Toward changing of the pathophysiologic basis of acute hydrocephalus after subarachnoid hemorrhage: a preliminary experimental study.

BACKGROUND: Acute hydrocephalus (ventricular enlargement within 72 hours) is a common complication in patients with aneurysmal subarachnoid hemorrhage (SAH). Cerebrospinal fluid (CSF) secretion may be increased in the early phases of SAH, but it has not been proved definitively. We studied the histologic features of choroid plexus (CP) in the early and late phases of SAH. METHODS: This study was conducted on 20 rabbits, with 5 rabbits in the control group, 5 rabbits in the sham group, and 10 rabbits in the SAH group. In the SAH group, five of the animals were decapitated after 2 days of cisternal blood injections, and the other five animals were decapitated after 14 days of injections. The CP of lateral ventricles were obtained from coronary sections of brains at the level of the temporal horns of the lateral ventricles. Sections were stained with hematoxylin and eosin and Masson trichrome for SAH-related damage and examined stereologically to discern water-filled vesicles, which were counted. Sections were compared statistically. RESULTS: The mean numbers of water vesicles were different after SAH between the early decapitated group (group III) and the late decapitated group (group IV). The mean numbers of water vesicles were 2.80 (± 0.05) in the control group (group I), 2.76 (± 0.02) in the sham group (group II), 14.68 (± 0.06) in the early decapitated group (group III), and 4.78 (± 0.13) in the late decapitated group (group IV). Total number of fluid-filled vesicles of CP was also assessed stereologically; the total numbers were 840 (± 16) in group I, 828 (± 7) in group II, 4404 (± 19) in group III, and 1434 (± 41) in group IV. The numbers of water-filled cisterns were significantly increased in the early phases of SAH (P < 0.05). CONCLUSIONS: In SAH with aneurysm rupture, increased CSF secretion seems to be triggered by hemorrhage in the early phase, but it is not possible in the late phase because of CP degeneration. In the early phase of hemorrhage, CSF secretion may be stimulated by the irritant receptor glossopharyngeal and vagal nerve endings, which innervate the healthy CP epithelium and arteries. Our findings may be accepted as being causative. It is likewise possible that CSF blockage per se leads to hydrocephalus, and the morphologic changes are sequelae that occur later in the course of disease. This is the first study to show the water vesicles of CP as a causative factor in the development of acute hydrocephalus after SAH.

Endovascular treatment of severe vasospasm in nonaneurysmal perimesencephalic subarachnoid hemorrhage.

BACKGROUND: Nonaneurysmal perimesencephalic subarachnoid hemorrhage (SAH) has usually a benign prognosis and uneventful course; however, recent reports suggest that these patients may develop severe symptomatic vasospasm. METHODS: Description of the clinical course of one patient with nonaneurysmal perimesencephalic SAH who required intraarterial infusion of calcium antagonists and transluminal balloon angioplasty for treatment of symptomatic vasospasm. The perimesencephalic clot burden was quantified to determine if there is a relationship with the development of symptomatic vasospasm. RESULTS: Despite maximized clinical management, the patient described in this report developed vasospasm and delayed cerebral ischemia (DCI), requiring multiple endovascular interventions. The volumetric quantification of subarachnoid blood was 15.4 ml, and was mostly localized in the cisternal space. CONCLUSIONS: Nonaneurysmal perimesencephalic SAH may have a "malignant" course requiring close neurocritical care monitoring and multiple clinical and endovascular interventions. Moreover, large cisternal hemorrhage was correlated with the development of DCI in this patient with non-aneurysmal SAH.

Cerebellopontine cistern: microanatomy applied to vestibular schwannomas.

The microanatomy of the cerebellopontine cistern (CPC) is of interest to many surgeons and has been the subject of controversial works especially concerning the study of the subarachnoid space in the internal acoustic meatus (IAM). The CPC lies in the cerebellopontine angle between the brainstem, cerebellum and petrous bone. It contains in its upper part the trigeminal nerve with the superior petrosal vein. The cochleovestibulofacial bundle occupies the middle portion and lies between the pontomedullary sulcus and the IAM. The glossopharyngeal, vagus and accessory nerves are located in the inferior part of the cerebellopontine angle close to the vertebral artery and the posteroinferior cerebellar artery. The acousticofacial cistern is a lateral extension of the CPC in the IAM. The anatomy of the meningeal layers within the IAM is discussed especially concerning 'the arachnoidal cleavage plane' in acoustic neuroma surgery.

