Thoracic intradural arachnoid cyst: possible pitfalls with myelo-CT and MR

Summary A thoracic intradural arachnoid cyst presenting as an intradural extramedullary mass highly suggestive of psammoma on myelogram and myelo-CT is reported in a 34-year-old female. High densities of the cyst were related to collection of contrast media within the cyst. However MR examination of the thoracic spinal cord including sagittal T1 (without and with contrast) and T2 studies failed to demonstrate the mass. Lack of MR changes were related on one hand to the small size of the cyst and to the absence of mass effect on the spinal cord, and on the other hand to a CSF-like signal of the contents of the cyst. Only combination of myelography, myelo-CT and MR allows precise diagnosis of small intradural arachnoid cysts; however MR is the method of choice for evaluation of large intradural subarachnoid cysts.     

MRI of spinal intradural arachnoid cyst formation following tuberculous meningitis

Secondary intradural arachnoid cyst involving the spine is uncommon. It is usually secondary to trauma, haemorrhage, surgery or inflammation. We present two cases of treated tuberculous meningitis, which presented with gradual onset of quadriplegia and paraplegia, respectively. MRI revealed intradural (cervical and thoracic) arachnoid cysts (ventral and dorsal to the spinal cord) with myelomalacic cord changes. Ventral location of such spinal arachnoid cysts, and being secondary to tuberculous arachnoiditis are distinctively uncommon features. The rarity of this condition and the relevance of MRI in the accurate diagnosis have been discussed here.     

An unusual spinal intradural arachnoid cyst

Spinal intradural arachnoid cysts are seen most frequently in the thoracic region, particularly near the midline posteriorly. A thoracic intradural arachnoid cyst in this typical location is reported, with the additional unusual finding of herniation of the spinal cord through an anterior defect in the dura mater. The MRI findings are described.     

Spinal cord atrophy associated with arachnoiditis as demonstrated by computed tomography

Summary Two cases showing the features of spinal arachnoiditis on metrizamide myelography were examined by concurrent computed tomography. This showed severe atrophy and deformity of the spinal cord with its cross sectional shape changing dramatically from one segmental level to the next. These features may be the result of traction on the cord by arachnoid adhesions. Filling defects in the canal or apparent enlargement of the cord may result from pouches of subarachnoid space which are not in free communication with the contrast material.     

Spinal meningeal cyst

A case of meningeal cyst of the spine in the thoraco-lumbar region is described. Although water-soluble myelography may disclose a filling defect and possibly reveal communication between the cyst and the subarachnoid space, computerized tomographic myelography more readily reveals communication between the cyst and the subarachnoid space. This finding allows accurate diagnosis of a spinal meningeal cyst and rules out other mass lesions. A classification comprising three categories is made: spinal extradural meningeal cysts without spinal nerve root fibers (Type I), spinal extradural meningeal cysts with spinal nerve root fibers (Type II) and spinal intradural meningeal cysts (Type III). Final characterization is based on operative inspection and histological examination.     

Radiologic evaluation of spinal cord fissures

The clinical course and radiographic studies were reviewed of eight patients with posttraumatic spinal cord fissures (rents in the spinal cord communicating with the subarachnoid space). Five patients had spinal cord fissures associated with symptomatic intramedullary cysts that required shunting to alleviate progressive neurologic deficits and intractable pain. Their metrizamide myelograms showed contrast medium passing immediately from the subarachnoid sac into the spinal cord and their immediate metrizamide CT scans delineated the entire extent of the secondary cord cysts. Intraoperative sonography confirmed the presence of the cord fissures with sizeable cysts, detected adhesions, and guided myelotomies and the subsequent shunting and collapse of the cysts. Since neurologic improvement followed the shunting procedures in all five patients treated for progressive symptoms, it was concluded that early radiologic evaluation of posttraumatic spinal cord fissures with symptomatic cord cysts is crucial in the clinical management of these patients.     

