MR-gated intracranial CSF dynamics: evaluation of CSF pulsatile flow

This article describes a new imaging method, called MR-gated intracranial CSF (liquor) dynamics, or MR-GILD. Pulsatile flow in CSF pathways is revealed by the difference between diastolic- and systolic-gated images. The images clearly demonstrate the ventricles, cisterns, and vascular structures. The dependence of CSF movement on arterial pulse transformation is analyzed, illustrative cases are given to show some pathologic variations, and the use of MR-GILD for neurosurgical patients is discussed.     

Iopamidol and metrizamide in cervical myelography: side effects, EEG, and CSF changes

Two nonionic contrast media, iopamidol and metrizamide (Amipaque), were used for cervical myelography (C1-C2 puncture) in 95 consecutive patients. Both contrast media gave excellent radiographic results. Headache and vagal symptoms were similar in both groups, whereas metrizamide produced more electroencephalographic changes and epileptic seizures. Meningeal irritation occurred in both groups and was severe in three cases. Cerebrospinal fluid showed protein and cellular changes of inflammatory type in both groups. Iopamidol is considered to be the more suitable contrast medium for cervical myelography despite its slight neurotoxicity.     

Volumetric analysis of white matter,gray matter,and CSF using fractional volume analysis

Quantitative cerebral tissue volumes may be useful for an objective assessment of pathological changes in brain. Accurate determination of tissue volumes is complicated, however, by the partial volume averaging (PVA) effect. We have, therefore, developed a new pulse sequence that minimizes the PVA through the use of inversion-recovery (IR) and double inversion-recovery (DIR) techniques. This pulse sequence simultaneously acquires four different sets of images to provide the necessary information for volumetric analysis and reduces potential spatial misregistration of images due to patient motion. The image sets acquired from the proposed pulse sequence are 1) gray matter visible, 2) white matter visible, 3) FLAIR, and 4) fast spin-echo proton-density weighted images. An algorithm has been implemented to correct for differential T₁-weighting and for tissue quantitation.     

Interactive segmentation of cerebral gray matter, white matter, and CSF: Photographic and MR images

Digital photography of postmortem brain slices was compared with magnetic resonance imaging (MRI) for morphological analysis of human brain atrophy. In this study, we used two human brains obtained at autopsy: a cognitively defined nondemented control (70-yr-old male) and a demented Alzheimer's disease (AD) subject (82yr-old female). For each of two brains, interactive manual image segmentation was performed by two observers on two image sets: (a) four coronal T1-weighted MR images (5 mm slices); and (b) four digitized photographic images from comparable rostrocaudal levels. Microcomputer image analysis software was used to measure the areas of three segmented cerebral compartments—gray matter (GM), white matter (WM) and CSF—for both image types. Resegmentation error was defined as the absolute difference between the areas derived from two segmentation trials divided by the value from trial 1 and multiplied by 100. This yielded the percent difference between the area measurements from the two trials. We found intea-observer agreement was better (error rates 1–18%) than inter-observer agreement (3–70%) with best agreement for WM and least for CSF, the smallest object class. MRI overestimated GM area relative to digitized photographs in the control but not the AD brain. The results define limitations of manual image segmentations and comparison of MRI with pathologic section photographic images.     

Method for quantification of brain, ventricular, and subarachnoid CSF volumes from MR images.

We describe a simple, rapid, and semiautomated method of MR analysis based on mathematical modeling of MR pixel intensity histograms. The method is shown to be accurate and reliable for regional analysis of brain, central, and subarachnoid CSF volumes. Application of the method to five young and six older subjects revealed significant age-related changes in regional brain volumes whereas no difference was found for traced central CSF volumes or subarachnoid CSF volumes. We conclude that this is a simple method that can be applied to further studies of quantification of brain structure in healthy aging and brain disease.     