Inhibitory effects of eicosapentaenoic acid on chronic cerebral vasospasm after subarachnoid hemorrhage: possible involvement of a sphingosylphosphorylcholine-rho-kinase pathway.

BACKGROUND AND PURPOSE: Rho-kinase (ROK)-mediated Ca2+ sensitization of vascular smooth muscle (VSM) contraction plays a pivotal role in cerebral vasospasm (CV). We previously demonstrated that sphingosylphosphorylcholine (SPC) induces Ca2+ sensitization through sequential activation of the Src family protein tyrosine kinases (Src-PTKs) and ROK in vitro, and that Ca2+ sensitization is inhibited by eicosapentaenoic acid (EPA) through the selective inactivation of Src-PTK. In this study, we examined whether SPC induced CV in vivo, and, if it did, whether EPA would inhibit CV, as induced by SPC or in an in vivo model of subarachnoid hemorrhage (SAH). METHODS: Changes in the diameter of the canine basilar artery were investigated by angiography after administering SPC into the cisterna magna. Then, Y27632, a specific Rho-kinase inhibitor, or EPA was injected intracisternally and the effects of both agents were investigated. In another experiment using a single-hemorrhage model, Y27632 or EPA was injected on day 7 after SAH and the changes in the diameter of the canine basilar artery were investigated. RESULTS: At cerebrospinal fluid concentrations of 100 and 300 micromol/l, SPC induced severe vasoconstriction (maximum vasoconstriction by SPC (100 micromol/l): 61.8 +/- 8.2%), which was markedly reversed by Y27632 (96.3 +/- 4.4%) or EPA (92.6 +/- 12.8%). SAH caused severe vasospasm on day 7 (67.6 +/- 7.8%), which was significantly blocked by Y27632 (95.5 +/- 10.6%) or EPA (90.0 +/- 4.4%). CONCLUSIONS: SPC is a novel mediator of ROK-induced CV in vivo. The inhibition of CV induced by SPC or after SAH by EPA suggests beneficial roles of EPA in the treatment of CV. Our findings are compatible with the notion that the SPC-ROK pathway may be involved in CV.

Surgical anatomy and landmarks for the basal vein of rosenthal.

OBJECT: The basal vein of Rosenthal (BV) courses from the premesencephalic cistern, through the ambient cistern, and terminates in the quadrigeminal cistern. The aim of this study was to describe and quantitate the surgical anatomy of this structure and specifically to provide landmarks for identifying this vessel along its course. These data may be of use, for example, to surgeons using subtemporal operative approaches through regions where this vessel is concealed. METHODS: The authors examined 15 latex-injected adult cadaveric brains (30 sides) to delineate the morphological characteristics of the BV. Dissections of the BV were then performed and measurements were made between this structure and the tentorial incisura at the anterior, middle, and posterior borders of the lateral midbrain. All specimens were found to have a left and right BV with varying morphological characteristics. The mean distance between the BV and posterior cerebral artery at the midpoint of the lateral midbrain was 16 mm. The BV was always found superomedial to the posterior cerebral artery along the lateral aspect of the midbrain, and the BV ranged in diameter from 1 to 5 mm. The BV drained into the vein of Galen in all but two specimens. The mean distances from the tentorial edge to the BV at the anterior, middle, and posterior borders of the lateral midbrain were 11, 1 3, and 4 mm, respectively. No statistically significant differences were found when comparing left and right sides or male and female specimens. CONCLUSIONS: The authors hope that these data will help the neurosurgeon operating near the BV to avoid injury to this important structure.

Description of endoscopic ventricular anatomy in myelomeningocele.

