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.     

MR demonstration of altered cerebrospinal fluid flow by obstructive lesions

We investigated the MR imaging appearance of flowing cerebrospinal fluid (CSF) in the brain in the presence of obstructive lesions of the ventricular pathways. The pulsatile movement of CSF through the ventricular system is seen as an area of low signal intensity that has been termed the CSF flow-void sign (CFVS). This is best appreciated in areas of narrowing within the ventricular system; that is, the aqueduct of Sylvius, foramen of Magendie, and interventricular foramina. MR studies of 27 patients with lesions affecting the ventricular pathways were reviewed for the presence of the CFVS. Single-echo T1-weighted and T2-weighted multisection techniques were used in all cases. The CFVS was always seen more prominently on the T2-weighted images. The presence of the CFVS indicated patency of the ventricular pathway in which it was identified. The absence of the CFVS in the presence of hydrocephalus indicated that a possible obstructive lesion was present, but it did not directly indicate the level of the obstruction. The CFVS was absent in the aqueduct of Sylvius in 13 patients with obstruction or stenosis of the aqueduct, but it was also absent in one patient with a colloid cyst of the interventricular foramina. In three patients with preoperative and postoperative MR, the CFVS was seen in the area of interest only after resection of the obstructing lesion. We concluded that the presence of the CFVS is a useful indicator of the patency of the ventricular pathway in which it is seen. The absence of the CFVS at a location in which it is normally seen may indicate the presence of an obstruction, but it must be correlated with other signs to be interpreted correctly.     

The MR appearance of syringomyelia: new observations

Fifty-eight patients with spinal cord cavities were studied with MR imaging. Patients were separated into four groups, and the appearance of the cavities were compared. There were 24 patients (41.4%) with communicating syringomyelia (associated with the Chiari I malformation). Sixteen patients (27.6%) had posttraumatic syringomyelia, nine patients (15.5%) had associated tumors, and nine patients (15.5%) had idiopathic syringomyelia. The characteristics of each syrinx, the spinal cord, and the appearance of the cerebellar tonsils were analyzed on T2- and T1-weighted images. There is a striking similarity in the appearance of many syrinx cavities regardless of the cause. Characteristics that were found in some patients in every group included areas of increased intensity on T2-weighted images, the presence of the CSF flow-void sign (CFVS) in the syrinx cavity, eccentric cavities, "beaded" cavities, and cord enlargement. Tonsillar ectopia alone does not indicate that a syrinx is of the "communicating" type, since it was present in two of 16 patients (13%) with trauma and in two of five patients (40%) with tumors. T1-weighted images were most useful in evaluating the anatomic characteristics of the syrinx and the cerebellar tonsils. Most syrinx cavities involved the cervicothoracic junction. The average length was between five and nine vertebral segments (depending on category) but varied between one and 20 vertebral segments. T2-weighted images revealed areas of increased intensity in the spinal cord in 13 patients without tumors. Two of these cases were shown to represent gliosis on histopathologic review. The CFVS was present in the syrinx cavities of 23 patients (40%), probably reflecting pulsatile movements of the syrinx fluid. It has been proposed that such movements are a cause of syrinx propagation, and the observation of the CFVS may have prognostic significance. The development and progression of the CFVS was documented in serial MR examinations in one patient over an 18-month period. The theories of syrinx development and propagation are reviewed.     

Importance of absence of CSF pulsation artifacts in the MR detection of significant myelographic block at 1.5 T

MR imaging was performed on 21 patients who had high-grade myelographic block due to various diseases in all spinal compartments (extradural, intradural/extramedullary, and intramedullary) and in all portions of the spinal canal (cervical, thoracic, and lumbosacral). Loss of CSF pulsation artifacts due to significant compression of the spinal cord was demonstrated on non-motion-compensated T2-weighted examinations in each case. We believe that the absence of such artifacts on these sequences indicates significant spinal cord compression in patients without classic signs and symptoms of cord compression but with intraspinal disease identified on T1-weighted studies.     

MRI of acute spinal epidural hematomas.

PURPOSE: The purpose of this work was to determine the MR findings that characterize acute spinal epidural hematomas (ASEHs). METHOD: The MR findings of 17 patients with ASEH (9 cervical, 7 thoracic, and 2 lumbar) were reviewed. Fifteen of the hematomas were secondary to trauma and two were spontaneous. Correlation with CT (8 cases) and surgical findings (11 cases) was also performed. RESULTS: Imaging findings in ASEH were the following: (a) a variable signal intensity (on T1-weighted images, 10 showed isointensity to cord and 7 were slightly hyperintense; T2-weighted images showed hyperintensity with areas of hypointensity); (b) capping of epidural fat; (c) direct continuity with the adjacent osseous structures; (d) compression of epidural fat, subarachnoid sac, and spinal cord; (e) usually posterolateral location in the spinal canal. CONCLUSION: Epidural hematomas in the spinal canal are lesions capable of producing sudden spinal cord and/or cauda equina compression. MR provides characteristic findings that allow a prompt diagnosis of acute epidural hematomas.     