Iotrol, a new myelographic agent: 1. Radiography, CT, CSF clearance, and brain penetration

Four new myelographic agents, metrizamide, iopamidol, iohexol, and iotrol, were studied in the subarachnoid space of cynomolgus monkeys. Plain films and computed tomographic scans documented the transport of each material throughout the space and into the brain. At the concentration used (300 mg I/ml), all gave good radiopacity for myelography and delineation of the cerebral subarachnoid space. All four cleared similarly from the ventricular system. Metrizamide, however, penetrated the brain in greater degree and persisted longer than the other three agents. Next in persistence was iopamidol and least, and both statistically equal, iotrol and iohexol.     

Effect of BOLD on sight stimulation and artifact of CSF: identification of activating signal and CSF artifact

This study used functional magnetic resonance imaging (fMRI) for brain function evaluation. fMRI data were collected by a block paradigm, and brain function was evaluated. In the block paradigm, the BOLD effect causes a several-second delay in hemodynamics, and analytical processing is done in consideration of this time lag. However, irrelevant artifacts caused by the BOLD effect frequently occur in analytical processing. Therefore, there is a limit to obtaining a sufficient activating reaction in the analytical system, which is normally equipped with MRI. Thus, obtaining the activating reaction is limited because the corresponding misregistration correction, angle correction, time series correction, and so on, are insufficient in an analytical system equipped with MRI. It has become standard to use analytical systems such as SPM. We examined the mean curve of the activating part and the area of artifact. As a result, it was possible to identify the activating signal and the artifact signal, and it became possible to obtain an adequate response from a system that is normally equipped with an activating signal in which artifacts are few.     

Effect of arginine vasopressin, acetazolamide, and angiotensin II on CSF pressure at simulated altitude

To test the hypothesis that arginine vasopressin (AVP) in the cerebral spinal fluid (CSF) influences CSF dynamics at simulated altitudes, cannulae were bilaterally implanted into the lateral ventricles of rabbits and rats. Recordings of CSF pressures at ambient and at various reduced barometric pressures identified an increase in CSF pressure in animals at simulated altitudes. Samples of CSF collected before and immediately after altitude exposures and assayed for AVP did not show a significant change in AVP concentration. Brain water content did not change after 6-8 h of reduced barometric pressure. Intraarterial injections of acetazolamide reduced CSF pressures, whereas intraventricular injection had no effect. Intraventricular angiotensin II (AII) elevated CSF pressures both at ambient (744-755 mm Hg) and reduced barometric pressures. When AII was preceded by saralasin, an AII blocker, the rise in CSF pressure with AII injection was prevented. Indeed, saralasin given alone, reduced or prevented the rise in CSF pressure seen at simulated altitudes. Intraventricular AVP did not influence CSF pressures nor did prostaglandins E2 and F1 alpha and norepinephrine. In AVP-deficient (Brattleboro) rats, response to intraventricular AVP depended on barometric pressure; i.e. CSF pressure rose when the rat was exposed to reduced barometric pressures and fell when the rat was exposed to ambient pressure. We suggest that hypobaric stress could cause an increase in AII content of the central nervous system which, in turn, would lead to an increase in CSF pressure. The exact mechanism of CSF pressure increase after AII increase remains to be investigated.     