OBJECTIVE: The purpose of this work is to present our endoscopic neuroanatomical findings of a series of myelomeningocele and hydrocephalus patients, treated with endoscopic third ventricular cisternostomy (ETVC), in order to describe ventricular configuration abnormalities in this group of patients, in which this neurosurgical procedure has limited performance. METHOD: We checked the videos of 10 endoscopic third ventricular cisternostomies of myelomeningocele patients taken during 24 months as from December 1998. A previous guideline is designed to record anatomic variables in the lateral ventricles, IIIrd ventricle, and basal cisterns. The topic is analyzed in view of the necropsy and imaging background data. RESULTS: The ETVC of lateral ventricles showed: absence of septum (9/10); absence of anteroseptal vein (8/10); absence of choroid plexus and thalamostriate vein (0/10); absence of fornix (1/10): small foramen of Monro (4/10). The ETVC of the IIIrd ventricle showed: impossibility of recognizing any mammillary bodies (4/10); presence of septations (5/10); presence of atypical veins in the floor (6/10); translucent floor (5/10); floor umbilications (5/10); absence of infundibulum (4/10); arachnoid adherences (7/10); and visual contact of basilar artery (4/10). CONCLUSION: There are categorical structural alterations in the ventricular system of myelomeningocele patients that are well correlated with previous necropsy and imaging reports. The ventricular system of dysraphic children presents severe anatomic alterations, which alter the reference points of the classical endoscopic third ventricular cisternostomy.

[Microanatomical study of the choroidal fissure in ventricular and cisternal approaches]. / Estudo microanatômico da fissura coroidéia na abordagem dos ventrículos e cisternas cerebrais.

The choroidal fissure is a narrow cleft in the medial part of the lateral ventricle, in a C-shaped arc, between the fornix and the thalamus, where the choroidal plexus join. Due to absence nervous tissue between ependyma and pia-mater along this invagination, it is an important route in brain ventricles and cisterns. Five brains were studied by injecting colored silicone arteries and veins and five brains without colored silicone, in a total number of 20 brain hemispheres. It was analyzed and revised the neural, arterial and venous relationships and surgical approaches in all parts of the choroidal fissure. In conclusion, the previous knowledge detailed this microanatomy is primordial for neurosurgeons that will approach brain ventricular and cisternal lesions because the neurosurgeons gain a tridimensional notion that will be indispensable during surgery.

Estudo microanatômico da fissura coroidéia na abordagem dos ventrículos e cisternas cerebrais / Microanatomical study of the choroidal fissure in ventricular and cisternal approaches

The choroidal fissure is a narrow cleft in the medial part of the lateral ventricle, in a C-shaped arc, between the fornix and the thalamus, where the choroidal plexus join. Due to absence nervous tissue between ependyma and pia-mater along this invagination, it is an important route in brain ventricles and cisterns. Five brains were studied by injecting colored silicone arteries and veins and five brains without colored silicone, in a total number of 20 brain hemispheres. It was analyzed and revised the neural, arterial and venous relationships and surgical approaches in all parts of the choroidal fissure. In conclusion, the previous knowledge detailed this microanatomy is primordial for neurosurgeons that will approach brain ventricular and cisternal lesions because the neurosurgeons gain a tridimensional notion that will be indispensable during surgery.

A fissura coroidéia é uma estreita fenda situada na parte medial dos ventrículos laterais, em formato de "C", entre o fórnix e o tálamo e onde o plexo coróide se adere. O fato de não haver tecido nervoso entre o epêndima e a pia-máter ao longo deste acidente anatômico torna-o uma importante via no acesso aos ventrículos e cisternas cerebrais. Foram estudados cinco cérebros, injetando-se artérias e veias com material siliconado colorido e cinco cérebros sem realce colorido dos vasos, num total de 20 hemisférios cerebrais. Foram analisadas e revisadas as relações neurais, arteriais e venosas, bem como as abordagens cirúrgicas em cada parte da fissura coroidéia. Concluiu-se que o conhecimento prévio detalhado desta microanatomia é fundamental para os neurocirurgiões que vão abordar lesões nos ventrículos e cisternas cerebrais, pois se obtém uma noção tridimensional que será indispensável durante o ato cirúrgico.

Visualization of the intracisternal angioarchitecture at the posterior fossa by use of image fusion.

