颅内疾病对导水管脑脊液流量的影响

目的：探讨用磁共振相位对比电影(PC cine)对导水管脑脊液定量测量的临床应用价值。方法：将35例中枢神经系统不同疾病分三组，用PC cine方法进行导水管脑脊液流量测量。结果：在脑血管病组伴白质改变时导水管流量增加；梗阻性脑积水导水管流量减少，流动波形异常；交通性脑积水导水管流量增加，波形圆钝。结论：磁共振PC cine方法测量导水管脑脊液流量简单易行，可为临床提供更多的影像信息。     

Cerebrospinal fluid flow in patients with dilated ventricles studied with MR imaging

The purpose of this study was to measure the cerebrospinal fluid (CSF) velocity and flow in the aqueduct in patients with wide ventricles with or without signs of normal pressure hydrocephalus (NPH) before and after shunt surgery. We studied 18 patients with wide ventricles with MRI and measured the CSF velocity values in the aqueducts. Twelve patients with the clinical triad of NPH were examined. Six patients were studied only before shunt surgery and 6 patients were studied both before and after shunt surgery. Three patients with wide ventricles without clinical triad of NPH, and 3 patients with hydrocephalus following subarachnoid hemorrhage were also examined. Seven NPH patients with hyperdynamic CSF flow and three NPH patients with normal CSF velocity and flow values showed a positive clinical response to shunt surgery. Two of the three patients with hydrocephalus and hyperdynamic CSF flow values in the aqueduct secondary to subarachnoid bleeding responded to shunt surgery. One patient with same disease and low CSF velocity and flow values did not respond. No change was detected in the CSF flow values of the aqueduct when measurements before and after shunt surgery were compared. Ventriculoperitoneal shunting does not change the CSF dynamics in the aqueduct. Received: 8 March 1999; Revised: 30 November 1999; Accepted: 23 February 2000     

Flowing cerebrospinal fluid in normal and hydrocephalic states: appearance on MR images

The signal intensity of the cerebrospinal fluid (CSF) in the cerebral aqueduct and lateral ventricles on magnetic resonance (MR) images was evaluated in 16 healthy individuals and in 32 patients with various forms of hydrocephalus (20 with chronic normal pressure hydrocephalus [NPH], seven with acute communicating hydrocephalus, and five with hydrocephalus ex vacuo [atrophy]). The low signal intensity frequently observed in the cerebral aqueduct is believed to reflect the pulsatile motion of CSF, which is related to the cardiac cycle. While this "aqueductal flow void phenomenon" can be observed in healthy individuals, it is most pronounced in patients with chronic, communicating NPH; is less evident in patients with acute, communicating hydrocephalus; and is least evident in patients with atrophy. Ventricular compliance is known to be essentially normal in atrophy; mildly decreased in acute, communicating hydrocephalus; and severely decreased in NPH. The degree of aqueductal signal loss is believed to reflect the velocity of the pulsatile CSF motion, which in turn depends on the relative ventricular compliance and surface area.     

Fast multiphase MR imaging of aqueductal CSF flow: 1. Study of healthy subjects

Gradient-echo MR sequences are more sensitive to flow phenomena than spin-echo sequences are. We investigated aqueductal CSF flow by fast multiphase imaging. Fast multiphase imaging offers the opportunity to perform a dynamic study of fluid motion that is synchronous with the cardiac cycle. A section perpendicular to the cerebral aqueduct was imaged in 18 healthy volunteers. Serial, gated (every 50 msec from the ECG R wave), flow-compensated modulus images with 70 degrees-flip-angle excitation pulses were obtained with a single acquisition. The behavior vs time of CSF signal in the aqueduct was compared with that in the lateral ventricles. The former showed a peak at 0.47 +/- 0.1 fractions of a heart cycle after the R wave. No periodicity with the heart rate was observed for the ventricular CSF signal intensity. The mean CSF signal intensity in the aqueduct was found to range from about twice to three times that in the lateral ventricles over a cardiac cycle. Fast multiphase imaging is a sensitive and practical sequence for the MR investigation of aqueductal CSF flow. Its potential in patients with hydrocephalus is studied in a companion article.     

