the demographics and prevalence of hypertension in 20,767 Medicare patients with an unruptured aneurysm and compared these to a random sample of the hospitalized Medicare population. The prevalence of hypertension in patients with unruptured aneurysms was 43.2% compared with 34.4% in the random sample. Patients who survived their initial hospitalization were separated into two groups: those with an unruptured cerebral aneurysm as the primary diagnosis and those with an unruptured cerebral aneurysm as a secondary diagnosis. Follow-up data for 18,119 patients were examined to determine the risk of subarachnoid hemorrhage (SAH) associated with age, gender, race, hypertension, insulin-dependent diabetes mellitus, and surgical treatment. For patients with an unruptured cerebral aneurysm as the primary diagnosis, hypertension was found to be a significant risk factor for future SAH (risk ratio: 1.46, 95% confidence interval (CI): 1.01-2.11), whereas surgical treatment (risk ratio: 0.29, 95% CI: 0.09-0.97) had a significant protective effect. Advancing age had a small but significant protective effect in both groups. Elderly patients identified with unruptured aneurysms are more likely to have coexisting hypertension than the general hospitalized population. In elderly patients hospitalized with an unruptured cerebral aneurysm as their primary diagnosis, hypertension is a risk factor for subsequent SAH, whereas surgical treatment is a protective factor against SAH.

Cost-effectiveness of emergency intraarterial intracerebral thrombolysis: a pilot study

PURPOSE

To assess the clinical efficacy and cost-effectiveness of emergency thrombolysis as a treatment strategy for thromboembolic intracerebral events.

METHODS

Thirty-four patients with symptoms suggestive of middle cerebral artery occlusion were included. Eight of these patients were treated with intraarterial urokinase. Effectiveness was determined by comparing the admission National Institutes of Health stroke score to the 24-hour National Institutes of Health stroke score. The cost and length of stay of both populations were derived and used as measures of direct cost. The likelihood of admission to extended care facilities and estimated length cost of admission was used as a measure of indirect cost.

RESULTS

The control population became slightly worse, with a change in National Institutes of Health score of -0.5, whereas the treated population improved slightly, with a change in National Institutes of Health score of +5.12. Analysis of the direct costs data between the two populations revealed a slight increased mean for the treated population ($15,202) as compared with the control population ($13,478). The unpaired t test, however, revealed no significant cost difference between the two groups. By reducing the number of completed strokes by one third or by decreasing the severity by the same factor (as shown in our study), the likelihood of admission to an extended nursing facility also is decreased. The cost saving per patient from extended care facilities is approximately $3435.

CONCLUSION

The emergency application of intraarterial thrombolysis with urokinase results in a statistically significant positive change in National Institutes of Health score by at least five points. A statistically significant benefit is realized through the use of intraarterial urokinase. A statistically insignificant additional cost is shown by this study. This insignificant cost is more than offset by the saved nursing home costs.