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.     

正常儿童椎体骨髓转换过程中磁共振信号强度的变化

目的:分析椎体骨髓磁共振T1WI信号强度比值(SIR)与年龄、性别的关系,探讨正常儿童椎体骨髓转换的发生规律.方法:回顾性分析105例正常儿童的脊柱磁共振T1加权序列图像,同时选择血液系统疾病患儿共32例作为病例组对照研究.采用GE 0.2T Profile Gold永磁型开放式磁共振扫描仪行脊柱矢状面SE T1WI扫描.测定椎体磁共振SIR,并对所获得的数据与年龄、性别的关系及正常组和病例组间的比较进行统计学处理.结果:椎体SIR值与年龄变化的关系研究表明,颈椎、腰椎骨髓SIR值与年龄呈正相关,统计学具有显著性意义(P＜0.01),而胸椎骨髓SIR值则与年龄无显著相关性(P=0.06);无论是颈椎、胸椎还是腰椎的SIR值与性别均无显著相关性(P＞0.05);病例组患儿椎体T1信号强度较正常组儿童明显减低,各年龄组病例与正常组间的SIR值差异均具有显著性意义(P＜0.01).结论:儿童年龄段(0～17岁)颈椎和腰椎骨髓转换发生较早,5岁后的骨髓信号较前发生明显增高,而且血液系统疾病患者椎体骨髓T1信号较正常显著减低.因此,利用SIR定量测定法对弥漫性骨髓疾病具有更高的敏感性.     

Dyke award. Imaging of spinal CSF pulsation by 2DFT MR: significance during clinical imaging

Understanding the MR appearance of spinal CSF is important in interpreting clinical spine images because the diagnosis of spinal pathology requires an accurate delineation of spinal CSF from spinal cord and thecal sac. During conventional 2DFT MR imaging of the spine, CSF pulsation caused two interdependent flow phenomena, signal loss and phase-shift images. Signal loss was observed as decreased signal intensity arising from pulsatile spinal CSF. Phase-shift images were observed as signal intensity arising from and morphologically identical to the spinal subarachnoid space but symmetrically displaced from it along the phase-encoding axis of MR images, either added to or subtracted from stationary signal intensity. These phenomena were common, occurring in most cervical and thoracic long-TR images. Both phenomena were less apparent in the lumbar region in most cases. CSF pulsation flow phenomena decreased CSF-spinal cord and CSF-thecal sac conspicuity, thereby obscuring normal and pathologic anatomy and, at times, simulating pathology. The areas of signal loss showed variable but characteristic patterns in the cervical and thoracic spine corresponding to regions of greatest flow. Signal loss in the axial plane was more pronounced when thin slices were used. Phase-shift images degraded overall image quality secondary to spatial mismapping of spinal CSF signal intensity. With the use of CSF gating, both signal loss and phase-shift images were eliminated. Understanding these features will be important in the accurate interpretation of MR spine images because analysis of CSF pulsation flow phenomena provides physiologic and pathologic information, and awareness of their existence avoids diagnostic confusion.     

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.     

Coronal MR imaging of the normal 3rd, 4th, and 5th lumbar and 1st sacral nerve roots

Seven healthy volunteers underwent coronal MR imaging at 1.5 tesla of the normal 3rd, 4th, and 5th lumbar, and 1st sacral nerve roots. Coronal slices, 3-mm-thick with a 0.3-mm gap between the slices were obtained (TR/TE 600/22) through the lumbar spinal canal. All the nerve roots were visible on at least one image. One can routinely expect to demonstrate the 3rd, 4th, and 5th lumbar, and 1st sacral nerve roots on T1-weighted, 3-mm-thick coronal MR scans. We found no correlation between the degree of lumbar lordosis and the lengths of the visible nerve roots. Five patients with one of the following spinal problems: anomaly, tumor, disk herniation, and failed back surgery syndrome were examined according to our protocol. In all these cases coronal MR imaging gave the correct diagnosis.     