OBJECTIVE: Magnetic resonance (MR) images most clearly visualize intracranial tissues but have some limitations in terms of detailed analysis of the intracisternal vasculature. To compensate for these shortcomings, an image fusion of three-dimensional digital subtraction angiography (DSA) and MR images, DSA-MR fusion, has been developed. The goal of this study was to evaluate the usefulness of DSA-MR fusion for the visualization of the intracisternal arteries and veins at the posterior fossa. METHODS: Ten consecutive patients (five with neurovascular compression syndrome and five with brain tumors) underwent preoperative DSA-MR fusion. The DSA-MR fusion images were compared with intraoperative findings. RESULTS: Image fusion was performed within 20 minutes, and the registration error was insignificant in all cases. Image fusion successfully visualized the clear three-dimensional relationships among the intracisternal arteries and veins, cranial nerves, brain tissues, and a lesion, and a specific vessel was easily identified. The findings of the DSA-MR fusion images were surgically confirmed in all patients. CONCLUSION: Using this advanced image fusion technique coupled with its reasonable postprocessing time, neurosurgeons may more easily and precisely understand the surgical anatomy before surgery than analyzing three-dimensional DSA and MR images separately.

Milrinone reduces cerebral vasospasm after subarachnoid hemorrhage of WFNS grade IV or V.

The preventative effect of cisternal irrigation with milrinone against vasospasm was evaluated in 12 patients with subarachnoid hemorrhage (SAH) of World Federation of Neurosurgical Societies grade IV or V treated between September 1999 and September 2000. All aneurysms were clipped or embolized within 72 hours of the onset of SAH. Inlet and outlet tubes were placed in either the supratentorial cisternal space, lateral ventricle, or spinal subarachnoid space. Lactated Ringer solution containing urokinase (120 IU/ml), ascorbic acid (3.5 mg/ml), and milrinone (3.6 microg/ml) was continuously infused at 30 ml/hr for as long as 2 weeks. Angiographical vasospasm was detected in only two of the 11 patients who received milrinone irrigation and underwent postoperative angiography. Vasospasm may have resulted from irrigation obstruction associated with pneumocephalus in one patient and clot in the sylvian fissure in the other patient. The outcome of the milrinone irrigation therapy was significantly better than that of the conventional therapy. This study suggests that cisternal irrigation with milrinone is safe and effective, and reduces the occurrence of vasospasm in patients with poor grade aneurysmal SAH.

Effect of hypertension on the integrity of blood brain and blood CSF barriers, cerebral blood flow and CSF secretion in the rat.

Hypertension has been related to the development of brain damage, dementia and other CNS dysfunctions. Disruption of the blood-brain barrier (BBB) is thought to contribute to these disorders. In this study, the integrity of both blood-brain and blood-CSF barriers during chronic hypertension was investigated. For this, the entry of [14C]sucrose and of lanthanum into brain tissue, choroid plexus, and CSF was studied. Also brain regional blood flow and brain [14C]sucrose volume of distribution were measured using indicator fractionation and ventriculo-cisternal perfusion methods, respectively. The above measurements were performed in normotensive (WKY) rats and in the spontaneously hypertensive rats (SHR). Choroid plexus and CSF uptakes of [14C]sucrose were found to be significantly greater in SHR compared to WKY rats (P<0.05). Intercellular entry of lanthanum was observed in choroidal tissue of SHR but not in that of WKY rats and at the BBB. Choroid plexus blood flow was significantly greater in SHR, 2.82+/-0.21 ml g(-1) min(-1), compared to 2.4+/-0.08 ml g(-1) min(-1) in WKY (P<0.05). There were no significant differences (P>0.05) in brain % water content and extracellular fluid [14C]sucrose volume of distribution between SHR and WKY rats. However, choroid plexus showed greater % water content in SHR (85.7+/-1.9%) compared to the WKY rats (81.5+/-1.7%). These results suggest that chronic hypertension in SHR may cause more pronounced defects in the integrity of the blood-CSF barrier than in the BBB.

Effects of cerebrospinal fluid acidity on cerebral blood flow and autoregulation in rats.

Using a ventriculocisternal perfusion method, the effects of cerebrospinal fluid (CSF) acidity of nonrespiratory origin on cerebral blood flow (CBF) and autoregulation of CBF were investigated. Three groups (six rats each) were studied: one group of sham operated rats, one control group with ventriculocisternal perfusion at normal pH (mean inflow pH +/- SD, 7.42 +/- 0.02), and one experimental group with ventriculocisternal perfusion at low pH (mean inflow pH +/- SD, 6.81 +/- 0.01). CBF was measured by the intracarotid xenon 133 method. Autoregulation was studied by repetitive measurements of CBF during an initial increase and then stepwise reduction of mean arterial blood pressure (MABP). No difference in CBF was found between sham operated and control rats with unperturbed pH (mean cisternal outflow pH +/- SD, 7.42 +/- 0.03) of CSF), and autoregulation was intact in both groups. In the experimental group, the mean CBF +/- SD was increased by 58%, from 127 +/- 33 mL/(100 g.min) before ventriculocisternal perfusion to 201 +/- 54 mL/(100 g.min) (P <.00001) during perfusion with acid CSF (mean cisternal outflow pH +/- SD, 7.23 +/- 0.04). In this group, the relationship between CBF and MABP was linear, thus indicating disrupted autoregulation. In conclusion, CSF acidity significantly increases CBF and impairs autoregulation of CBF.

