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CASE REPORT |
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| Ahead of print
publication |
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Multiple extradural arachnoid cysts causing cord compression
Pratik R Patel, Murtaza M Dadla, Trimurti D Nadkarni
Department of Neurosurgery; B. Y. L. Nair Ch. Hospital and Topiwala National Medical College, Mumbai, Maharashtra, India
| Date of Submission | 24-Nov-2020 |
| Date of Decision | 26-Jan-2021 |
| Date of Acceptance | 30-Jan-2021 |
| Date of Web Publication | 19-Jul-2021 |
Correspondence Address:
Trimurti D Nadkarni,
Department of Neurosurgery, B.Y.L. Nair Ch. Hospital, Topiwala National Medical College, Mumbai, Maharashtra.
India
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/jpn.JPN_305_20
 Abstract | | |
Spinal arachnoid cysts (SACs) are an uncommon cause of spinal cord compression. A nine-year-old female child presented with pain, stiffness, and weakness in both lower limbs. The girl could walk with support. She had clinical features suggestive of Marfan’s syndrome. On examination, she had spastic paraparesis. Neuroimaging revealed multiple extradural arachnoid cysts (EACs) causing cord compression, extending from the cervical to sacral level. Computerized tomography (CT) myelogram did not demonstrate a communication of the EAC with the spinal subarachnoid space at any level or within adjacent cysts. The patient underwent a dorsal laminoplasty (D6 to D8) with excision of the underlying EAC, which was causing maximum compression. Postoperatively, the patient showed significant improvement in her gait. She could walk independently at the time of discharge. The EACs are rare and the present case is the only case to have extensive spinal cord involvement from cervical to sacral levels and only the second in literature in which multiple EACs caused symptomatic cord compression. The relevant literature is reviewed.
Keywords: Arachnoid cyst, extradural, Marfan’s syndrome, spinal compression
| Introduction | |  |
The SACs are relatively rare, accounting for 1% to 3% of all mass lesions in the spinal canal. They are often asymptomatic and found incidentally. SAC is a herniation of the arachnoid mater due to a congenital anomaly or developing secondary to other causes such as trauma, infection, inflammation, or iatrogenic (lumbar puncture or postsurgical).[1] A small defect in the arachnoid mater induces cerebrospinal fluid (CSF) accumulation, leading to arachnoid membrane herniation both intradurally and extradurally where a dural defect coexists. Symptomatic SACs may be accompanied by pain, motor weakness, urinary incontinence, myelopathy, and sensory changes, which are believed to be caused by mass effect and root compression. SAC may increase in size during exercise, strenuous activity or because of increased intracranial pressure and flow of CSF into the cyst.[2]
When surgical intervention is required, there is no consensus on the preferred surgical technique. However, repair of the dural defect appears to be important. The total removal of the SAC remains controversial.[3] The present case describes the management of symptomatic cord compression due to multiple SACs involving the entire spinal cord in a pediatric patient.