椎管内硬脊膜外蛛网膜囊肿的低场强MRI诊断

目的:探讨椎管内硬脊膜外蛛网膜囊肿的低场强MRI表现特征,提高对该病的认识。方法:回顾性分析12例经手术病理证实的硬脊膜外蛛网膜囊肿的临床及MRI表现特征,其中10例行Gd DTPA增强扫描,7例行X光平片或CT片检查。结果:本组病例发病于胸腰段8例,位于脊髓背侧9例,呈典型的椎管内硬脊膜外占位病变征象,囊肿的信号强度与脑脊液一致或相近,上、下缘与硬脊膜外脂肪毗邻,上或下方邻近硬脊膜的显示,可为硬脊膜外囊肿的定位诊断提供有力的佐证,囊肿与蛛网膜下腔相交通时,孔道区囊肿内可出现流空信号,可确定孔道的具体位置,为手术提供可靠可靠的依据。结论:MRI是目前评价椎管内硬脊膜外蛛网膜囊肿的定位和定性诊断最佳影像学方法和首选检查手段。     

中枢神经系统肠源性囊肿的MR诊断与鉴别诊断

目的探讨中枢神经系统肠源性囊肿的MRI表现及其鉴别诊断。方法回顾性分析7例经手术和病理证实的肠源性囊肿的临床和MRI资料。结果 7例肠源性囊肿,桥前池1例,椎管内髓外硬膜下6例,3例病变位于颈段,2例位于上段胸段,1例位于腰段。6例椎管内肠源性囊肿,5例囊肿位于脊髓腹侧,均可见"脊髓嵌入征"。多数囊肿T1Wl呈等或稍高于脑脊液信号,T2WI等或稍低于脑脊液信号。6例行MR增强扫描,5例囊壁及囊液均未见强化,1例囊壁轻度强化。结论 MRI对肠源性囊肿的诊断及鉴别诊断有重要价值。     

Morphology and dimensions of the thoracic cord by computer-assisted metrizamide myelography

Computed tomographic (CT) measurements of the thoracic spine and its contents were obtained in 33 patients undergoing metrizamide myelography for various spinal disorders. Twenty-eight of these patients had symptoms referable to the cervical or lumbar region and form the basis of this study. Five patients had symptoms referable to the thoracic spine. Sagittal and coronal CT measurements of the thoracic cord and subarachnoid space were obtained in all cases. In addition, macroscopic measurements of the thoracic cord were obtained from 10 autopsies for correlation with the CT findings. The technical aspects of the measurements are discussed; the normal morphology of the thoracic cord and thecal sac is presented; and the metrizamide CT pattern associated with pathologic lesions involving the thoracic cord is analyzed.     

Digital Subtraction Cystography for Detection of Communicating Holes of Spinal Extradural Arachnoid Cysts

Objective

The purpose of this study was to demonstrate the usefulness of digital subtraction cystography to identify communicating holes between a spinal extradural arachnoid cyst (SEAC) and the subarachnoid space prior to cyst removal and hole closure.

Materials and Methods

Six patients with SEAC were enrolled in this retrospective study. Digital subtraction cystography and subsequent CT myelography were performed for every patient. The presence and location of the communicating holes on cystography were documented. We evaluated the MRI characteristics of the cysts, including location, size, and associated spinal cord compression; furthermore, we reviewed cystographic images, CT myelograms, procedural reports, and medical records for analysis. If surgery was performed after cystography, intraoperative findings were compared with preoperative cystography.

Results

The location of the communicating hole between the arachnoid cyst and the subarachnoid space was identified by digital subtraction cystography in all cases (n = 6). Surgical resection of SEAC was performed in 4 patients, and intraoperative location of the communicating hole exactly corresponded to the preoperative identification.

Conclusion

Fluoroscopic-guided cystography for SEAC accurately demonstrates the presence and location of dural defects. Preoperative digital subtraction cystography is useful for detection of a communicating hole between a cyst and the subarachnoid space.     

Metrizamide-enhanced computed tomography of intracranial arachnoid cysts

Between July 1981 and August 1983 the authors studied 21 patients with intracranial arachnoid cysts using metrizamide-enhanced CT. With this method we are able to determine the degree of communication between the cysts and the surrounding subarachnoid space as well as to assess the evolving character of some of these lesions. This information will allow a more rational choice of surgical treatment.     