MR of aqueductal stenosis: evidence of a broad spectrum of tectal distortion

The MR scans of 18 patients with nontumoral aqueductal stenosis and six patients with neoplastic stenosis of the aqueduct were reviewed in order to document and understand the variable appearance of the aqueduct and periaqueductal region on MR. The mesencephalic tectum is often distorted in patients with benign aqueductal narrowing. This distortion results in a number of different MR appearances ranging from an elongated and thin to a short and broad tectum. When compressed by a dilated suprapineal recess, the distorted tectum is sometimes difficult to differentiate from the bulbous enlargement caused by a tectal glioma. Patients in whom distortion of the tectum is the result of hydrocephalus and aqueductal stenosis should be recognized to avoid unnecessary diagnostic procedures and misdiagnosis.     

Magnetic resonance imaging of the cerebral aqueduct

Summary 1.5 Tesla MRI examinations were evaluated for aqueductal configuration, hydrocephalus and flow-related signal void in 70 patients with juxtaaqueductal pathology and in 20 normal controls. In the 70 cases with pathology, the aqueduct was obliterated or distorted in 34, dilated in 3, normal in 29 and not evaluable in 4. A definite flow-related signal void indicated CSF movement within the aqueduct in all normal examinations. Flow-related signal void was absent in some, but not all, patients with aqueductal obliteration and distortion. CSF turbulence can create an intra-aqueductal signal void in the dilated proximal aqueduct, despite more distal obstruction. Thus hydrocephalus related to aqueductal obstruction is frequently, but not always, associated with absence of signal void.     

Cardiac-gated phase MR imaging of aqueductal CSF flow

The direction of CSF flow within the cerebral aqueduct was studied by cardiac-gated magnetic resonance (MR) phase images in five healthy volunteers and 10 patients with presumably normal cerebral CSF circulation. Caudal CSF flow was observed during systole and cranial flow during diastole. Using phantom based calibrations of the imager, aqueductal CSF velocities of 3-5 mm/s were calculated. Cardiac-gated phase MR is a potentially major tool for the investigation of the CSF circulation.     

Flow dynamics of cerebrospinal fluid: assessment with phase-contrast velocity MR imaging performed with retrospective cardiac gating.

To visualize the flow of cerebrospinal fluid (CSF) throughout the ventricles and subarachnoid space, measure mean and maximum CSF velocities, and quantitate CSF flow through the aqueduct of Sylvius, magnetic resonance (MR) imaging was performed with a sagittal technique that is flow-sensitive in the craniocaudal direction (along the readout axis) and a high-resolution axial technique sensitive to through-plane flow in three healthy subjects and 19 patients with known or suspected disorders of the CSF circulation. In both techniques, retrospective cardiac gating was used to cover the complete cardiac cycle. The sagittal technique was superior in overall assessment of CSF flow dynamics, including the motion of adjacent brain parenchyma. The high-resolution axial technique provided an accurate measurement of the rate of CSF flow through the aqueduct; only this technique provided sufficient accuracy to enable distinction between normal and hyperdynamic CSF flow. It is concluded that assessment of CSF flow dynamics is a useful adjunct to routine MR imaging in communicating and obstructive hydrocephalus.     

Marked cerebrospinal fluid void: indicator of successful shunt in patients with suspected normal-pressure hydrocephalus

The authors blindly reviewed the charts of 20 patients with normal-pressure hydrocephalus (a disease of unknown cause characterized radiologically as chronic communicating hydrocephalus and clinically by gait apraxia, dementia, and incontinence) who had undergone creation of a ventriculoperitoneal shunt. The initial clinical response to surgery was graded excellent, good, fair, or poor; 5-year follow-up was available in 55% of cases. The magnetic resonance (MR) images obtained in these patients were also blindly reviewed for the magnitude of cerebrospinal fluid (CSF) flow void (graded on the basis of extent rather than degree of signal loss) in the cerebral aqueduct. A significant (P less than .003) correlation existed between good or excellent response to surgery and an increased CSF flow void. The presence of associated deep white matter infarction on MR images did not correlate with a poor response to surgery. On the basis of these findings, it is suggested that patients who fulfill the clinical criteria of NPH and have an increased CSF flow void undergo creation of a shunt.     

