Cerebrospinal fluid absorption mechanism--based on measurement of CSF flow rate in shunt tube

The cerebrospinal fluid (CSF) absorption mechanism in cases of hydrocephalus was investigated on the basis of measurements of CSF flow in a shunt tube after ventriculo-peritoneal shunt surgery, monitoring of intracranial pressure, CT findings, radioisotope cisternography, cerebral blood flow, EEG, PSP tests and changes in neurological findings. The subjects were 6 males and 7 females aged from 18 to 70. CSF flow rates in the shunt tubes were between 0.01 and 1.93 ml/min. Calculating the daily volume of CSF flow, the subjects were divided into two groups: Group A (8 patients) with a volume of less than 150 ml/day (0.01-0.25 ml/min), and Group B (5 patients) with between 150 and 500 ml/day (0.01-1.93 ml/min). Monitoring of intracranial pressure prior to the shunt operation was performed in 10 cases. These pressure values ranged between 4 and 25 mmHg (mean: 7-8 mmHg), and there was no difference between the two groups. The pre-and post-operative radioisotope cisternography findings indicated improvement of ventricular dilatation, periventricular lucency and ventricular reflux. After the shunt operations, there was neurological improvement in 6 of the 8 Group A cases but only in 2 of the 5 Group B cases. Considering the CSF flow volumes of the two groups, it appears that in Group A the shunt tube is not the main CSF circulation pathway. This could mean that resistance to CSF absorption in the cerebrospinal space has decreased after the shunt operation and there has been recovery of the physiological CSF absorption pathways. In other words, neurological improvement can be expected in this group A.     

Clinical evaluation of shunt implantations using Sophy programmable pressure valves: comparison with Codman-Hakim programmable valves.

We describe our experience with Sophy programmable valve shunts, compared with Codman-Hakim programmable shunts in cases with normal pressure hydrocephalus (NPH) after subarachnoid hemorrhage (SAH). A total of 147 consecutive patients underwent 204 shunt implantations (102 Sophy valves, 51 Codman-Hakim valves, 51 nonprogrammable valves). Of these, 23 Sophy and 25 Codman-Hakim valves respectively were implanted into patients with NPH after SAH. Comparison of reprogramming rate and frequency in cases with NPH after SAH between Sophy and Codman-Hakim valves revealed similar reprogramming rates (65.2 vs. 64.0%) but a higher frequency with the former (1.70 vs. 1.08 times/person). The mean difference between initial and final pressure was 65.3+/-45.8mmH(2)O in cases with Sophy valves, and 25.0+/-14.1mmH(2)O with Codman-Hakim valves. The average period which was required to determine the final pressures with Sophy and Codman-Hakim valves were 56.5+/-45.0 days and 43.3+/-45.7 days, respectively. Total incidence of complications of Sophy and Codman-Hakim valve shunt systems in cases with NPH after SAH were 26.1% (6/23) and 16% (4/25), respectively. Total instances requiring shunt revision with Sophy valves in cases of NPH after SAH were 6 of 23 (26.1%), while for Codman-Hakim valves the figure was 2 of 25 (8.0%). Sophy, as well as Codman-Hakim programmable valve shunts, allow alteration of opening pressure after the implantation according to patients' conditions, which may contribute to reduction of revision. Similar reprogramming rates but lower frequency, and smaller difference between initial and final pressure in Codman-Hakim valves may be ascribed to finer pressure ranges and ease of reprogramming, which facilitates earlier reprogramming and decisions regarding final optimal opening pressure.     