慢性脊髓创伤的MRI表现

目的　探讨慢性脊髓损伤的MRI表现及其形成机制。材料与方法　分析 2 8例慢性脊髓损伤者的MRI表现及临床资料 ,其中男 2 1例 ,女 7例 ,平均年龄 39岁。伤后行MRI复查时间为 1个月～ 12年。MRI取常规SE序列T1WI、T2 WI矢状、横断面。结果　 2 8例中有 16例发生在颈髓 ,上胸髓及脊髓圆锥各 6例。其中脊髓囊变 13例 ;慢性脊髓受压 5例 ,均合并有其他类型的病理改变 ;脊髓软化 4例 ;脊髓空洞 2例 ;脊髓萎缩 3例 ;脊髓栓系 1例。结论　慢性脊髓损伤分别表现为脊髓囊变、空洞、萎缩、软化、栓系及慢性受压 6种病变 ,脊髓囊变与脊髓瞬间压迫伤有关 ,其病变局限。脊髓空洞及脊髓萎缩均与脊髓持续受压有关 ,病变潜在进展。脊髓软化可能由伤后脊髓缺血引起 ,脊髓栓系是伤后蛛网膜粘连造成     

Focal Anterior Displacement of the Thoracic Spinal Cord without Evidence of Spinal Cord Herniation or an Intradural Mass

Objective

We report magnetic resonance imaging (MRI) findings on focal anterior displacement of the thoracic spinal cord in asymptomatic patients without a spinal cord herniation or intradural mass.

Materials and Methods

We identified 12 patients (male:female = 6:6; mean age, 51.7; range, 15-83 years) between 2007 and 2011, with focal anterior displacement of the spinal cord and without evidence of an intradural mass or spinal cord herniation. Two radiologists retrospectively reviewed the MRI findings in consensus.

Results

An asymmetric spinal cord deformity with a focal dented appearance was seen on the posterior surface of the spinal cord in all patients, and it involved a length of 1 or 2 vertebral segments in the upper thoracic spine (thoracic vertebrae 1-6). Moreover, a focal widening of the posterior subarachnoid space was also observed in all cases. None of the patients had myelopathy symptoms, and they showed no focal T2-hyperintensity in the spinal cord with the exception of one patient. In addition, cerebrospinal fluid (CSF) flow artifacts were seen in the posterior subarachnoid space of the affected spinal cord level. Computed tomography myelography revealed preserved CSF flow in the two available patients.

Conclusion

Focal anterior spinal cord indentation can be found in the upper thoracic level of asymptomatic patients without a spinal cord herniation or intradural mass.     

Diffuse arachnoid ossification and multiple arachnoid cysts presenting with progressive thoracic myelopathy

An ossified arachnoid membrane combined with cystic formation is rarely reported as a cause of spinal cord compression. We report the case of a 60-year-old man who presented with diffuse ossification of the arachnoid membrane (arachnoid ossification) and multiple cystic changes (arachnoid cyst) at the thoracic and lumbar spine. The lesions were surgically removed and progressive deterioration was prevented, although no marked improvement of neurological symptoms was attained.     

Elimination of metrizamide from the spinal subarachnoid space: a study of patients with abolished intracranial circulation

Two absorptive pathways for contrast media injected into the lumbar subarachnoid space have been postulated: (1) through the intracranial parasagittal arachnoid granulations and (2) direct absorption through the spinal arachnoid villi into the blood. To study the capacity of the spinal absorptive pathway, serial measurements of metrizamide concentrations in blood serum and urine were obtained before and after lumbar intrathecal injection of contrast medium in four patients with arrested intracranial blood circulation ("brain death") and intracranial pressure exceeding systolic blood pressure who had no circulation of cerebrospinal fluid from the spinal subarachnoid space to the parasagittal arachnoid granulations. These measurements indicated a high capacity of the spinal absorptive pathway for metrizamide elimination.     

