Clinically manifest or silent primary and secondary syringomyelia. The magnetic resonance findings

The MR scans were retrospectively reviewed of 40 patients who had been diagnosed as having syringomyelia. Our results demonstrate that syringomyelia can be found in asymptomatic patients as well as in many with atypical symptomatology. Our study stresses MR efficacy in investigating this pathologic condition. As a matter of fact, MR allowed us to visualize the cavity, its extension, the eventual association with Arnold Chiari type-I malformation and/or syringobulbia. In all cases cord enlargement and the presence of septations could also be demonstrated. In most cases the possible pathogenesis of syringomyelia could also be supposed.     

MR imaging of syringomyelia and hydromyelia

The relative effectiveness of plain computed tomography (CT), metrizamide CT, conventional myelography, and magnetic resonance (MR) imaging was compared for the examination of cystic spinal cord lesions. Intramedullary cavities in 18 patients were demonstrated by MR imaging: cavities were uncomplicated in 13 patients, associated with spinal tumors in two, and studied after occipital craniectomy for treatment of Chiari malformation and syringomyelia in two. Cavities were shown by MR imaging in all enlarged spinal cords, but a cavity was shown in only one of four small cords. The rostral limits of the cavities were demonstrated better than were the caudal extensions. Ventricular communication was not demonstrated. Chiari malformation was shown only in cavities that did not involve the medulla. Syringes associated with tumor were indistinguishable from uncomplicated cavities, but the tumor had abnormal signal on long spin-echo sequences in two cases. Cystic cord tumor (one case) had an inhomogeneous appearance. Caudal displacement of the cerebellar hemisphere through the surgical defect associated with compression of the fourth ventricle was shown in two cases after posterior fossa craniectomy. Thirteen patients were studied with metrizamide CT also. MR imaging proved to be as accurate as metrizamide CT in the diagnosis of intramedullary cavities that result in spinal cord enlargement, but it was less sensitive in detecting cavities within normal-sized or diminished spinal cords. It had the advantage that tumor tissue could be distinguished from associated syrinx cavities by differences in signal characteristics; and cerebellar ectopia was evaluated easily on sagittal MR views.     

MR evaluation of Chiari I malformations at 0.15 T

Twelve patients with known or presumed Chiari I malformations and two with clinical diagnoses of multiple sclerosis were examined by magnetic resonance (MR) imaging. MR confirmed or established the diagnosis of Chiari I malformation in all 14 cases. The spin-echo technique with a short time to echo (TE = 40 msec) and a short time to recover (TR = 1000 msec) provided optimum imaging of tonsillar position, hydromyelia cavities, and cervicomedullary "kinking." Long TE (greater than 80 msec) and TR (greater than 2000 msec) increase the signal intensity of cerebrospinal fluid and may obscure the pathology. Sagittal, transaxial, and coronal images provided complementary data; sagittal and coronal views best imaged the abnormal spinal cord and tonsils, but slitlike cavities were best seen on transaxial images. Cervicomedullary kinking was found in 10 (71%) of 14 patients and in 90% of the hydromyelic patients. This high incidence suggests that in other radiologic techniques tonsillar herniation masks the kinking. Symptoms of the Chiari I malformation overlap those of demyelinating diseases and brain tumors. Our early experience suggests MR is the preferred noninvasive procedure for identifying Chiari I malformation. Moreover, the ability to portray the variable cavity morphology of hydromyelia directly offers the potential for improved shunt placement.     

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.     

MR of postoperative syringomyelia

Twenty-seven MR scans of 20 patients surgically treated for syringomyelia were reviewed. Thirteen patients had syringomyelia associated with the Chiari I malformation, four cases were posttraumatic, and three were idiopathic. The operations performed included syringosubarachnoid and syringoperitoneal shunts, myelotomies, and foramen magnum decompressions. Three of the foramen magnum decompressions had associated posterior fossa duroplasties, two had fourth-ventricle-to-subarachnoid shunts, and two had plugging at the obex. On 20 scans of patients in whom the syrinx cavity had been shunted, the shunt catheter was seen in 15 (75%). When adequately treated by shunting, syringes are completely collapsed and show no flow void. Nine patients were treated by foramen magnum decompression; all were well seen by MR. Three of these patients had a poor clinical result; these were the only patients in whom CSF was not seen between the foramen magnum and the neural structures of the posterior fossa on any images. The proposed mechanisms of syrinx formation and extension are discussed and related to the surgical procedures used to treat syringomyelia.     

