Quantitative Local Cerebral Blood Flow Change after Cerebrospinal Fluid Removal in Patients with Normal Pressure Hydrocephalus Measured by a Double Injection Method with N-Isopropyl-p-[123I] Iodoamphetamine

Summary.  The efficacy of cerebrospinal fluid (CSF) shunting surgery for normal pressure hydrocephalus (NPH) is difficult to predict. The CSF removal test is useful but quantification of the results is difficult. A method to quantitatively measure cerebral blood flow (CBF) by single photon emission computed tomography twice within 30 min after double injection of N-isopropyl-p-[¹²³I] iodoamphetamine using a background subtraction method to correct for the temporal profile was utilized in tandem with CSF removal via a lumbar spinal tube in 22 patients of NPH to produce maps of baseline CBF and quantitative CBF change after CSF removal. All 22 patients with NPH underwent ventriculoperitoneal shunting surgery and were divided into two groups according to improvement in clinical symptoms and signs (responder group, N=15; nonresponder group, N=7). Baseline clinical characteristics and baseline CBF values were not significantly different between the two groups. Regional and whole brain CBF changes in the responder group (range 98–105%, whole brain 101±39%) were significantly higher than those in the nonresponder group (range 41–48%, whole brain 46±40%) (P<0.01). Discrimination analysis showed that an increase of more than 80% in CBF after CSF removal was predictive of response to shunt surgery with 77% accuracy. This new quantitative CSF removal test could be useful for selecting good candidates for CSF shunting surgery among patients with NPH.     

Investigation of normal pressure hydrocephalus by 123I-IMP SPECT.

We evaluated N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) single photon emission computed tomography (SPECT) as a method for identifying normal pressure hydrocephalic (NPH) patients eligible for shunting procedures. 123I-IMP SPECT scans were taken before and after cerebrospinal fluid (CSF) taps in NPH cases. Post-subarachnoid hemorrhagic (SAH) patients showed apparent frontal blood flow reduction but non-SAH cases did not. The frontal blood flow increased in comparison with the temporal flow after CSF tapping in SAH cases who benefited most from shunting. Cerebral blood flow study before and after CSF removal is a potential method for classifying NPH patients likely to benefit from the shunting operation.     

Risk factors for the occurrence of chronic subdural haematomas after neurosurgical procedures

Summary ¶Chronic subdural haematoma (CSDH) is a rare clinical complication of neurosurgical procedures. CSDH occurs sporadically after aneurysm clipping surgery and revascularisation surgery but the risk factors are not known. The present study reviewed 6613 consecutive neurosurgical procedures performed from January 1987 to July 2001, and identified 621 cases of CSDH. Fifty of these 621 cases had a past history of neurological disorders treated by neurosurgery. This study evaluated these 50 cases in order to elucidate the clinical and radiological characteristics of CSDH after neurosurgery and to investigate the etiology for identifying in the risk factors of CSDH as a postoperative complication. The incidence of CSDH after neurosurgery was 0.8% (50/6613). Twenty-seven of the 50 patients with a past history of neurosurgery had undergone aneurysm clipping surgery. The incidence after clipping surgery was 2.4%. Twelve of these 27 cases also underwent ventriculoperitoneal shunting. Three patients had postoperative CSDH after arachnoid cyst opening and/or shunting. The incidence was highest at 7.5%. Three patients had postoperative CSDH after brain tumour surgery. The incidence was low at 0.4%. However, the ventricular cerebrospinal fluid (CSF) space was opened during tumour removal in 2 of these 3 patients.Communication of the subarachnoid space to the subdural space is considered to be one of the causative factors and excessive CSF shunting facilitates formation of CSDH after neurological surgery. Repair of arachnoid tearing during neurosurgery and avoidance of excessive CSF shunting may reduce the risk of CSDH after neurosurgery.Published online May 19, 2003     

Symptomatic spinal extramedullary mass lesion secondary to chronic overdrainage of ventricular fluid--case report

A 69-year-old man presented with progressive nuchal pain and spastic gait 2 years after undergoing ventriculoperitoneal (VP) shunting for a pineal astrocytoma with obstructive hydrocephalus. The neurological manifestations were compatible with radiculomyelopathy caused by an upper cervical lesion. Magnetic resonance imaging showed an enhanced extramedullary mass lesion tightly constricting the upper cervical spinal cord. The pressure of the shunt system was 150 mmH2O, and lumbar puncture revealed normal cerebrospinal fluid (CSF) pressure of 170 mmH2O. After removal of the shunt system, the clinical symptoms and neuroradiological findings markedly improved. This symptomatic spinal mass lesion was thought to be formed secondary to chronic depletion of ventricular CSF through the VP shunt.     

