Induction of Leptomeningeal Cells Modification Via Intracisternal Injection.

The protocol outlined here describes how to safely and manually inject solutions through the cisterna magna while eliminating the risk of damage to the underlying parenchyma. Previously published protocols recommend using straight needles that should be lowered to a maximum of 1-2 mm from the dural surface. The sudden drop in resistance once the dural membrane has been punctured makes it difficult to maintain the needle in a steady position. Our method, instead, employs a needle bent at the tip that can be stabilized against the occipital bone of the skull, thus preventing the syringe from penetrating into the tissue after perforation of the dural membrane. The procedure is straightforward, reproducible, and does not cause long-lasting discomfort in the operated animals. We describe the intracisternal injection strategy in the context of genetic fate mapping of vascular leptomeningeal cells. The same technique can, furthermore, be utilized to address a wide range of research questions, such as probing the role of leptomeninges in neurodevelopment and the spreading of bacterial meningitis, through genetic ablation of genes putatively implicated in these phenomena. Additionally, the procedure can be combined with an automatized infusion system for a constant delivery and used for tracking cerebrospinal fluid movement via injection of fluorescently labelled molecules.

Lymphatic outflow of cerebrospinal fluid is reduced in glioma.

Glioblastoma is a malignant brain tumor with mean overall survival of less than 15 months. Blood vessel leakage and peritumoral edema lead to increased intracranial pressure and augment neurological deficits which profoundly decrease the quality of life of glioblastoma patients. It is unknown how the dynamics of cerebrospinal fluid (CSF) turnover are affected during this process. By monitoring the transport of CSF tracers to the systemic blood circulation after infusion into the cisterna magna, we demonstrate that the outflow of CSF is dramatically reduced in glioma-bearing mice. Using a combination of magnetic resonance imaging (MRI) and near-infrared (NIR) imaging, we found that the circulation of CSF tracers was hindered after cisterna magna injection with reduced signals along the exiting cranial nerves and downstream lymph nodes, which represent the major CSF outflow route in mice. Due to blockage of the normal routes of CSF bulk flow within and from the cranial cavity, CSF tracers were redirected into the spinal space. In some mice, impaired CSF clearance from the cranium was compensated by a lymphatic outflow from the sacral spine.

Single amyloid-beta injection exacerbates 4-aminopyridine-induced seizures and changes synaptic coupling in the hippocampus.

Accumulation of amyloid-beta (Aß) in temporal lobe structures, including the hippocampus, is related to a variety of Alzheimer's disease symptoms and seems to be involved in the induction of neural network hyperexcitability and even seizures. Still, a direct evaluation of the pro-epileptogenic effects of Aß in vivo, and of the underlying mechanisms, is missing. Thus, we tested whether the intracisternal injection of Aß modulates 4-aminopyridine (4AP)-induced epileptiform activity, hippocampal network function, and its synaptic coupling. When tested 3 weeks after its administration, Aß (but not its vehicle) reduces the latency for 4AP-induced seizures, increases the number of generalized seizures, exacerbates the time to fully recover from seizures, and favors seizure-induced death. These pro-epileptogenic effects of Aß correlate with a reduction in the power of the spontaneous hippocampal network activity, involving all frequency bands in vivo and only the theta band (4-10 Hz) in vitro. The pro-epileptogenic effects of Aß also correlate with a reduction of the Schaffer-collateral CA1 synaptic coupling in vitro, which is exacerbated by the sequential bath application of 4-AP and Aß. In summary, Aß produces long-lasting pro-epileptic effects that can be due to alterations in the hippocampal circuit, impacting its coordinated network activity and its synaptic efficiency. It is likely that normalizing synaptic coupling and/or coordinated neural network activity (i.e., theta activity) may contribute not only to improve cognitive function in Alzheimer's disease but also to avoid hyperexcitation in conditions of amyloidosis.

Differential Diagnoses and Their Implications of Dandy-Walker Malformation or Isolated Cisterna Magna, a Case Study: Baby V.

We explore the outcome of a fetus with a posterior fossa abnormality thought to be a Dandy-Walker malformation based on prenatal ultrasound imaging. The infant was later diagnosed by magnetic resonance imaging (MRI) as having an isolated cisterna magna. When assessing brain abnormalities, there is increased accuracy of prenatal MRI versus prenatal ultrasound. Accurate diagnosis of an infant is paramount so that an inheritance pattern, risk of recurrence, involvement of other systems, and a prognosis can be determined. Communicating with the family and supporting them with the correct information is then enhanced. It should be standard protocol to obtain a fetal MRI if an abnormal prenatal ultrasound of the brain is detected. Further research is needed to assess the accuracy of using MRI versus ultrasonography prenatally to diagnose posterior brain abnormalities.