Flow-sensitive MR imaging of ventriculoperitoneal shunts: in vitro findings, clinical applications, and pitfalls

To determine ventriculoperitoneal shunt patency during routine MR imaging of the head, 23 patients were studied with T1-weighted fast-field-echo scans. Without knowledge of the results of previous MR/CT studies or of the patients' clinical history, we reviewed the fast-field-echo studies and divided them according to those judged to have shunt flow (18) and those judged not to have flow (five). Fast-field-echo sequences showed high signal intensity, consistent with CSF flow and shunt patency in 17 medium-pressure systems and one high-pressure system. No signal was seen in five patients with high-pressure valve shunts. Combined clinical evaluation and MR/CT studies showed that three patients had probable shunt malfunction. One patient had true shunt malfunction; and although malfunction was thought to be present in two symptomatic patients, surgical revision showed the shunts to be patent. The possibility of temporary shunt obstruction is postulated to explain the clinical and MR findings in those two cases. The remaining two cases (9% of the patients) had no clinical evidence of shunt malfunction, and the MR findings probably reflected periodic CSF flow. One patient had an intracranial segment that was not connected and showed no flow on MR. No false-positive results (apparent flow in a nonfunctioning shunt) occurred. Using a standard medium-pressure shunt system, we constructed and imaged a phantom, which confirmed our clinical observations. T1-weighted fast-field-echo sequences may be useful in assessing patency of medium-pressure CSF shunt systems.     

Cerebrospinal fluid flow and production in patients with normal pressure hydrocephalus studied by MRI

An interleaved velocity-sensitised fast low-angle shot pulse sequence was used to study cerebrospinal fluid (CSF) flow in the cerebral aqueduct, and supratentorial CSF production in 9 patients with normal pressure hydrocephalus (NPH) and 9 healthy volunteers. The peak aqueduct CSF flow, both caudal and rostral, was significantly increased in patients with NPH. No significant difference in the supratentorial CSF production rate was found between patients (mean 0.60+/–0.59 ml/min) and healthy volunteers (mean 0.68+/–0.31 ml/min). Our method may be useful for investigation and monitoring of patients with NPH before and after ventriculoperitoneal shunt operations.     

Cerebrospinal fluid flow waveforms: MR analysis in chronic adult hydrocephalus

Henry-Feugeas MC, Idy-Peretti I, Baledent O, et al. Cerebrospinal fluid flow waveforms: MR analysis in chronic adult hydrocephalus. Invest Radiol 2001;36:146-154.RATIONALE AND OBJECTIVES: To analyze changes in cerebrospinal fluid (CSF) hydrodynamics in chronic adult hydrocephalus. METHODS: Phase-contrast cine-MR acquisitions were used to explore the ventricular system and the upper ventral cervical spaces of 16 patients. The aqueductal jet was explored in 32 control subjects. RESULTS: The duration of pulsatile caudal CSF flow (ie, CSF systole) was abnormally short in patients with active idiopathic and obstructive hydrocephalus. The duration of CSF cervical systole was normal in patients with stable hydrocephalus. The aqueductal stroke volume could be increased in stable communicating hydrocephalus. Patients who responded to shunting had shortened CSF systoles and hyperpulsatile ventricular patterns. Successful CSF diversion resulted in longer CSF systoles and CSF ventricular patterns that were no longer hyperpulsatile. CONCLUSIONS: Magnetic resonance analysis of CSF flow can show craniospinal dissociation and limitation of CSF outflow from the ventricles in both obstructive and communicating hydrocephalus; it should help determine the response to shunting in communicating hydrocephalus.     