CSF flow measurement in syringomyelia

BACKGROUND AND PURPOSE: CSF circulation has been reported to represent a major factor in the pathophysiology of syringomyelia. Our purpose was to determine the CSF flow patterns in spinal cord cysts and in the subararachnoid space in patients with syringomyelia associated with Chiari I malformation and to evaluate the modifications of the flow resulting from surgery. METHODS: Eighteen patients with syringomyelia were examined with a 3D Fourier encoding velocity imaging technique. A prospectively gated 2D axial sequence with velocity encoding in the craniocaudal direction in the cervical region was set at a velocity of +/- 10 cm/s. Velocity measurements were performed in the larger portion of the cysts and, at the same cervical level, in the pericystic subarachnoid spaces. All patients underwent a surgical procedure involving dural opening followed by duroplasty. Pre- and postoperative velocity measurements of all patients were taken, with a mean follow-up of 10.2 months. We compared the velocity measurements with the morphology of the cysts and with the clinical data. Spinal subarachnoid spaces of 19 healthy subjects were also studied using the same technique. RESULTS: A pulsatile flow was observed in syrinx cavities and in the pericystic subarachnoid spaces (PCSS). Preoperative maximum systolic cyst velocities were higher than were diastolic velocities. A systolic velocity peak was well defined in all cases, first in the cyst and then in the PCSS. Higher systolic and diastolic cyst velocities are observed in large cysts and in patients with a poor clinical status. After surgery, a decrease in cyst volume (evaluated on the basis of the extension of the cyst and the compression of the PCSS) was observed in 13 patients. In the postoperative course, we noticed a decrease of systolic and diastolic cyst velocities and a parallel increase of systolic PCSS velocities. Diastolic cyst velocities correlated with the preoperative clinical status of the patients and, after surgery, in patients with a satisfactory foraminal enlargement evaluated on the basis of the visibility of the cisterna magna. CONCLUSION: CSF flow measurement constitutes a direct evaluation for the follow-up of patients with syringomyelic cysts. Diastolic and systolic cyst velocities can assist in the evaluation of the efficacy of surgery.     

MR imaging in multiple sclerosis: comparison with clinical, CSF, and visual evoked potential findings

MR examinations of 136 patients with multiple sclerosis (MS) were evaluated to correlate the results with clinical, CSF, and visual evoked potential (VEP) findings. In addition, 22 of the 136 patients were studied several times during a 5-month follow-up period. It was demonstrated that MR is superior to CSF and VEP findings in establishing cerebral alterations in MS. A relationship between the results of CSF and VEP examinations and the MR results could not be detected. Negative CSF and VEP results corresponded to positive MR imaging and vice versa. In our series, five negative MR results were obtained in patients with clinically proved MS. The extent of alterations shown up by MR corresponds to the duration of the disease; in particular, more confluent abnormalities in the periventricular region were found in patients with long-standing disease. More plaques were found in patients with a primary relapsing/remitting course of the disease than with the primary chronic progressive form. The clinical course and the grade of disability did not correspond to differences in MR imaging. Follow-up demonstrated that most lesions remain unchanged (72-79%); increases and decreases in the size of the plaques seem to depend on the clinical course. These results suggest that MR is the most sensitive technique for establishing the diagnosis of MS.     

Evaluation of CSF flow patterns of posterior fossa cystic malformations using CSF flow MR imaging

Introduction Differential radiologic diagnosis of cystic malformations of the posterior fossa is often difficult with conventional imaging techniques because of overlapping features of these entities. Posterior fossa cystic malformations occupy the cerebrospinal fluid (CSF) spaces. They may create secondary dynamic effects on the movements of CSF. The aim of this study was to investigate CSF flow alterations in posterior fossa cystic malformations with CSF flow MR imaging.Methods The study included 40 patients with cystic malformations of the posterior fossa. The patients underwent cardiac-gated phase-contrast cine MR imaging. CSF flow was qualitatively evaluated using an in-plane phase-contrast sequence in the midsagittal plane. The MR images were displayed in a closed-loop cine format.Results Twelve of the patients had communicating arachnoid cyst, seven had non-communicating arachnoid cyst, ten had mega cisterna magna, six had Dandy-Walker malformation, two had Dandy-Walker variant, and three had Blake’s pouch cyst. CSF flow MR imaging indicated the regions of no, slow or higher flow, direction of flow, and abnormal cystic fluid motion. Each malformation displayed a distinct CSF flow pattern.Conclusion Phase-contrast cine MR imaging for CSF flow evaluation may be a useful adjunct to routine MR imaging in the evaluation of the cystic malformations of the posterior fossa because it can improve the specificity in differentiating such malformations.Electronic Supplementary Material Supplementary material is available in the online version of this article at Part of this article was presented as a poster exhibition at the ESNR 28th Annual Congress and 12th Advanced Course, 11–14 September 2003, Istanbul.     

