Triventricular Hydrocephalus Research Articles

Cerebelitis aguda en Pediatría: nuestra experiencia

IntroductionAcute cerebellitis is a rare inflammatory disease with a highly variable clinical course that ranges from benign self-limiting symptoms to a fulminant presentation associated with a high risk of death due to compression of the posterior fossa, acute hydrocephalus, and intracranial hypertension. MethodsWe reviewed clinical, laboratory, and radiological findings from children diagnosed with acute cerebellitis between May 2007 and November 2016. We analysed treatments and clinical and radiological progression. ResultsNine children met the diagnostic criteria for cerebellitis. Headache, vomiting, and drowsiness were the most frequent initial symptoms; ataxia, dysarthria, and dysmetria were the most common cerebellar signs. Cerebellitis was diagnosed with magnetic resonance imaging, which revealed cerebellar involvement (unilateral or bilateral); computerised tomography images either were normal or showed indirect signs such as triventricular hydrocephalus due to extrinsic compression of the aqueduct of Sylvius. Corticosteroids were the most commonly used treatment (6 patients). One patient required surgery due to triventricular hydrocephalus. Eight patients recovered completely, whereas the ninth displayed neurological sequelae. ConclusionsCerebellitis is a medical and surgical emergency; diagnosis requires a high level of suspicion and an emergency brain magnetic resonance imaging study. It is a clinical-radiological syndrome characterised by acute or subacute encephalopathy with intracranial hypertension and cerebellar syndrome associated with T2-weighted and FLAIR hyperintensities in the cerebellar cortex (unilaterally or bilaterally) and possible triventricular dilatation. Treatment is based on high-dose corticosteroids and may require external ventricular drain placement and decompressive surgery.

Hydrocephalus and Danty Walker Cyst, a Study of 33 Cases in Friendship Hospital Sino-Guinea of Kipe in Guinea

Malformations (or cysts) are developmental malformations in which the Cerebellar Vermis may be partially or completely absent, with resulting dilation of the 4th Ventricle forming a Cyst. It is thought that the defect arises from abnormal embryogenesis of the roof of the 4th Ventricle. A milder form is termed the Dandy-Walker Variant. This disorder may account for approximately 5% to 10% of cases of Ventriculomegaly. This study aims to reveal particular cases of Danty Walker Cases when associated with hydrocephalus, in the African context. It is a retrospective and descriptive study carried out at the Neurosurgery department of the Friendship hospital of Kipe in Guinea for 36 months, from June 2012 to August 2015. Of the 120 patients hospitalized for hydrocephalus, 32 cases have exhibited the Dandy Walker cyst. Among the 32 patients, 15 were of male and 17 were of female gender at a sex ratio (H/F) of 0.88; 1. The dominant clinical symptoms that were observed in our subjects were macrocrania (32 cases), bulging fontanelle (25 cases), sunsetting eyes (19 cases). The degree of macrocrania was noted to be minimal in 1 case only, mild in 5 cases, moderate in 8 cases, and excessive in 18 cases. Furthermore, CT scan results showed evidence of triventricular hydrocephalus in 14 cases, and tetraventricular hydrocephalus in 18 cases. The anatomical variations encountered among others were, MDW in 15 cases, DWV in 11 cases et DWC in 6 cases. The calculated Evan’s index was equal to 0.3 in 6 patients and greater than 0.3 in 26 patients. The operative techniques most commonly widely conducted were DVP (16 caes), VCS (13 cases) and DKP (3 cases). The average duration of hospitalization was 20 days with extreme range of 1 to 49 days. The post operative period was uneventful in 16 cases, clinically unchanged in 5 cases and post operative deaths were reported in 11 cases. The principal causes of death originated from the presence co-existing infections, respiratory distress, anemia and malarial sickness.

Secondary vein of Galen malformation with hydrocephalus: Treated with combined endovascular and endoscopic approach