Uncovering the Forgotten Effect of Superior Cervical Ganglia on Pupil Diameter in Subarachnoid Hemorrhage: An Experimental Study.

AIM: To investigate the relationship between neuron density of the superior cervical sympathetic ganglia and pupil diameter in subarachnoid hemorrhage. MATERIAL AND METHODS: This study was conducted on 22 rabbits; 5 for the baseline control group, 5 for the SHAM group and 12 for the study group. Pupil diameters were measured via sunlight and ocular tomography on day 1 as the control values. Pupil diameters were re-measured after injecting 0.5 cc saline to the SHAM group, and autologous arterial blood into the cisterna magna of the study group. After 3 weeks, the brain, superior cervical sympathetic ganglia and ciliary ganglia were extracted with peripheral tissues bilaterally and examined histopathologically. Pupil diameters were compared with neuron densities of the sympathetic ganglia and ciliary ganglia which were examined using stereological methods. RESULTS: Baseline values were; normal pupil diameter 7.180±620 ?m and mean neuron density of the superior cervical sympathetic ganglia 6.321±510/mm3, degenerated neuron density of ciliary ganglia was 5±2/mm3 after histopathological examination in the control group. These values were measured as 6.850±578 ?m, 5.950±340/mm3 and 123±39/mm3 in the SHAM group and 9.910±840 ?m, 7.950±764/mm3 and 650±98/mm3 in the study group. A linear relationship was determined between neuron density of the superior cervical sympathetic ganglia and pupil diameters (p < 0.005). Degenerated ciliary ganglia neuron density had an inverse effect on pupil diameters in all groups (p < 0.0001). CONCLUSION: Highly degenerated neuron density of the ciliary ganglion is not responsible for pupil dilatation owing to parasympathetic pupilloconstrictor palsy, but high neuron density of the pupillodilatatory superior cervical sympathetic ganglia should be considered an important factor for pupil dilatation.

Quadrigeminal cisterna lipoma: report of two cases and literature review / Lipoma da cisterna quadrigeminal: relato de dois casos e revisão da literatura

Intracranial lipomas are congenital, benign and slow-growing tumors. The incidence were 0.1 to 0.5 percent of all primary brain tumors and are often diagnosed in incidental findings of neuroradiological investigation. Lipoma in quadrigeminal region occurs in 25 percent of intracranial lipomas and has been reported as lipomas in quadrigeminal cistern (perimesencephalic cistern), quadrigeminal plate, ambiens cistern or superior medullary velum. MRI is the most major exam. The treatment is conservative in most cases, surgical removal is hampered by their deep location and contiguous with adjacent neurovascular structures. The authors report two cases of lipoma in the quadrigeminal region, incidental findings and discuss the clinical findings, neuroimaging and treatment.

Lipomas intracranianos são tumores congênito, benigno e de crescimento lento. Sua incidência é de 0.1 a 0.5 por cento de todos os tumores cerebrais primários e são frequentemente diagnosticados em achados incidental de investigação neuroradiológica. Lipoma na região quadrigeminal ocorre em 25 por cento dos lipomas intracranianos e tem sido relatados como lipomas na cisterna quadrigeminal (cisterna perimesencefálica), placa quadrigeminal, cisterna ambiens ou véu medular superior. O exame de eleição é ressonância magnética. O tratamento é conservador na maioria dos casos, a remoção cirúrgica é dificultada pela sua localização profunda e da contiguidade com estruturas neurovasculares adjacentes. Os autores relatam dois casos de lipoma na região quadrigeminal achados incidentalmente e discutem os achados clínicos, imagem e tratamento.

CSF flow pathways through the ventricle-cistern interfaces in kaolin-induced hydrocephalus rats-laboratory investigation.