Late onset X-linked hydrocephalus with normal cerebrospinal fluid pressure

A family with X-linked hydrocephalus with normal cerebrospinal fluid (CSF) pressure and in which three brothers and a grandson of case 1, a proband, were affected is reported. The symptoms at onset were epileptic attacks that started in adulthood in the three brothers and at the age of 6 years in the grandson. In the three brothers, from 10 to 27 years after the onset of epileptic episodes, disorganization of intelligence and psychiatric deterioration were gradually noticed by their families. At the same time, they showed occasional urinary incontinence. Brain computed tomography (CT) scans revealed dilatation of the ventricular systems. Based on the results of the measurement of CSF pressure and radioactive-iodinated human serum albumin (RISA)-cysternography, two of the brothers were diagnosed as having normal pressure hydrocephalus (NPH), and they were treated neurosurgically. However, no obvious improvement in clinical symptoms was observed. Although the grandson had shown normal psychomotor development during his early childhood, temporal epilepsy and temper tantrums started at the age of 6 years. Computed tomography-scanning revealed dilatation of the ventricular system similar to the other three cases at the age of 8 years. With the diagnosis of NPH, the patient underwent a shunt operation, which resulted in no obvious effects. As it is reasonable to surmise that the pathological gene would have been transferred via the daughter of the proband to the grandson, it is suggested that the inheritance manner might be X-linked recessive. The cases presented here are different from the cases of hydrocephalus due to stenosis of the aqueduct Sylvius (HSAS) and other types of X-linked hydrocephalus reported previously in terms of the age of onset, course, symptoms, and CT findings. Thus, it is suggested that the present cases might be a new type of X-linked hydrocephalus.     

Auditory evoked brain stem responses in patients with normal pressure hydrocephalus following subarachnoid hemorrhage and elderly dementia

There have been many reports that had discussed the effectiveness of shunt surgery in dementia patients. But it is not always reliable to predict such effectiveness before the operation. We used auditory evoked brain stem responses (ABR) to investigate the degree of brain damage in normal pressure hydrocephalus (NPH) and predict the effectiveness of shunt surgery. Fifteen patients with subarachnoid hemorrhage were divided into three groups, 5 cases without any symptoms of NPH, 6 cases with one of three symptoms of NPH and 4 cases with full blown symptoms of NPH which improved after shunt surgery, it is NPH. Eleven cases of aged patients were classified into two groups, Elderly normal (6 cases) and Elderly dementia (5 cases) groups, Younger normal group was composed of 8 healthy persons. Interpeak latencies (IPL's) on ABR was used as indexes of evaluating brain stem function, I-V IPL was used as central transmission time (CTT). CTT of Younger normal group and Elderly normal group were not different. It showed that CTT was a reliable parameter of ABR independently of age. There was significant prolongation of CTT in the patients of NPH and Elderly dementia group in comparison with other groups, However between them significant differences were not present. We concluded that there was some degree of brain stem dysfunction in the patients of NPH as well as dementia patients suggesting one aspect of the pathogenesis of NPH. But we could not distinguish the patients of NPH from other dementia patients by the analysis of ABR.     

Quantitative SPECT cisternography in normal pressure hydrocephalus

Twenty-one patients with normal pressure hydrocephalus (NPH), 8 patients with various brain diseases with an element of hydrocephalus, and 7 patients with miscellaneous dementia disorders were investigated with quantitative radionuclide cisternography (RC) using single photon emission computerized tomography (SPECT). The total intracranial counts as well as the counts in the lateral and third ventricles were measured. All 15 NPH patients accessible for postoperative examination were improved after shunt surgery. In all groups the ventricular and total intracranial counts level increased during the measurement period but remained constant in distribution in each group. The NPH patients had a higher relative count value in the lateral and third ventricles compared to the patients with miscellaneous dementia disorders. The relative values in the third and lateral ventricles were predictive for the outcome of shunt surgery. Quantitative SPECT RC appears to be a useful diagnostic procedure in NPH investigations.     

The importance of the intrathecal infusion test in the diagnosis of normal pressure hydrocephalus.