B-waves in cerebral and spinal cerebrospinal fluid pulsation measurement by magnetic resonance imaging

OBJECTIVE: Noninvasive measurement of B-waves is possible by magnetic resonance (MR) imaging using echo planar imaging (EPI) sequences. In this study, the proportion of B-waves in the cerebrospinal fluid (CSF) of the spinal canal and in the aqueductus cerebri was evaluated under normal and pathologic conditions, respectively. The proportion of the influence of pulse and respiration on the CSF pulsations was estimated. METHODS: The spinal CSF was evaluated in 7 volunteers at 5 spinal levels (C1, C2/3, C 6/7, T5, and T12). Examination of the CSF frequencies at the aqueduct was performed in 14 volunteers, 10 patients with normal pressure hydrocephalus, and 5 patients with an aqueductal stenosis. An EPI sequence was applied at 1.5 T. During the 8-minute measurement time, pulse and respiration were coregistered. A MATLAB routine analyzed the spectral portion of the B-waves and the pulse- and respiration-dependent frequencies of the CSF. RESULTS: The amount of B-waves was small in cerebral (2.5%) and spinal measurements (3.4%) but significantly higher in the spinal CSF (P < 0.001). There was no statistically different amount of B-waves in the aqueduct for volunteers and hydrocephalic patients and between the different spinal levels in healthy volunteers. Spinal measurements revealed a rising portion of respiration-related frequencies from C1 to T12, whereas the portion of pulse-related frequencies declined. CONCLUSIONS: The data support that B-waves are a physiologic phenomenon. They can be delineated in the spinal and cerebral CSF. A higher amount of spinal B-waves reflects a stronger venous and respiratory influence.     

Intracranial compartment volumes in normal pressure hydrocephalus: volumetric assessment versus outcome

BACKGROUND AND PURPOSE: Although enlargement of the cerebral ventricles plays a central role in the diagnosis of normal pressure hydrocephalus (NPH), there are no reports on the use of volumetric assessment to distinguish between patients who respond to ventriculoperitoneal shunt surgery and those who do not. The purpose of this study is to explore the association between preoperative intracranial compartment volumes and postoperative improvement. METHODS: Twenty-six patients (17 men; mean age, 75 years [range, 54-87 years]) with a clinical or radiologic suspicion of NPH were included in the study. Gait, cognition, and bladder function were evaluated by clinical rating. MR imaging of the brain was acquired at 0.5 T and 1.5 T. Total intracranial volume, ventricular volume, brain volume, and pericerebral CSF volume were determined by volumetric assessment. Four imaging variables were determined: ventricular volume ratio, brain volume ratio, pericerebral CSF volume ratio, and the ratio of ventricular volume to pericerebral CSF volume. All patients underwent ventriculoperitoneal shunt surgery. RESULTS: Clinical follow-up was assessed 1 year after shunt surgery. No difference in the mean ventricular volume ratio, the mean brain volume ratio, the mean pericerebral CSF volume ratio, and the mean ratio between ventricular and pericerebral CSF volume was found between subjects who improved on gait or cognition or bladder function and those who did not. CONCLUSION: Volumetric assessment has no predictive value in differentiating between NPH patients who respond to ventriculoperitoneal shunt surgery and those who do not.     

Fast multiphase MR imaging of aqueductal CSF flow: 2. Study in patients with hydrocephalus

The signal intensity in the region corresponding to the cerebral aqueduct was evaluated in three patients with noncommunicating tension hydrocephalus (caused by aqueductal obstruction in two and type I Arnold-Chiari malformation in the other), seven patients with suspected normal-pressure hydrocephalus (three of whom subsequently underwent successful shunting), and 10 patients with ex vacuo (atrophic) hydrocephalus. A gradient-echo MR sequence, called fast multiphase imaging, was used. Serial images corresponding to different phases of the cardiac cycle were acquired. No flow-related enhancement was observed over the entire cardiac cycle in the patients with noncommunicating hydrocephalus. Patients with normal-pressure hydrocephalus showed a higher aqueductal CSF signal intensity, consistent with increased systolic flow rates, than patients with ex vacuo hydrocephalus. When comparing the above two groups of patients with a control group of healthy volunteers, significantly higher and lower values of the (mean) maximum aqueductal signal intensity were found in the normal-pressure hydrocephalus patients and the ex vacuo hydrocephalus patients, respectively. Fast multiphase MR evaluation of aqueductal CSF flow may help to differentiate patients with different types of hydrocephalus.     