The Cervical Spinal Canal Tapers Differently in Patients with Chiari I with and without Syringomyelia

BACKGROUND AND PURPOSE:The cause of syringomyelia in patients with Chiari I remains uncertain. Cervical spine anatomy modifies CSF velocities, flow patterns, and pressure gradients, which may affect the spinal cord. We tested the hypothesis that cervical spinal anatomy differs between Chiari I patients with and without syringomyelia.MATERIALS AND METHODS:We identified consecutive patients with Chiari I at 3 institutions and divided them into groups with and without syringomyelia. Five readers measured anteroposterior cervical spinal diameters, tonsillar herniation, and syrinx dimensions on cervical MR images. Taper ratios for C1–C7, C1–C4, and C4–C7 spinal segments were calculated by linear least squares fitting to the appropriate spinal canal diameters. Mean taper ratios and tonsillar herniation for groups were compared and tested for statistical significance with a Kruskal-Wallis test. Inter- and intrareader agreement and correlations in the data were measured.RESULTS:One hundred fifty patients were included, of which 49 had syringomyelia. C1–C7 taper ratios were smaller and C4–C7 taper ratios greater for patients with syringomyelia than for those without it. C1–C4 taper ratios did not differ significantly between groups. Patients with syringomyelia had, on average, greater tonsillar herniation than those without a syrinx. However, C4–C7 taper ratios were steeper, for all degrees of tonsil herniation, in patients with syringomyelia. Differences among readers did not exceed differences among patient groups.CONCLUSIONS:The tapering of the lower cervical spine may contribute to the development of syringomyelia in patients with Chiari I.

Patients with a Chiari I malformation frequently develop syringomyelia, in theory the result of CSF flow obstructed by ectopic cerebellar tonsils. Phase-contrast MR imaging studies of CSF flow in the foramen magnum support this theory. Oscillatory CSF fluid flow has greater velocities and greater complexity in patients with Chiari I than in healthy subjects.¹ Why some patients with Chiari I develop syringomyelia and other do not has not yet been explained. How hyperdynamic CSF flow at the craniovertebral junction causes syringomyelia lower in the cervical spine has also not been elucidated.Abnormal tonsil position is not a necessary or a sufficient cause for syringomyelia because not all patients with Chiari I have syringomyelia and not all patients with syringomyelia have tonsillar herniation. The extent of tonsillar herniation does not predict the presence of syringomyelia. Therefore, factors other than tonsil herniation may have a role in the pathogenesis of syringomyelia. For example, one factor may be the size of the posterior cranial fossa; another pathogenetic factor may be the patency of the central canal within the cervical or thoracic spinal cord.^2,3The possibility that cervical spinal canal anatomy has a role in the pathogenesis of syringomyelia has not been extensively studied. The spinal canal narrows between C1 and C4 in healthy subjects⁴ and in patients with Chiari I.⁵ The tapering of the upper cervical spinal canal causes peak CSF velocities to increase from C1 to C4.^6,7 Taper ratios, the slope of a line fit to spinal canal diameters at multiple spinal levels, differ between patients with Chiari I and controls.^5,8 We designed this study to test the hypothesis that Chiari I patients with syringomyelia have different cervical spinal canal taper ratios than Chiari I patients without syringomyelia.     

Delayed metrizamide CT enhancement of syringomyelia: postoperative observations

Delayed metrizamide computed tomography (CT) was performed both preoperatively and postoperatively in 11 syringomyelia patients. Change of syrinx size between the studies was easily assessed on CT. The morphologic change of the syrinx gave useful information about its continuity. One of our cases had reoperation as a result of this CT information. All cases with Chiari I malformation still showed filling of the syrinx cavity by metrizamide after posterior fossa decompression and obex plugging. This supports the idea that the abnormal fluid circulation maintaining syringomyelic cavities is more than just the flow through the obex to the central canal but may also be from fluid passage through the cord substance.     

