Pial vascular behavior during bilateral and contralateral cervical sympathetic stimulation.

The present study in cats investigates the effect of cervical sympathetic stimulation on changes of diameter of pial arteries and veins, CBF, and intracranial pressure (ICP) using the cranial window and hydrogen clearance techniques. During 20 min of bilateral stimulation, pial arteries maximally constricted by 12%, veins by 13-15%. While the constriction of the large arteries remained stable during the whole 20-min period of bilateral stimulation, small arteries escaped after some 2 min. A similar though weaker trend was noted for the veins. CBF was reduced at 2 min by 31%, and was not different from resting at 18 min. Contralateral stimulation for 20 min induced early constriction only in small arteries, while all other vessels remained more or less unreactive. This phenomenon is explained by interhemispheric arterial collaterals that bring sympathetic fibers mainly to small arteries contralaterally. ICP was lowered initially by 47 +/- 12% during bilateral and by 23 +/- 5% during contralateral stimulation. ICP escaped after 2 and 5 min during bilateral and contralateral stimulation, respectively, and even started to rise after some 10 min. From these data, it is concluded that the sympathoadrenergic system exerts a short-lasting protective effect upon cerebral vascular volume. Small arteries escape from constriction as a consequence of primarily myogenic counteraction of pial and intraparenchymal vessels, and probably additional metabolic dilatation of intraparenchymal vessels.

Effect of serotonin and its antagonist ketanserin on pial vessels.

The effect of serotonin (5-HT) and its antagonist ketanserin on the cerebral circulation was investigated in two series totaling 24 cats using the cranial window technique. 5-HT elicited a marked dilatation of small pial arteries, whereas large arteries tended to constrict. Intravenous administration of ketanserin reversed the constriction of large arteries, causing dilatation, and reduced the extent of small arteries' dilatation. In a randomized study, i.v. administration of ketanserin in its solvent versus the solvent alone revealed a strong dilatatory effect of the solvent on pial arteries (17 +/- 1.8%), which partly jeopardized a possible constrictory effect of ketanserin, as ketanserin plus solvent induced less dilatation of small pial arteries than the solvent alone. The present data support the view that serotonin exerts a dual effect on cerebral arteries, namely, dilatation of small and constriction of large vessels. The antagonist ketanserin reverses this effect, but the strong dilatatory effect of the solvent alone masks the antiserotoninergic effect.

Cerebral veins: fluorescence histochemistry, electron microscopy, and in vitro reactivity.

Pial veins, choroid plexus veins, and the cerebri magna vein were investigated with regard to their ultrastructural organization, adrenergic nerve supply, and in vitro reactivity. The vessel walls consisted of a continuous layer of endothelial cells, large amounts of collagenous material, and occasional pericytes. Smooth muscle cells were observed only in a few specimens from the cerebri magna vein. All veins were surrounded by adrenergic nerve fibres. Potassium (124 mM) and noradrenaline (10(-5) - 10(-4) M) induced small contractions (0.2-0.5 mN) of isolated veins during in vitro conditions. The magnitude of these responses was less than one-tenth of that obtained in small pial arteries.

Acute operation and preventive nimodipine improve outcome in patients with ruptured cerebral aneurysms.