Quantitative multiregional CSF kinetics using serial, metrizamide enhanced computed tomography.

Two rhesus monkeys studied by serial metrizamide (Amipaque) enhanced computer tomography (CT) imaging were used to quantitatively analyze cerebrospinal fluid (CSF) kinetics in multiple anatomical regions. Time--density curves were generated for the cisterna magna, suprasellar cistern, quadrigeminal cistern, and sylvian fissure, If clinical, biochemical, and routine static CT scanning indicate a profile suggesting normal pressure hydrocephalus, then CSF kinetics may be quantitatively and dynamically studied by CT imaging with metrizamide enhancement. This multiregional approach may be applied in an attempt to accurately distinguish normal pressure hydrocephalus from cerebral atrophy as a means of predicting which patients will likely profit from surgical diversionary shunting.     

Normal MRI appearance and motion-related phenomena of CSF

OBJECTIVE: The purpose of this article is to review the normal appearance of CSF, flow physics in relation to CSF flow dynamics, and commonly encountered appearances and artifacts of CSF due to superimposed flow effects. CONCLUSION: Normal CSF has inherent MRI properties of low signal intensity on T1-weighted sequences and high signal intensity on T2-weighted sequences. However, the normal CSF signal is frequently altered by superimposed flow phenomena that can confound interpretation.     

CSF pulsation patterns in occlusive hydrocephalus

Fifteen patients with solid and cystic occlusions of the cerebrospinal fluid (CSF) circulation pathways were examined with MRI using an ECG retrogated two-dimensional FISP sequence to determine whether there are certain defined pathological CSF flow patterns in these patients. All patients were clinically still compensated. The results of the measurements of CSF flow velocities at different locations in the CSF system were compared with the results from 8 healthy volunteers. In all patients with occlusive processes of the intraventricular CSF pathways (4 aqueduct stenoses, 1 membranous occlusion of the fourth ventricular outlets, 1 solid tumour at the foramen of Monro and 1 solid fourth ventricular tumour) we observed hyperdynamic CSF pulsation above the lesion. This was transmitted into the spinal canal. Close by a solid occlusion within the aqueduct the flow velocity curve over the RR cycle was typically shifted, resulting in a mirroring of the flow velocity curve compared with normals. In cystic lesions (n = 4) there was transmission of the pulsation wave through the lesion and therefore no mirroring of the flow velocity curve. This technique allows very good delineation of cystic structures in the peripineal region (n = 4), also due to the opposite direction of flow within the cyst compared with the surrounding CSF spaces, depending on the extent of communication. Correspondence to: U. Kunz     

Automated Quantitation of Spinal CSF Volume and Measurement of Craniospinal CSF Redistribution following Lumbar Withdrawal in Idiopathic Intracranial Hypertension