Our goal is to describe a case of hydrocephalus in the setting of a Yasargil Type IV-C secondary vein of Galen malformation (VGM), treated with a combined endscopic and endovascular approach. We retrospectively reviewed the records of a patient admitted to the neurosurgical department hydrocephalus related to a secondary VGM. A 47 year old male, presents with 8 months of progressive headaches and gait ataxia. Imaging displays a triventricular hydrocephalus, a tectal AVM, and an aneurysmal dilation of the great vein of Galen. Angiography displays a tectal AVM supplied by bilateral posterior choroidals with drainage into the vein of Galen. In addition there were direct high-flow arteriovenous fistulas into the vein of Galen via meningeal feeders. The diagnosis of a Yasargil Type IV-C secondary VGM was made. The patient was treated via a combined endoscopic and endovascular approach. An endoscopic third ventriculostomy (ETV) was conducted for his hydrocephalus. He subsequently underwent a partial endovascular embolization of the left tentorial arterial feeder 1.5 months after his ETV. Post-operatively his hydrocephalus resolved, and his complex secondary VGM completely obliterated after a single partial embolization. Secondary VGMs with associated high-flow arteriovenous fistulas are rare. Our case provides a nice example a combined endoscopic and endovascular approach aimed at achieving cure of the hydrocephalus and the Yasargil Type IV-C secondary VGM. We were able to avoid the placement of shunt hardware via ETV treatment of the patient's hydrocephalus. Furthermore, our case displays the impact of partial embolization on control and potential cure of these complex vascular malformations.

Cavum septum pellucidum: a novel endoscopic approach to the posterior third ventricle

Results The patient was referred for neurosurgical opinion due to a 2-week history of gait instability on a background of progressive ataxia and urinary incontinence. MRI showed triventricular hydrocephalus due to a tectal plate mass with thalamic extension. On examination, his GCS was 15/15 and he demonstrated truncal ataxia, gait instability, and upper limb dysmetria. He was admitted for an endoscopic third ventriculostomy with biopsy. Operative approach: The patient was anaesthetised and placed supine. Incision and burr hole were over the left coronal suture. A third ventriculostomy was performed for hydrocephalus. The tumour was then approached through the cavum septum pellucidum. Septal fenestrations allowed easy access to the cavum. Internal cerebral veins were identified and the velum interpositum opened with sharp scissors. The opening was dilated and an endoscope advanced into the posterior third ventricle. The tumour was identified and biopsies obtained. He had a satisfactory recovery and was discharged 6 days later. Histology showed a low-grade glioma, which remained stable on follow-up MRI.

Endoscopic Third Ventriculostomy: Our Experiences, Complications of the Intervention, Dysfunctions

Introduction: Endoscopic third ventriculostomy is the most frequently used endoscopic intervention in the word. It becomes treatment of choice for intraventricular obstructions, obstructive hydrocephalus. The indication usually for ETV is primary or secondary aqueductal stenosis. Whether we use shunting procedures or endoscopic third ventriculostomy depends on age of the patient, etiology, anatomy, and especially experience of the neurosurgeons. The long-term effectiveness is not well established for the ETV. Methods: Overall 50 patients were selected by the author who underwent for endoscopic third ventriculostomy in the last 5 years treated by one neurosurgeon. The inclusion criterion was no additional treatment of hydrocephalus in the follow-up 5 year. Results: Over 70% of the patients were successfully treated with ETV. In the follow-up period headache, ataxia, and emesis occurs. The patients who had previously malfunctioning shunt, become shunt independent. Failures usually occur after the ETV: either insufficient opening on the floor of the third ventricle (early failure) or closure of the stoma (late failure). Conclusion: Endoscopic third ventriculostomy is an effective, successful treatment of choice for the patients suffered from obstructive, triventricular hydrocephalus. Most of the patients previously had malfunctioning shunts, becomes shunt-free.

A difficult Endoscopic Third Ventriculostomy procedure: perforation of a thick Liliequist membrane with high basilar artery location.

Endoscopic Third Ventriculostomy (ETV) is a minimally invasive and safe method used in the treatment of obstructive hydrocephalus. However, arterial bleeding episodes that arise from narrowing of the safe perforation area due to a higher location of the basilar artery (BA) may have tragic consequences. Liliequist membrane (LM) or other membranous structures located in the prepontine cistern also affect the success rates with ETV and complicate the procedure. We present herein a safe and successful perforation of the thick LM after retracting BA in a triventricular hydrocephalus case having a high BA protruding into the third ventricle. ETV is an effective and minimally invasive treatment modality in selected cases. Although some case-specific factors may affect the procedural success and feasibility, favorable and safe outcomes are certainly achievable by overcoming these obstacles with increasing experience.