Sixty-five patients with ruptured aneurysms were operated upon within 48 to 72 hours after subarachnoid hemorrhage (SAH) and were treated with a regimen of intra- and postoperative nimodipine for the prevention of symptomatic vasospasm. The clinical grading (Hunt and Hess) was I to III in 49 patients and IV or V in 16. The SAH was mild in 15 patients, moderate in 27, and severe in 23; 12 patients harbored an intracerebral hematoma, and 6 had intraventricular bleeding. Acute hydrocephalus was observed on preoperative computed tomography (CT) in 19 patients. On CT 3 days postoperatively (i.e., Day 3-4 after SAH), 30 of 65 patients still had subarachnoid blood; however, severe symptomatic vasospasm as the deciding threatening event during the delayed postoperative period was not encountered in this series. Transient symptoms of ischemia were noted in 2 patients (3%) and were accompanied by angiographic spasm in 1. Irreversible neurological deficit occurred in 2 patients (3%); in 1 of these, it was a complication of postoperative control angiography. Of the patients preoperatively graded I or II, 96% had an excellent to fair outcome 6 months postoperatively, and 1 patient (4%) had died because of a surgical complication. Among patients preoperatively graded III or IV, 86% had an excellent to fair outcome, and the remaining 14% had a poor outcome. Shunt-dependent hydrocephalus developed in 7% of the patients. Acute surgical repair of ruptured cerebral aneurysms and preventive topical and intravenous administration of nimodipine reduce management complications and improve outcome; above all, ischemic lesions from symptomatic vasospasm are reduced to a minimum.

Effect of intravenous mannitol on cat pial arteries and veins during normal and elevated intracranial pressure.

In two series of cats, totaling 12 animals, the effect of 1 g of intravenous mannitol per kg over 15 minutes on pial vessels (cranial window technique, multichannel videoangiometry) and intracranial pressure (ICP) was investigated under circumstances of normal ICP and ICP elevated to 20 mm Hg by the cisternal infusion of mock cerebrospinal fluid. Under conditions of normal ICP, mannitol induced an 18% reduction of ICP at the end of the infusion and a further decrease to 38% below the initial level 10 minutes later. Pial veins and arteries remained more or less unreactive over 35 minutes, with changes never exceeding 2 to 3%. Administration of mannitol during elevated ICP (20 mm Hg) reduced ICP by 15% during the administration period; during the subsequent 15 minutes, ICP returned to pretreatment levels. Pial arteries remained unreactive during mannitol infusion; however, they started to dilate during the subsequent 15 minutes to +8%. Venous calibers showed no noticeable changes. It is concluded that mannitol in clinically relevant doses does not exert a significant constrictive effect on cerebral arteries and veins and that mannitol acts on ICP probably via an osmotic effect rather than by a direct effect on cerebral blood volume.

Virtual endoscopy for planning and simulation of minimally invasive neurosurgery.

OBJECTIVE: This article demonstrates the usefulness and the problems of present-state software for virtual endoscopy as a tool for the planning and simulation of minimally invasive neurosurgical procedures. METHODS: The software Navigator (General Electric Medical Systems, Buc, France) was applied for virtual endoscopic visualization of three-dimensional magnetic resonance data sets of healthy volunteers and neurosurgical patients, using a clinical magnetic resonance scanner (1.5-T Signa Hispeed; General Electric Medical Systems). Classical approaches for minimally invasive procedures were simulated. RESULTS: Virtual endoscopy provided impressive three-dimensional views of intracranial and intracerebral cavities, with visualization of many anatomic details of the brain's inner and outer surfaces. The method proved to be especially suited for the simulation and planning of operations of intraventricular lesions, for which the technical limitations of the present state of development of this method have fewer implications. However, the present state of technology, as described in this article, has two major shortcomings: 1) the blood vessels cannot be visualized together with the brain tissue and cranial nerves; and 2) different tissue compartments cannot be stained in their original coloring, which would facilitate their recognition and thus orientation in space by anatomic landmarks. Another important disadvantage at this stage is time consumption for many single working steps. CONCLUSION: Virtual endoscopy is a promising tool for teaching and training in intracranial neuroanatomy as well as for planning and simulation of minimally invasive (e.g., endoscopic), mainly intraventricular, operations. Direct clinical application is, at this stage of development, limited by several technical shortcomings of visualization and quantification of distances and modeling of surfaces.

Disturbed cerebrospinal fluid circulation after subarachnoid hemorrhage and acute aneurysm surgery.