BACKGROUND AND PURPOSE:Automated methods for quantitation of tissue and CSF volumes by MR imaging are available for the cranial but not the spinal compartment. We developed an iterative method for delineation of the spinal CSF spaces for automated measurements of CSF and cord volumes and applied it to study craniospinal CSF redistribution following lumbar withdrawal in patients with idiopathic intracranial hypertension.MATERIALS AND METHODS:MR imaging data were obtained from 2 healthy subjects and 8 patients with idiopathic intracranial hypertension who were scanned before, immediately after, and 2 weeks after diagnostic lumbar puncture. Imaging included T1-weighted and T2-weighted sequences of the brain and T2-weighted scans of the spine. Repeat scans in 4 subjects were used to assess measurement reproducibility. Whole CNS CSF volumes measured prior to and following lumbar puncture were compared with the withdrawn amounts of CSF.RESULTS:CSF and cord volume measurements were highly reproducible with mean variabilities of −0.7% ± 1.4% and −0.7% ± 1.0%, respectively. Mean spinal CSF volume was 77.5 ± 8.4 mL. The imaging-based pre- to post-CSF volume differences were consistently smaller and strongly correlated with the amounts removed (R = 0.86, P = .006), primarily from the lumbosacral region. These differences are explained by net CSF formation of 0.41 ± 0.18 mL/min between withdrawal and imaging.CONCLUSIONS:Automated measurements of the craniospinal CSF redistribution following lumbar withdrawal in idiopathic intracranial hypertension reveal that the drop in intracranial pressure following lumbar puncture is primarily related to the increase in spinal compliance and not cranial compliance due to the reduced spinal CSF volume and the nearly unchanged cranial CSF volume.

The total amount of CSF and its craniospinal distribution are important for understanding of CSF-related brain and spinal cord disorders and CSF physiology in general. Changes in CSF circulation or distribution between the cranium and spinal canal or both have been observed in several neurologic disorders, including Alzheimer disease,¹ idiopathic normal pressure hydrocephalus,² idiopathic intracranial hypertension (IIH),³ and even during pregnancy.⁴ A change in body posture also affects the craniospinal CSF distribution, with a shift from the cranium to the spinal canal contributing to the lower intracranial pressure observed in the upright-versus-supine postures.⁵ CSF volume in the spinal canal is also influenced by abdominal compression and hyperventilation.⁶ In addition, the amount of CSF in the thecal sac has been shown to influence the effectiveness of spinal anesthesia.⁷ Not only the spinal CSF volume but also the spinal cord volume is of clinical relevance, especially for cord atrophy progression such as in multiple sclerosis.⁸MR imaging–based automated methods of quantitation of brain tissues and intracranial CSF volumes^9,10 have considerably advanced the quantitative-based diagnostic capability of many neurologic problems, yet comparable methods for the spinal cord and the spinal CSF volumes are not widely available. Measurement of the spinal CSF volume in MR imaging is challenging because of the overall smaller volumes compared with the brain and cranial volumes and due to the length of the spinal canal, which necessitates the use of multiple overlapping acquisitions with potentially varying image nonuniformity.Previous studies on dose response in epidural anesthesia focused on measurements of the CSF volumes in the low thoracic and lumbosacral regions.^4,6,11 The CSF volume in the whole spinal canal was reported only in a small number of studies that were constrained by limited image resolution and manual delineation of the CSF space.^11,12 A recent advancement toward automated spinal CSF volume measurements is the development of a method that uses thresholding and voxel connectivity.¹³ Recent effort in the assessment of spinal cord atrophy in multiple sclerosis includes semiautomated approaches for the measurement of the cord cross-sectional areas in both cervical and thoracic regions.¹⁴This article describes an iterative method of delineating the CSF spaces and the spinal cord throughout the spinal canal. Measurement reproducibility was assessed from repeat measurements in the same subjects. The method efficacy is demonstrated by its application to studying the impact of CSF withdrawal by lumbar puncture (LP) on the craniospinal CSF redistribution in IIH. Only limited information on CSF redistribution following withdrawal is available, even though this is a commonly used diagnostic procedure in CSF-related disorders.     

Dorsal CSF space at CI-II level

Summary The width of the dorsal CSF space at the CI-II lateral puncture site was measured, both in extension and in the neutral position of the head, in 60 patients undergoing cervical myelography. The sagittal diameter of the dorsal CSF space did not change in 22 patients, was larger in extension in 27 patients, and larger in the neutral position in 11 patients. In three patients with a large dorsal CSF space the change in diameter was more than 2 mm whereas in other patients the change was minimal. Lateral CI-II puncture may be performed safely both in extension and in the neutral position. Distribution of the contrast medium was more satisfactory if the head was extended.