Disturbed Cerebrospinal Fluid Circulation Research Articles

Порушення ліквороциркуляції в пацієнтів з мальформацією Кіарі: предиктори розвитку сирингомієлітичних кіст і динаміка післяопераційного регресу

Актуальність. Мальформація Кіарі (МК) — це дефект розвитку центральної нервової системи, що проявляється невідповідністю розмірів задньої черепної ямки і розташованих у цій ділянці структур мозку і, як наслідок, опусканням мигдаликів мозочка (МК типу 1), зазвичай з каудальним зміщенням нижніх відділів стовбура мозку, у великий отвір (МК типу 1.5). Унаслідок порушення ліквороциркуляції в 60–90 % пацієнтів із МК спостерігається сирингомієлія. Матеріали та методи. Проведено ретроспективний аналіз клінічних даних 24 пацієнтів із мальформацією Кіарі типу 1 і 1.5, які перенесли оперативні втручання в Ужгородському обласному клінічному центрі нейрохірургії і неврології в період з грудня 2006 р. по грудень 2017 р., під час яких були виконанi субокципітальна декомпресивна краніектомія, ламінектомія на рівні С1, пластика твердої мозкової оболонки. Середній період спостереження після операції становив 5 років. Результати. У пацієнтів, у яких симптоми тривали понад 3 роки, частота утворення сирингомієлітичних кіст становила 57 %. Динаміка регресу порушень ліквороциркуляції в післяопераційному періоді значно варіює залежно від віку. Висновки. Ризик утворення порожнин, заповнених рідиною, у спинному мозку вищий у пацієнтів із МК типу 1 і 1.5, які хворіють понад 3 роки. Хірургічне лікування є ефективним методом, що використовується для корекції порушень ліквороциркуляції. Пункція кісти не є обов’язковою під час хірургічних втручань.

Home telemonitoring of intracranial pressure.

As technical progress advances, telemonitoring has become an important part of patient care in many areas of medical treatment. However, distanced surveillance of intracranial pressure (ICP) could not be established so far. With the recent introduction of a telemetric ICP measurement probe, new possibilities arise. Here, we report on a new home setup enabling home telemonitoring of intracranial pressure. Twenty patients suffering from disturbances of cerebrospinal fluid circulation, who underwent insertion of a telemetric ICP measurement probe, were provided with medical equipment to read ICP at home and save the data on an internet-enabled computer. Training in handling the equipment was performed during in-patient stay; recorded and uploaded ICP data was then analyzed online. Therefore, the treating medical team was able to access the ICP data via a secure internet connection while telephone conferencing with the patient. Almost 7400h of ICP data were recorded at home and evaluated via an internet connection according to the telemonitoring setup. This corresponds to an average record time of about 370h per patient. ICP profiles were observed following endoscopic treatment, shunting procedures, or valve adjustments. The mean distance between the patients' residence and the consulting hospital was 172km (range, 16-649km). ICP measurements have become accessible for telemonitoring purposes. This new management of hydrocephalus reflects an alternative method in patient care, especially for those who live far away from specialized centers.

Agreement between transverse T2-weighted and three-dimensional constructive interference in steady state sequences in the evaluation of spinal cord disease in dogs

The constructive interference in steady state (CISS) sequence has been widely used in human neuroimaging. It has been shown to be advantageous in the evaluation of intra-axial and extra-axial cystic...

Brain Capillary Ultrastructure in Idiopathic Normal Pressure Hydrocephalus: Relationship With Static and Pulsatile Intracranial Pressure.

Idiopathic normal pressure hydrocephalus (iNPH) is a neurodegenerative disease of unknown cause. We investigated the morphology of capillaries in frontal cortex biopsies from iNPH patients and related the observations to overnight intracranial pressure (ICP) scores. A biopsy (0.9×10 mm) was taken from where the ICP sensor subsequently was inserted. Brain capillaries were investigated by electron microscopy of biopsies from 27 iNPH patients and 10 reference subjects, i.e. patients (not healthy individuals) without cerebrospinal fluid circulation disturbances, in whom normal brain tissue was removed as part of necessary neurosurgical treatment. Degenerating and degenerated pericyte processes were identified in 23/27 (85%) iNPH and 6/10 (60%) of reference specimens. Extensive disintegration of pericyte processes were recognized in 11/27 (41%) iNPH and 1/10 (10%) reference specimens. There were no differences in basement membrane (BM) thickness or pericyte coverage between iNPH and reference subjects. The pulsatile or static ICP scores did neither correlate with the BM thickness nor with pericyte coverage. We found increased prevalence of degenerating pericytes in iNPH while the BM thickness and pericyte coverage did not differ from the reference individuals. Observations in iNPH may to some extent be age-related since the iNPH patients were significantly older than the reference individuals.