Idiopathic normal pressure hydrocephalus: Analysis of factors related to cerebrospinal fluid dynamics determining functional prognosis

Summary This investigation has been undertaken to analyze the findings with both the cerebrospinal fluid (CSF) pressure (Pcsf) and CSF pulse pressure (PP) in order to predict the outcome of patients with the syndrome of idiopathic normal pressure hydrocephalus (NPH). Accordingly, a prospective clinical study was planned in which two groups of patients with NPH, having analogous prevalence of several matched clinical and radiological parameters, were separated on the basis of their positive or negative response to shunting. Both the resting Pcsf and CSF PP profiles were compared in these two groups, and between them and normal controls. CSF PP amplitude and CSF PP latency correlated directly in conditions associated with either normal or high compliance (controls and patients with Alzheimer-like disorders), whereas this correlation was inverse in states of low compliance (NPH). On the other hand, shunt-responders showed a resting Pcsf significantly higher than both non-responders and controls.The following conclusions were obtained: 1) CSF PP is a high-amplitude and relative low-latency wave in NPH when compared with controls; 2) CSF PP amplitude and latency correlate directly in normal subjects and in those with primary cerebral atrophy; 3) a non-reversible stage of NPH could be conceived in contradistinction to the reversible one, in both of which an inverse correlation between the amplitude and the latency takes place, the main difference between them being the resting Pcsf, which is significantly lower in the former than in the latter, depending on the degree of atrophic changes developed.     

The predictive value of external continuous lumbar drainage,with cerebrospinal fluid outflow controlled by medium pressure valve,in normal pressure hydrocephalus

Summary Background. Although sporadic studies have described temporary external cerebrospinal fluid (CSF) lumbar drainage as a highly accurate test for predicting the outcome after ventricular shunting in normal pressure hydrocephalus (NPH) patients, a more recent study reports that the positive predictive value of external lumbar drainage (ELD) is high but the negative predictive value is deceptively low. Therefore, we conducted a prospective study in order to evaluate the predictive value of a continuous ELD, with CSF outflow controlled by medium pressure valve, in NPH patients.Method. Twenty-seven patients with presumed NPH were admitted to our department and CSF drainage was carried out by a temporary (ELD) with CSF outflow controlled by a medium pressure valve for five days. All patients received a ventriculoperitoneal shunt using a medium pressure valve based upon preoperative clinical and radiographic criteria of NPH, regardless of ELD outcome. Clinical evaluation of gait disturbances, urinary incontinence and mental status, and radiological evaluation with brain CT was performed prior to and after ELD test, as well as three months after shunting.Findings. Twenty-two patients were finally shunted and included in this study. In a three-month follow-up, using a previously validated score system, overall improvement after permanent shunting correlated well to improvement after ELD test (Spearman’s rho = 0.462, p = 0.03). When considering any degree of improvement as a positive response, ELD test yielded high positive predictive values for all individual parameters (gait disturbances 94%, 95% CI 71%–100%, urinary incontinence 100%, 95% CI 66%–100%, and mental status 100%, 95% CI 66%–100%) but negative predictive values were low (< 50%) except for cognitive impairment (85%, 95% CI 55%–98%).Conclusion. This study suggests that a positive ELD-valve system test should be considered a reliable criterion for preoperative selection of shunt-responsive NPH patients. In case of a negative ELD-valve system test, further investigation of the presumed NPH patients with additional tests should be performed.     

Auditory brainstem responses before and after shunting in patients with suspected normal pressure hydrocephalus.

Auditory brainstem responses (ABRs) were studied in 15 adults with suspected normal pressure hydrocephalus (NPH) before and after shunting. The patients were divided into Groups A (shunt-ineffective) and B (shunt-effective). The pre- and postoperative ABRs of each patient were compared with those of 20 normal volunteers, and the relationships between ABRs and certain clinical findings were investigated. Preoperatively, nine patients (60%) showed prolonged central conduction time (CCT) (interpeak latency of wave I-V or neural-axonal conduction time) relative to the mean control value plus 2 SD. There was no significant difference between Groups A and B in the percentage of patients with abnormal CCT, and no specific ABR abnormalities that were predictive of the efficacy of shunting. However, a significantly higher percentage of Group B patients (p less than 0.05) showed a postoperative reduction in the CCT of more than 1 SD of the mean control value. In Group A, the CCT was positively correlated with preoperative clinical disability. These results suggest that brainstem dysfunction may be reversed by shunting, but is not correlated with clinical disability in patients in whom shunting is effective, that is, in those with NPH. It appears that measurement of ABRs is a useful technique for the clinical monitoring of shunted patients.     