MR of CSF flow phenomenon mimicking basilar artery aneurysm

CSF motion from transmitted vascular pulsations can result in focal areas of CSF hypointensity on MR images because of signal mismapping from phase shift. When this CSF flow void occurs adjacent to the basilar artery in the prepontine cistern, it may be mistaken for a basilar artery aneurysm on proton-density and T2-weighted spin-echo images. Head MR scans of 50 consecutive patients referred for various indications were reviewed, and this phenomenon was noted in the prepontine cistern in 38 patients. Fifteen of these images had an appearance mimicking an aneurysm. When doubt exists, dynamic high-resolution CT scans should be sufficient for clarification.     

Degenerative disc disease of the lumbar spine: a prospective comparison of fast T1-weighted fluid-attenuated inversion recovery and T1-weighted turbo spin echo MR imaging

OBJECTIVE: To compare fast T1-weighted fluid-attenuated inversion recovery (FLAIR) and T1-weighted turbo spin-echo (TSE) imaging of the degenerative disc disease of the lumbar spine. MATERIALS AND METHODS: Thirty-five consecutive patients (19 females, 16 males; mean age 41 years, range 31-67 years) with suspected degenerative disc disease of the lumbar spine were prospectively evaluated. Sagittal images of the lumbar spine were obtained using T1-weighted TSE and fast T1-weighted FLAIR sequences. Two radiologists compared these sequences both qualitatively and quantitatively. RESULTS: On qualitative evaluation, CSF nulling, contrast at the disc-CSF interface, the disc-spinal cord (cauda equina) interface, and the spinal cord (cauda equina)-CSF interface of fast T1-weighted FLAIR images were significantly higher than those for T1-weighted TSE images (P<0.001). On quantitative evaluation of the first 15 patients, signal-to-noise ratios of cerebrospinal fluid of fast T1-weighted FLAIR imaging were significantly lower than those for T1-weighted TSE images (P<0.05). Contrast-to-noise ratios of spinal cord/CSF and normal bone marrow/disc for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted TSE images (P<0.05). CONCLUSION: Results in our study have shown that fast T1-weighted FLAIR imaging may be a valuable imaging modality in the armamentarium of lumbar spinal T1-weighted MR imaging, because the former technique has definite superior advantages such as CSF nulling, conspicuousness of the normal anatomic structures and changes in the lumbar spinal discogenic disease and image contrast and also almost equally acquisition times.     

Computed tomography of the spine and spinal cord

Configurations of 50 normal lumbar canals at each vertebral level were assessed and the dimensions of the canal at these levels measured. The appearances of the contents of the canal and their absorption values were carefully analyzed in the lumbar, cervical, and thoracic regions. Of 75 scans of patients with specific spinal symptoms, 38 showed abnormalities representing 19 pathological entities. The appearances of these lesions on scans are compared with normal scans, and the usefulness of CT scans in assessing lesions of the bone and within the canal is discussed.     

MR imaging of syringohydromyelia and Chiari malformations in myelomeningocele patients with scoliosis

The brain and spinal cord were examined with MR imaging in 30 myelomeningocele patients 3-32 years old to study the prevalence of syringohydromyelia and Chiari malformations and to correlate these conditions with developmental scoliosis and spontaneously arrested hydrocephalus. Twelve patients had neurologic deficits above the level of the myelomeningocele and 10 had spontaneously arrested hydrocephalus. MR visualized syringohydromyelia in four patients with widened or focally bulging spinal cords and in eight patients with atrophic spinal cords. All patients had Chiari malformations, 28 of type II and two of type I. Syringohydromyelia was not correlated with type of scoliosis, result of ventriculoperitoneal shunting procedures, radiologic level of the myelomeningocele, or extent of the Chiari malformation. The two patients with the most rapid progression of thoracic scoliosis had the most extensive syringohydromyelia and radiologically low lumbar levels. Neurologic deterioration due to syringohydromyelia and Chiari malformations is probably more common in myelomeningocele than has been recognized previously and may cause developmental scoliosis, loss of ambulation, impaired extremity function, and progressive cranial nerve paralysis.     

Chordomas: their CT appearance in the cervical, thoracic and lumbar spine

We reviewed 25 CT scans of 21 patients who had chordomas in the cervical, thoracic, or lumbar spine. Nine patients were studied at the time of initial presentation and 12 after tumor recurrence. All scans showed vertebral body destruction coupled with an associated soft tissue mass located anteriorly or laterally. Additional CT findings included septated areas of low attenuation within the tumor, amorphous soft tissue calcification, tumor extension into the spinal canal, disk space involvement, and contrast enhancement.     