Hypervascular intracisternal acoustic neuroma.

The diagnosis of acoustic neuroma is usually evoked in a patient presenting with a long history of hearing disturbance in whom an enhancing lesion within the internal auditory canal and/or the cerebellopontine angle is found on MRI. Hypervascularity with arteriovenous shunting and early filling of enlarged veins is a common feature of malignancy and has been reported very rarely in benign acoustic neuroma. We present the case of a patient without hearing disturbance, who showed a highly vascular lesion with no component in the internal auditory canal, making the preoperative diagnosis of acoustic neuroma very challenging. We discuss here the intracisternal site of origin and hypervascularity of acoustic neuroma, and also the differential diagnoses and management of such tumors.

[Radiosurgery of choroidal and cisternal cerebral arteriovenous malformations]. / Radiochirurgie des malformations artério-veineuses cérébrales choroïdiennes et cisternales.

PURPOSE: Cerebral arteriovenous malformations surrounded by cerebrospinal fluid seemed to exhibit worse response to radiosurgery than others. We searched to verify if this is was true and to find causes. MATERIAL: and methods. From our series of 705 patients with cerebral arteriovenous malformations treated by radiosurgery, 3,8% (27/705) had choroidal or cisternal arteriovenous malformations. Revelation mode was hemorrhage in 86% of cases but sometimes headaches occurred before hemorrhage; thus overall hemorrhage rate was 96%. Mean age of revelation was 24. Mean size was 20 mm, mean volume was 4 cc. Spetzler & Martin's grades were 35% in grade II, 43% in grade III and 22% in grade IV. Location was ventricular in 63% of cases and cisternal in 37%. Mean dose at reference isodose was 24 Gy with a higher rate of monoisocenters. We looked for differences between this population of arteriovenous malformations and the rest of the series for patients, treatments prior radiosurgery, cerebral arteriovenous malformations's characteristics, dosimetric parameters and complications. Statistical analysis was done with a Pearson chi2 test and Spearman non parametric correlation test. RESULTS: Obiteration rate was 47.6% with a mean delay of 26 months. Differential characteristics of choroidal or cisternal arteriovenous malformations were: younger age of revelation, higher frequency of hemorrhage, of intra or paranidal aneurysms, of deep unique drainage, a higher Spetzler grade and a smaller rate of complete recovering. Mortality and clinical morbidity due to radiosurgery were 0%. Actuarial rate of hemorrhage after radiosurgery was 4,34% per year and per patient or per hemorrhage. This rate was higher than in the global series. Parenchymal changes seen on MRI were less frequent (26,6%) and less serious (no grade 4 radionecrosis-like parenchymal changes). CONCLUSION: Choroidal or cisternal arteriovenous malformations seem to respond less to radiosurgery than others. One potential explanation is the higher frequency of multiafferences of these arteriovenous malformations with anastomoses of anterior and posterior choroidal arteries. However, radiosurgery still stay a treatment of choice for these arteriovenous malformations with little adaptations of the irradiation strategy.

Expression of inducible nitric oxide synthase in rats following subarachnoid hemorrhage.