PURPOSE: The goal of this study was to identify direct cerebrospinal fluid (CSF) pathways in the interface between ventricles and cisterns. Such routes are hypothesized to be involved in alternative CSF flows in abnormal circumstances of CSF circulation. METHODS: Chronic obstructive hydrocephalus models were induced in ten Sprague-Dawley rats with kaolin injection into the cisterna magna. Three weeks after the kaolin injection, when thick arachnoid fibrosis obliterated the fourth ventricular outlets, cationized ferritin was stereotactically infused as a tracer into the lateral ventricle in order to observe the pathways from the ventricles to the subarachnoid space. Animals were killed in 48 h and brains were sectioned. CSF flow pathways were traced by the staining of ferritin with ferrocyanide. RESULTS: Eight out of ten rats developed hydrocephalus. The subarachnoid membranes of the convexity and basal cisterns were severely adhered such that most of the ferritin remained in the ventricles whereas basal and convexity cisterns were clear of ferritin. In six out of the eight hydrocephalus rats, ferritin leaked from the third ventricle into the quadrigeminal cistern, and from the lateral ventricle into the ambient cistern. CONCLUSIONS: The interfaces between the third ventricle and the quadrigeminal cistern, and between the lateral ventricle and the ambient cistern appear to be alternative CSF pathways in a pathologic condition such as obstructive hydrocephalus.

Experimental subarachnoid hemorrhage: double cisterna magna injection rat model--assessment of delayed pathological effects of cerebral vasospasm.

Aneurysmal subarachnoid hemorrhage comprises of an early phase after the bleeding and a late phase of delayed consequences of the bleeding. The development of delayed injury mechanisms, like the reduction of cerebral blood flow (CBF) due to cerebral vasospasm (CVS), seems mainly to depend on the amount and the duration of the subarachnoid blood clot. The reduction of CBF may lead to cerebral ischemia and delayed neurological deterioration. The rat double cisterna magna injection model reproduces the time course of the delayed consequences of CVS and imitates the clinical setting more precise than other rodent subarachnoid hemorrhage models. Therefore, the rat double cisterna magna injection model seems to be predisposed to be used to mimick the delayed consequences of subarachnoid hemorrhage. We reviewed the existing literature on this animal model and propose a standard protocol including technical considerations, as well as advantages and limitations of this model.

Intracisternal cyclodextrin prevents cerebellar dysfunction and Purkinje cell death in feline Niemann-Pick type C1 disease.

Niemann-Pick type C1 (NPC) disease is a lysosomal storage disease caused by mutations in the NPC1 gene, leading to an increase in unesterified cholesterol and several sphingolipids, and resulting in hepatic disease and progressive neurological disease. We show that subcutaneous administration of the pharmaceutical excipient 2-hydroxypropyl-ß-cyclodextrin (HPßCD) to cats with NPC disease ameliorated hepatic disease, but doses sufficient to reduce neurological disease resulted in pulmonary toxicity. However, direct administration of HPßCD into the cisterna magna of presymptomatic cats with NPC disease prevented the onset of cerebellar dysfunction for greater than a year and resulted in a reduction in Purkinje cell loss and near-normal concentrations of cholesterol and sphingolipids. Moreover, administration of intracisternal HPßCD to NPC cats with ongoing cerebellar dysfunction slowed disease progression, increased survival time, and decreased the accumulation of brain gangliosides. An increase in hearing threshold was identified as a potential adverse effect. These studies in a feline animal model have provided critical data on efficacy and safety of drug administration directly into the central nervous system that will be important for advancing HPßCD into clinical trials.

Rat cisterna magna double-injection model of subarachnoid hemorrhage - background, advantages/limitations, technical considerations, modifications, and outcome measures.

The pathophysiological changes following aneurysmal subarachnoid hemorrhage (SAH) are commonly divided into early consequences (developing shortly after the bleeding) and delayed consequences of the bleeding. The development of delayed injury mechanisms, e.g., reduced cerebral blood flow (CBF) caused by cerebral vasospasm (CVS) or development of delayed ischemic neurological deficits (DIND), seem mainly to depend on the amount and duration of the subarachnoid blood clot. CVS may progress to cerebral ischemia and infarction, and therefore lead to delayed neurological deterioration. The rat double-hemorrhage model reproduces the time course of the delayed pathophysiological consequences of CVS, which imitates the clinical setting more precisely than other rodent models. Furthermore, this model is adjustable via various technical considerations or modifications. Therefore, the double-hemorrhage model is predisposed to be used to mimic the delayed effects of SAH and to investigate the use of drugs on morphological ischemic, functional, and vasospastic effects.

A rabbit cisterna magna double-injection subarachnoid hemorrhage model.

In recent years, the shift of research interest in the pathological condition after subarachnoid hemorrhage (SAH) from delayed cerebral vasospasm to early brain injury and the development of molecular genetic approaches in animal experiments has resulted in a diversification of animal SAH models. The properties of each animal SAH model thus need to be validated and the purpose of using each animal model should be clarified. This study presents the settings and technical procedures for a rabbit cisterna magna double-injection SAH model and discusses the advantages and limitations of using this model.