Cardiovascular risk factors in Chiari malformation and idiopathic intracranial hypertension.

ObjectivesBoth Chiari malformation type 1 (CMI, i.e., the idiopathic caudal ectopy of cerebellar tonsils into foramen magnum) and idiopathic intracranial hypertension (IIH) are characterized by reduced intracranial compliance (ICC) due to disturbed circulation of cerebrospinal fluid (CSF). An increasing body of evidence links cardiovascular disease to CSF circulation disturbances. The aim of this study was to explore whether the prevalence of cardiovascular risk factors in patients with CMI or IIH is higher than in the general population.Materials and MethodsAmong the patients with CMI or IIH treated at our department during the period 2003–2014, we identified those with history of arterial hypertension (AH), myocardial infarction (MI), angina pectoris (AP), or diabetes mellitus (DM). For comparison with a control population, we retrieved information about the prevalence of AH, MI, AP, and DM among participants of the North‐Trøndelag Health Study 3 (HUNT3).ResultsData from 48 CMI and 52 IIH cases were available. Compared to data from the 42,461 individuals participating in the HUNT3, we found increased prevalence of DM in male CMI as well as female IIH cases, and of AH in female IIH cases. Body mass index (BMI) was significantly increased in both female and male IIH cases. Prevalence of MI and AP in the CMI and IIH cohorts was extremely low and therefore not further studied.ConclusionsThis study provided evidence of an increased prevalence of DM in male CMI as well as female IIH cases and of AH in female IIH cases. Although requiring further exploration, these findings point to AH and DM as potential risk factors in the pathophysiology of CMI and IIH.

Cerebral critical closing pressure in hydrocephalus patients undertaking infusion tests

Objectives:Links between cerebrospinal fluid (CSF) compensation and cerebral blood flow (CBF) have been studied in many clinical scenarios. In hydrocephalus, disturbed CSF circulation seems to be a primary problem, having been linked to CBF disturbances, particularly in white matter close to surface of dilated ventricles. We studied possible correlations between cerebral haemodynamic indices using transcranial Doppler (TCD) ultrasonography and CSF compensatory dynamics assessed during infusion tests.Methods:We analysed clinical data from infusion tests performed in 34 patients suspected to suffer from normal pressure hydrocephalus, with signals including intracranial pressure (ICP), arterial blood pressure (ABP) and TCD blood flow velocity (FV). Cerebrospinal fluid compensatory parameters (including elasticity) were calculated according to a hydrodynamic model of the CSF circulation. Critical closing pressure (CrCP) was calculated with the cerebrovascular impedance methodology, while wall tension (WT) was estimated as CrCP-ICP. Closing margin (CM) was expressed as the difference between ABP and CrCP.Results:Intracranial pressure increased during infusion from 6.7 ± 4.6 to 25.0 ± 10.5 mmHg (mean ± SD; P < 0.001), resulting in CrCP rising by 22.9% (P < 0.001) and WT decreasing by 11.3% (P = 0.005). Closing margin showed a tendency to decrease, albeit not significantly (P = 0.070) due to rising ABP (9.1%; P = 0.005). Closing margin at baseline ICP was inversely correlated to brain elasticity (R = (0.358; P = 0.038), while being significantly different from zero for the whole duration of the tests (52.8 ± 22.8 mmHg; P < 0.001). Neither CrCP nor WT was correlated with CSF compensatory parameters.Discussion:Critical closing pressure increases and WT decreases during infusion tests. Closing margin at baseline pressure may act as an indicator of the cerebrospinal compensatory reserve.