The possible expression of the inducible isoform of nitric oxide synthase (iNOS) was examined in a rat model of subarachnoid hemorrhage (SAH). Subarachnoid hemorrhage was induced by the injection of autologous blood into the cisterna magna using stereotactic technique under general anesthesia. The rats were then killed at specific time intervals between 4 hours to 7 days after SAH. Reverse-transcriptional polymerase chain reaction (RT-PCR) revealed the expression of iNOS mRNA in the homogenate obtained from the tissue around the circle of Willis one day after SAH (Day 1). No iNOS mRNA was detected either in the sham-operated animals, or at any of the other time intervals after SAH. An immunohistochemical study was performed to examine the localization of iNOS-positive cells in the central nervous system. Inducible NOS immunoreactivity was thus observed in the mononuclear cells and polymorphonuclear cells infiltrating into the subarachnoid space of the basal cistern on Day 1. This immunoreactivity persisted faintly on Day 2, but had completely disappeared on Day 7. A vascular diameter study disclosed a vasoconstrictive change in the middle cerebral artery after SAH. Taken together, these results are thus considered to confirm the expression of iNOS in the infiltrated inflammatory cells after the insult of SAH, which may therefore play an introductory role in the development of the pathological series of events after SAH, including vasospasm.

Nimodipine does not increase cerebral blood flow during subarachnoid hemorrhage in the rat.

The purpose of this study was to determine the effects of nimodipine, a calcium antagonist, on regional cerebral blood flow (CBF) in experimental subarachnoid hemorrhage (SAH) rats. Regional CBF was measured by the radioactive microspheres method. Experimental SAH was induced by a single injection of autologous arterial blood (0.3 ml) into the cisterna magna in anesthetized rats. Rats subjected to SAH showed an immediate and marked reduction of CBF in all brain regions throughout the experimental period. The infusion of nimodipine (1 microgram/kg/min) was started 30 min before the induction of the experimental SAH and continued during the experiments. Nimodipine did not prevent the reduction of regional CBF after SAH. It is concluded that nimodipine only increases regional CBF in normal animals, but dose not affect the reduction of CBF after experimental SAH.

The neurovascular relationships and the blood supply of the trochlear nerve: surgical anatomy of its cisternal segment.

We examined in detail the cisternal segments of 15 trochlear nerves in brain stems injected with India ink and fixed in formalin. The nerves were found to emerge as singular trunks (33.3%), singular trunks with accessory rootlets (13.3%), or two or three roots with (26.7%) or without accessory rootlets (26.7%). The nerves were in close relationship or in contact with the superior cerebellar artery, that is, with the main trunk of the superior cerebellar artery, its medial and lateral terminal stems, the accessory superior cerebellar artery, and the vermian, paravermian, collicular, and lateral hemispheric arteries as well as their small branches. Some of these vessels were connected by anastomoses in 86.7% of the cases. The anastomotic channels varied from 40 to 530 microns in diameter. The cisternal segment of each trochlear nerve was usually supplied by a single long artery, which most often arose from the vermian artery (26.7%) or the collicular artery (26.7%). The feeding vessel ranged from 30 to 80 microns in caliber. We discuss the possible clinical significance of the anatomic data observed in the present study.

The neurovascular relationships and the blood supply of the abducent nerve: surgical anatomy of its cisternal segment.

Twenty-eight abducent nerves were examined after injecting india ink and gelatin into the vertebrobasilar arterial system. All the abducent nerves were found to be crossed and/or penetrated by the surrounding vessels. The ventral surface of the nerves was crossed by the anterior inferior cerebellar artery (AICA) (75.0%), the posterior inferior cerebellar artery (17.85%), the common trunk of the AICA and posterior inferior cerebellar artery (7.14%), the internal auditory artery (14.28%), the anterolateral artery (46.43%), the pontomedullary artery (92.86%), and the corresponding veins (46.43%). The dorsal surface of the cisternal segment was crossed by the AICA (35.71%), the inferolateral pontine artery (10.71%), the anterolateral artery (82.14%), and the certain veins (46.43%). Sixty-four percent of the cisternal segments were penetrated by one or more of the following vessels: the AICA (25.0%), the anterolateral artery (17.86%), the pontomedullary artery (3.57%), and/or by the corresponding veins (42.86%). The majority of the cisternal segments of the abducent nerves were supplied by the anterolateral arteries (85.71%), and only some of them by the AICA (14.29%) or the pontomedullary artery (7.14%). The authors discuss the possible clinical significance of the anatomical data.

Neuropeptide investigations with an ovine surgical model.

An ovine surgical model for peptide investigations is presented. Techniques for exteriorization of the carotid artery, catheterization of the sagittal sinus, hypophysectomy via a transnasopharyngeal approach, and ventricular and cisternal cannulation in the sheep are employed within the model. Several experimental applications in neurosurgical research are presented.