The intrathecal infusion test is a reliable method in diagnosing normal pressure hydrocephalus. Between May 1982 and January 2000 we investigated 300 patients suspected of having normal pressure hydrocephalus (NPH) by carrying out an intrathecal infusion test in a constant flow technique. The resistance to cerebrospinal fluid outflow (R(out)) in the intrathecal infusion test was the main criterion of grouping patients into those with normal pressure hydrocephalus or those with cerebral atrophy. A further differentiation into early stage and late stage was made by measuring the compliance (C(p)) - this being the secondary criterion. In 162 patients (54%) the diagnosis of NPH could be confirmed. Of these, 154 patients (95%) underwent a shunt operation. Graduation of NPH and cerebral atrophy following the results of the infusion test at an early stage and an advanced stage allow the conclusion of prognostic evaluations about the course of disease to be made. Patients with NPH in an early stage report in the follow up an improvement of their symptoms after a shunt operation in 65 percent of cases, and those with advanced stage NPH, in 50 percent of cases. The computer aided infusion test allows a reliable differentiation between patients with NPH and those with cerebral atrophy.     

Auditory event-related potentials differentiate patients with normal pressure hydrocephalus and patients with concomitant Alzheimer's disease verified by brain biopsy

We studied 51 patients with clinical symptoms and CT findings suggesting normal pressure hydrocephalus (NPH). Tests included head MRI, auditory event-related potentials (ERPs), thorough neuropsychological testing and intraventricular intracranial 24 h pressure recording and infusion testing. A brain biopsy was also obtained to verify a concomitant dementing process (Alzheimer's disease; AD). Patients were divided into subgroups according to the need of shunt and the biopsy findings, and their ERPs were analysed blindly. The present results suggest that non-invasive ERPs aid in the differentiation of pure NPH from NPH with concomitant AD.     

Measurement of peak CSF flow velocity at cerebral aqueduct, before and after lumbar CSF drainage, by use of phase-contrast MRI: utility in the management of idiopathic normal pressure hydrocephalus

OBJECTIVE: Since it was first described, normal pressure hydrocephalus (NPH) and its treatment by means of cerebrospinal fluid (CSF) shunting have been the focus of much investigation. Whatever be the cause of NPH, it has been hypothesized that in this disease there occurs decreased arterial expansion and an increased brain expansion leading to increased transmantle pressure. We cannot measure the latter, but fortunately the effect of these changes (increased peak flow velocity through the aqueduct) can be quantified with cine phase-contrast magnetic resonance imaging (MRI). This investigation was thus undertaken to characterize and measure CSF peak flow velocity at the level of the aqueduct, before and after lumbar CSF drainage, by means of a phase-contrast cine MRI and determine its role in selecting cases for shunt surgery. PATIENTS AND METHODS: 37 patients with clinically suspected NPH were included in the study. Changes in the hyperdynamic peak CSF flow velocity with 50 ml lumbar CSF drainage (mimicking shunt) were evaluated in them for considering shunt surgery. RESULTS: 14 out of 15 patients who were recommended for shunt surgery, based on changes peak flow velocity after lumbar CSF drainage, improved after shunt surgery. None of the cases which were not recommended for shunt surgery, based on changes in CSF peak flow velocity after lumbar CSF drainage, improved after shunt surgery (2 out of 22 cases). CONCLUSION: The study concluded that the phase-contrast MR imaging, done before and after CSF drainage, is a sensitive method to support the clinical diagnosis of normal pressure hydrocephalus, selecting patients of NPH who are likely to benefit from shunt surgery, and to select patients of NPH who are not likely to benefit from shunt surgery.     

Changes in CSF pressure induced by acetazolamide administration test--as an indicator of shunt operation for so-called normal pressure hydrocephalus

Lumber subarachnoid pressure was monitored via intrathecally introduced catheter in 9 patients, who showed ventricular dilatation on brain CT and were suspected of normal pressure hydrocephalus. During the pressure measurement, 500 mg of acetazolamide was rapidly injected intravenously and changes of CSF pressure were recorded. The results of the study were compared to clinical signs, brain CT findings and results of continuous pressure monitoring. The types of response of CSF pressure induced by acetazolamide administration were classified into 2 groups. In 5 cases (Group A), more than 50 percent increase of CSF pressure compared to the resting value was noted. On the contrary, in the remaining 4 cases (Group B), CSF pressure showed only slight increase (less than 25 percent or none). VP shunt was performed in 4 cases in Group A. Definite improvement of clinical symptoms was observed in all of these surgically treated cases. Correlation was found between the response to Acetazolamide administration and the appearance of B wave in the continuous spinal pressure monitoring. This study suggests that Acetazolamide test may be useful diagnostic test to select the patients for shunt operation.     