The rabbit blood shunt subarachnoid haemorrhage model.

The recently introduced rabbit blood shunt subarachnoid haemorrhage model is based on the two standard procedures of subclavian artery cannulation and transcutaneous cisterna magna puncture. An extracorporeal shunt placed in between the arterial system and the subarachnoid space allows examiner-independent SAH in a closed cranium. Despite its straightforwardness, it is worth examining some specific features and characteristics of the model. We outline technical considerations to successfully perform the model with minimal mortality and morbidity. In addition, we discuss outcome measures, advantages and limitations, and the applicability of the model for the study of early brain injury and delayed cerebral vasospasm after SAH.

The single and double blood injection rabbit subarachnoid hemorrhage model.

Over the past 30 years, the rabbit subarachnoid hemorrhage model (SAH) has been used for investigating the post-hemorrhage pathology, especially with respect to understanding of the mechanisms of cerebral vasospasm. However, the molecular mechanisms of cerebral vasospasm remain to be elucidated. Furthermore, it is not clear whether the rabbit SAH model is suitable for the investigation of pathological conditions other than cerebral vasospasm, such as early brain injury. Therefore, the properties of the rabbit SAH model need to be validated, and the reasons for using the rabbit should be clarified. This review explores the settings and technical issues of establishing a rabbit cisterna magna single and double blood injection SAH model and discusses the characteristics and feasibilities of the models.

Matricellular protein: a new player in cerebral vasospasm following subarachnoid hemorrhage.

INTRODUCTION: Matricellular protein (MCP) is a class of nonstructural and secreted extracellular matrix proteins that exert diverse functions, but its role in vascular smooth muscle contraction has not been investigated. MATERIAL AND METHODS: First, rat subarachnoid hemorrhage (SAH) models were produced by endovascular perforation and examined for tenascin-C (TNC) and osteopontin (OPN) induction (representatives of MCPs) in vasospastic cerebral arteries using immunostaining. Second, recombinant TNC (r-TNC), recombinant OPN (r-OPN), or both were injected into a cisterna magna in healthy rats, and the effects on the diameter of basilar arteries were determined using India ink angiography. RESULTS: In SAH rats, TNC immunoreactivity was markedly induced in the smooth muscle cell layers of spastic cerebral arteries on day 1 but not in control animals. The TNC immunoreactivity decreased on day 3 as vasospasm improved: OPN immunoreactivity, on the other hand, was more induced in the arterial wall on day 3. r-TNC injections caused prolonged contractions of rat basilar arteries, which were reversed by r-OPN, although r-OPN itself had no effect on the vessel diameter. CONCLUSIONS: MCPs, including TNC and OPN, may contribute to the pathophysiology of cerebral vasospasm and provide a novel therapeutic approach against it.

Nimodipine attenuation of early brain dysfunctions is partially related to its inverting acute vasospasm in a cisterna magna subarachnoid hemorrhage (SAH) model in rats.

Subarachnoid hemorrhage (SAH)-induced brain injury is highly related to neurological deficits and mortality. Regional cerebral blood flow (rCBF) changes and vasoconstriction are two complications that occur soon after SAH experimentally. In this study we investigated the changes in rCBF and vertebro-basilar arterial diameter in a cisterna megna SAH model in Sprague-Dawley rats and intended to explore whether improving early rCBF reduction and cerebral vasospasm could contribute to alleviating blood-brain barrier (BBB) dysfunction. In rats for rCBF, vasospasm and BBB permeability assessments, nimodipine (NDP) or saline was administered intravenously 5 minutes after SAH. rCBF within the first 60 minutes after SAH was measured by laser Doppler flowmetry. BBB permeability indexed by Evans Blue extravasation was assessed 4 hours after SAH. Angiography for the caliber changes of the vertebro-basilar artery were conducted 30 minutes post SAH. Pronounced rCBF reduction and vasospasm were observed soon after SAH, followed by BBB permeability increment. NDP administration could improve rCBF and attenuate vasospasm, followed by the alleviation of BBB permeability. Our results demonstrate that early improvement of cerebral circulation by NDP may contribute to the reduction in brain injury indexed by BBB disruption.

Cerebrospinal fluid pathways from cisterns to ventricles in N-butyl cyanoacrylate-induced hydrocephalic rats.

