The role of computerized rheoencephalography in the assessment of normal pressure hydrocephalus. Preliminary report

BACKGROUND AND PURPOSE: It is generally agreed that the positive result of lumbar cerebrospinal fluid (CSF) withdrawal offers a reliable means for selection of patients likely to respond to shunting in normal pressure hydrocephalus (NPH). However the studies of cerebral hemodynamics in NPH are performed Routinely only in few neurosurgical centers. We therefore studied the effect of CSF withdrawal on cerebrovascular autoregulation (CVA) in this condition by means of computerized rheoencephalography [REG]. MATERIAL AND METHODS: The study group consisted of 27 patients with presumed posttraumatic NPH. In each patient both the tap test and infusion test were performed. Psychometric tests and rheoencephalographic examinations were made twice: before and after CSF withdrawal. The obvious restoration of the functional state of CVA after CSF withdrawal was considered as a positive result of the tap test. RESULTS: Fourteen patients with a positive tap test and/or with resistance to CSF outflow (Rout) of more than 11 mmHg/ml/min were shunted. The improvement was obtained in 10 of them. Only one patient with a positive tap test did not improve. CONCLUSIONS: Our study suggests that restoration of CVA after CSF withdrawal is associated with high likelihood of shunt success, but not vice versa. Evaluation of CVA using REG seems to offer a new diagnostic tool in selecting patients likely to respond to shunting. Further studies are necessary to optimize the amount of CSF withdrawal, the delay between CSF withdrawal and control examinations and methodology of neuropsychological examinations.     

Does compliance predict ventricular reduction after shunting for normal pressure hydrocephalus

Ventricular reduction after shunting for normal pressure hydrocephalus (NPH) was classified on the basis of magnitude and rate of reduction in 35 adult patients. Brain compliance and resistance to outflow of cerebrospinal fluid (RCSF) were determined before shunting. Rapid and marked ventricular reduction (n = 11) was associated with a significantly lower compliance than slow and moderate to marked (n = 16) or minimal to mild (n = 8) reduction. Otherwise ventricular size before as well as after shunting did not correlate with compliance or RCSF. It is concluded that both rate and magnitude of ventricular reduction after shunting for NPH vary widely. Reduced compliance seems to be the best predictor of rapid and marked reduction.     

Predictors of outcome in patients with normal-pressure hydrocephalus.

Despite knowledge emerging over the last 40 years, the postoperative results after shunt implantation in patients diagnosed with normal-pressure hydrocephalus (NPH) have not improved significantly over the last decade. For that reason predictors have to be identified in order to preoperatively predict outcome. From 1982 to 2000 we prospectively studied 200 patients diagnosed with NPH. From the patients, who were surgically treated by a shunt implantation we reexamined 155 (78%) postoperatively a mean time interval of 7 months. The NPH was graded according to the results of the intrathecal infusion test in an early stage NPH (without brain atrophy) and late stage NPH (with brain atrophy). In our study, we focussed attention on the possible predictors: patients age, length of disease, clinical signs (gait ataxia, dementia and bladder incontinence), aetiology idiopathic/secondary as well as implanted valve type and the value of resistance to cerebrospinal fluid outflow. To measure the outcome we used the NPH recovery rate and as the statistical test the chi(2) according to Pearson. In 80 patients with an early stage NPH (without cerebral atrophy), a short course of disease (<1 year), a slight degree of dementia and an implanted Miethke-Dual-Switch valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only a minimal relevance to outcome. Those 75 patients with a late state NPH (with cerebral atrophy) had a better outcome when dementia was not present, the outflow resistance was above 20mm Hg/min/ml, the CSF tap-test was positive and a Miethke-Dual-Switch valve was implanted.     