Multifocal tuberculosis revealed by cerebellar ataxia: One case

WCN 2013 No: 2765 Topic: 10 — Neurorehabilitation Multifocal tuberculosis revealed by cerebellar ataxia: One case A. Khadir, M. El Bouchikhi, S. Lahrabli, F. Lmidmani, A. El Fatimi. Service de Medecine Physique et Readaptation Fonctionnelle Chu Ibn Rochd, Casablanca, Morocco Introduction: Multifocal tuberculosis is uncommon and is defined by the achievement of two extra-pulmonary sites with or without pulmonary involvement. Multifocal tuberculosis is grave and responsible for 16–25% cases mortality. It is mainly associated with immunocompromised person. Purpose: To describe the characteristics of multifocal tuberculosis in an immunocompetent. Case report: 38-year-old woman with history of epilepsy consulted for difficulty in walking, ataxia and weight loss of 10 kg, physical examination found a dyspnea, a normal conscious, a normal voluntary control, a vivacious deep tendon reflexes, balance disorder, enlargement of support polygon, drunken gait, all in a context of apyrexia and impaired general condition. The chest X-ray objectified a miliary tuberculosis, chest CT scan was in favor of pulmonary tuberculosis and lymph nodes, cerebral MRI showed nodular lesions in the left region of occipital lobe with triventricular hydrocephalus in favor of neuromeningeal tuberculosis. The diagnosis of multifocal tuberculosis (pulmonary, cerebral and lymphoid) was retained. Patient received her BCG vaccination without any immunocompromised therapy. Immunocompromised disease was not found. Management was 12 month of antibacillar treatment with rehabilitation. Clinical, laboratory studies and radiological evolution were good. Discussion: Multifocal tuberculosis is a severe form which can affect even immunocompetent patient particularly in the Moroccan context, hence the need for a systematic dissemination checkup assessment for better management. This treatment should be instituted as soon as possible to avoid the sequelae. Conclusion: Multifocal tuberculosis is severe, to improve its prognosis, we emphasize the importance of early diagnosis and therefore the treatment. doi:10.1016/j.jns.2013.07.1925 Abstract — WCN 2013 No: 2757 Topic: 10 — Neurorehabilitation Atypical evolution of Guillain Barre syndrome: One case A. Khadir, H. Kassimi, F. Lmidmani, A. El Fatimi. Department of Physical Medicine and Rehabilitation Functional Chu Ibn Rochd,

Cranial growth restriction, a fundamental measure for success of the endoscopy in children under 1 month of age. Is it possible to improve the outcome?

BackgroundEndoscopic third ventriculostomy has been shown to be efficient for the treatment of non-communicating hydrocephalus. However, it is not recommended as the first option in the treatment of obstructive hydrocephalus in children under 3months of age, because the success rate is less than 35%. MethodsWe reviewed all the cases of triventricular hydrocephalus treated between 2007 and 2011 in patients under 1month of age in the case of normal term births or under 1month of corrected age, in the case of pre-term births. The first treatment option was endoscopic fenestration and a restriction of cranial volume during the two months after surgery. ResultsTen patients under 1month of age underwent 13 ventriculostomies for non-communicating hydrocephalus of varying etiology (suprasellar arachnoid cyst (3), stenosis of the Sylvian aqueduct (2), post-infectious meningitis (3), and intrauterine bleeding (2)). Three required surgical endoscopic revision at 3, 4, and 5months, respectively, after the initial surgery due to progressive ventricular enlargement. One of these three patients presented with Klebsiella pneumoniae ventriculitis as a complication after the second endoscopy. After a mean follow-up of 32months, none has required a shunt. ConclusionsIn our limited experience in triventricular hydrocephalus in patients under 1month, the third ventriculostomy technique may be a better option than the shunt in selected cases.

Chiari I malformation associated with premature unilateral closure of the posterior intraoccipital synchondrosis in a preterm infant

The authors report a case of a preterm infant at 29 weeks of gestation who gradually developed a Chiari malformation Type I (CM-I) with hydrocephalus due to a premature unilateral fusion of the posterior intraoccipital synchondrosis. Brain ultrasonography results in the 1st week of life were normal. Follow-up ultrasonography showed progressive development of triventricular hydrocephalus. Brain MRI demonstrated the presence of a CM-I and a deformation of the occipital bone. A complementary CT scan was obtained, showing a closure of the right posterior intraoccipital synchondrosis, resulting in a deformation of the posterior cranial fossa. This case shows the close relationship between a malformation of the skull base and the secondary development of a brain malformation. The authors discuss the anatomy of the occipital bone and suggest a probable theory for the premature closure of this synchondrosis and the consequent development of a CM-I. The originality of this case lies in the observation of the natural history of a brain malformation in a preterm infant.