Early reversal of acidosis and metabolic recovery following ischemia

Tissue acidosis is believed to be a key element in ischemic injury of neural tissue. The goal of this study was to determine whether persisting postischemic acidosis or the extent of acidosis would affect metabolic recovery following an ischemic event. Intracellular pH (pHi), adenosine triphosphate, phosphocreatine, and lactate levels were measured in the cerebral cortex during the early stages of reperfusion, following either 5 or 10 minutes of global ischemia in both normo- and hyperglycemic gerbils. A total of 130 gerbils were injected with a solution containing 1.5 ml Neutral Red (1%) (+/- 2.5 gm/kg glucose); 30 minutes later, the gerbils were placed under halothane anesthesia, and the carotid arteries were occluded for either 5 or 10 minutes. The brains were frozen in liquid nitrogen at 0, 15, 30, 60, and 120 seconds after reperfusion; they were sectioned and the block face was photographed to determine the pHi by using Neutral Red histophotometry. At the conclusion of the ischemia, the pHi in all groups had decreased significantly from a control value of 7.05 +/- 0.03) (mean +/- standard error of the mean). In normoglycemic brains, the pHi values fell to 6.71 +/- 0.04 and 6.68 +/- 0.11 after 5 and 10 minutes of ischemia, respectively. Hyperglycemic brains were more acidotic; values fell to 6.57 +/- 0.10 and 6.52 +/- 0.24 after 5 and 10 minutes of ischemia, respectively. Lactate levels were approximately fivefold greater than those of control tissue in normoglycemic brains, while lactate levels in hyperglycemic brains were increased eightfold. The adenosine triphosphate and phosphocreatine levels were depleted at the end of ischemia in all groups. After 2 minutes of reflow activity, the pHi levels in both normo- and hyperglycemic brains were restored to those of control values in the '5-minute ischemic group, while the pHi levels remained significantly depressed in the 10-minute ischemic group. Restoration of high-energy phosphates was similar in normoglycemic brains regardless of ischemic duration, recovering to only 20% of the restoration obtained in control tissue at 2 minutes. In hyperglycemic brains, however, there was complete recovery of high-energy phosphates by 2 minutes of reflow activity following 5 minutes of ischemia. Extending the ischemic period to 10 minutes in hyperglycemic brains slowed the rate of metabolic recovery to that observed in normoglycemic brains. The results indicate that the reflow period permits the rapid restoration of pHi levels substantially before the normalization of primary energetic compounds.(ABSTRACT TRUNCATED AT 400 WORDS)

Immediate recovery of pituitary function after transsphenoidal resection of pituitary macroadenomas

Mild hyperprolactinemia frequently accompanies the hypopituitarism associated with pituitary macroadenomas not secreting PRL. Because of this association, hypopituitarism was postulated to be due to compression of portal vessels. We postulate that resumption of hypothalamic control over pituitary function occurs immediately after adenomectomy. To test this hypothesis, we examined pituitary function before and after transsphenoidal adenomectomy in 26 ACTH-deficient patients and 23 subjects with normal adrenal and thyroidal functions (control group). Glucocorticoids, given only to ACTH-deficient subjects, were withdrawn 36 h after surgery. ACTH, cortisol, and PRL levels were measured twice daily in all patients. Both ACTH and PRL levels increased hours after surgery in controls and returned to baseline over 4 days. In all hypopituitary subjects, PRL levels decreased by 50% within hours of adenomectomy and remained so until discharge. ACTH levels, measured simultaneously, increased within hours in 17 of 26 hypopituitary patients, all of whom recovered normal adrenal function before discharge. Nine additional patients had low ACTH levels and required cortisol replacement. The reciprocal changes in PRL and ACTH levels measured simultaneously, hours after surgery, support the hypothesis that hypopituitarism is reversible and largely caused by compression of the protal vessels and the resulting interruption of delivery of hypothalamic hormones. The persistence of hypopituitarism in some patients suggests that ischemic necrosis of the anterior pituitary could limit recovery.

Temporary vessel occlusion in spontaneously hypertensive and normotensive rats. Effect of single and multiple episodes on tissue metabolism and volume of infarction

Temporary occlusion of an intracranial artery is frequently necessary in the surgical management of intracranial aneurysms, arteriovenous malformations, and tumors. While the risks of vessel damage associated with clip application have been lessened by improved design, the threat of ischemic damage remains. It is unclear whether multiple, brief periods of clip application are more or less safe than a single period of occlusion, and whether the underlying cerebrovascular status influences the outcome from either method. The effect of each of these paradigms (single: 1-hour occlusion; multiple: three 20-minute episodes separated by 10 minutes of reperfusion) on histopathological outcome was assessed in a middle cerebral artery (MCA) occlusion model using both normotensive and spontaneously hypertensive rats. The mean volume of infarction (+/- standard error of the mean) was not different between the single-ischemic (49.4 +/- 17.3 cu mm) and the multiple-ischemic (42.9 +/- 12.9 cu mm) episode groups of normotensive rats, whereas in the spontaneously hypertensive rats a significant difference existed between the volume of infarction for the single-occlusion group (126.7 +/- 18.7 cu mm) and the multiple-occlusion group (162.4 +/- 15.5 cu mm) (p < 0.05). The metabolic data obtained from spontaneously hypertensive animals did not provide an explanation for the larger infarction in that there were no significant differences between the single- and multiple-occlusion groups with respect to tissue glucose, adenosine triphosphate, or lactate levels. The results suggest that intermittent reperfusion may have different effects depending not only on the degree and duration of ischemia and reperfusion, but also on the underlying cerebrovascular status.