Predictors of outcome in patients with normal pressure hydrocephalus

Despite emerging knowledge over 40 years, the postoperative results after shunt implantations in patients diagnosed for normal pressure hydrocephalus (NPH) did not improve significantly during the last decade. For that reason predictors have to be identified in order to predict preoperatively the course of disease. From 1982 until 2000 we examined in a prospective study 200 patients diagnosed for NPH. From the patients, who were surgically treated by a shunt implantation we could reexamine 155 (78%) in a meantime interval of seven month after the operation. The NPH was graduated according to the results of the intrathecal infusion test in an early state NPH (without brain atrophy) and late state NPH (with brain atrophy). In our study, we focussed the attention on the possible predictors: patients age, length of disease, clinical signs--like gait ataxia, dementia and bladder incontinence, aetiology idiopathic/secondary as well as implanted valve type and the value of resistance to cerebrospinal fluid outflow. To measure the outcome we used the NPH-Recovery-Rate, as statistical test the Chi-square according to Pearson. In 80 patients with an early stage NPH (without cerebral atrophy) a short course of disease (< 1 year), a just slight distinct of dementia and an implanted Miethke-Dual-Switch valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only a minimal relevance for the outcome. Those 75 patients with a late state NPH (with cerebral atrophy) had a better outcome when dementia was not present, the outflow resistance was above 20 mm Hg*min/ml, the CSF tap-test was positive and a Miethke-Dual-Switch valve was implanted.     

Predictors of outcome in patients with normal-pressure hydrocephalus

Despite emerging knowledge of over 40 years, the postoperative results after shunt implantations in patients diagnosed for normal-pressure hydrocephalus (NPH) have not improved significantly in the last decade. For this reason, predictors have to be identified in order to preoperatively predict the course of disease. From 1982 to 2000, we examined in a prospective study 200 patients diagnosed for NPH. Of the patients who were surgically treated by a shunt implantation we could re-examine 155 (78%) in a mean time interval of 7 months after operation. The NPH was graduated according to the results of the intrathecal infusion test in an early state NPH (without brain atrophy) and late state NPH (with brain atrophy). In the study we focused our attention on the possible predictors: patient's age, length of disease, clinical signs--like gait ataxia, dementia and bladder incontinence, etiology idiopathic/secondary as well as implanted valve type and the value of resistance to cerebrospinal fluid outflow. To measure the outcome we used the NPH recovery rate, as statistical test the chi(2) according to Pearson. In 80 patients with an early stage NPH (without cerebral atrophy) and a short course of disease (<1 year), slightly distinct dementia and an implanted Miethke Dual-Switch valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only a minimal relevance for the outcome. Those 75 patients with a late state NPH (with cerebral atrophy) had a better outcome when dementia was not present, the outflow resistance was >20 mm Hg.min/ml, the CSF tap test was positive and a Miethke Dual-Switch valve was implanted.     

Reduction of ventricular size after shunting for normal pressure hydrocephalus related to CSF dynamics before shunting.

Reduction of ventricular size was determined by repeated computed tomography in 30 adult patients shunted for normal pressure hydrocephalus (NPH) and related to the pressure-volume index (PVI) and resistance to outflow of cerebrospinal fluid (Rcsf) measured before shunting. Rapid and marked reduction of ventricular size (n = 10) was associated with a significantly lower PVI than slow and moderate to marked (n = 13) or minimal to mild reduction (n = 7). Otherwise no relationship could be found between the reduction of ventricular size and PVI or Rcsf. It is concluded that both rate and magnitude of reduction of ventricular size after shunting for NPH are extremely variable. High brain elasticity seems to be the best predictor of rapid and marked reduction.     

腰穿放液试验在正常压力脑积水病人术前评估中的应用及意义

目的评价腰穿放液试验在正常压力脑积水病人术前评估中的应用价值。方法对2008年6月至2011年3月期间入选的60例正常压力脑积水病人进行前瞻性研究。病人先行腰穿放液试验,5天后行脑室-腹腔分流术。腰穿放液前、放液后24h及分流术后1周分别对病人"三联征"进行定量评估,并通过筛检试验统计方法分析腰穿放液试验预测正常压力脑积水分流手术的有效性。结果腰穿放液试验阳性36例,行分流手术后临床症状改善35例,1例未改善;腰穿放液试验阴性24例,分流术后改善8例,16例未改善。提示分流手术总有效率71.7%;腰穿放液试验对正常压力脑积水分流手术的灵敏度为81.4%,特异度94.1%,阳性预测率97.2%,阴性预测率66.7%。结论正常压力脑积水术前腰穿放液试验阳性者分流手术可望获得良好疗效。     

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.     

Abnormal cerebrospinal fluid-blood flow dynamics. Implications in diagnosis, treatment, and prognosis in normal pressure hydrocephalus.