Hidden aqueductal stenosis associated to bilateral idiopathic foramina of Monro stenosis mimicking a Chiari I malformation? Case report

A 39-year old man came to our outpatient clinic with long history of unspecific symptoms and signs. Cerebral MRI showed herniation of the cerebellar tonsils of more than 1cm below the foramen magnum and a triventricular hydrocephalus. A diagnosis of Chiari I malformation was retained. After an osteo-dural decompression of the posterior fossa, post-operative MRI revealed an aqueductal stenosis with triventricular hydrocephalus. An endoscopic-third- ventriculostomy showed an idiopathic stenosis of the right foramen of Monro. Residual symptoms and persistence of biventricular hydrocephalus justified a ventriculo-peritoneal shunt. Aqueductal and foramina of Monro stenosis can mimick a Chiari I malformation.

Aqueductal developmental venous anomaly as an unusual cause of congenital hydrocephalus: a case report and review of the literature

IntroductionAqueductal stenosis may be caused by a number of etiologies including congenital stenosis, tumor, inflammation, and, very rarely, vascular malformation. However, aqueductal stenosis caused by a developmental venous anomaly presenting as congenital hydrocephalus is even more rare, and, to the best of our knowledge, has not yet been reported in the literature. In this study, we review the literature and report the first case of congenital hydrocephalus associated with aqueductal stenosis from a developmental venous anomaly.Case presentationThe patient is a three-day-old, African-American baby girl with a prenatal diagnosis of hydrocephalus. She presented with a full fontanelle, splayed sutures, and macrocephaly. Postnatal magnetic resonance imaging showed triventricular hydrocephalus, suggesting aqueductal stenosis. Examination of the T1-weighted sagittal magnetic resonance imaging enhanced with gadolinium revealed a developmental venous anomaly passing through the orifice of the aqueduct. We treated the patient with a ventriculoperitoneal shunt.ConclusionsTen cases of aqueductal stenosis due to venous lesions have been reported and, although these venous angiomas and developmental venous anomalies are usually considered congenital lesions, all 10 cases became symptomatic as older children and adults. Our case is the first in which aqueductal stenosis caused by a developmental venous anomaly presents as congenital hydrocephalus. We hope adding to the literature will improve understanding of this very uncommon cause of hydrocephalus and, therefore, will aid in treatment.

Preoperative endoscopic third ventriculostomy in children with posterior fossa tumors: an institution experience

To assess the effectiveness and safety of pre-resection endoscopic third ventriculostomy (ETV) in permanently relieving hydrocephalus in children with posterior fossa tumors. 17 pediatric patients with posterior fossa tumors and associated triventricular obstructive hydrocephalus underwent ETV before definitive tumor resection, and ETV was repeated after tumor resection if hydrocephalus with increased intracranial pressure persisted or recurred. The medical records, operative notes and imaging studies were retrospectively reviewed. 18 ETV procedures were performed in 17 patients, consisting of 11 males and 6 females, age range (1.5 to 13 years; mean 6±3.86). Follow-up periods ranged from 6 to 23 months (mean follow-up 13.9±5.4 months). ETV was successful in relieving hydrocephalus during the follow-up period in 15 out of 17 patients (88.2%). Prior to surgical excision of the posterior fossa tumors, no failures of ETV were detected and all of the 17 patients showed marked clinical improvement and radiological disappearance of signs of active hydrocephalus. Preoperative ETV is a highly effective long-term CSF diversion procedure for treatment of hydrocephalus associated with posterior fossa tumors in children. In experienced hands, ETV has a very low complication rate.