Neuroendoscopic Removal of Intraventricular Hemorrhage Combined with Hydrocephalus

The neuroendoscope is playing an increasing role in the diagnosis and treatment of several types of lesions, in particular in the ventricular system. Hydrocephalus associated with intraventricular hemorrhage (IVH) is a good indication for neuroendoscopic surgery. We describe herein our experiences with 17 cases of IVH combined with hydrocephalus treated using a neuroendoscope. The subjects comprised 17 patients with IVH combined with hydrocephalus treated in our department, including cases of thalamic hemorrhage (n=10), caudate hemorrhage (n=5), moya-moya disease (n=1), and dural arteriovenous fistula (n=1). We used a flexible fiberscope that was inserted into the anterior horn of the lateral ventricle. Hematoma was easily evacuated through the working channel of the neuroendoscope by manual maneuvers. Hematomas in the third ventricle, aqueduct and fourth ventricle could also be evacuated. With the addition of septostomy, hematomas in the contralateral lateral ventricle could also be evacuated. All patients underwent successful procedures with good outcomes. No permanent morbidity and mortality was associated with any neuroendoscopic procedures. Shunt insertion was required in 3 cases due to malabsorption of cerebrospinal fluid (CSF) in the chronic stage. Neuroendoscopic procedures with a flexible fiberscope for the removal of IVH allow resolution of the disturbed CSF circulation. This procedure improves the safety and accuracy of treatment for IVH combined with hydrocephalus.

Diffusion-weighted magnetic resonance imaging of cerebrospinal fluid in patients with and without communicating hydrocephalus

Recent concepts about cerebrospinal fluid (CSF) circulation in communicating hydrocephalus (CoHy), which is also termed "restricted arterial pulsation hydrocephalus," suggest reduced arterial pulsations of subarachnoid vessels with a smaller amount of CSF shifted in subarachnoid spaces during the early systole. The postulated restriction of subarachnoid arterial pulsations in CoHy should induce a smaller motion artifact and reduced local stream effects in CSF in magnetic resonance (MR) diffusion-weighted imaging (DWI). To investigate the maximum diffusivity in CSF in patients with and without CoHy using DWI. 12 patients without CSF circulation disturbances and six cases with proven CoHy were assessed. Diffusion was measured in six non-collinear directions without triggering the arterial pulse wave (scan time 6:45 min, voxel size 2x2x2 mm). Due to expected artifacts, the calculated maximum diffusivity was called apparent diffusivity. Regional high and low apparent diffusivity was assessed in CSF spaces on newly created 3D CSF motion maps. Patients with regular CSF circulation exhibited high apparent diffusivity in CSF in basal subarachnoid spaces, whereas apparent diffusivity was low there in patients with CoHy. DWI opens a feasible approach to study CSF motion in the neurocranium. Restricted arterial pulsations seem to be involved in CoHy.

High resolution CISS imaging of the spine.

Spatial resolution remains one of the major problems and goals in spinal imaging. The high spatial resolution afforded by a novel sequence, constructive interference in steady state (CISS), provides a further refinement to MRI, the modality of choice in the investigation of suspected intraspinal pathology. Both complex and subtle abnormalities are more fully elucidated using CISS. It is now used in our institution as an adjunct to conventional imaging sequences in the diagnostic evaluation of complex intraspinal pathology. The anatomical information provided by CISS is of particular value in planning surgical interventions, most notably in the management of intraaxial and extraaxial cystic abnormalities, dysraphic malformations and disturbances of cerebrospinal fluid circulation, including post-traumatic and post-surgical scarring.

Treatment of subdural effusion with hydrocephalus after ruptured intracranial aneurysm clipping.

This study was conducted to determine whether a ventriculoperitoneal shunt alone was effective in treating subdural effusion with hydrocephalus. Using only a ventriculoperitoneal shunt, we successfully treated eight patients who had subdural effusion with hydrocephalus after ruptured intracranial aneurysmal clipping, despite ventricular deformity and midline shift. For all of the patients, both the subdural effusion and ventriculomegaly subsided and clinical symptoms lessened after surgery. Ventriculoperitoneal shunting alone is an effective and satisfactory procedure; no subdural peritoneal shunt is needed for patients with subdural effusion accompanied by hydrocephalus. To-and-fro communication between the subdural effusion and ventricles is considered to be present in these patients. When selecting the treatment for subdural effusion, it is important to consider whether hydrocephalus (disturbance of cerebrospinal fluid circulation) is present.

Posterior cranial fossa surgery in 454 children. Comparison of results obtained in pre-CT and CT era and after various types of management of dura mater.