Increased cerebral blood flow (CBF) has been proposed as responsible for the clinical improvement after cerebrospinal fluid (CSF) shunting in patients with normal pressure hydrocephalus (NPH). In order to determine any abnormal CSF-CBF pressure-flow relationships in NPH, measurements of regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) were made before and after lowering CSF pressure (CSFP) in 15 patients with NPH, and in ten patients with presumed hydrocephalus ex vacuo. Maximal reduction of rCBF and rCBV occurred in the territory of the anterior cerebral artery in NPH but no in dementia due to brain atrophy. Both CBF and rCBV increased after lowering the CSFP by lumbar puncture in patients with NPH. Patients with higher preoperative rCBF and maximal increases in rCBR and rCBV after lowering CSFP showed the most consistent clinical improvement after CSF shunting. Evidence is offered that CBF autoregulation is impaired in NPH. The CBF test assists in both diagnosis and selection of patients for CSF shunting.     

Shunting normal pressure hydrocephalus: the predictive value of combined clinical and CT data.

The value of an ordinal global scale derived from combined clinical and CT data (clin/CT scale) to predict the clinical outcome in 112 patients shunted for presumed normal pressure hydrocephalus (NPH) was analysed. The clinical data were retrospectively collected, all CT scans were re-evaluated, and the clin/CT scale was determined blind to the results of further ancillary tests and to the post-surgical outcome. The scale ranked three classes of prediction: on the basis of clinical and CT characteristics, improvement after shunting was probable, possible, or improbable. The predictive value of the clin/CT scale for the subgroup of communicating NPH was established for two different strategies, depending on the strictness of selection criteria for shunting. In the subgroup of patients with presumed communicating NPH, the prevalence of shunt responsiveness was 29%; the best strategy was to shunt only patients with probable shunt-responsive NPH: the sensitivity was 0.54, the specificity 0.84, and the predictive accuracy 0.75, with a limited number of ineffective shunts (11%) and missed improvements (13%). The study illustrates its need to assess the pre-test probability of NPH based on combined clinical and CT data, before establishing the clinical usefulness of an ancillary test.     

The value of temporary external lumbar CSF drainage in predicting the outcome of shunting on normal pressure hydrocephalus

OBJECTIVE: It has been reported that temporary external lumbar CSF drainage (ELD) is a very accurate test for predicting the outcome after ventricular shunting in patients with normal pressure hydrocephalus (NPH). However, only a limited number of patients have been studied for assessing the predictive accuracy of ELD. Therefore, the value of ELD in predicting the outcome after a ventriculoperitoneal shunt in patients with presumed NPH was assessed. METHODS: All patients with presumed NPH were invited to participate in this study. Clinical assessment, MRI, and neuropsychological evaluation were followed by a lumbar CSF tap test consisting of removing 40 ml CSF. When this test resulted in marked clinical improvement of gait impairment, mental disturbances, or both, the patient was shunted without further tests. In patients with either questionable or no improvement after the CSF tap test, ELD was carried out. The value of ELD for predicting the outcome after shunting was calculated by correlating the results of ELD with that of ventriculoperitoneal shunting. RESULTS: Between January 1994 and December 2000, 49 presumed NPH patients from three institutes were included. Forty three had idiopathic, and the remaining six had secondary NPH. Forty eight patients were shunted; 39 had an ELD of whom 38 completed the test. After 2 months 35 of the 48 (73%) shunted patients had improved. The predictive value of a positive ELD was 87% (95% confidence interval (95% CI) 62-98) and that of a negative ELD 36% (95% CI 17-59). In two patients serious test related complications (meningitis) occurred without residual deficit. CONCLUSION: The study suggests that although the predictive value of a positive ELD is high, that of a negative ELD is deceptively low because of the high rate of false negative results. The costs and invasiveness of the test and the possibility of serious test related complications further limits its usefulness in managing patients with presumed NPH.     

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.     

Psychotic symptoms in normal-pressure hydrocephalus.