Isotope cisternography and conductance to outflow of CSF in normal pressure hydrocephalus

Summary In 50 patients with normal pressure hydrocephalus (NPH) the findings on lumbar isotope cisternography (ICG) were compared to the conductance to outflow of CSF (C_out) as measured by lumbo-ventricular perfusion. The purpose was to identify those ICG-characteristics that imply a low C_out and thus may indicate CSF shunting therapy.Normal ICG was found only in three patients, where C_out was not, or only moderately, decreased. There was a significant correlation between a low C_out and occurrence of ventricular retention and absent parasagittal accumulation at 24 hours or later, following injection. These findings may, however, also be present in patients with no, or only moderate, decreased C_out, where CSF shunting may seem unjustified. It is concluded, that the indication for CSF shunting cannot be based on the results of ICG alone.     

Diamox® Challenge Test to Decide Indications for Cerebrospinal Fluid Shunting in Normal Pressure Hydrocephalus

Summary ? Objective. The indications for cerebrospinal fluid (CSF) shunting in patients with normal pressure hydrocephalus (NPH) have not been established. Establishment of clear-cut indications for this procedure is essential to ensure cost-effective, and safe treatment. We report the usefulness of the Diamox^? challenge test in evaluating indications for CSF shunting in patients with NPH.  Methods. Pre- and post-operative responses in cerebral blood flow (CBF) and intracranial pressure (ICP) to intravenous administration of Diamox^? 1000mg (Diamox^? administration) were analysed in 41 patients with NPH who were treated by ventriculoperitoneal (VP) shunt with a programmable valve and an on-off valve.  Results. The preoperative response of ICP to Diamox^? administration was more than 10 mmHg in most patients in whom the shunt was effective (shunt effective group), however, it was less than 10 mmHg in most patients in whom the shunt was ineffective (shunt non-effective group). Furthermore, the postoperative response of ICP to Diamox^? administration decreased to less than 10 mmHg in most patients in the shunt effective group. The increases in CBF in response to Diamox^? administration were similar in the two groups both before and after placement of the VP shunt.  Conclusion. Patients in whom ICP increased by more than 10 mmHg in response to Diamox^? administration were regarded to have poor CSF circulation and to thus be candidates for CSF shunting. The Diamox^? challenge test is a simple, safe procedure, useful in evaluating the response to treatment.     

Normal pressure hydrocephalus: survey on contemporary diagnostic algorithms and therapeutic decision-making in clinical practice

Summary Background. There is no agreement on the best diagnostic criteria for selecting patients with normal pressure hydrocephalus (NPH) for CSF shunting. The primary objective of the present study was to provide a contemporary survey on diagnostic algorithms and therapeutic decision-making in clinical practice. The secondary objective was to estimate the incidence of NPH.Method. Standardized questionnaires with sections on the incidence of NPH and the frequency of shunting, evaluation of clinical symptoms, and signs, diagnostic studies, therapeutic decision-making and operative techniques, postoperative outcome and complications, and the profiles of different centers, were sent to 82 neurosurgical centers in Germany known to participate in the care of patients with NPH.Findings. Data were analyzed from 49 of 53 centers which responded to the survey (65%). The estimated annual incidence of NPH was 1.8 cases/100.000 inhabitants. Gait disturbance was defined as the most important sign of NPH (61%). There was a wide variety in the choice of diagnostic tests. Cisternography was performed routinely only in single centers. Diagnostic CSF removal was used with varying frequency by all centers except one, but the amount of CSF removed by lumbar puncture differed markedly between centers. There was poor agreement on criteria for evaluation of continuous intracranial pressure recordings regarding both the amplitude and the relative frequency of B-waves. Both periventricular and deep white matter lesions were present in about 50% of patients being shunted, indicating that vascular comorbidity in NPH patients has gained more acceptance. Programmable shunts were used by more than half of the centers, and newer valve types such as gravitational valves have become more popular.Conclusions. According to the present survey, new diagnostic and therapeutic concepts on NPH have penetrated daily routine to a certain extent. Wide variability, however, still exists among different neurosurgical centers.     