Evaluation of experimental early acute cerebral ischemia before the development of edema: use of dynamic, contrast-enhanced and diffusion-weighted MR scanning

The ability of dynamic, contrast-enhanced, magnetic susceptibility-weighted scanning to delineate early experimental acute cerebral infarction was compared with that of heavily T2-weighted and diffusion-weighted spin echo scanning. Spontaneously hypertensive rats, which had undergone right middle cerebral artery occlusion, were studied from 15 min to 3 h post ligation on a 1.5-T clinical whole-body imager. In contrast to the diffusion- and T2-weighted spin echo scans, the dynamic, contrast-enhanced technique clearly and consistently delineated the nonperfused regions as early as 15 min post ligation.

Glutamate-induced energetic stress in hippocampal slices: evidence against NMDA and glutamate uptake as mediators

The introduction of exogenous glutamate to normally respiring hippocampal slices produced substantial reductions in ATP, phosphocreatine (PCr) and intracellular pH (pHi) when the concentration exceeded 1 mM. These changes were not prevented by addition of MK-801 (an NMDA receptor antagonist), nor were they mimicked by NMDA or high potassium. In addition, the glutamate-induced metabolic alterations were not prevented by addition of aspartate-b-hydroxymate or sodium substitution by choline, both of which should inhibit high-affinity sodium-dependent glutamate uptake. These results suggest that glutamate alone can produce marked energetic stress in neural tissue, even when glucose and oxygen are maintained at control levels; and that the energetic stress does not appear to be specifically mediated by NMDA-induced depolarization, or by high-affinity uptake of glutamate.

Protein kinase C activity in permanent focal cerebral ischemia

Protein kinase C (PKC) activity was investigated in a model of focal stroke in the rat. Following 6 h of left middle cerebral artery occlusion, rat brains were frozen in situ. In the peripheral ischemic zone, total PKC activity declined by close to two-thirds (1.07 +/- 0.35 vs 2.77 +/- 0.12 nmol/min/mg protein; p less than 0.05, n = 4), and the proportion of total activity associated with the particulate fraction decreased from 33.3 +/- 1.5% to 16.2 +/- 1.4% (p less than 0.01, n = 4). Thus, overall particulate PKC activity in the ischemic zone was less than 20% of control. The cerebral energy metabolite profile of tissue from the ipsilateral hemisphere, corresponding to the region where samples were obtained for PKC activity assay, suggests that this tissue may have been part of the ischemic penumbra before further deterioration.

Use of the delayed mask for improved demonstration of aneurysms on intraarterial DSA

PURPOSE

We retrospectively explored the use of the delayed mask technique for intraarterial digital subtraction angiography (IADSA) to demonstrate the anatomy of aneurysm necks.

METHODS

The delayed mask technique was utilized in 22 patients who had craniotomies for aneurysms demonstrated at angiography. The operative notes were compared to the angiographic findings of both the traditionally masked IADSA and the delayed mask IADSA. In addition, an in vitro model was constructed to examine the relationship between the size of the aneurysm neck and the ability to indirectly define its anatomy by demonstrating the flow jet.

RESULTS

In 12 of 22 cases, the delayed mask technique demonstrated a systolic jet that was not demonstrated by traditional subtraction techniques. In nine of 12 cases, the delayed mask technique gave more specific information regarding the size, location, and orientation of the aneurysm neck.

CONCLUSION

The delayed mask technique can add important information regarding the anatomy of aneurysm without adding time or risk to the procedure.