Two patients with a psychiatric history of about 20 years, and clinical and neuroradiological signs of normal-pressure hydrocephalus (NPH) are reported. One had a periodic psychosis subsequent to a tuberculous meningitis, and this overshadowed the slight classical symptoms of NPH. She had received at least 120 treatments with electro-convulsive therapy. The second patient suffered from a paranoid psychosis; other signs of NPH were moderate though progressive. Both patients showed definite improvement of their NPH symptoms after ventriculo-atrial shunting, and psychotic symptoms ceased totally. Follow-up was 5 years for the patient with periodic psychosis. The other patient died from septicaemia 2.5 years after shunting. A large-scale screening of patients with psychiatric symptoms or dementia, particularly when combined with gait disturbance, should be done by using computerized tomography. Patients suspected of having NPH should then be referred for further examination with the aim of selecting patients suitable for shunting. These measures seem well motivated from humanitarian as well as economic points of view.     

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.     

Quantitative electroencephalography in idiopathic normal pressure hydrocephalus: relationship to CSF outflow resistance and the CSF tap-test

Quantitative electroencephalography from the occipito-parietal region, gait, and psychometric tests were performed in patients with idiopathic normal pressure hydrocephalus (NPH) before and after drainage of 40 ml CSF. The results were compared to those in demented controls. The EEG results were also analyzed with respect to possible correlations with clinical, CSF dynamics, and psychometric variables. Significant differences between NPH patients and demented controls were not found neither in baseline EEG variables nor regarding the CSF tap-test-related change in EEG. The EEG-response to the CSF tap-test did not often exceed the day-to-day test-retest variability. In NPH patients, EEG slowing (relative delta and theta power) correlated significantly with CSF outflow-resistance (p< 0.002). Relative theta power correlated with the Thurstone's Identical Forms test (p<0.05). Significant correlations between EEG and Bingley's Memory Test were found for the control group but not among NPH patients (p<0.05). Thus, EEG band-power variables seem to reflect some of the pathophysiology involved in idiopathic normal pressure hydrocephalus, particularly increased resistance to CSF outflow. The practical value of the presently applied EEG method in NPH-diagnosis and prognostic evaluation seems to be limited, however.     

Alzheimer's disease,normal-pressure hydrocephalus,and senescent changes in CSF circulatory physiology: a hypothesis

There is evidence that production and turnover of CSF help to clear toxic molecules such as amyloid-beta peptide (Abeta) from the interstitial-fluid space of the brain to the bloodstream. Two changes in CSF circulatory physiology have been noted as part of ageing: first, a trend towards lower CSF production, hence a decrease in CSF turnover; and second, greater resistance to CSF outflow. Our hypothesis is that, all else being equal, the initially dominant physiological change determines whether CSF circulatory failure manifests as Alzheimer's disease (AD) or as normal-pressure hydrocephalus (NPH). If CSF production failure predominates, AD develops. However, if resistance to CSF outflow predominates, NPH results. Once either disease process takes hold, the risk of the other disorder may rise. In AD, increased deposition of Abeta in the meninges leads to greater resistance to CSF outflow. In NPH, raised CSF pressure causes lower CSF production and less clearance of Abeta. The disorders may ultimately converge in vulnerable individuals, resulting in a hybrid as has been observed in several clinical series. We postulate a new nosological entity of CSF circulatory failure, with features of AD and NPH. NPH-AD may cover an important subset of patients who carry the diagnosis of either AD or NPH.     

Impact of duration of symptoms on CSF dynamics in idiopathic normal pressure hydrocephalus

Czosnyka Z, Owler B, Keong N, Santarius T, Baledent O, Pickard JD, Czosnyka M. Impact of duration of symptoms on CSF dynamics in idiopathic normal pressure hydrocephalus.
Acta Neurol Scand: 2011: 123: 414–418.
© 2010 John Wiley & Sons A/S. Objective – Cerebrospinal fluid (CSF) pressure–volume compensation may change over time as part of normal ageing, where the resistance to CSF outflow increases and the formation of CSF decreases with age. Is CSF compensation dependent on duration of symptoms in idiopathic normal pressure hydrocephalus (iNPH)? Methods – We investigated 92 patients presenting with iNPH. Mean age was 73 (range 47–86). There were 60 men and 32 women. They all presented with gait disturbance and ventricular dilatation. Memory deficit occurred in 72% and urinary incontinence in 52% of patients. All patients underwent computerized CSF infusion tests. Sixty‐four shunted patients were available for follow‐up, and their improvement was expressed using the NPH score. Results – Mean intracranial pressure (ICP) was 10.1 ± 5.1 mmHg, and mean resistance to CSF outflow was 17.3 ± 5.2 mmHg/(ml/min). Mean duration of symptoms was 24 ± 19 months (range from 2 weeks to 86 months). Baseline ICP, magnitude of ICP pulse waveform, brain compliance and improvement after shunting (72% of patients improved) did not exhibit any dependency on the duration of symptoms. The resistance to CSF outflow showed a strong tendency to decrease in time with the duration of symptoms beyond 2 years (R = −0.702; P < 0.005). Conclusion – This is a preliminary observation, and it suggests that for patients with duration of symptoms longer than 2–3 years, the threshold for normal resistance to CSF outflow should be duration‐adjusted.     