In 138 patients with ruptured cerebral aneurysms operated on within 48 to 72 hours after subarachnoid hemorrhage, an external ventricular drainage catheter was inserted before craniotomy and was used intermittently during the first week after surgery. In 51 patients, intracranial pressure (ICP) was measured intraoperatively. The majority of patients showed increased ICP intraoperatively irrespective of the preoperative Hunt and Hess grade and the amount of subarachnoid blood accumulation or intraventricular blood clot. Intraoperative drainage of cerebrospinal fluid allowed easy access for aneurysm dissection by making the brain slack in more than 90% of patients. Postoperative ICP measurements revealed that significant brain swelling did not occur in the majority of patients. In 7 patients, persistently elevated ICP (greater than 20 mm Hg) was recorded. Nine patients (8%) developed shunt-dependent hydrocephalus; all of these patients had suffered an intraventricular hemorrhage. Measurements of the volumes of cerebrospinal fluid drained did not allow prediction of shunt-dependent hydrocephalus.

Effect of the barbiturate methohexital on cerebral vessels and intracranial pressure.

Reactions of pial arteries and veins as well as intracranial pressure (ICP) and mean arterial pressure during intravenous administration of methohexital were observed in two groups of cats totaling 24 animals in order to investigate hypothesized direct barbiturate effects on cerebral vascular volume. Group 1 had bolus injection of 1 mg/kg followed by infusion of 0.1 mg/kg/min over 60 minutes. This induced a 6 to 7% arterial dilatation at 50 to 60 minutes (not significant); a 20% reduction of pial vein calibers was observed (P less than 0.01). In Group 2, the same treatment protocol administered under conditions of ICP elevation to 20 mm Hg by the cisternal infusion of mock cerebrospinal fluid resulted again in consistent, although less extensive, venous caliber reduction (5 to 7%, P less than 0.01). In Group 2 controls, pial arteries dilated by 15 to 20%; this reaction was suppressed in the methohexital-treated animals. After stopping methohexital, however, arteries in the methohexital group dilated to almost the same extent as in controls. Mean arterial pressure remained stable in both groups. ICP was not reduced by methohexital. EEG-activity was slightly increased during treatment. We conclude that methohexital has a direct effect on vessel caliber and thus cerebral blood volume via absolute diminution of venous vessels and suppression of ICP-induced autoregulative arterial dilatation. This direct vascular effect, however, seems to be counterbalanced by unknown intracranial mass effects that prevent a reduction in ICP.

The cerebral venous system.

The authors discuss the gross and microscopic anatomy and the physiology of the cerebral venous system. Cerebral veins under pathological circumstances (hypercapnia, arterial hypertension, and increased intracranial pressure), pharmacological observations, the venous blood-brain barrier, and traumatic involvement are reviewed. Neoplastic involvement and radiological aspects are included. Surgical reconstruction of venous sinuses (including the Donaghy technique), tumor removal, sinus thrombectomy, and extraanatomical bypass of the transverse sinus are discussed.

Computerized tomography and prognosis in early aneurysm surgery.

A study of computerized tomography (CT) scans was performed in a consecutive series of 100 patients with ruptured saccular cerebral aneurysms who were admitted, diagnosed, and operated on within 72 hours after subarachnoid hemorrhage (SAH) and treated with calcium antagonists. The aneurysms were in the anterior portion of the circle of Willis in 95% of patients and in the posterior portion in 5%; 12% had multiple aneurysms. Preoperative neurological grades according to Hunt and Hess were I to III in 74% of patients and IV or V in 26%. Subarachnoid hemorrhage as determined by CT scanning was minor in 20%, moderate in 43%, and severe in 37% of patients. All patients received intraoperative and postoperative administration of the calcium antagonist nimodipine. Three days postoperatively, SAH (as measured by CT) was significantly reduced in the majority of patients but was still moderate in 18%. In the postoperative course, 2% of patients developed delayed ischemic neurological symptoms due to vasospasm. In two additional patients, ischemic symptoms were transient and fully reversible. At the 6-month follow-up interval, a significant prognostic difference was found between two patient groups with different CT scan findings. Among the patients with SAH only, the rate of good outcome (no or minimal deficit) was 93% when the preoperative neurological Grade was I or II; but even with a Grade of III to V, there was a good outcome in 84% of patients. By contrast, in patients with additional intracerebral and/or intraventricular hemorrhage, the good-outcome rate was only 44%. From these data it is concluded that morphological preoperative CT findings are of prognostic value and may even be superior to clinical grading in predicting outcome.