椎管内结核性蛛网膜炎的MR成像

目的评估ＭＲＩ对椎管内结核性蛛网膜炎的诊断价值。材料与方法对１６例椎管内结核性蛛网膜炎的ＭＲＩ表现、Ｇｄ－ＤＴＰＡ增强ＭＲＩ的作用和追踪ＭＲＩ的变化进行分析。结果ＭＲＩ显示脊膜炎１２例，表现为蛛网膜下腔狭窄和消失、脑脊液分房和神经根增厚。在增强ＭＲＩ上，受累的软脊膜和硬膜呈线形、弥漫性斑块状和结节状或环形显著增强。脊髓受累见于全部１６例，包括脊髓水肿９例；脊髓空洞７例。在全部１６例中，髓内结核瘤２例。结论ＭＲＩ可以直接显示脊膜、脊髓和神经根受累后的形态学和病理学改变，增强ＭＲＩ可以更清楚地显示出髓内和髓外病变的程度。因此，ＭＲＩ对椎管内结核性蛛网膜炎的诊断价值，无论是在急性期或慢性粘连期，均优于脊髓造影和ＣＴ脊髓造影     

创伤后脊髓囊变的MRI研究

目的 :探讨创伤后脊髓囊变的MRI表现及与其临床预后的关系。材料和方法 :回顾性分析 67例脊髓囊变病例的临床和MRI表现。结果 :67例伤后髓内囊变 ,颈髓 3 9例 ,胸髓 2 8例 ,囊变的位置与脊柱骨折、脱位位置一致 ;囊变的平均长度 (T1WI矢状位上下范围 )为 14mm ;脊髓囊变的信号变化同脑脊液 ;其大小、形态、位置同临床症状无明显关系。结论 :髓内囊变是慢性期脊髓损伤常见的病理改变 ;髓内囊变是同一水平骨折、脱位椎体直接撞击脊髓引起。髓内囊变为一局限性、稳定性病变。     

Interventional MR imaging with an endospinal imaging coil: preliminary results with anatomic imaging of the canine and cadaver spinal cord

Percutaneous intraspinal navigation (PIN) is a new minimally invasive approach to the subarachnoid space. Using conventional radiographic fluoroscopy, entrance is gained to the lumbar subarachnoid space, allowing navigation throughout the spinal canal. Using an antenna/guidewire introduced via PIN, we performed endospinal MR imaging of the thoracic spinal cord in a cadaver and canine subject. Comparison images were obtained with an optimal surface coil. PIN allows endospinal MR imaging of the spinal cord, providing significant signal-to-noise ratio gains over conventional imaging.     

MR phase imaging and cerebrospinal fluid flow in the head and spine

Summary Motion of the cerebrospinal fluid (CSF) in and around the brain and spinal cord was examined in healthy subjects and in a number of patients with abnormalities of the CSF circulation. The pulsatile motion of the CSF was determined by spin echo phase (velocity) imaging, sometimes in combination with gradient echo phase contrast cine. Differences in flow patterns across CSF spaces were observed: flow reversal in the cerebellomedullary cistern and lumbar area relative to cervical CSF, and in the posterior versus the anterior subarachnoid space in the spinal canal. Flow communication was demonstrated in known communicating cysts or cavities. Differences in flow were also noted across spinal narrowing or block, and across the walls of a variety of cystic lesions in the brain and spinal cord. MR phase imaging of CSF flow provides pathophysiological information of potential clinical importance for the assessment of diseases affecting the CSF circulation.     

Coexistence of schizencephaly and middle cranial fossa arachnoid cyst: a report of two patients

Two patients are presented with large cerebral schizencephalic clefts and large temporal arachnoid cysts. Neuropathological studies suggest that arachnoid cysts may either arise due to an aberration in the formation of the subarachnoid space or by its splitting. A recently proposed theory for the formation of schizencephaly is that this condition is an extreme variant of cortical dysplasia, in which the infolding of cortex extends all the way into the lateral ventricle. In light of these data, and based on the imaging findings in our two patients with large cerebral schizencephalic clefts and large temporal arachnoid cysts, we propose that the mechanism which causes schizencephaly (deep cortical infolding) may lead to some kind of a traction effect and splitting of the leptomeninges resulting in the formation of an arachnoid cyst adjacent to the schizencephalic cleft. This appears to be a significant observation because the pathogenesis of arachnoid cysts is still controversial. Received 23 October 1995; Revision received 17 May 1996; Accepted 23 May 1996