Spontaneous resolution of syringomyelia in a child with Chiari I malformation: a case report

Cervicothoracic syringomyelia is a frequent feature in Chiari I malformation. It can be symptomatic or not, and is well demonstrated by magnetic resonance imaging (MRI). Its spontaneous resolution is uncommon. The authors report a case of spontaneous resolution of a thoracic syrinx in an 18-year-old patient with a Chiari I malformation. MRI study performed 6 years previously because of worsening headaches demonstrated a Chiari I malformation associated with a syrinx cavity. The cavity disappearance was noted after improvement of the symptoms.     

Magnetic resonance 4D flow analysis of cerebrospinal fluid dynamics in Chiari I malformation with and without syringomyelia

Objective

To analyse cerebrospinal fluid (CSF) hydrodynamics in patients with Chiari type I malformation (CM) with and without syringomyelia using 4D magnetic resonance (MR) phase contrast (PC) flow imaging.

Methods

4D-PC CSF flow data were acquired in 20 patients with CM (12 patients with presyrinx/syrinx). Characteristic 4D-CSF flow patterns were identified. Quantitative CSF flow parameters were assessed at the craniocervical junction and the cervical spinal canal and compared with healthy volunteers and between patients with and without syringomyelia.

Results

Compared with healthy volunteers, 17 CM patients showed flow abnormalities at the craniocervical junction in the form of heterogeneous flow (n?=?3), anterolateral flow jets (n?=?14) and flow vortex formation (n?=?5), most prevalent in patients with syringomyelia. Peak flow velocities at the craniocervical junction were significantly increased in patients (?15.5?±?11.3 vs. ?4.7?±?0.7 ?cm/s in healthy volunteers, P?P?Conclusions 4D-PC flow imaging allowed comprehensive analysis of CSF flow in patients with Chiari I malformation. Alterations of CSF hydrodynamics were most pronounced in patients with syringomyelia.

Key Points

? Analysis of CSF flow is important in patients with Chiari I malformation ? 4D-PC MRI allows analysis of CSF in patients with Chiari I. ? Chiari I patients show characteristic qualitative and quantitative alterations of CSF flow. ? Alterations of CSF hydrodynamics are most pronounced in patients with associated syringomyelia.     

Lipomyeloschisis associated with thoracic syringomyelia and Chiari I malformation

Co-existence of Chiari I malformation and myelomeningocele is uncommon. Syringomyelia, when associated with a Chiari I malformation, classically involves the cervical spinal cord. Intramedullary extension of lipoma is unusual in lipomyeloschisis. A patient with lumbar lipomyelomeningocele with tethered cord, lower thoracic syringomyelia and Chiari I malformation, shown by MRI is reported.     

CSF pulsations within nonneoplastic spinal cord cysts

Because of its sensitivity to fluid motion, MR imaging was used to investigate fluid dynamics in syringomyelia. Three major findings characterized syringomyelia: pulsatile fluid in cysts, nonpulsatile fluid in cysts, and damaged cord tissue. The fluid in preoperative syrinx cavities pulsated in a fashion similar to subarachnoid CSF. Pulsation was more prominent in large cysts but was also seen in small cysts. Nonpulsatile cysts were generally of smaller diameter, were shorter in length, and often were single; they could, however, coexist with pulsatile cysts. Nonpulsatile cysts had etiologies similar to those of pulsatile cysts: Chiari malformation, trauma, and unknown. Damaged cord, characterized by abnormal high signal on T2-weighted sequences, was seen in 15 of 16 patients and could be either focal or diffuse but was always adjacent to syrinx cavities. Postsurgical MR scans had a lower incidence of pulsatile cysts. In five patients with both pre- and postoperative MR scans, shunting of the cyst reduced the size of the pulsating cyst (two patients) or reduced the size of the cyst and eliminated pulsation altogether (three patients). Axial, T2-weighted images are recommended in the investigation of spinal cord cysts to determine the presence or absence of pulsatile fluid. The presence of pulsation indicates a nonneoplastic cyst. The absence or reduction of CSF pulsation may prove to be a valuable indicator of the success of a shunting procedure.     