Differentiation of normal pressure hydrocephalus and cerebral atrophy by computed tomography and spinal infusion test

Summary The diagnostic value of computed tomography (CT) and spinal infusion test (SIT) was investigated in 27 patients with normal pressure hydrocephalus (NPH) and 35 patients with cerebral atrophy. The most consistent CT finding of NPH was dilatation of the temporal horns, that of cerebral atrophy widening of the convexity sulci. However, 43% of patients with cerebral atrophy demonstrated no cortical atrophy. The SIT showed an excellent relation with isotope cisternography and continuous intracranial pressure recording. NPH and cerebral atrophy were correctly differentiated in 71% by CT and SIT. A normal SIT and a CT scan without the typical features of NPH exclude impairment of cerebrospinal fluid absorption. An abnormal SIT and a CT scan showing ventricular enlargement without dilatation of convexity sulci, require isotope cisternography and possibly intracranial pressure recording to determine the degree of the absorption deficit.

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Zusammenfassung Der diagnostische Wert von Computertomographie (CT) und Spinalen Infusions-Test (SIT) wurde bei 27 Patienten mit Normal Pressure Hydrocephalus (NPH) und 35 Patienten mit zerebraler Atrophie untersucht. Der häufigste CT-Befund des NPH war Erweiterung der Temporalhörner und bei zerebraler Atrophie eine Erweiterung der Konvexitätssulci. Aber 43% der Patienten mit zerebraler Atrophie zeigte keine Rindenatrophie. Der SIT zeigte eine sehr gute Korrelation mit Isotopenzisternographie und kontinuierlicher intrakraniellen Druckmessung. NPH und zerebrale Atrophie wurden korrekt differenziert in 71% mittels CT und SIT. Ein normaler SIT und ein CT-Scan ohne die typischen Merkmale von NPH schließen Liquorrückresorptionsstörungen aus. Ein abnormer SIT und ein CT-Scan, der einen Hydrozephalus ohne Erweiterung der Konvexitätssulci zeigt, erfordern eine Isotopenzisternographie und eventuell intrakranielle Druckmessung zur Ermittlung des Grades der Liquorrückresorptionsstörung.

     

Ventricular cerebrospinal fluid neurofilament protein levels decrease in parallel with white matter pathology after shunt surgery in normal pressure hydrocephalus

Normal pressure hydrocephalus (NPH) is characterized by disturbed cerebrospinal fluid (CSF) dynamics and white matter lesions (WML). Although the morphology of these lesions is described, little is known about the biochemistry. Our aim was to explore the relationship between ventricular CSF markers, periventricular WML and postoperative clinical outcome in patients with NPH. We analysed lumbar and ventricular concentrations of 10 CSF markers, 12 clinical symptoms and signs, magnetic resonance imaging (MRI) periventricular white matter hyperintensities (PVH) and ventricular size before and 3 months after shunt surgery in 35 patients with NPH. Higher ventricular CSF neurofilament protein (NFL), an axonal marker, correlated with more extensive PVH. A larger postoperative reduction in NFL correlated with larger reduction in PVH and a more pronounced overall improvement. Albumin ratio, HMPG, NPY, VIP and GD3 increased postoperatively whereas NFL, tau and HVA decreased. Variations in ventricular size were not associated with CSF concentrations of any marker. We conclude that NPH is characterized by an ongoing periventricular neuronal dysfunction seen on MRI as PVH. Clinical improvement after shunt surgery is associated with CSF changes indicating a restitution of axonal function. Other biochemical effects of shunting may include increased monoaminergic and peptidergic neurotransmission, breakdown of blood brain barrier function, and gliosis.     

