Idiopathic normal pressure hydrocephalus (iNPH) is a syndrome manifesting with gait disturbance, dementia and urinary incontinence without any preceding disorders in elderly patients. The rapid increase of the elderly population in Japan prompted us to make guidelines for the management of iNPH. The Japanese guidelines committee started work in March 2002. The guidelines were made according to evidence-based medicine and were published in May 2004. The Japanese guidelines are summarized as follows: 1)lt is simple and practical. 2) Three levels of diagnosis for iNPH (possible, probable and definite) are proposed to make preoperative diagnosis more accurate. 3) Gait disturbance is a major symptom, and such cases are most suitable for CSF shunting operation, 4) The CSF tap test is regarded as a best predictor, when it is positive. 5) Use of a programmable shunt valve is recommended. 6) Flow-charts for diagnosis, indication of shunt operation and prevention of complications are made for wider use. Thus, the Japanese guidelines are useful to make diagnosis more precise and treatment more appropriate.

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The triad symptoms of idiopathic normal pressure hydrocephalus (iNPH), i.,e., dementia, gait disturbance, and urinary incontinence may appear commonly in the elderly suffering from various brain diseases as well as in those with various non-neurological diseases. Therefore, it is often not easy to differentiate iNPH from other neurological diseases with non-neurological conditions in the elderly. Although ventriculomegaly is a neuroimaging feature of iNPH, differentiation from brain atrophy is not necessarily straight-forward, and in fact many patients with iNPH are often misdiagnosed as having degenerative dementia such as Alzheimer disease. While the prevalence of iNPH is modest, detection of it is particularly important. Disregarding the possibility of iNPH before further diagnostic workup is really unfortunate, as iNPH is possibly curable. On the other hand, as complications associated with shunt surgery and CSF shunting are not negligible, overdiagnosis should be avoided. Since the guidelines for management of iNPH were published, iNPH has been increasingly recognized. In this paper, we focused on the clinical signs and on the neuroimaging and tap test that are all essential for the diagnosis.

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Idiopathic normal pressure hydrocephalus (iNPH) is again in the spotlight after the publication of Japanese guideline for iNPH. As diagnosis method has considerably changed, neurologists should become familiar with the new method. Moreover, neurologists should be capable of making a diagnosis in clinical practice because patients with iNPH presenting with gait disturbance as the first symptom are supposed to consult neurology. Several subcortical dementias are accompanied with gait disturbance, such as iNPH. Each condition has a relatively high incidence and it is even difficult for neurologists to make an accurate diagnosis. Therefore, neurologists familiar with these conditions need to be involved in the diagnosis of iNPH.

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In the management of probable Idiopathic Normal Pressure Hydrocephalus (iNPH) diagnosed according to the Guidelines for Management of iNPH, the role of the neurosurgeon is to provide effective treatment while minimizing complications. The neurosurgeon decides whether surgery is indicated or not by taking account of the patient's general condition, the family's intentions, and an environment which allows long-term observation. Therapies selected are mainly V-P shunt and L-P shunt. When using a shunt system, a programmable differential pressure valve is recommended. Especially, postoperative management should include proper precautions and countermeasures against overdrainage of the cerebrospinal fluid. Improvement of the patient's quality of life and reduction of burden of care are expected through adequate treatment and postoperative management.

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We studied the effectiveness of rehabilitation in 20 patients with idiopathic normal pressure hydrocephalus (iNPH) who treated by lumbo-peritoneal shunt (LPS). All patients suffered from gait disturbance, dementia, and urinary disturbance. After LPS, gait disturbance was improved in all patients and the Barthel index was improved in 60% of all patients. However, we found that all patients had very low activity levels in their life style. Three patients lived alone at home, 6 patients lived alone in the daytime and 11 patients lived with an old partner. They did not have enough motivation and support to walk at home after discharge. We performed a community based rehabilitation to keep these 15 patients in condition and to monitor their shunt function. They maintained a good level of activity over one year by attending the community based rehabilitation. We emphasized that community based rehabilitation had a very important role in maintaining the shunt function of LPS in patients with iNPH.

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Dynamic radioisotope cisternography was performed in eight cases, which were diagnosed as iNPH (idiopathic normal pressure hydrocephalus) clinically, and in 5 cases as secondary NPH following subarachnoid hemorrhage. ^<111>-DTPA was administrated by lumbar tap with a 25-gauge needle, then the hole axis was scanned at 10 minutes, 1, 3, 6 and 24 hours after injection. Tracer transfer from the CSF to the blood was also measured continuously every 10 minutes for 60 minutes, then every 1 hour for 6 hours and then 12 and 24 hours after injection. Tracer was dispersed evenly and reached the cerebral convexity around 6 hours after injection, when the concentration of tracer in the blood reached the maximum. However, the tracer concentration kept increasing even 24 hours after injection in those cases with iNPH. Three cases had an early peak of radioisotopic count at 60 minutes before the tracer filled the cerebral cisterns. All of the cases, which required a shunt after SAH, had early peaks of their isotopic counts at between 3 to 6 hours after injection. The study of tracer transfer from the CSF to the blood could be applied to the new interpretation of abnormal CSF dynamics in clinical situations. The absorption of the tracer was accelerated in the spine of some cases of iNPH and in other places in the cases with SAH.

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We report a case of triventricular hydrocephalus associated with Chiari malformation type I. Triventricular hydrocephalus is characterized by the dilatation of both the lateral and third ventricles without expansion of the fourth ventricle. For this case, cerebrospinal fluid (CSF) circulation was evaluated in order to predict the effect of endoscopic third ventriculostomy (ETV). The present case was a 60-year-old male who was admitted to our hospital for progressive gait disturbance. On admission, magnetic resonance imaging (MRI) showed triventicular hydrocephalus and Chiari malformation type I. No aqueductal stenosis or obstruction were observed ; however, ballooning of the third ventricle was not observed despite being dilated. Radioisotope (Rl) cisternography indicated delayed CSF absorption, although reflux into the ventricles was not seen. As the cause of hydrocephalus was primarily considered to be the obstruction of CSF outflow from the forth ventricle, ETV was performed. During the procedure, ventriculography revealed the obstruction of both foramen of Luschka, but did not reveal the obstruction of the foramen of Magendie. Therefore, we judged this case to have communicating hydrocephalus. Finally ventriculo-peritoneal shunt and ETV were performed because impaired CSF absorption was observed preoperatively and no ventricular obstruction was noted in the ventriculography findings. The ventriculo-peritoneal shunt reduced the ventricular size and improved the patient's gait and cognitive functioning. For cases of triventricular hydrocephalus associated with Chiari malformation type I, EVT should be considered important for the evaluation of CSF circulation.

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Two patients with severe subarachnoid hemorrhage caused by vertebral artery (VA) dissecting aneurysms underwent endovascular coil embolization. As both patients developed devastating rebleeding, endovascular trapping was performed and the affected VA was occluded although the posterior inferior cerebellar artery (PICA) originated from the affected portion. Extraventricular drainage was placed for the accompanying acute hydrocephalus. Both patients developed massive cerebellar and brainstem infarction and deteriorated. Computed tomographic scans clearly showed upward dislocation of the brainstem beyond the tentorium. Clinical management of severe posterior fossa subarachnoid hemorrhage complicated by PICA involved VA dissection and acute hydrocephalus is hazardous, especially when rebleeding occurs. Tolerance to PICA and VA occlusion is unpredictable. Proximal VA occlusion or stent assisted embolization might have been an option in these two cases.

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