Phase-contrast MR imaging of the cervical CSF and spinal cord: volumetric motion analysis in patients with Chiari I malformation

BACKGROUND AND PURPOSE: Most previous MR studies of the dynamics of Chiari I malformation have been confined to sagittal images and operator-dependent measurement points in the midline. To obtain a deeper insight into the pathophysiology of the Chiari I malformation, we performed a prospective study using axial slices at the level of C2 to analyze volumetric motion data of the spinal cord and CSF over the whole cross-sectional area. METHODS: Eighteen patients with Chiari I malformation and 18 healthy control subjects underwent cardiac-gated phase-contrast imaging. Cross-sectional area measurements and volumetric flow/motion data calculations were made for the following compartments: the entire intradural space, the spinal cord, and the anterior and posterior subarachnoid space. RESULTS: The most striking feature was an increased early systolic caudal and diastolic cranial motion of the spinal cord in the patients. CSF pulsations in the anterior subarachnoid space were unchanged at systole but showed an impaired diastolic upward flow. In the posterior compartment, the CSF systole was slightly shortened, with an impairment of diastolic upward flow. Fourteen of the 18 patients had associated syringeal cavities. This subgroup showed an increased systolic downward displacement of the cord as compared with patients without a syrinx. CONCLUSION: Obstruction of the foramen magnum in patients with Chiari I malformation causes an abrupt systolic downward displacement of the spinal cord and impairs the recoil of CSF during diastole.     

后颅窝扩大成形术治疗Chiari畸形颅颈减压术后小脑下垂

 目的报告颅颈减压术后小脑下垂应用颅骨成形术进行有效治疗的处理经验.方法对5例曾行后颅颈减压术,但术后临床症状加重有小脑下垂表现的Chiari畸形合并脊髓空洞症患者采用钛网实施后颅窝扩大成形术,男4例,女l例,平均年龄32.3岁.结果随访6～18月,平均13个月,5例患者术后临床症状及体征均改善,复查MRI显示扩大成形的后颅窝容积稳定,成形良好,枕大池重建,脊髓空洞均有不同程度缩小,后颅窝容积有效扩大11.33～24.1 ml,平均16.74 ml.结论后颅窝扩大成形术扩大成形良好,临床效果满意,是治疗后颅颈减压术后小脑下垂的有效治疗方法.     

脊髓空洞症外科治疗的多因素疗效分析

目的分析脊髓空洞症外科治疗疗效的影响因素。方法采用多因素逐步回归分析方法，对７８例获得随访者以年龄、性别、病程、感觉障碍、运动障碍、合并Ｃｈｉａｒｉ畸形、空洞最大径和手术方式为自变量进行疗效分析。结果运动功能障碍、空洞大小、病程和年龄依次是影响疗效的主要因素，而手术方式、合并Ｃｈｉａｒｉ畸形、感觉障碍和性别对疗效影响不大。结论多因素分析疗效结果较为可靠；综合评价患者病情，科学选择手术适应证并采取适当的手术方式是提高疗效的主要因素。     

Cervical diastematomyelia and syringohydromyelia in a myelomeningocele patient

A case of cervical diastematomyelia and syringohydromyelia in a 16-year-old female myelomeningocele patient is reported. Progressive weakness of the upper extremity led to an MR examination of the brain and spine, which revealed hydrocephalus, Chiari II malformation, cervical diastematomyelia with a syringohydromyelic cavity in each hemicord and a large dural sac in the lumbar region. Operative therapy consisted of detethering and shunting of the two syringes. Soon after surgery her symptoms improved. The need for early complete MR imaging of myelomeningocele patients presenting with new symptoms is emphasized. Received 20 March 1996; Revision received 30 May 1996; Accepted 10 July 1996     

Syringomyelia in association with posterior fossa cysts

This paper presents three patients with a triad of syringomyelia, midline posterior fossa cysts, and hydrocephalus. In the first patient, the clinical presentation was related to spinal cord cavitation, and the cranial anomalies were unexpected. In cases 2 and 3, the brain anomalies dominated the clinical picture, and syringomyelia was unexpected. These cases show that an examination of the whole neuraxis is as important in patients with midline posterior fossa cysts as it is in patients with developmental syringomyelia or Chiari I malformation.     