可调压式分流管治疗脑积水

目的探讨使用可调压式分流管行脑室-腹腔分流术治疗脑积水的临床效果。方法采用可调压式分流管行脑室.腹腔分流术治疗脑积水18例。其中高压性脑积水6例;等压性脑积水10例;等压性脑积水伴穿通畸形2例。术前根据患者头颅CT及MRI提示脑积水类型设定阀门压力,术中测量颅内压并根据分流管末端滴速重新调整阀门压力。术后一周复查头颅CT了解脑积水缓解情况。出院后随访1-11月,根据头颅CT所示脑积水缓解情况再行阀门压力调整。结果脑积水症状缓解16例(88.9%);症状缓解不满意2例(11.1%)。18例均无出血、颅内感染及死亡。结论使用可调压式分流管行脑室一腹腔分流术,可在术前、术中、术后调整阀门压力,缓解脑积水症状,分流效果优于传统不可调压式分流管。     

Shunt removal or replacement based on intraventricular infusion tests

In 14 children with indewelling ventriculoatrial or ventriculoperitoneal shunts, the need for continued shunt treatment was judged to be uncertain based on clinical symptoms and signs and CT scans. Ventricular outflow resistance (R₀) was determined by implantation of a ventricular catheter and steady state infusion of artificial cerebrospinal fluid (CSF) according to the formula R₀ = (P_p-P₀)/Infusion rate, where P₀ is the opening pressure in the lateral ventricle and P_p the plateau pressure recorded at that particular infusion rate. R₀ was determined during general anesthesia and stready state ventilation was ensured by mechanical ventilator. Ventricular fluid pressure (VFP) and arterial blood pressure (ABP) were recorded by standard fluid pressure transducers. The cerebral perfusion pressure (CPP = ABP-VFP) was kept above 30 mmHg by reducing the infusion rate in cases of unacceptable increase in VFP. R₀ was determined with the shunt clamped. During steady state infusion at the plateau pressure the shunt was unclamped to test shunt patency. Four children had normal R₀ values with the shunt clamped. Their shunts were removed. They have done well clinically, and control CT scans have not demonstrated increased ventricular size. Three children demonstrated pathologic R₀ values (above 12 mmHg/ml per min) that normalized after shunt unclamping; i.e. each had a well-functioning shunt. Seven children demonstrated increased R₀ values even after shunt unclamping. Their shunts were replaced, and clinical improvement has been observed in 6 of them. Ventricular infusion tests appear useful to evaluate shunt dependence and function in difficult cases.     

Lack of relationship between resistance to cerebrospinal fluid outflow and intracranial pressure in normal pressure hydrocephalus

OBJECTIVE: To explore whether calculation of resistance to cerebrospinal fluid (CSF) outflow (Rout) by the lumbar constant rate infusion test in a reliable way predicts the intracranial pressure (ICP) profile in normal pressure hydrocephalus (NPH). METHODS: A prospective study was undertaken including 16 cases with clinical signs of normal pressure hydrocephalus that were investigated with both continuous ICP monitoring and the lumbar constant rate infusion test. Intracranial pressure monitoring was performed for about 24 h, and supplied with a simultaneous lumbar constant rate infusion test at the end of the monitoring period. The pressure recordings were analysed using the Sensometrics Pressure Analyser. Various characteristics of the pressure curves were compared. RESULTS: The continuous ICP recordings were considered as normal (mean ICP<11.5 mmHg) in all 16 cases. The lumbar infusion test showed an apparently abnormal resistance to CSF outflow (Rout) (> or =12.0 mmHg/ml/min) in 12 of 16 cases. There was no relationship between lumbar Rout and mean ICP during sleep. We could not find any relationship between lumbar Rout and number of nightly ICP elevations of 1525 mmHg lasting 0.5 or 1 min. Neither resistance to CSF outflow (Rout) nor mean ICP during sleep was related to the ventricular size. CONCLUSIONS: The results of this prospective study revealed no significant relationship between resistance to CSF outflow (Rout) and the ICP profile in NPH cases. The results also suggest that caution should be made when predicting the ICP profile on the basis of measuring the lumbar CSF pressure for a few minutes duration.     