Hydrocephalus as a cause of disturbances of gait in the elderly

To investigate the possible role of symptomatic normal-pressure hydrocephalus (NPH) in unexplained walking difficulties of the elderly, we used CT to measure lateral ventricular size. We compared data in 50 patients over the age of 60 with a disturbance of gait and 80 control subjects of similar age who walked well and were mentally sound. Forty-six of the 50 gait patients (92%) had a ventricular span of more than 12 mm, whereas only 5 of the 80 controls (6.3%) had ventricles of that size. There was a narrow zone of overlap. Seventeen of the gait patients later improved after surgical shunting or test withdrawal of lumbar CSF. These findings demonstrate that hydrocephalus is an important cause of disturbances of walking in the elderly. The validity of the study, the clinical picture in NPH, and the nature of NPH are discussed.     

Magnetic resonance spectroscopic determination of a neuronal and axonal marker in white matter predicts reversibility of deficits in secondary normal pressure hydrocephalus

BACKGROUND: Normal pressure hydrocephalus (NPH) is considered to be a treatable form of dementia, because cerebrospinal fluid (CSF) shunting can lessen symptoms. However, neuroimaging has failed to predict when shunting will be effective. OBJECTIVE: To investigate whether 1H (proton) magnetic resonance (MR) spectroscopy could predict functional outcome in patients after shunting. METHODS: Neurological state including Hasegawa's dementia scale, gait, continence, and the modified Rankin scale were evaluated in 21 patients with secondary NPH who underwent ventriculo-peritoneal shunting. Outcomes were measured postoperatively at one and 12 months and were classified as excellent, fair, or poor. MR spectra were obtained from left hemispheric white matter. RESULTS: Significant preoperative differences in N-acetyl aspartate (NAA)/creatine (Cr) and NAA/choline (Cho) were noted between patients with excellent and poor outcome at one month (p = 0.0014 and 0.0036, respectively). Multiple regression analysis linked higher preoperative NAA/Cr ratio, gait score, and modified Rankin scale to better one month outcome. Predictive value, sensitivity, and specificity for excellent outcome following shunting were 95.2%, 100%, and 87.5%. Multiple regression analysis indicated that NAA/Cho had the best predictive value for one year outcome (p = 0.0032); predictive value, sensitivity, and specificity were 89.5%, 90.0%, and 88.9%. CONCLUSIONS: MR spectroscopy predicted long term post-shunting outcomes in patients with secondary NPH, and it would be a useful assessment tool before lumbar drainage.     

Idiopathic normal pressure hydrocephalus: the CSF tap-test may predict the clinical response to shunting

A follow-up study was performed in nine patients with idiopathic normal pressure hydrocephalus (NPH) 37 months (mean) after shunting and 10 non-operated controls with comparable degrees of ventricular enlargement, gait disorder, and dementia. Five operated patients vs. no controls reported sustained general improvement (p<0.02). Objectively improved gait at follow-up (compared with preoperative status) was found in five of the six tested NPH-patients vs. none of the controls (p< 0.005). Improved gait and/or psychometric function was found in four of six NPH vs. none of eight control patients (p<0.02) after drainage of 40 ml cerebrospinal fluid (CSF tap-test). Improved gait during the CSF tap-test predicted continued improvement at follow-up. Temporal horn size was the only radiological variable which showed a (moderate) positive correlation with resistance to CSF absorption and rate of pressure increase. The size of the third ventricle diminished in parallell with clinical improvement.