The prognostic value of clinical characteristics and parameters of cerebrospinal fluid hydrodynamics in shunting for idiopathic normal pressure hydrocephalus

Summary Background. It is difficult to predict which patients with symptoms and radiological signs of normal pressure hydrocephalus (NPH) will benefit from a shunting procedure and which patients will not. Risk of this procedure is also higher in patients with NPH than in the overall population of hydrocephalic patients. The aim of this study is to investigate which clinical characteristics, CT parameters and parameters of cerebrospinal fluid dynamics could predict improvement after shunting. Methods. Eighty-three consecutive patients with symptoms and radiological signs of NPH were included in a prospective study. Parameters of the cerebrospinal fluid dynamics were measured by calculation of computerised data obtained by a constant-flow lumbar infusion test. Sixty-six patients considered candidates for surgery were treated with a medium-pressure Spitz-Holter valve; in seventeen patients a shunting procedure was not considered indicated. Clinical and radiological follow-up was performed for at least one year postoperatively. Findings. The odds ratio, the sensitivity and specificity as well as the positive and negative predictive value of individual and combinations of measured parameters did not show a statistically significant relation to clinical improvement after shunting. Conclusions. We conclude that neither individual parameters nor combinations of measured parameters show any statistically significant relation to clinical improvement following shunting procedures in patients suspected of NPH. We suggest restricting the term normal pressure hydrocephalus to cases that improve after shunting and using the term normal pressure hydrocephalus syndrome for patients suspected of NPH and for patients not improving after implantation of a proven well-functioning shunt. An erratum to this article is available at .     

Management of idiopathic normal-pressure hydrocephalus: a multiinstitutional study conducted in Japan.

OBJECT: A cooperative study was undertaken to identify factors that could be used to predict a favorable outcome after extracranial cerebrospinal fluid (CSF) diversion (shunting) in patients with suspected idiopathic normal-pressure hydrocephalus (NPH). METHODS: Questionnaires concerning patients with suspected idiopathic NPH were sent to 14 members of the Committee for Scientific Research on Intractable Hydrocephalus, sponsored by the Ministry of Health and Welfare of Japan. After the questionnaires were returned, a retrospective analysis of the responses was undertaken. To be included in the study, patients had to be 65 years of age or older and had to have undergone surgery between October 1995 and October 1998. Clinical measures included degrees of gait disturbance, dementia, and urinary incontinence as evaluated before. 3 months after, and 3 years after shunt placement. Diagnostic tests in various combinations included lumbar puncture in which CSF was withdrawn; intracranial pressure monitoring; measurements of CSF outflow resistance, level of serum alpha-1-antichymotrypsin, cerebral arteriovenous differences of oxygen content, and cerebral blood flow; and computerized tomography cisternography. In this study, 120 patients were identified as having idiopathic NPH and these patients underwent placement of shunts. A ventriculoperitoneal shunt with a programmable valve was used in two thirds of the patients. At the end of 3 months (early assessment), there was an 80% overall rate of clinical improvement, which dropped to 73.3% of the 105 patients who could be evaluated at the end of the 3-year study. Of the three variables, gait disturbance was most improved, both at early and late testing periods. Shunt complications occurred in 22 (18.3%) of the patients. CONCLUSIONS: Patients suspected of having idiopathic NPH did not form a homogeneous group, making it difficult to select those who would most likely respond to CSF diversion. Of the diagnostic studies, the most reliable result was improvement in clinical symptoms following a lumbar puncture in which CSF was withdrawn. The use of a programmable valve is recommended because it offers advantages in preventing problems of over- and underdrainage.     