Predictive value of quantitative cisternography in normal pressure hydrocephalus

Twenty-five patients with normal pressure hydrocephalus (NPH) and 16 patients with cerebral atrophy were investigated by quantitative cisternography using anterior images of the head 3, 6 and 24 h after a lumbar injection of 200 MBq 99mTc DTPA (diethylene-triamine-penta-acetic acid). The activity in the lateral ventricles, basal cisterns, hemispheric convexities and total intracranial region was measured. Ratios between these regions/quantities were calculated. Fifteen of the NPH patients improved while 10 were unchanged after ventriculo-peritoneal shunt surgery. The ratio between ventricular and total intracranial activity (V/T) correlated positively with the degree of improvement after shunt surgery. All NPH patients with a V/T ratio higher than 32% improved after the operation but a V/T ratio less than 32% did not exclude the possibility of improvement. With regard to quantitative measurements, the radionuclide cisternography procedure can be reduced to imaging at 24 h.     

Impaired cerebral circulation and the effect of glycerol infusion in the acute stage of hypertensive intracerebral hematoma

The purpose of the present study was to clarify the mechanism of reduction in cerebral blood flow (CBF) in the acute stage of hypertensive intracerebral hematoma and the effect of glycerol infusion on the reduced CBF. We examined 55 cases. Thirty-eight cases showed putaminal hematoma and 17 presented thalamic hematoma. The range of consciousness was from alert to stupor. CBF was measured by single photon emission CT with Xe-133 inhalation within five days after the onset of the hemorrhage. A CBF map was obtained at a slice 5 cm above the OM-line and mean CBF of the affected and non-affected hemispheres was calculated. In 20 of 55 cases, 500 ml of glycerol was intravenously infused for 60 minutes and thereafter CBF was measured again. Epidural pressure was also recorded at the affected frontal area during glycerol infusion in three of the 20 cases. CBF reduced more profoundly in the area around the hematoma on the CBF map. Mean CBF of the affected hemisphere was negatively correlated with the volume of hematoma by a quadratic regression. After glycerol infusion, 13 of 20 cases showed a significant increase in mean CBF of the affected hemisphere, while the other seven cases showed no increase. Mean CBF increased with a higher percentage in cases with ventricular hemorrhage than without ventricular hemorrhage. In three cases where epidural pressure was measured during glycerol infusion, mean CBF increased and epidural pressure decreased. The increase in mean CBF was proportional to a rise in perfusion pressure calculated as pressure difference between mean systemic arterial pressure and mean epidural pressure, indicating impaired autoregulation in these cases.(ABSTRACT TRUNCATED AT 250 WORDS)     

The importance of the intrathecal infusion test in the diagnostic of normal-pressure hydrocephalus.

OBJECTIVE: The intrathecal infusion test is a reliable method for diagnosing normal-pressure hydrocephalus (NPH). METHODS: Between May 1982 and January 1997, we investigated 200 patients suspected of having NPH by carrying out an intrathecal infusion test with a constant-flow technique. The resistance to cerebrospinal fluid outflow in the intrathecal infusion test was the main criterion for grouping patients into those with NPH or those with cerebral atrophy. A further differentiation into early stage and advanced stage was made by measuring the compliance, this being the secondary criterion. RESULTS: In 107 patients (54%), the diagnosis of NPH could be confirmed. Of these, 102 patients (95%) underwent a shunt operation. Graduation of NPH and cerebral atrophy following the results of the infusion test at an early stage and an advanced stage allows prognostic evaluations about the course of disease to be made. Patients with NPH at an early stage reported an improvement of their symptoms in the follow-up after a shunt operation in 65% of cases, while 50% of those with advanced-stage NPH reported improvement. CONCLUSION: The computer- aided infusion test allows a reliable differentiation between patients with NPH and those with cerebral atrophy.     