OBJECT: Cerebrospinal fluid typically enters the subarachnoid space from the ventricles via the fourth ventricular foramina. However, there is clinical evidence that CSF also flows in the opposite direction. Ventricular reflux of CSF from a cistern is a well-known phenomenon in radioisotope studies in patients with normal-pressure hydrocephalus. Additionally, the presence of ventricular blood in acute subarachnoid hemorrhage is frequently observed. The goal of this investigation was to examine the potential CSF pathways from cisterns to ventricles. The authors examined pathways in rat models in which they occluded the fourth ventricular outlets and injected a tracer into the subarachnoid space. METHODS: The model for acute obstructive hydrocephalus was induced using N-butyl cyanoacrylate (NBCA) in 10 Sprague-Dawley rats. After 3 days, cationized ferritin was infused into the lumbar subarachnoid space to highlight retrograde CSF flow pathways. The animals were sacrificed at 48 hours, and the brains were prepared. The CSF flow pathway was traced by staining the ferritin with ferrocyanide. RESULTS: Ferritin was observed in the third ventricle in 7 of 8 rats with hydrocephalus and in the temporal horn of the lateral ventricles in 4 of 8 rats with hydrocephalus. There was no definite staining in the aqueduct, which suggests that the ventricular reflux originated from routes other than through the fourth ventricular outlets. CONCLUSIONS: The interfaces between the quadrigeminal cistern and third ventricle and those between the ambient cistern and lateral ventricle appear to be potential sites of CSF reflux from cisterns to ventricles in obstructive hydrocephalus.

Acute cardiorespiratory effects of intracisternal injections of mercuric chloride.

The present studies were conducted to changes arising from mercury poisoning in the central nervous system (CNS), with a focus on determining the receptors and neurotransmitters involved. Currently, little is known regarding the neurological basis of the cardiopulmonary effects of mercury poisoning. We evaluated changes in systolic arterial pressure (SAP), diastolic arterial pressure (DAP), respiratory rate (RR) and heart rate (HR) following a 5 µl intracisternal (i.c) injection of mercuric chloride (HgCl(2)) and the participation of the autonomic nervous system in these responses. 58 animals were utilized and distributed randomly into 10 groups and administered a 5 µL intracisternal injection of 0.68 µg/kg HgCl(2) (n=7), 1.2 µg/kg HgCl(2) (n=7), 2.4 µg/kg HgCl(2) (n=7), 60 µg/kg HgCl(2) (n=7), 120 µg/kg HgCl(2) (n=3), saline (control) (n=7), 60 µg/kg HgCl(2) plus prazosin (n=6), saline plus prazosin (n=6), 60 µg/kg HgCl(2) plus metilatropina (n=4) or saline plus metilatropina (n=4)HgCl(2). Anesthesia was induced with halothane and maintained as needed with urethane (1.2 g/kg) administered intravenously (i.v.) through a cannula placed in the left femoral vein. The left femoral artery was also cannulated to record systolic arterial pressure (SAP), diastolic arterial pressure (DAP) and heart rate (HR). A tracheotomy was performed to record respiratory rate. Animals were placed in a stereotaxic frame, and the cisterna magna was exposed. After a stabilization period, solutions (saline or HgCl(2)) were injected i.c., and cardiopulmonary responses were recorded for 50 min. Involvement of the autonomic nervous system was assessed through the i.v. injection of hexamethonium (20 mg/kg), prazosin (1 mg/kg) and methylatropine (1 mg/kg) 10 min before the i.c. injection of HgCl(2) or saline. Treatment with 0.68, 1.2, 2.4 µg/kg HgCl(2) or saline did not modify basal cardiorespiratory parameters, whereas the 120 µg/kg dose induced acute toxicity, provoking respiratory arrest and death. The administration of 60 µg/kg HgCl(2), however, induced significant increases (p<0.05) in SAP at the 30°, 40° and 50° min, timepoints and DAP at the 5°, 10°, 20°, 30°, 40° and 50° timepoints. RR was significantly decreased at the 5°, 10°, 20°, 40° and 50° min timepoints; however, there was no change in HR. Hexamethonium administration, which causes non-specific inhibition of the autonomic nervous system, abolished the observed cardiorespiratory effects. Similarly, prazosin, a α(1)-adrenoceptor blocker that specifically inhibits sympathetic nervous system function, abolished HgCl(2) induced increases in SAP and DAP without affecting HR and RR. Methylatropine (1 mg/Kg), a parasympathetic nervous system inhibitor, exacerbated the effects of HgCl(2) and caused slow-onset respiratory depression, culminating in respiratory arrest and death. Our results demonstrate that increases in SAP and DAP induced by the i.c. injection of mercuric chloride are mediated by activation of the sympathetic nervous system.