0.6 T MR imaging of the cervical spine: multislice and multiecho techniques

During a 6 month period, 50 patients with signs and symptoms referable to the cervical spine were studied with a 0.6 T superconducting magnetic resonance (MR) imaging unit. The last 23 of these 50 patients were studied with combined multislice and multiecho techniques. In 38 of the 50 patients, abnormalities were demonstrated on MR images. Intramedullary lesions included syringomyelia (three cases), primary tumors (two), metastatic neoplasm (one), cord atrophy secondary to trauma (one), and multiple sclerosis (one). Intradural, extramedullary lesions included two neurofibromas and two Chiari malformations. The rest of the lesions were extradural: degenerative changes (10), spinal stenosis with cord compression (five), disk degeneration and/or herniation (five), postoperative changes (four), metastases to bone/epidural disease (three), and neurofibromatosis (one). Two patients had more than one abnormality. The MR findings were compared with available routine radiographs, computed tomographic (CT) scans with and without metrizamide, and myelograms. MR imaging was consistently better than routine CT scanning in the detection of lesions of the spinal cord and in directly imaging the effects on the spinal cord of extrinsic abnormalities such as spinal stenosis. Metrizamide-enhanced CT scanning detected all cases of syringomyelia, but it involved an invasive procedure. Myelography alone was slightly less sensitive and considerably less specific than MR in detecting intramedullary lesions and in distinguishing cord neoplasms from syringomyelia. Multislice, multiecho techniques with up to 240 msec echo times (TEs) were particularly helpful in the detection and characterization of extradural processes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Significance of cerebellar tonsillar position on MR

It has been noted that a low degree of ectopia of the cerebellar tonsils on MR is of questionable significance. We measured the position of the cerebellar tonsils with respect to the inferior aspect of the foramen magnum in 200 normal patients and in 25 patients with a firm diagnosis of Chiari I malformation. In the normal group, the mean position of the tonsils was 1 mm above the foramen magnum with a range from 8 mm above the foramen magnum to 5 mm below. In the patients with Chiari I malformations, the mean position was 13 mm below the foramen magnum with a range from 3 mm below the foramen magnum to 29 mm below. Fourteen percent of normal patients had tonsils extending slightly below the foramen magnum. If 2 mm below the foramen magnum is taken as the lowest extent for tonsils in a normal patient, our sensitivity in predicting symptomatic patients is 100% and our specificity is 98.5% (three false positives). If 3 mm below the foramen magnum is taken as the lowest normal tonsillar position, our sensitivity is 96% and our specificity is 99.5%. MR demonstration of less than 2 mm of tonsillar ectopia is probably of no clinical significance in the absence of syringomyelia.     

Chiari II malformation: MR imaging evaluation

The purpose of this study was to explore the value of high-detail MR imaging in the diagnosis of the Chiari II malformation. Twenty-four patients with known Chiari II malformation as diagnosed by CT scanning were evaluated with cranial MR scans. Two patients also had spine scans. The sagittal-plane images were the most informative, and abnormalities of the telencephalon, diencephalon, mesencephalon, rhomboencephalon, upper spinal cord, and mesencephalon were shown extremely well. We found MR to be an easy and accurate method for demonstrating the abnormalities of the Chiari II malformation, and it is our procedure of choice.     

Conventional and CT metrizamide myelography in Arnold-Chiari I malformation and syringomyelia

Four normal controls and 26 cases of Arnold-Chiari I malformations and/or syringomyelia were reviewed. The pathologic cases included five isolated Arnold-Chiari I malformations, nine communicating syringomyelia, five idiopathic syringomyelia, four posttraumatic syringomyelia, one syringomyelia with hemangioblastoma, and two postshunt syringomyelia. The objectives of this study were to compare the accuracy of conventional metrizamide myelography with CT metrizamide myelography and to study indirectly the hydrodynamics of CSF flow in syringomyelia by comparing the sequential enhancement patterns of the spinal cords and cord cavities in the different groups of patients. Twenty-five patients underwent conventional metrizamide myelography immediately before CT metrizamide myelography, and one patient underwent CT metrizamide myelography only. Scans were obtained 1-2 hr, 4-8 hr, and 12-24 hr after injection of metrizamide, but not all patients were scanned during all three intervals. CT metrizamide myelography was found to be more sensitive than conventional metrizamide myelography in the diagnosis of both Arnold-Chiari I malformation and syringomyelia. Performing just an immediate and a delayed scan was found to be more cost-effective than doing all three scans. Contrary to previous reports, it was found that delayed (12-24 hr) scans demonstrated more syrinx cavities than intermediate ones. In studying the sequential enhancement patterns of the spinal cords and cord cavities, some interesting trends were observed that tend to support the theories of Aboulker and of Ball and Dayan of transneural passage of CSF into cord cavities in syringomyelia.