At the Department of Neurosurgery, Hradec Kralové, 454 children (aged under 18 years) were operated on for posterior cranial fossa lesions in a period of 49 years (1948-1996). The majority (402) had tumours: cerebellar astrocytomas 149 (37.1%), medulloblastomas 139 (34.6%), brain stem gliomas 46 (11.4%), ependymomas 28 (7.0%), and others 40 (9.9%). Postoperative mortality was compared for the pre-CT era (1948-1977) and the CT era (1978-1996): astrocytomas (8.6%:4.7%), medulloblastomas (14.9%:2.9%), brain stem gliomas (21.7%:19.0%), ependymomas (18.2%:6.3%), and others (40.0%:7.4%). The initially high mortality was due to insufficient intracranial decompression, brain oedema and disturbances of cerebrospinal fluid circulation. Obstructive hydrocephalus was treated in 53 children with tumours and 25 with aqueduct stenoses, by Torkildsen's drainage in 5.5%, and/or by catheterisation of aqueduct in 12.3%. The main postoperative complications of medial posterior fossa surgery in 429 children operated on were: pseudomeningocele (12.3%), active hydrocephalus (6.2%) and CSF leakage (4.6%). Only 8.2% had shunts placed for these complications. We presume that this low percentage of shunts used results from a frequent use of duraplasties and drains installed at the primary operation. The dura mater was initially (1948-1954) left open (50 cases), and later (1955-1958) also sutured (37 cases), and from 1958, onward, and especially from 1961, reconstructed by a medial approach by means of various grafts (377 cases). In all, duraplasty was performed in 81.6% of cases. The grafts used for dura mater reconstruction were prepared from autogeneic (1.6%), allogeneic (72.3%), xenogeneic (24.8%), or synthetic (1.3%) material. They were successful in 99.2% of cases (all materials). Our own suture technique for posterior fossa duraplasty is presented.

Correlation between intracranial pressure (ICP) and changes in CT images of cerebral hemorrhage

The relationship between intracranial pressure and CT images was investigated in 80 cases of cerebral hemorrhage that occurred between 1984 and 1990. In traumatic intracerebral hematoma, positive correlation was found between intracranial pressure and both shift of midline structures and volume of hematoma except in the occipital lobe or at the base of the frontal lobe. In nontraumatic intracerebral hematoma, increased intracranial pressure was found to correlate with changes in the configuration of the lateral ventricles, intraventricular hemorrhage, and compression of the basal cisterns and cortical sulci. No correlation between intracranial pressure and hematoma volume was observed, most likely due to the number of elderly patients in the subject population. In nontraumatic subarachnoid hemorrhage, positive correlation existed between increased intracranial pressure and intraventricular hemorrhage as well as Evans' ratio calculated using repeat CT images that were obtained due to disturbances in cerebrospinal fluid circulation. These results suggest that the degree by which intracranial pressure increases in patients with cerebral hemorrhage can be estimated by the changes in CT images. [Neural Res 1998; 20: 225-230]

Increased frequency of aberrant CSF circulation in schizophrenic patients compared to healthy volunteers

In a previous cisternographic study of the cerebrospinal fluid (CSF) circulation in schizophrenic patients, indications for disturbed flow dynamics were found in 10 of 30 subjects. In order to replicate and investigate the clinical and pathophysiological significance of this finding, 39 schizophrenic patients and 42 healthy subjects were examined with an improved method for measurement of CSF circulation. (99m)Tc-DTPA was injected intrathecally and the gamma cisternograms were evaluated blindly. Correlations between cisternography findings and age, duration of disease, previous hospitalizations, positive or negative symptomatology, exposure to neuroleptics, psychiatric family history, CT findings and CSF levels of protein, tryptophan and monoamine metabolites, were calculated. Seven of the patients showed abnormalities in the cisternograms with a slow or obstructed flow of CSF over the convexities (P < 0.01) whereas none of the healthy volunteers showed abnormalities. There were no correlations between disturbed CSF circulation in the patients and the clinical and biochemical parameters, thus the significance of the deviations, similar to other biological aberrations found in schizophrenic patients, is not known. Recent developments in magnetic resonance imaging offer new possibilities to further examine CSF circulation abnormalities in schizophrenia.

Concentration gradients for monoamine metabolites in lumbar cerebrospinal fluid.