Rapid metabolic failure in spontaneously hypertensive rats after middle cerebral artery ligation

The metabolic characteristics of the penumbral region were examined in spontaneously hypertensive rats one hour after permanent middle cerebral artery occlusion. The effect of hyperglycemia on this region was examined by providing a glucose load prior to occlusion. The depressed concentrations of adenosine triphosphate and elevated levels of lactate in the penumbral region were similar to those found in the ischemic focus. The purported neuroprotective effect of hyperglycemia in the penumbral region was not reflected in an increased high-energy phosphate level in the penumbral region. The rapid deterioration of the metabolic status of this region in this strain of rat suggests that the increased consistency of infarction may come at the expense of the penumbral region, and thus this model may not be well suited for the study of metabolic changes and perhaps even therapeutic intervention.

Improvement of pituitary function after surgical decompression for pituitary tumor apoplexy

Hypopituitarism is a major manifestation of pituitary adenoma apoplexy. We postulated that the acute deterioration in pituitary function may be caused by compression of portal vessels and the pituitary stalk, secondary to a sudden increase in intrasellar contents. If this were the case, one would predict improvement in pituitary function to occur after surgical decompression. We studied pituitary function in eight patients presenting with the clinical syndrome of pituitary adenoma apoplexy before and on multiple occasions after urgent surgical decompression. Partial or complete hypopituitarism was seen in all subjects at the time of presentation. Serum cortisol levels were inappropriately low (5.9 +/- 1.4 micrograms/dL; 162.8 +/- 38 nmol/L) for the degree of stress in seven patients and appropriately elevated in only one subject (55.3 micrograms/dL; 1525.7 nmol/L). High normal increments in cortisol levels were noted in three subjects given test doses of cosyntropin. Patients were given glucocorticoids before, during, and for 2 days after surgery. Serum cortisol concentrations measured on or after the third day when glucocorticoids had already been stopped were normal in seven subjects and consistently low in one. These seven subjects were discharged on no replacement and were subsequently documented by dynamic testing to have normal pituitary-adrenal function. Gonadal function improved in two of four men and in one of two women who had hypogonadism on presentation. Improvement in thyroid function was documented in two of three subjects with preoperative hypothyroidism. Gradual improvement and almost complete resolution of the neuroophthalmological abnormalities occurred days to weeks after decompression. These observations demonstrate that urgent surgical decompression after pituitary tumor apoplexy was associated with improvement not only in neurological defects but also in pituitary function. The rapid improvement in pituitary function indicates not only that the hypopituitarism was reversible, but also that it might be caused by compression of the portal circulation and pituitary stalk by the sudden increase in intrasellar contents.

Intracranial aneurysms: evaluation by MR angiography

The purpose of this study was to compare the accuracy of a volume gradient-echo MR angiography (MRA) technique with that of intraarterial digital subtraction angiography (IA DSA) in the identification of intracranial aneurysms. The intracranial vasculature was examined in 47 patients by MRA and compared with IA DSA findings in 19 of these patients who had saccular or giant intracranial aneurysms. The remaining 28 patients, in whom no aneurysm was found, served as a control group. MRA was performed with the use of a velocity-compensated gradient-echo sequence (TR = 40-50/TE = 7-15) with a 15 degrees flip angle. The sensitivity and specificity were calculated for the evaluation of the cine 3D reconstructions (cine MRA) only, cine MRA + inspection of the individual partitions, and cine MRA + individual partitions + spin-echo studies. Of 21 aneurysms, of which three were missed in two patients, the sensitivity varied from 67% for cine MRA only to 86% for the cine MRA + partitions + spin-echo studies; of the 19 patients, among whom it was assumed that the diagnosis of any one aneurysm in a patient would lead to angiography and detection of additional aneurysms, the sensitivity varied from 73% for the cine MRA only to 95% for the cine MRA + partitions + spin-echo studies. The results of this study suggest that MRA can define the circle of Willis sufficiently to allow detection of intracranial aneurysms as small as 3-4 mm. MRA holds promise as a truly noninvasive screening examination of intracranial vasculature in patients at risk for aneurysms.