CSF hydrodynamics after subarachnoid hemorrhage

Recent reports have shown that despite an apparently satisfactory recovery from previous subarachnoid hemorrhage (SAH), many patients still have minor sequelae when specifically looked for. The cause of this so-called post-SAH-encephalopathy is uncertain. This prospective study comprises 54 patients who underwent aneurysmal surgery after SAH between September 1978 and March 1985. One patient died, and 6 patients were non-biased drop-outs. CSF hydrodynamics, determined by infusion test and isotope cisternography, were evaluated on the remaining 47 patients in the recovery stage. Five patients (11%) were found to have typical clinical, CSF dynamic and radiological manifestations of normal pressure hydrocephalus (NPH), and all were shunted with good results. Twelve (26%) had abnormal results consistent with disturbed CSF-hydrodynamics, although there were no clinical or radiological findings supporting the diagnosis of shunt-demanding NPH. Disturbed CSF-hydrodynamics as one of the possible etiological factors of post-SAH-encephalopathy is discussed.     

Heterogeneous cerebral glucose metabolism in normal pressure hydrocephalus.

The regional cerebral metabolic rate for glucose (rCMRglu) has never been investigated in large consecutive groups of patients with normal pressure hydrocephalus (NPH), a potentially treatable form of dementia with an unpredictable outcome after shunt surgery. Using PET and 18F-2-fluorodeoxyglucose, rCMRglu was studied in 18 patients who fulfilled hydrodynamic criteria for NPH and in whom a biopsy of the frontal cortex was obtained. When compared with an age matched group of 11 healthy subjects, the patients with NPH showed a significant rCMRglu reduction in all cortical and subcortical regions of interest. Individual metabolic patterns, however, disclosed a large topographical heterogeneity. Furthermore, histopathological examination identified Alzheimer's disease or cerebrovascular disease in six cases, and no parenchymal disease or non-specific degenerative processes in the remaining 12. After separating the patients according to the histological diagnosis, the rCMRglu patterns were still heterogeneous, the abnormalities ranging from focal to diffuse in both subgroups. After shunt operation, 11 patients did not improve or worsened clinically. Six patients improved; of those, two had Alzheimer changes and two cerebrovascular changes in their biopsy. The metabolic pattern of these six patients did not differ from the rest of the NPH group. The results indicate that the NPH syndrome may be non-specifically associated with different degenerative disorders. The metabolic heterogeneity, together with the heterogeneous histopathological findings, indicate the necessity of reevaluating the pathogenesis of the NPH syndrome, and may account for the high variability in the success rate of shunt surgery series.     

Cerebral hemodynamics before and after shunting in normal pressure hydrocephalus

OBJECTIVE: To study the relationship between cerebral hemodynamics and clinical performance in normal pressure hydrocephalus (NPH), before and after surgery. MATERIAL AND METHODS: Ten patients were studied prospectively before and 3 months after shunt surgery by means of transcranial Doppler (TCD). Clinical performance was scored by means of an NPH scale and the modified Rankin scale. RESULTS: Peak systolic and mean cerebral blood flow velocity (MCV) were lower and cerebrovascular CO2 reactivity was higher after shunt surgery. The three patients with clinical improvement had higher preoperative end diastolic cerebral blood flow velocity and MCV. All postoperative cerebral blood flow velocities were higher in patients with clinical improvement. CONCLUSION: Our data suggest that higher cerebral blood flow velocity before surgery in patients with NPH is related to clinical improvement after shunt surgery. Cerebral hemodynamic parameters may develop into predictors of successful shunt surgery in patients with normal pressure hydrocephalus.