MR ventriculography for the study of CSF flow

BACKGROUND AND PURPOSE: Various MR techniques have been used to assess CSF flow and to image the subarachnoid spaces and ventricles. Anecdotal reports describe the use of intrathecal and intraventricular gadolinium-based contrast agents in humans and animals. We sought to determine the clinical usefulness of gadolinium-enhanced MR ventriculography for assessing CSF flow in patients with various neurologic conditions. METHODS: Five patients (three female and two male patients aged 6 months to 65 years) were included in the study. After performing sagittal, coronal, and axial T1-weighted MR imaging of the brain, 0.02-0.04 mmol of gadodiamide was injected into the lateral ventricle. Sagittal, coronal, and axial T1-weighted imaging was repeated soon after the injection. We were specifically looking for the site of obstruction to CSF flow in those patients with hydrocephalus, communication between cysts and ventricles, elucidation of suspicious intraventricular lesions, and patency of third ventriculostomies. RESULTS: MR ventriculography showed good delineation of the ventricular system in all patients. In one patient with carcinomatosis and hydrocephalus, a block to contrast material flow was detected at the right foramen of Luschka. In another patient with hydrocephalus, partial block to the flow of contrast material was demonstrated at the right foramen of Monro. In a patient with hydrocephalus and a posterior fossa cyst, flow of contrast material was blocked between the third ventricle and the cyst, with a thin streak of contrast material in the aqueduct. As an assessment of the patency of a third ventriculostomy, MR ventriculography showed flow of contrast material into the suprasellar cisterns from the third ventricle in one patient and absence of flow in another. CONCLUSION: MR ventriculography is a safe technique for assessing CSF flow, with application in determining the site of obstruction in hydrocephalus, in assessing communication between cysts and the ventricle, and in determining the functioning status of endoscopic third ventriculostomies.     

Magnetic resonance demonstration of normal CSF flow

The magnetic resonance (MR) imaging appearance and incidence of flowing cerebrospinal fluid (CSF) in the brain were investigated. The MR scans of 46 randomly selected patients with normal examinations were retrospectively reviewed. All patients were studied using both T2-weighted and T1-weighted spin-echo pulse sequences. Thirty-one patients (67%) had decreased intensity in the aqueduct of Sylvius on the T2-weighted images when compared with the intensity of CSF in the lateral ventricles. This was termed the CSF flow-void sign. The feature was present in the caudal fourth ventricle in 15 patients (32%) and in the third ventricle in two patients (4%) on T2-weighted scans. It was seen in only 13% of patients on T1-weighted scans. It is believed the CSF flow-void sign represents pulsatile CSF flow. Its recognition is important because it explains the inhomogeneity in the appearance of the CSF, which could be confused with pathologic processes. It may be valuable in the routine evaluation of MR examinations if it does reflect CSF circulatory dynamics.     

The MR appearance of CSF flow in patients with ventriculomegaly

The purpose of this study was to investigate the MR imaging appearance of mobile CSF in the ventricular system in patients with ventriculomegaly caused by brain atrophy and extraventricular obstructive hydrocephalus. Pulsatile CSF often has decreased intensity relative to less mobile areas of CSF, particularly on T2-weighted scans. At times, the flow-related signal dropout causes striking heterogeneity in the appearance of CSF. This has been termed the CSF flow-void sign (CFVS) and is most likely caused by spin-phase shifts and time-of-flight effects created as a result of CSF turbulence and increased velocity of CSF pulsatile flow. The effect is most pronounced in areas where a larger volume of CSF moves through a small channel or foramen, such as the aqueduct of Sylvius or foramen of Magendie. The scans of 40 patients with ventriculomegaly caused by brain atrophy or extraventricular obstructive hydrocephalus were reviewed for the presence of the CFVS. All patients had the CFVS in the aqueduct of Sylvius on T2-weighted spin-echo sequences. The sign was present in the fourth ventricle in 96%, in the third ventricle in 70%, in the foramen of Magendie in 65-77%, and in the foramina of Monro in 33%. The sign was more pronounced in patients with larger ventricles but could not be used to differentiate patients with brain atrophy from those with extraventricular obstructive hydrocephalus.     