Intracranial aneurysms: evaluation by MR angiography

The purpose of this study was to compare the accuracy of a volume gradient-echo MR angiography (MRA) technique with that of intraarterial digital subtraction angiography (IA DSA) in the identification of intracranial aneurysms. The intracranial vasculature was examined in 47 patients by MRA and compared with IA DSA findings in 19 of these patients who had saccular or giant intracranial aneurysms. The remaining 28 patients, in whom no aneurysm was found, served as a control group. MRA was performed with the use of a velocity-compensated gradient-echo sequence (TR = 40-50/TE = 7-15) with a 15 degree flip angle. The sensitivity and specificity were calculated for the evaluation of the cine 3D reconstructions (cine MRA) only, cine MRA + inspection of the individual partitions, and cine MRA + individual partitions + spin-echo studies. Of 21 aneurysms, of which three were missed in two patients, the sensitivity varied from 67% for cine MRA only to 86% for the cine MRA + partitions + spin-echo studies; of the 19 patients, among whom it was assumed that the diagnosis of any one aneurysm in a patient would lead to angiography and detection of additional aneurysms, the sensitivity varied from 73% for the cine MRA only to 95% for the cine MRA + partitions + spin-echo studies. The results of this study suggest that MRA can define the circle of Willis sufficiently to allow detection of intracranial aneurysms as small as 3-4 mm. MRA holds promise as a truly noninvasive screening examination of intracranial vasculature in patients at risk for aneurysms.

Impairment of metabolic recovery with increasing periods of middle cerebral artery occlusion in rats

We examined the consequences of reflow on metabolic recovery following increasing periods of focal ischemia. The middle cerebral artery of 21 Sprague-Dawley rats was occluded with a snare ligature for 1, 2, or 6 hours followed by 5, 4, or 0 hours of reflow, respectively (seven rats in each group). All animals were injected with neutral red for visual confirmation that the affected regions were reperfused. The brains were frozen in situ, and the concentrations of adenosine triphosphate, phosphocreatine, glycogen, and lactate were determined in those areas corresponding to the normally perfused medial ipsilateral cortex, the perifocal region, and the ischemic focus. Values for the 6 hours' occlusion with no reflow group served as a control to demonstrate restoration of metabolite concentrations. In both groups with reflow, the levels of high-energy phosphates were greater than control, but this effect of reflow was primarily significant for the group with 1 hour's occlusion (p less than 0.05). The levels of glycogen and lactate provided additional evidence that the extent of metabolite restoration was graded; following 2 hours of occlusion, metabolite recovery was compromised (p less than 0.05). Our data strongly support the concept that the window of opportunity for effective treatment of focal ischemia by reperfusion is narrow (of short duration).

The evolution of focal ischemic damage: a metabolic analysis

Focal cerebral ischemia in the rat was induced by left middle cerebral artery occlusion. The area of ischemia was determined by infusion of a qualitative perfusion indicator, neutral red. The temporal evolution of alterations in regional energy metabolism was assessed by direct microquantitative histochemical analysis of high-energy phosphates, glucose, glycogen, and lactate content of the tissue. Perfusion analyses demonstrated a perifocal region of diminished, but not absent perfusion up to 6 hr after occlusion. By 24 hr, there was an abrupt demarcation between perfused and nonperfused regions. Profound metabolic alterations were seen as early as 20 min after occlusion. Although there was an area of intermediate metabolic derangement in the more medial portions of the lateral ipsilateral cortex up to 6 hr, by 24 hr there was an abrupt transition from normal to abnormal cortex. No evidence of metabolic recovery was seen in this model of permanent occlusion.