Developmental outcome of children with enlargement of the cisterna magna identified in utero.

An enlarged cisterna magna can be identified during routine ultrasound screening in the second half of pregnancy. It is important to be able to give an accurate prognosis. We evaluated the developmental outcome of these children. A total of 29 fetuses with a large cisterna magna identified in utero were compared to 35 children with a normal fetal ultrasound. The children were evaluated by the Gesell Developmental Schedules and the Peabody Developmental Motor Scale. The study group showed a significantly worse performance in the Gesell test. However, the overall performance for both groups was within normal limits. Four children in the study group had a borderline developmental quotient. Both groups performed similarly in the Peabody test. Walking age was significantly delayed in the study group. Children with an enlarged cisterna magna may be at risk for mild developmental delay. In cases of nonisolated enlargement of the cisterna magna, the outcome may be guarded.

New experimental model of acute aqueductal blockage in cats: effects on cerebrospinal fluid pressure and the size of brain ventricles.

It is generally assumed that cerebrospinal fluid (CSF) is secreted in the brain ventricles, and so after an acute blockage of the aqueduct of Sylvius an increase in the ventricular CSF pressure and dilation of isolated ventricles may be expected. We have tested this hypothesis in cats. After blocking the aqueduct, we measured the CSF pressure in both isolated ventricles and the cisterna magna, and performed radiographic monitoring of the cross-sectional area of the lateral ventricle. The complete aqueductal blockage was achieved by implanting a plastic cannula into the aqueduct of Sylvius through a small tunnel in the vermis of the cerebellum in the chloralose-anesthetized cats. After the reconstitution of the occipital bone, the CSF pressure was measured in the isolated ventricles via a plastic cannula implanted in the aqueduct of Sylvius and in the cisterna magna via a stainless steel cannula. During the following 2 h, the CSF pressures in the isolated ventricles and cisterna magna were identical to those in control conditions. We also monitored the ventricular cross-sectional area by means of radiography for 2 h after the aqueductal blockage and failed to observe any significant changes. When mock CSF was infused into isolated ventricles to imitate the CSF secretion, the gradient of pressure between the ventricle and cisterna magna developed, and disappeared as soon as the infusion was terminated. However, when mock CSF was infused into the cisterna magna at various rates, the resulting increased subarachnoid CSF pressure was accurately transmitted across the brain parenchyma into the CSF of isolated ventricles. The lack of the increase in the CSF pressure and ventricular dilation during 2 h of aqueductal blockage suggests that aqueductal obstruction by itself does not lead to development of hypertensive acute hydrocephalus in cats.

Severe intracranial hypertension in slit ventricle syndrome managed using a cisterna magna-ventricle-peritoneum shunt.

OBJECT: Severely increased intracranial pressure (ICP) can be life threatening in patients who had previously undergone shunt treatment but who do not experience ventricular enlargement. The authors analyzed the utility of placing shunts into the cisterna magna concurrently with ventricular shunts in patients who were not candidates for lumboperitoneal (LP) shunt placement. METHODS: Ten patients treated with cisterna magna-ventricle-peritoneum (CMVP) shunts for complex problems of shunt function were reviewed retrospectively. All patients had documented increases in ICP and ventricles that did not expand despite life-threatening increases (> 80 mm Hg in one case) in ICP. Between 1995 and 2003, 10 patients (four males and six females, age range 4-32 years) were identified as having life-threatening increases in ICP despite small or slit-like ventricles on imaging studies. Each episode was documented with intraparenchymal pressure monitoring. All patients had documented ventricular catheter failures at the time of the intervention, and all had undergone at least one previous attempt to treat the condition with a valve upgrade and replacement of the ventricular catheter. Three patients had achondroplasia, four had spina bifida, and three had a preexisting Chiari malformation Type I. All patients improved after the procedure, and none suffered permanent complications. For at least 48 hours after surgery, all patients underwent intraparenchymal monitoring of ICP (an intraparenchymal monitor was used that documented normal ICP). CONCLUSIONS: The CMVP shunts are an excellent option for patients who are not candidates for LP shunts but who have high ICP and ventricles that do not enlarge at shunt failure. The ability to access the spinal fluid in the cortical subarachnoid space presumably accounts for this success.