Effect of intracranial pressure on bridging veins in rats.

The behavior of bridging veins at their entrance into the superior sagittal sinus during elevated intracranial pressure (ICP) was investigated in rats using a cranial window and infusion of mock cerebrospinal fluid. The bridging veins became slightly smaller as the ICP rose (maximum reduction 17%). Compression or collapse of the veins was not observed, even at an ICP level of 100 mm Hg, and there was no cuffing of bridging veins upstream of the entrance. Both the scanning electron microscopic investigation based on resin vessel casts and the histological examination of whole-head coronal sections indicated that the narrowest points of the bridging veins are at their entrance to the superior sagittal sinus, caused by the oval aperture with thickened wall structure in the lateral sinus wall to which the bridging veins are connected. The present data thus support the concept that cerebral blood flow during intracranial hypertension is not reduced by venous cuffing or compression of the lateral lacunae and bridging veins; by contrast, the arteriovenous pressure difference seems to remain the determining factor even at high ICP. Thus, blood flow through the brain stops when ICP approaches the level of blood pressure.

Diagnosis and treatment of middle fossa arachnoid cysts and subdural hematomas.

Nine cases with temporal fossa arachnoid cysts were diagnosed by computerized tomography (CT). Five patients also had subdural hematomas, three of them following head trauma. When the hematoma was chronic and of equal hypodensity with the cyst, a clear-cut differentiation was not possible from the CT scan. The presence of a subdural hematoma could only be suggested by thickened arachnoid structures crossing the hypodense area, indicating the wall between cyst and hematoma. The cyst could often be diagnosed by bulging of the skull bone and a temporal lobe defect. Differences in density between cyst and hematoma, such as in subacute subdural hematoma, delineated both entities. Typical examples are demonstrated. Treatment consisted of evacuation of the hematoma and excision of the cyst in all cases.

Endoscopic surgery versus medical treatment for spontaneous intracerebral hematoma: a randomized study.

A controlled randomized study of endoscopic evacuation versus medical treatment was performed in 100 patients with spontaneous supratentorial intracerebral (subcortical, putaminal, and thalamic) hematomas. Patients with aneurysms, arteriovenous malformations, brain tumors, or head injuries were excluded. Criteria for inclusion were as follows: patients' age between 30 and 80 years; a hematoma volume of more than 10 cu cm; the presence of neurological or consciousness impairment; the appropriateness of surgery from a medical and anesthesiological point of view; and the initiation of treatment within 48 hours after hemorrhage. The criteria of randomization were the location, size, and side of the hematoma as well as the patient's age, state of consciousness, and history of hypertension. Evaluation of outcome was performed 6 months after hemorrhage. Surgical patients with subcortical hematomas showed a significantly lower mortality rate (30%) than their medically treated counterparts (70%, p less than 0.05). Moreover, 40% of these patients had a good outcome with no or only a minimal deficit versus 25% in the medically treated group; the difference was statistically significant for operated patients with no postoperative deficit (p less than 0.01). Surgical patients with hematomas smaller than 50 cu cm made a significantly better functional recovery than did patients of the medically treated group, but had a comparable mortality rate. By contrast, patients with larger hematomas showed significantly lower mortality rates after operation but had no better functional recovery than the medically treated group. This effect from surgery was limited to patients in a preoperatively alert or somnolent state; stuporous or comatose patients had no better outcome after surgery. The outcome of surgical patients with putaminal or thalamic hemorrhage was no better than for those with medical treatment; however, there was a trend toward better quality of survival and chance of survival in the operated group.

The first 100 transsphenoidally operated pituitary adenomas in a non-specialised centre: surgical results and tumour-recurrence.