Magnetic resonance angiography of the extracranial carotid arteries and intracranial vessels: a review

MRI is uniquely suited for evaluation of vascular structures due to its sensitivity to a variety of flow-related phenomena. Recent work has demonstrated that high quality magnetic resonance angiograms (MRA) of the carotid arteries and intracranial vasculature can be achieved by using gradient-echo techniques with short echo times. These MRAs are displayed like conventional arteriograms, but are acquired in a noninvasive fashion with a minimal increase in examination time. We used MRA to visualize 50 of 54 carotid bifurcations tested, with good correlation to the intra-arterial angiograms. We examined the intracranial vasculature in over 40 patients, and demonstrated aneurysms, vascular malformations, and occlusions.

Intracranial circulation: preliminary clinical results with three-dimensional (volume) MR angiography

The authors assessed the clinical utility of a magnetic resonance angiography technique in the evaluation of intracranial circulation. Eighteen patients with a low likelihood of cerebrovascular disease (control group) and 40 patients with suspected cerebrovascular disease were imaged with a FISP (fast imaging with steady precession) sequence (repetition time of 50 msec, echo time of 15 msec, velocity compensation in the read and section-select directions with acceleration compensation in the read direction, 15 degrees anisotropic volume, and a 1.25-mm partition thickness). Ninety-four percent of images in the control group and 72% of images in the group with cerebrovascular disease were considered useful for diagnosis. This technique can provide accurate images of intracranial circulation and can be performed in conjunction with two-dimensional spin-echo or gradient-echo imaging. It was most useful in the evaluation of patent intracranial aneurysms, vessel displacement, and large-vessel occlusive disease. Disadvantages included limited field of view, persistent signal voids, limited spatial resolution, and inadequate depiction of lesions with slow flow.

Three-dimensional (volume) gradient-echo imaging of the carotid bifurcation: preliminary clinical experience

This study was designed to test the accuracy of magnetic resonance (MR) imaging with a FLASH (fast low-angle shot) 40 degrees volume pulse sequence by comparing it with intraarterial digital subtraction angiography (DSA) in patients with suspected carotid artery stenoses. Fifteen patients referred for evaluation of anterior circulation in cerebrovascular disease composed the pilot group. Twelve patients underwent correlative intraarterial DSA examinations. The FLASH volume sequence, with an echo time of 7.7 seconds, produced high-signal-intensity vascular images for 28 of 30 bifurcations. Of the 24 carotid bifurcations studied with DSA, 22 were depicted with MR angiography. Among the depicted bifurcations, 21 showed good correlation with the DSA images. These included four of four normal bifurcations, three of three with mild stenosis, four of four with moderate stenosis, eight of nine with severe stenosis, and two of two with occlusions. With respect to ulceration, three of four MR angiographic studies showed good correlation with DSA images. This preliminary experience indicates that the method is reproducible and capable of delineating carotid lesions in patients and that it can be performed in conjunction with conventional spin-echo imaging of the brain with only a small increase in patient examination time.

Herniation of the suprasellar visual system and third ventricle into empty sellae: morphologic and clinical considerations

Intrasellar herniation of the optic nerve, optic chiasm, optic tract (suprasellar visual system, SVS), and anteroinferior third ventricle can occur into primary or secondary empty sellae. The anatomic part of this study evaluated the appearance of the SVS in subjects with normal sellae (n = 52), the patterns and prevalence of SVS herniation in enlarged primary empty sellae (n = 24), and the patterns of intrasellar herniation of the SVS in secondary empty sellae (n = 8). The clinical part of this study was to correlate the visual status with the anatomic patterns of the intrasellar herniated SVS. High-resolution MR and CT were used to define the anatomy. MR was superior to CT in all groups in defining accurately the SVS relationship to the sella turcica. In the normal group, the SVS invariably had a straight-line appearance formed by the optic nerve, optic chiasm, and floor of the third ventricle and was above the sella. The SVS was herniated in three of 24 enlarged primary empty sellae. A difference in the appearance of the hypothalamic and infundibular recesses in the primary empty sella group with SVS herniation (dilated recesses and formation of an obtuse angle) and in the secondary empty sella group with SVS herniation (nondilated recesses and formation of an acute angle) was observed. Visual disturbances in primary empty sellae with SVS herniation were present in two of three subjects. Visual disturbances may be absent or minimal in primary empty sellae and secondary empty sellae with herniation of the SVS. Progression of the symptoms--visual field defects, optic atrophy, and loss of vision--is not inevitable. There was no correlation between the severity of visual symptoms and the degree of herniation of the SVS in either the primary or secondary sellae. We found that intrasellar herniation of the SVS into a primary or secondary empty sella is well delineated with MR, and MR should facilitate decisions concerning surgery or therapy. Visual disturbances proved to be an unreliable indicator of herniation.