Concentration gradients in lumbar cerebrospinal fluid (CSF) for the monoamine metabolites homovanillic acid (HVA), 5-hydroxy-indoleacetic acid (5-HIAA) and 4-hydroxy-3-methoxyphenylglycol (HMPG) were studied in 9 healthy controls and 47 neuropsychiatric patients without diseases causing disturbed CSF circulation. In a serial sampling of the first 24 ml of CSF, steep concentration gradients between the first (0-4th ml) and last (21st-24th ml) portions of CSF were found for HVA (99 +/- 59% increase; p < 0.001) and 5-HIAA (88 +/- 54% increase; p < 0.001), while the concentration gradient was slight for HMPG (11 +/- 7% increase; p < 0.001). The existence of marked concentration gradients for the monoamine metabolites HVA and 5-HIAA gives further evidence for an active transport system for these metabolites and indicates that the lumbar CSF-HVA and 5-HIAA levels reflect the dopamine and serotonin metabolism in the brain. Moreover, the existence of pronounced concentration gradients for HVA and 5-HIAA stresses the importance of making analyses on a standardized volume of CSF.

Differentiation between ischemic and hemorrhagic stroke by transcranial color-coded real-time sonography.

Transcranial color-coded real-time sonography was applied to 20 patients with ischemic stroke and 28 patients with spontaneous intracerebral hemorrhage. In all patients the sonographic diagnosis corresponded closely to cranial computed tomography findings. Recent hemorrhages were visualized as a hyperechodense mass. The high contrast to minor echodense adjacent parenchyma led to a clear sonographic distinction. Older clots were characterized by a continuous decrease of echodensity and subsequently were interspersed by hypoechodense zones. In the acute stage of ischemic infarction, the vessel occlusion (17/20) and collateral vascular supply (10/20) could be depicted in the color-B-mode in two perpendicular planes and further verified by the Doppler mode. Brain edema was not visualized. Although in the acute stage no change of echo texture was observed within the infarction, hyperechodense regions (7/11) could be observed in some patients during the time course. Complications of intracerebral hemorrhage and ischemic stroke, such as disturbance of cerebrospinal fluid circulation, midline shift, and compression of adjacent territories, were depicted by transcranial color-coded sonography. These preliminary results illustrate that transcranial color-coded real-time sonography may be helpful in the early noninvasive differential diagnosis as well as long-term follow-up in patients with cerebrovascular disorders.

The Pseudotumor Syndrome

We report a series of eight cases that show a close resemblance to, but are not identical with, pseudotumor cerebri (PTC) as normally defined. The majority of these cases are characterized by raised intracranial pressure without ventriculomegaly. They include two cases of cranial venous outflow obstruction in which clinical or radiologic abnormalities precluded the diagnosis of PTC proper (cases 1 and 2); one case of chronic meningitis in which an abnormal cerebrospinal fluid (CSF) composition precluded the diagnosis of PTC (case 3); two cases without either papilledema or a measured increase of CSF pressure, which in other respects, particularly in response to treatment, resembled PTC (cases 4 and 5); and three cases of what is thought to represent an infantile form of PTC (cases 6 through 8). The purpose of the analysis of these cases is twofold. First, it is argued that these cases throw light on the mechanism of PTC itself, supporting a concept of a disturbance of CSF circulation in this condition, and that they are themselves illuminated by considerations of typical PTC. Second, the cases are used to frame a proposed classification of the pseudotumor syndrome aimed at broadening the diagnostic criteria applied currently to PTC. It is suggested that the pseudotumor syndrome has a single underlying mechanism (disturbed CSF circulation) and that recognition of this mechanism not only clarifies the pathophysiologic processes of PTC but also has important diagnostic and therapeutic implications.

Diagnosis and monitoring of subarachnoid hemorrhage by transcranial color-coded real-time sonography

Thirty-six patients with acute spontaneous subarachnoid hemorrhage (26 caused by rupture of an aneurysm) were examined by transcranial color-coded real-time sonography by using a 2.25-MHz ultrasound transducer. In 20 of these 26 patients (76%), the aneurysm could be identified by a characteristic abnormal blood flow pattern within the aneurysm in coronal and axial scanning planes by transcranial color-coded real-time sonography. Blood within the basal cisterns, on top of the tentorium, and within the ventricles and parenchyma was sonographically detected by increased echodensity in 75%. In addition, cerebrospinal fluid circulation disturbances and cerebral vasospasm were detected in two-dimensional B-mode images in 85% and 100%, respectively. In Doppler mode, intravascular blood flow velocity could be quantified. We conclude that transcranial color-coded real-time sonography, a new, noninvasive method for diagnosis and follow-up of patients with subarachnoid hemorrhage, allows detection of the primary vascular lesion and monitoring of complications.