The surgical treatment of Chiari I malformation

Summary A retrospective study was undertaken on 133 patients with a Chiari I malformation treated within the last 16 years at the Departments of Neurosurgery at the Nordstadt Hospital Hannover, Germany, and the University of California, Los Angeles, U.S.A. Ninety-seven patients presented with symptoms related to accompanying syringomyelia and 4 with associated syringobulbia. They underwent 149 surgical procedures and were followed for a mean of 39±52 months. A decompression at the foramen magnum was performed in 124 patients, while 22 of those with syringomyelia were treated by shunting (7 syringosubarachnoid shunts, 15 syringoperitoneal or -pleural shunts), and 3 by ventriculoperitoneal shunts for hydrocephalus.Except for ventriculoperitoneal shunting, at least a short-term decrease in size of an associated syrinx was observed for all procedures in the majority of cases. However, no long-term benefit was observed for syrinx shunting operations. The best clinical longterm results were obtained with decompression of the foramen magnum in patients with (86% free of a clinical recurrence) and without syringomyelia (77% free of a clinical recurrence). We advise against syrinx shunting, a large craniectomy, and obex plugging which are associated with higher recurrence rates. Instead, surgery should consist of a small craniectomy, opening of the dura, archnoid dissection to establish normal cerebrospinal fluid (CSF) outflow from the 4th ventricle, and a fascia lata durai graft.     

Relationship of new-onset systemic hypertension and normal pressure hydrocephalus

Communicating normal pressure hydrocephalus (NPH) is an important remote complication of traumatic brain injury (TBI). The diagnosis of this hydrocephalus depends largely on clinical signs and symptoms, including cognitive deterioration, gait changes and incontinence. However, many of these signs are also seen during post-traumatic amnesia, making early recognition of this syndrome difficult. A case study of one man post-TBI, who presented with new-onset hypertension as a sign of NPH, prompted a retrospective chart review of all patients admitted over a 2-year period with a diagnosis of NPH. Ninety per cent of patients had one or more of the classic triad of NPH and 25% of patients had symptoms suggestive of raised intracranial pressure (unexplained nausea, headache and visual disturbance). Mean systolic and diastolic blood pressures among the 20 subjects for six consecutive days pre-operatively compared with those for days 8-14 and 15-21 post-operatively showed no significant differences; a subgroup of five patients (25%), however, demonstrated a significant change in blood pressure temporally related to shunting. We suggest that demonstration of new-onset systemic hypertension may also be a clinical sign suggestive of NPH useful in the evaluation of the TBI patient.     

Intracranial cerebrospinal fluid distribution and its postoperative changes in normal pressure hydrocephalus

Summary  Background. This study was conducted to investigate the usefulness of intracranial cerebrospinal fluid (CSF) volume measurement using MR-based methods in the management of patients with normal pressure hydrocephalus (NPH).  Methods. The study group comprised 19 patients with NPH who showed a favorable outcome after ventricular shunting, 15 normal volunteers (NV), and 15 patients with cerebrovascular disease (CVD). A 3D-fast asymmetric spin echo MR imaging sequence and the region-growing method were used to extract the CSF space from MR images. Ventricular volume (VV) and intracranial CSF volume (ICV) were measured and the VV/ICV ratio was calculated in each case. In NPH patients, the CSF volume was measured again after shunting.  Findings. The mean VV and VV/ICV ratio in the NPH group (91.1 mL and 45.2%, respectively) were significantly (p<0.01) higher than those in the NV group (26.5 mL and 13.7%) and in the CVD group (44.5 mL and 17.8%). On the other hand, mean ICV values were not significantly different among the three groups. The VV was markedly decreased postoperatively (mean −40.7%), whereas the ICV was unchanged, resulting in a marked reduction in the VV/ICV ratio (mean −39.3%).  Interpretation. These results suggest that patients with NPH have a unique intracranial CSF distribution, with an enlarged VV and a slightly increased ICV, resulting in a high VV/ICV ratio. Shunting led to dramatic improvement in our patients. It is likely that CSF measurement can provide valuable information in the management of patients with NPH.     

Cerebrospinal fluid ascites complicating ventriculoperitoneal shunting. Report of four cases

Four cases of cerebrospinal fluid (CSF) ascites secondary to ventriculoperitoneal shunting are described. It is possible to differentiate CSF ascites from a CSF-filled pseudocyst by the characteristic bowel gas pattern on films of the abdomen and by the presence of shifting dullness. Two of the patients had active shunt infections, and had ascitic fluid with a protein level greater than 3 gm% and a white blood cell (WBC) count greater than 1000/cu mm. Both were treated successfully with antibiotics and removal of the shunt from the peritoneum. Two other patients had no evidence of infection, protein levels of less than 2 gm%, and WBC count less than 100 cu mm. These disorders resolved spontaneously. A review of 18 cases reported in the literature shows that the etiology of CSF ascites in the absence of shunt infection is multifactorial, and no features are consistently present in all cases. Ascites without infection may resolve spontaneously without surgical intervention.     