Visually defined zones of focal ischemia in the rat brain

A technique to guide brain tissue sampling in experimental focal ischemia is described. This technique allows visual identification for accurate metabolic analysis of regions with variable tissue perfusion. After 2.5 hours of unilateral middle cerebral artery occlusion (MCAO) in the rat, intravenous infusion of the vital dye, neutral red (NR), identified three distinct regions: (a) an intensely stained region consisting of the entire contralateral hemisphere and the medial ipsilateral hemisphere; (b) a blanched region in the lateral ipsilateral hemisphere; and (c) a zone of intermediately stained tissue interposed between the medial and lateral ipsilateral regions. Close regional correlation between NR staining and the iodoantipyrine intensity of adjacent brain slices suggests that NR distribution is a qualitative indicator of brain perfusion. Using the NR staining pattern to guide tissue dissection for metabolite analysis of high energy phosphates (adenosine triphosphate and phosphocreatine) and glucose-related metabolites showed that the blanched region contained ischemic tissue, whereas values from the contralateral cortex resembled those of control tissue. The intermediately stained region exhibited a gradient of metabolic perturbation. Tissue near intensely stained regions resembled control tissue, and tissue near blanched regions resembled ischemic tissue. These results confirm the concept of a metabolic penumbra. When present, it occupies only the most medial area of the intermediate region at 2.5 hours after MCAO.

Large pituitary gland adenomas evaluated with magnetic resonance imaging

Magnetic resonance imaging (MRI), computed tomographic (CT) scanning, and angiography or digital subtraction angiography (DSA) were used preoperatively to evaluate 16 surgically proven cases of sellar tumor with extrasellar extension. There were 15 pituitary tumors and 1 schwannoma. The capabilities of MRI in evaluating these tumors were compared with CT scanning and angiography. Bone destruction and tumor calcification were better detected by CT scanning than by MRI. MRI was as effective as CT scanning in detecting a cyst or variation in tumor consistency. Neither MRI nor CT scanning was capable of distinguishing specific tumor types. In every case, MRI was superior to CT scanning for delineating spatial relationships of the tumor to the 3rd ventricle, the optic apparatus, adjacent brain, and parasellar vasculature. Vessel encasement by tumor was clearly seen on MRI when there was no direct indication of this on other studies. Cavernous sinus invasion was not demonstrated by CT scanning, but was indicated by MRI in 5 cases and was surgically confirmed in 3. MRI can provide more precise spatial information on extrasellar tumor extension. Vascular encasement and cavernous sinus invasion may be determined preoperatively. Treatment expectations and operative approaches can be guided by this information. When MRI is available, it is the test of choice for the preoperative evaluation of patients with suspected large pituitary gland (sellar region) tumors. Contrast-enhanced CT scanning and angiography can be used as supplementary studies to add information inherently unique to these techniques.

Radiculomeningeal vascular malformations of the spine: MR imaging

Three patients (two men, one woman; 63-81 years old) with radiculomeningeal vascular malformations of the spine were examined using high-resolution surface coil magnetic resonance (MR) imaging at 1.5 T. The findings included previously described high-velocity signal loss within the vessels of the malformation as well as previously unreported signal-intensity changes within the cord (long T1/long T2) distal to the malformation. The MR images correlate well with previous reports of location and pathophysiology of these dural lesions.