Symptomatic spinal epidural collections after lumbar puncture in children

BACKGROUND AND PURPOSE: Complications from lumbar puncture (LP) include headache; mild puncture-site pain; and, rarely, subdural, epidural, or subarachnoid hemorrhage. In infants, asymptomatic leakage of CSF documented with ultrasound is common. We report the MR imaging findings and clinical course of 25 symptomatic patients with spinal epidural collections after LP. MATERIALS AND METHODS: MR imaging and clinical records of 25 children with new symptoms following LP were retrospectively reviewed. RESULTS: All patients had abnormal dorsal spinal epidural collections. Signal-intensity characteristics of the collections were most commonly isointense to CSF on all pulse sequences. Significant anterior displacement of the dura with effacement of the subarachnoid space was frequently noted. All patients had fluid surrounding small foci of epidural fat, elevating them from their native interspinous fossa, resulting in a "floating" appearance. Eighteen collections involved the thoracic and lumbar spine; 4 involved the thoracic, lumbar, and sacral spine; 2 extended from the lumbar to the cervical level; and 1 was isolated to the lumbar spine. Five patients had follow-up MR imaging showing complete resolution of collections. The size of the collections was not directly related to the number of puncture attempts. Clinical symptoms resolved with time in all patients with conservative management. CONCLUSION: Symptomatic epidural fluid collections after LP are often extensive and may compromise the thecal sac. These collections are not usually the result of a difficult LP and have signal intensity characteristics most consistent with CSF leak rather than hemorrhage. Signs and symptoms typically resolve with time, without treatment and with no serious sequelae.     

脊髓亚急性联合变性的MRI诊断要点分析

目的分析脊髓亚急性联合变性(SCD)的MRI诊断要点。资料与方法回顾性分析15例临床确诊SCD的病人临床及MRI资料,分析其脊髓MRI表现特点,统计分析SCD病人受累脊髓节段数与血清VB12水平、发病时间的相关性。结果 15例SCD病人均于横断面影像上显示颈胸段脊髓对称性等或长T1、长T2信号,13例病变主要位于颈胸段水平脊髓后索,2例同时累及后索、侧索及前索。但于横断面T2WI上颈段与胸段脊髓异常信号形态各具特点。颈段脊髓受累时于横断面T2WI上呈脊髓内"倒V"形或"反兔耳"形的对称性高信号。胸段脊髓受累时于横断面T2WI上呈脊髓内"哑铃"形的对称性高信号。统计学分析显示15例SCD病人脊髓受累节段数与血清VB12水平呈负相关,而与病程长短无相关性。结论脊髓MR成像对于SCD脊髓疾病的诊断有重要价值。     

Spontaneous CSF otorrhea caused by abnormal development of the facial nerve canal

In two patients with surgically proved CSF fistula through the facial nerve canal, MR and CT examinations showed smooth enlargement of the geniculate fossa with CSF signal. In the clinical setting of CSF otorrhea or rhinorrhea, the presence of an enlarged labyrinthine facial nerve canal and enlarged geniculate fossa on CT scans and CSF intensity on MR images strongly suggests a CSF fistula through the facial nerve canal.     

MR imaging of traumatic spinal arachnoid cyst

We report a case of post-traumatic lumbar arachnoid cyst, which enlarged the spinal canal and eroded the posterior elements. Computed tomographic myelography and magnetic resonance (MR) were complementary, and both correctly characterized the cystic nature of the lesion. Communication between the cyst and the subarachnoid space was demonstrated on CT myelography, which also clearly showed bone changes in the spinal canal. Continuity of the cyst with the spinal subarachnoid space was seen clearly on sagittal MR, and the MR signal characteristics of the cyst were identical with CSF.     

自发性脊髓硬膜外血肿的MRI表现

目的 对自发性脊髓硬膜外血肿(SSEH)的临床及MRI表现进行分析。方法 搜集1994～2001年的8例SSEH患者，其中男5例，女3例，年龄16～50岁。8例患者均无外伤、血液病等病史，1例有高血压病史，于发病4h至3d后分别行MR检查。8例均经手术病理证实。结果 血肿发生于颈椎3例、胸椎2例、颈胸交界部2例、胸腰段1例；血肿位于硬膜外腔的侧后方或正后方，呈梭形，范围长短不一，境界清楚。其中1例血肿为血管畸形(AVM)所致，有2例局部伴有椎间盘突出。血肿信号随时间长短各有差异，在T1WI矢状面和冠状面7例表现为等信号，1例表现为略高信号；在T2WI矢状面和轴面，6例表现为混杂信号，2例表现为混杂高信号。结论 MRI对SSEH的定位、定性及鉴别诊断具有重要作用。