From 118 transsphenoidally operated patients, 100 had a pituitary adenoma; 33 prolactinomas, 20 HGH-producing, 2 ACTH-producing and 45 inactive adenomas. The first transsphenoidal operation did not cause any mortality; after reoperation for suspected recurrence on follow-up, 2 patients died; thus, the global management mortality was 1.8%. As surgical complications, diabetes insipidus occurred in 5%, hypopituitarism in 4%. Age at operation was significantly higher in female patients with micro- than with macroprolactinomas, and also markedly higher in men than in women with prolactinomas. Preoperative serum prolactin levels were related to tumour size and age and demonstrated an important prognostic factor of postoperative cure. The prognosis of preoperative visual field defects was dependent on preoperative duration. During a follow-up period of 1-6.3 years, 7 patients were reoperated for recurrence of their tumour after intervals of 2-4.5 years; 6 of these patients had had inactive macroadenomas, 1 an ACTH-producing macroadenoma. In 3 of these patients, radiation therapy had been performed. The highest recurrence-rate (19%) among 100 patients was found in patients with inactive macroadenomas with a follow-up of more than 2 years.

Autoregulatory response of pial vessels in the cat.

Pial vessel responses to mean arterial pressures (MAP) between 40 and 160 mmHg, induced by withdrawal and reinfusion of blood, were studied in twelve cats under barbiturate- and N2O-anaesthesia, using the cranial window technique and videoangiometry. Very minor changes of pial arterial calibres were noted between MAP 80 and 120 mmHg. During further reduction of MAP, small arteries dilated more than large arteries and measured 43 +/- 4.6% and 30 +/- 1.9% at MAP 40 mmHg, respectively. When MAP was elevated to 140 mmHg, large arteries constricted more than small ones; at MAP 160 mmHg, however, they started to redilate, while small arteries continued to constrict to -13 +/- 2.3%. Within the autoregulatory range, pial veins remained unchanged; at MAPs of 40 and 160 mmHg, venous calibre variations remained below 10%.

Penumbra around chronic cerebral infarction?

In a series of 13 patients with cerebrovascular occlusive disease regional cerebral blood flow (rCBF) measurements (two-dimensional intravenous 133Xe clearance method) and quantitative EEG analysis (sensorimotor rhythms) as well as electronic measurement of handforce were performed before and during intravenous infusion of 1 microgram kg/min of one of the lipophilic dihydropyridine calcium channel blocker nimodipine (Nimotop). The aim of the study was to test the hypothesis of the existence of hypoperfusion (ischaemic penumbra) in the surroundings of chronic cerebral infarcts. All 3 parameters improved in one patient. Sensorimotor rhythms increased in 5 patients, rCBF in 3. EEG and rCBF improved in 2 patients. In 3 instances, a redistribution of rCBF in favour of the peri-infarct zone was noted (significant increase of rCBF from 35 +/- 2 SEM to 53 +/- 4 ml/100 g/min (p less than 0.01), whereas rCBF fell from 61 +/- 5 to 46 +/- 2 ml/100 g/min on a collimator remote from the infarct but in the infarcted hemisphere. The parallel improvement of rCBF and EEG in brain regions surrounding chronic infarcts in 3 patients was interpreted as functional improvement as a consequence of nimodipine-induced normalization of peri-infarct hypoperfusion, i.e. reversal of flow-dependent neuronal silence and/or dysfunction.

Experimental intracerebral hemorrhage: description of a double injection model in rats.