Age-related changes of cerebral ventricular size

Thirty-one hydrocephalic patients were investigated prospectively by means of computed tomographic scan performed prior to and one week after cerebrospinal fluid (CSF) shunting. Planimetric measurements of the size of the cerebral ventricles were compared before and after shunting. Children under two years of age and elderly patients showed significantly less reduction of ventricular size (8.5 +/- 6.3% and 9.7 +/- 3.5% respectively) than older children and young adults (61.2 +/- 5.2%). The degree of reduction of ventricular size did not correlate with pre-operative size of ventricles, duration of disease, or clinical improvement. These findings suggest that reduction of ventricular size following CSF shunting is related to age. We postulate that the size of cerebral ventricles in hydrocephalic patients is not exclusively related to CSF dynamics, but also depends upon the intrinsic elastic properties of the cerebral parenchyma which vary with age.     

Wirbelsäulenerkrankungen und assoziierte ZNS-Fehlbildungen – Tethered-Cord und Arnold-Chiari-Fehlbildung

Tethered cord syndrome (TCS) and the Chiari malformation (CM) are generally related to congenital malformations, but both entities can be acquired.TCS often presents with progressing sensory and motor symptoms that can be attributed to increased tension of the spinal cord. Fixation of the spinal cord can occur congenitally (primary TCS) or in association with other intraspinal pathologies or postoperative scarring (secondary TCS). Exact diagnosis in the adult can be difficult if symptoms are interpreted as being related to degenerative disorders of the spine. In the presence of neurological symptoms, surgery is indicated. A preventive surgical procedure in asymptomatic patients is discussed controversially in the literature and is established in TCS patients only with correction of a scoliosis. However, most patients suffering from TCS benefit from surgical treatment.CM can be divided into four abnormal alterations of the posterior fossa, with most cases being of types I and II. In adults, Chiari type I is most common. Chiari I may present congenitally; however, it is also secondarily observed following lumboperitoneal shunting or in association with hydrocephalus. Surgical intervention is recommended depending on the extent of herniated tissue and the neurological symptoms. The optimal surgical procedure is still controversial. Most centers recommend bony decompression with dural graft extension for Chiari I.The appropriate treatment of both complex disorders requires a close and critical interdisciplinary approach in order to offer patients an individually adapted therapy.     

Age-dependent changes of cerebral ventricular size

Summary The age distributions of communicating hydrocephalus (CH), pseudotumour cerebri (PC) slit-ventricle syndrome (SVS), and chronic subdural haematomas (CSH) were reviewed in the medical literature.An age-related incidence was found: CH and CSH predominated in neonates less than 2 years and adults older than 55 years, while PC and SVS occurred mainly in older children and young adults. The latter two patient groups seem to show a greater resistance to ventricular dilatation in the presence of decreased CSF absorption. This may be related to larger volume and state of maturity of the cerebrum. On the other hand, neonates and the elderly more readily develop enlarged ventricles, in association with impairment of CSF absorption, or subdural fluid collections.Factors including status of cranial sutures, cerebral atrophy, cerebral water content, degree of cerebral myelination, and glial cell composition, may contribute to the age-related incidence of the four disorders investigated. Similarly, the development of ventriculomegaly may depend upon cerebral elastic properties besides the pri mary disturbance of CSF dynamics.The authors postulate that the size of cerebral ventricles in disorders of the cerebrospinal fluid (CSF) absorption is related to the elastic properties and volume of the brain. Furthermore, cerebral volume and elastic properties may also contribute to the age distribution of chronic subdural haematomas (CSH).     

Cysticercal meningitis--a pernicious form of neurocysticercosis which responds poorly to praziquantel

Chronic cysticercal meningitis was diagnosed in 6 of 260 cases of neurocysticercosis. Clinical features usually associated with meningitis, such as fever, cranial nerve palsies and nuchal rigidity, were absent and the diagnosis was reached because of persistently abnormal cerebrospinal fluid (CSF) associated with active neurocysticercosis on computed tomography. Other causes of chronic meningitis were excluded. Hydrocephalus, either obstructive or communicating, was present in all 6 patients. The results of medical treatment with praziquantel were poor and there was no improvement either clinically or in the CSF. Severe clinical sequelae, such as dementia, blindness and gait ataxia, were common despite protracted medical treatment and ventriculoperitoneal shunting.