P-165 - A case of hydrocephalus occlusus presenting as a manic episode

Normal Pressure Hydrocephalus(Hakim-Adams Syndrome)is a dilation of the ventricles without an increase of intracranial pressure.It corresponds to he classic triade of are gait disturbance, memory/cognitive problems,and urinary incontinence. Manic and depressive symptoms can be related to hydrocephalus occlusus even in the absence of neurological symptoms.These symptoms disappear after neurosurgery or pharmacological treatment. A 26 year old-male,from Cabo Verde,is interviewed in the Emergency Department in June 2011 presenting disturbance of general behaviour.He is being aggressive and presents flight of ideas.The diagnosis: “Hypomanic state” treated with lorazepam 6 mg/day and Olanzapine 5 mg/day. August 2011, the patient is reevaluated because of his behaviour:soliloquies,laughs,expansive mood, abnormal irritability, easily excited to enthusiasm and irritable humor. He also presents psychomotor agitation associated to delusion of persecution.He has not been taking his medication. No other neurological symptoms are detected. In Hospital he receives Risperidone 6 mg/day, Clorazepate Dipotassium45mg/day and Lormetazepam 2 mg /day disappearing most of the symptoms. A MRI was done, presenting triventricular hydrocephalus with absence of intraparenchymal damage.After monitoring the intracranial pressure, Neurosurgery decides not to perform surgery. In the case of not responding to Risperidone, studies have been published that Aripiprazole (atypical antipsychotic with a unique partial agonistic effect at D2receptors)is effective and safe in the treatment of manic episode. Some publications about the reduction of D2receptors demonstrated that the binding of striatal was reduced in NPH. Sometimes imaging tests are needed in patients with behavioural disturbance as manic symptoms in order to avoid misdiagnosis and it is crucial for the correct medical and chirurgical treatment.

Primary pineal glioblastoma: a case report

Glioblastoma is very rare in the pineal region. We report a case of glioblastoma in this region. This is the 18th case of primary glioblastoma in the pineal region and the second case that survived over two years according the literature. A 60-year-old man admitted with headache and ataxia that continued for the last 3 months. Physical examination was normal. Neurological examination revealed ataxia. There was no motor or sensory deficit. Computer tomography showed triventricular hydrocephalus and isodense rounded mass in the pineal region. Magnetic resonance images revealed a regular-edged heterogeneous contrast-enhanced tumor in pineal region. A ventriculoperitoneal shunt was inserted for hydrocephalus. After surgery, the ataxia and hydrocephalus were improved. Ten days later, serial stereotactic biopsies were performed. Histopathological specimens revealed glioblastoma. The patient was recommended to undergo radiotherapy and chemotherapy. The patient is still surviving without deficit two years after biopsy and shunt operation.

Rare association between cystic fibrosis, Chiari I malformation, and hydrocephalus in a baby: a case report and review of the literature

IntroductionCystic fibrosis, an epithelial cell transport disorder caused by mutations of the cystic fibrosis transmembrane conductance regulator gene, is not generally associated with malformations of the central nervous system. We review eight previously published reports detailing an infrequent association between cystic fibrosis and Chiari I malformation.Case presentationTo the best of our knowledge, our report describes only the ninth case of a baby presenting with a new diagnosis of cystic fibrosis and Chiari I malformation, in this case in a 10-month-old, full-term Caucasian baby boy from the United States of America. Neurosurgical consultation was obtained for associated developmental delay, macrocephaly, bulging anterior fontanel, and papilledema. An MRI scan demonstrated an extensive Chiari I malformation with effacement of the fourth ventricle, obliteration of the outlets of the fourth ventricle and triventricular hydrocephalus without aqueductal stenosis. Our patient was taken to the operating room for ventriculoperitoneal shunt placement.ConclusionsIt is possible that the cystic fibrosis transmembrane conductance regulator gene may play a previously unrecognized role in central nervous system development; alternatively, this central nervous system abnormality may have been acquired due to constant valsalva from recurrent coughing or wheezing or metabolic and electrolyte imbalances that occur characteristically in cystic fibrosis.

Role of Interpeduncular and Prepontine Cistern Cerebrospinal Fluid Flow Measurements in Prediction of Endoscopic Third Ventriculostomy Success in Pediatric Triventricular Hydrocephalus

Aim: The aim of the present study was to evaluate the correlation of the clinical success of the endoscopic third ventriculostomy (ETV) procedure with the measurements of cerebrospinal fluid (CSF) flow through the interpeduncular and prepontine cisterns in pediatric triventricular hydrocephalus. Methods: 51 children (age range: 25–201 months; mean: 55.3 months) with primary aqueductal stenosis who have been treated with ETV were included in the study. All patients were analyzed by conventional and cine magnetic resonance imaging (MRI) before and after endoscopic treatment. Both the stroke volume and the flow velocity of CSF in the interpeduncular and prepontine cisterns were evaluated. The MRI findings were correlated with clinical outcome. Simple descriptive and independent t tests were used for statistical analyses, and receiver operating characteristic curve analysis was used for the cutoff value of the ‘flow index’ (FI). Results: Among the 51 patients, 37 patients (72.5%) responded to ETV clinically during long-term follow-up. A further analysis was made for the prediction of who would respond to ETV, using the formula (stroke volume of prepontine cistern/stroke volume of interpeduncular cistern) ×100, which was defined as the FI. Early postoperative FI values of over 40% were significantly correlated with ETV success. Conclusion: Our results suggest that ETV success can be predicted by the ratio of early CSF stroke volume values of the interpeduncular and prepontine cisterns.