Advances in neuroradiologic imaging of the pituitary gland: changing concepts

A review of pituitary imaging is presented based on the history of neuroradiologic definition of the sellar contents as well as modern diagnostic techniques. The importance of normal pituitary and seller anatomy is stressed in an attempt to determine the limitations of defining abnormal sellar contents with the imaging techniques of computed tomography and magnetic resonance imaging. The sensitivity and specificity of these techniques are illustrated with histopathologic correlation.

Lead encephalopathy presenting as a posterior fossa mass. Case report

✓ A case of lead encephalopathy with clinical and computerized tomography evidence of a midline posterior fossa mass is presented. The pathophysiology and the predilection for posterior fossa involvement are discussed.

The occurrence of dural invasion in pituitary adenomas

This report describes 60 dural specimens from patients with pituitary adenomas treated by transsphenoidal microsurgery, and attempts to define more precisely the clinical and pathological correlation of microscopic dural invasion. Analysis of the adenomas was based on four characteristics; size, surgical invasiveness (based on the surgeon's assessment of involvement by tumor of bone, dura, or cavernous sinus), histological evidence of invasion, and immunohistochemical staining characteristics. The incidence of surgical invasiveness (24 cases, 40%) was greater than previously reported, but most important was the frequent occurrence of microscopic dural invasion (51 cases, 85%). There was a clear progression of microscopic evidence of dural invasion with increasing tumor size: 69%, 88%, and 94% of the dural specimens from microadenomas, macroadenomas, and tumors with suprasellar extension, respectively, showed microscopic dural invasion. A correlation of invasiveness with immunohistochemical classification of tumor type was not evident.

Cerebrospinal fluid penetration of moxalactam in ventriculostomy patients

The cerebrospinal fluid penetration of moxalactam was simultaneously investigated in three patients with presumed bacterial meningitis. When ratios of simultaneously drawn ventriculostomy to serum moxalactam levels of 1, 2, 3, and 4 h were examined, the penetration ratios were 7.8 +/- 2.4, 11.2 +/- 1.3, 14.2 +/- 2.5, and 15.0 +/- 4.9%, respectively. These ratios were not statistically different from the penetration of moxalactam calculated by the area under the concentration-time curve technique (8.97 +/- 1.89%).

Naloxone therapy during focal cerebral ischemia evaluation in a primate model

Conflicting reports have appeared in the literature regarding the effect of the opiate antagonist naloxone on ischemic neurologic deficits. We report the results of a study using naloxone in our model of focal cerebral ischemia in the awake primate. A total of 14 adult baboons were subjected to six-hour occlusion of the left middle cerebral artery (MCA). Seven animals served as controls and seven received treatment with naloxone (5 mg/kg) beginning 30 min after MCA occlusion and continuing until two hours after reperfusion. All animals developed profound hemiparesis and homonymous hemianopsia within seconds of inflating the MCA occluder. Acutely, therapy with naloxone partially reversed ischemic neurologic deficits in five of the seven treatment animals. Within minutes of receiving the loading dose of naloxone, responding animals were more alert and demonstrated improvements in motor function. Naloxone did not affect mortality: Three animals in the treatment group and two in the naloxone group died secondary to malignant intracranial pressure within 48 hours of the ischemic episode. In animals surviving the ischemic insult however, treatment with naloxone significantly improved neurologic outcome at 10 days (p less than 0.05). Neuropathologic examinations in these animals revealed amelioration of ischemic tissue damage, with three of the five suffering only small focal areas of infarction. (All control animals suffered large infarcts of the MCA territory.) Our results verify that naloxone can reverse ischemic deficits, and more importantly may improve the outcome from focal ischemic insults.

Liver abscess: complication of a ventriculoperitoneal shunt

Liver abscess is a previously unreported complication of ventriculoperitoneal shunting. We present such a case, which was diagnosed by computed tomography (CT) and managed by CT-guided percutaneous catheter drainage of the liver abscess, appropriate antibiotics, and shunt externalization.

New lumboperitoneal shunt catheter

A new catheter is described for percutaneous lumboperitoneal shunts. The method of introduction and indications for this shunt are reviewed.