Changes in size and magnetic resonance signal intensity of the cerebral CSF spaces during the cardiac cycle as studied by gated, high-resolution magnetic resonance imaging

In 1966, du Boulay demonstrated the pulsatile nature of CSF flow in the cerebral aqueduct by using air cineventriculography, which disturbs normal CSF dynamics by replacing part of the incompressible CSF with air. To investigate this phenomenon noninvasively, 35 normal volunteers were studied using high-resolution, cardiac-gated MR imaging. Specifically, we wished to document changes in size and configuration of the CSF spaces and the incidence and magnitude of signal loss (an indication of CSF motion) in these spaces as they related to time in the cardiac cycle. Changes in size and configuration were measurable in the third ventricle only (size increased during systole in seven of the 35 volunteers). Except for the lateral ventricles, some loss in signal intensity was seen in all CSF spaces at least during systole in all 35 volunteers--findings consistent with those of du Boulay. However, contrary to du Boulay's observations, asymmetric loss of signal, consistent with pulsatile CSF flow, was demonstrated at the level of the foramen of Monro in 15 of the 35 volunteers. Based on the pattern of flow void at the level of the foramen of Monro and on the expansion of the third ventricle during systole, we propose a theory of synchronous CSF flow at the foramen of Monro and aqueduct, which unifies our MR findings with du Boulay's cineventriculographic observations.     

Normal pressure hydrocephalus: vascular white matter changes on MR images must not exclude patients from shunt surgery.

BACKGROUND AND PURPOSE: White matter changes such as periventricular hyperintensity (PVH) and deep white matter hyperintensity (DWMH) are associated with both periventricular edema and ischemic white matter degeneration. Their diagnostic and predictive value in normal pressure hydrocephalus (NPH) is unclear. To identify prognostically important changes, we classified PVH and DWMH at MR imaging in a large series of patients with NPH, before and after ventriculoperitoneal shunt surgery. METHODS: Axial proton density- and T2-weighted turbo spin-echo sequences and coronal T1-weighted sequences were performed on a 0.5-T imager in 34 patients with NPH, before and 3 months after shunt surgery. PVH at the anterior, central, and posterior thirds of the lateral ventricles was assessed on transaxial images with a semiquantitative five-step scale describing the extension (in mm) and shape of the PVH. DWMH was quantified with a four-step scale. The number of cortical and subcortical lacunar infarctions, the flow void sign, and the width of the third and lateral ventricles were registered. Gait ability, need for sleep, urinary incontinence, living conditions, and psychometric test performance were assessed pre- and postoperatively. RESULTS: After shunt surgery, 25 patients improved and nine did not. PVH, DWMH, and other MR imaging variables before shunting did not differ between groups, and no MR imaging variable could predict the clinical effect of shunt surgery. Postoperatively, the width of PVH was reduced in the improved patients, and clinical improvement correlated with reduction in PVH. Only the irregular type of PVH located at the frontal horns was reduced postoperatively. The presence of risk factors or MR imaging changes normally associated with cerebrovascular disease had no negative influence on the outcome of shunt surgery. CONCLUSION: The presence of DWMH or subcortical lacunar infarctions in NPH did not predict a poor outcome from shunt surgery and should not be used as exclusion criteria for shunting. No MR imaging findings could predict outcome of shunt surgery in patients with NPH. Clinical improvement after surgery is associated with reduction in the irregular type of PVH located around the frontal horns.