Reversible posterior leukoencephalopathy syndrome in a patient with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is an autoimmune disorder characterised by fever, microangiopathic haemolytic anaemia, renal insufficiency, and thrombocytopenia. Neurological involvement, a prominent component of TTP, is characterised by a variety of brain lesions which include reversible cerebral oedema or magnetic resonance imaging (MRI) features of reversible posterior leukoencephalopathy syndrome (RPLS). TTP is frequently associated with deficiency of the von Willebrand factor-cleaving protease, ADAMTS13.Here, we report a case of TTP with severe acute encephalopathy. Posterior leukoencephalopathy and brainstem oedema with triventricular hydrocephalus were observed on MRI. The low activity of ADAMTS13 was not observed and ADAMTS-13 antibodies were absent. Neurological symptoms and patient's condition were completely resolved by plasma exchange therapy in addition to high dose of methylprednisolone.

Armored brain in patients with hydrocephalus after shunt surgery; review of the literatures

Armored brain or chronic calcified subdural hematoma is a rare complication of cerebrospinal fluid diversion with few cases reported in the literature. Seventeen patients with this pathology have been published. A complete review of the literatures regarding this topic has been collected and discussed. The author also presents a 12- year old boy with triventricular hydrocephalus who had undergone ventriculoperitoneal medium pressure shunt system since birth. The patient presented to our clinic with a 2-year history of seizures. The patient was conscious and without neurological deficits on examination. Computed tomography of the brain showed bilateral high density mass with surface calcification. X ray skull and MRI confirmed the calcified subdural hematoma bilaterally. We preferred conservative treatment and the patient continued his antiepileptic treatment. At one year follow up, the patient had the same neurological state. The case highlights the importance of frequent follow up CT brain after shunt surgery.

Anaesthetic considerations and perioperative features of endoscopic third ventriculostomy in infants: analysis of 57 cases

Endoscopic third ventriculostomy (ETV) is currently considered the best alternative to shunt systems in the treatment of triventricular hydrocephalus. However, there has been very few published data about the anaesthetic management and the complications of ETV procedure in infants. In this report, we detail our experience with 57 infants, who underwent ETV as an initial treatment for obstructive triventricular hydrocephalus between 2003 and 2010. Anesthesia chart-records were retrospectively investigated and perioperative data were classified according to the stages of the procedure. In this series, mean heart rate values showed a statistically significant difference in the period concerning the balloon dilatation of ventriculostomy orifice. An episode of bradycardia occurred in 2 patients during balloon dilatation. After the deflation of the balloon, bradycardia resolved immediately without administration of any medication. Video recordings of those two patients revealed that one of them had a narrow and opaque tuber cinereum, and the other had a shallow interpeduncular cistern. During ETV procedure in infants, bradycardia may be a serious complication especially when performing balloon dilatation of the ventriculostomy orifice. We believe that close communication between the surgeon and the anaesthetist is extremely essential in this stage of the procedure.

Ultrastructural changes in liliequist membrane in hydrocephalic process and its implications for endoscopic third ventriculostomy procedure

Fenestration of Liliequist membrane (LM) during endoscopic third ventriculostomy (ETV) is extremely important for the success of the procedure. It is noteworthy that LM usually shows a tough and dense stucture in long-standing hydrocephalus cases different from its usual arachnoidal membrane-like structure observed in new-onset hydrocephalus cases. The structural variation of LM in different hydrocephalic states was investigated histologically in this study. Specimens of LM obtained during endoscopic fenestration in 11 cases were examined under transmission-electron-microscopy. Six cases had long-standing hydrocephalus and five had new-onset triventricular hydrocephalus. None of the cases had a history of infection or hemorrhage. In cases with long-standing hydrocephalus, ultrastructural examinations revealed the existence of regular and dense bundles of type-I collagen among the fibroblast-like cells, which were closely connected by dense desmosomes and gap-junctions. In cases with new-onset hydrocephalus, it was observed that the cells usually had long cytoplasmic extentions and were connected with loose desmosomes. Sparse type-I collagen bundles were observed rarely among the cells. These results suggest that the structure of LM may change with the duration of the hydrocephalic process. This may help explain the tough and dense LM stucture observed during the ETV procedure in cases with long-standing-hydrocephalus.