Diagnosis and Monitoring of Subarachnoid Hemorrhage by Transcranial Color-Coded Real-Time Sonography

Abstract Thirty-six patients with acute spontaneous subarachnoid hemorrhage (26 caused by rupture of an aneurysm) were examined by transcranial color-coded real-time sonography by using a 2.25-MHz ultrasound transducer. In 20 of these 26 patients (76%), the aneurysm could be identified by a characteristic abnormal blood flow pattern within the aneurysm in coronal and axial scanning planes by transcranial color-coded real-time sonography. Blood within the basal cisterns, on top of the tentorium, and within the ventricles and parenchyma was sonographically detected by increased echodensity in 75%. In addition, cerebrospinal fluid circulation disturbances and cerebral vasospasm were detected in two-dimensional B-mode images in 85% and 100%, respectively. In Doppler mode, intravascular blood flow velocity could be quantified. We conclude that transcranial color-coded real-time sonography, a new, noninvasive method for diagnosis and follow-up of patients with subarachnoid hemorrhage, allows detection of the primary vascular lesion and monitoring of complications.

Quantitative Evaluations of Disturbances in Cerebrospinal Fluid Circulation with Indium-111 Cisternography

Quantitative evaluation of radioisotope (RI) cisternography was performed by single photon emission computed tomography (SPECT) in eight patients suspected of chronic hydrocephalus or malfunction of a shunt system, showing symptoms for two to 24 months, and one control patient with cerebrospinal fluid (CSF) leakage ten years after head trauma. Criteria of ventricular dilation by CT scan were satisfied in seven of the eight patients. The patients were given an injection of 1 ml of 1 mCi indium-111 diethylene triamine pentaacetic acid (In-Ill DTPA) via the lumbar route (seven cases) or ventricular catheter (two cases). Regular evaluations were scheduled (4, 7, 10-12, 24, 48 and 72 hours after injection). The region of interest, about 1.3 cm in radius and 0.8 cm in height, was placed in cisterna magna, sylvian cistern, basal cistern, and interhemispheric cistern as well as in the ventricle using a reconstructed image of a horizontal section by SPECT. Clearance curves were calculated with estimated decreasing count of RI each time by the method of exponential regression coefficients. Discrimination of the disease was attempted using the values of constant K of clearance curve and biological half-life time (BHT). Diagnosis of hydrocephalus was satisfactorily made in five patients demonstrating K values lower than 0.04 in all the cisterns expect for the cisterna magna, as well as BHT longer than 18-20 hours. Three of the five patients were treated with ventriculo-peritoneal (VP) shunt (two reconstructions of shunt systems and one VP shunt), and all of the improved. Although the remaining two patients were diagnosed as having hydrocephalus from the study, surgery was not performed, because of complicating psychiatric and malignant gastrointestinal diseases. Each patient diagnosed as Parkinson's disease or Alzheimer's disease showed a higher K value and shorter BHT than those in hydrocephalic patients. This tendency became clearer in the control patient with CSF leakage. Thus quantitative RI cisternography was highly valuable in the discrimination of chronic hydrocephalic from non-hydrocephalic patients with definitive dilation of the ventricles or symptoms similar to normal pressure hydrocephalus. This study may also be useful for estimation of the degree of impairment of CSF circulation.

Intracranial pressure, conductance to cerebrospinal fluid outflow, and cerebral blood flow in patients with benign intracranial hypertension (pseudotumor cerebri).

Intracranial pressure, conductance to cerebrospinal fluid outflow, and cerebral blood flow were investigated in 14 patients with benign intracranial hypertension (pseudotumor cerebri). Intracranial pressure was increased in 9 patients (20 to 30 mm Hg), borderline in 4 patients (15 to 18 mm Hg), and normal in 1 patient (8 mm Hg). Six patients had plateau waves, and all had B waves in more than 50% of the monitored time. Conductance to cerebrospinal fluid outflow, measured by a lumbo-lumbar perfusion method, was significantly reduced: 0.042 ml X mm Hg-1 X min-1 (+/- 0.004 [SEM]; normal, more than 0.080 ml X mm Hg-1 X min-1). Cerebral blood flow was measured by xenon 133 inhalation and single photon emission computer tomography. Mean hemispheric flow was normal in all cases, averaging 59 +/- 9 ml X 100 gm-1 X min-1. Only 2 patients showed focal low-flow areas. Thus, a disturbance of cerebrospinal fluid circulation seems to be of pathogenetic significance in benign intracranial hypertension.