For experimental purposes, the most common technique of producing an intracerebral hematoma in rats is the injection of unclotted autologous blood. All modifications of this model share the problem that size and extension of the hematoma are not reproducible, because the injected blood either ruptures into the ventricular system or it extends to the subarachnoid or subdural space. Therefore a double injection model of experimental intracerebral hemorrhage in rats has been developed using 19 male Sprague-Dawley rats. After inducing anesthesia a cannula was stereotactically placed into the caudate nucleus and an intracerebral hematoma was produced with the double injection method in which first a small amount of fresh autologous blood is injected which is allowed to clot (preclotting) in order to block the way back along the needle track; the actual hematoma is produced in a second step of the injection. The clot volume was measured on stained serial sections. A total injection volume of 50 microliters of autologous blood produced intracerebral hematomas of 41.1 +/- 10.0 microliters and of similar shapes. The double injection method allows to generate reproducible hematomas in rats. This new model of intracerebral hemorrhage will allow further investigation of fibrinolytic and cytoprotective therapies.

Fibrinolysis and aspiration of experimental intracerebral hematoma reduces the volume of ischemic brain in rats.

The hypothesis was tested in rats that brain ischemia by an intracerebral hematoma can be ameliorated by fibrinolysis and aspiration of the hematoma. Intraparenchymal blood clots were generated by the injection of 50 microliters of autologous blood into the right caudate nucleus in two portions seven minutes apart. Thirty or 120 min later 12 microliters recombinant tissue plasminogen activator (rtPA) or 0.9% NaCl were injected and after 30 min the resolved hematoma was aspirated. Six hours later cerebral blood flow (CBF) was determined by 14C-iodoantipyrine autoradiography. Tissue volumes of CBF < 10 ml 100 g-1 min-1 and CBF < 30 ml g-1 min-1 were determined. Clot and lesion volume were quantified histologically from serial sections stained for succinate-dehydrogenase (SDH) activity. In rtPA-treated rats the major part of the hematoma could be evacuated 30 min as well as 120 min after production of the clot. The volume of ischemic brain (CBF < 10) was significantly reduced (p < 0.05) in the rtPA group compared to saline-treated and control groups irrespective of the time of treatment. In contrast, no difference was found between the control group and the experimental groups when the volumes of brain tissue surrounding the lesion were compared which had values of CBF < 30 ml 100 g-1 min-1. In a rat model of intracerebral hemorrhage, treatment by local fibrinolysis followed by aspiration of the hematoma is effective in reducing the volume of ischemic brain tissue and of the remaining clot volume.

Pial arterial and venous reaction to intravenous infusion of nimodipine in cats.

The calcium-antagonist nimodipine was infused intravenously in ten cats using dosage rates of 0.5 to 3 micrograms kg-1 min-1. The reactions of pial arterial and venous vessels as well as mean arterial blood pressure (MAP) were studied. For analysis of pial vascular reactions, diameter variations were continuously monitored on 50 arterial and 22 venous portions using a multichannel videoangiometer. At 0.5 micrograms kg-1 min-1, pial arteries with a mean resting diameter of 81 microns dilated by 4% (p less than 0.0005); venous diameters decreased by 0.5% (n.s.); MAP declined by 2% (n.s.). At 1 microgram kg-1 min-1, arteries dilated by 25% (p less than 0.0005), venous diameters were diminished by 3.8% (n.s.), MAP decreased by 9% (n.s.). Further significant dilatation of pial arteries was observed at 2 and 3 micrograms kg-1 min-1, however, together with a significant fall of MAP. Arterial vessels smaller than 60 micrograms resting diameter dilated more than arteries above 60 micrograms. After the infusion was stopped, arterial dilatation by some 20% persisted for at least 20 minutes, even when MAP values returned to the resting level.

The effect of intravenous infusion of Tebonin (Ginkgo biloba) on pial arteries in cats.

The dilatory effect of intravenously infused Tebonin (extract of Ginkgo biloba) on pial arterial vessels (less than 100 micron diameter), has been measured using a multichannel videoangiometer through a closed cranial window in cats. After 20 minutes there was a significant dilatation of 7% which increased to 21% by one hour. Results from 6 cats treated with 0.3 mg/kg/min. Tebonin were compared with a group of 6 control cats; the same blood gas "steady state" situation applying to both groups. Results imply a cerebral metabolic effect of Ginkgo biloba that induced a slow rise in cerebral blood flow.