| Case Report | | |
A nine-year-old female child presented with chief complaints of back pain radiating to both lower limbs associated with lower limb stiffness and weakness for the past four months. She required assistance to walk. There was no involvement of bladder or bowel function. The patient had undergone closure of patent ductus arteriosus at two years of age. The elder sibling had a normal development. On general examination, the child had hypertelorism, flattened nasal bridge, low set ears, high arched cleft palate, and a long neck suggestive of Marfanoid features. The child had delayed mental development as she could speak only simple sentences and carry out simple commands. Motor examination revealed spastic paraparesis (Grade 3) with exaggerated deep tendon reflexes in both lower limbs. Due to the child’s mental impairment, a definitive sensory level could not be elicited. The child’s karyotyping was normal. Her 2D-echo of the heart was normal. Magnetic resonance (MR) images of the whole spine with contrast revealed a dilated neural canal with multiple CSF-filled extradural cysts, with septations extending from the lower cervical level to the sacral region [Figure 1]A. The cysts were also seen to herniate through the bilateral neural foramina, which were widened [Figure 1]B. The cysts were causing mass effect in the form of cord compression and posterior vertebral bodies scalloping [Figure 1]C. On a CT myelogram in the lumbar area, the dye ascended upto the D10-D11 vertebral level. Another myelogram done at D5 revealed the thoracic cyst, with contrast extending superiorly upto the C7 level. Thus, it was clear that the patient harbored multiple SACs that were not in communication. Further, the communication of the cyst to the spinal subarachnoid space could not be demonstrated even on delayed films. The SAC at D6 to D8 was the largest, with maximum cord compression as noted on radiology. The patient underwent partial excision of the dorsal wall of the SAC through a D6 to D8 laminoplasty [Figure 2]. On marsupializing the cyst, a rent was seen in the dura at D6-D7 level through which arachnoid was pouting. This rent was closed in a watertight fashion with 4-0 vicryl. Histopathology revealed features of a benign spinal arachnoid cyst [Figure 3]. | Figure 1: MR images A. Sagittal T2-weighted image of the entire spine demonstrating the multiloculated EACs extending from the lower cervical to sacral spinal level. B. Axial T2-weighted image at lumbar (L2) level that shows the extent of the EAC through the bilateral neural formina. C. Sagittal T2-weighted image of the dorsolumbar spine shows multiple septations within the cyst. Note the spinal cord that is displaced anteriorly and the scalloping of the dorsolumbar vertebral bodies
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 | Figure 2: Intraoperative photograph that shows the multiloculated extradural SAC as seen on performing D6 to D8 laminoplasty
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 | Figure 3: Photomicrograph of the SAC that shows a cyst wall lined by flattened epithelium (double arrow) overlying fibrocollagenous tissue (single arrow)
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Postoperatively, the child had subjective improvement in the stiffness of both lower limbs. There was a gradual improvement in power and at the time of discharge the patient could walk without support.
| Discussion | | |
The SACs are rare lesions that are commonly solitary and occur usually in the thoracic spine. Cloward reported that 80% occurred in the thoracic spine.[4] The present case is unique, as it is the first in literature documenting involvement of the entire spine (cervical (C7) to sacral (S5)) by mutiple cysts. A similar case report of multiple extradural cysts but with involvement from T2 to S1 is documented.[5]
Several theories have been proposed as to the mechanism of cyst expansion, which include a one-way ball–valve mechanism between the subarachnoid space and the cyst, an increase in the intraspinal pressure that could stimulate the movement of CSF into the cyst or active secretion by the cells lining the cyst.[6]
Nabors et al. described the most commonly used classification system, which separates the cysts into three major categories based on their location.[7] Type I cysts are extradural arachnoid cysts (EACs) without nerve root involvement; type I cysts are further subcategorized as EAC (type Ia) and sacral meningocele (type Ib). Type II cysts are EAC with nerve root involvement. Type III cysts are intradural meningeal cysts.
The SACs are most commonly identified on MR imaging. They appear as homogeneous low-intensity signals on T1W sequences and high-intensity signals on T2W sequences, consistent with CSF characteristics. Cinematic MR techniques can identify a pulsating flow void to determine the location of the dural defect.[8] Diffusion-weighted MR can help differentiate an epidermoid cyst from an arachnoid cyst. CT myelography is used to define the SACs. Although sensitive in determining whether a communication exists, it does not pinpoint the location of the communication very well.[9] As noted in our case, our attempts to localize sites of communication of SACs with subarachnoid space failed on radiology, though at surgery a communication was identified and treated. However, in the case reported by Myles et al., they could preoperatively establish the location, size, number of cysts, as well as sites of dural defects on CT myelography.[5]
The standard treatment of an isolated SAC is complete surgical removal of the cyst. Various surgical strategies have been described, ranging from complete microsurgical resection to simple fenestration followed by closure of dural defect. For EACs (types I and II), resection of the cyst followed by closure of the dural connection to the cyst is the preferred treatment. In the present case, as there were mutiple cysts extending from the cervical to sacral level, extensive mutilevel excision of the cysts would lead to the risk of spinal deformity and instability. Hence, on neuroradiology, the cyst of greatest size causing maximum cord compression was marsupialized. Lee et al. demonstrated that recurrence of the cyst was dependent on the adequacy of dural closure and not on the completeness of surgical excision.[10]
The most commonly performed procedure involves laminectomies, spanning the entire length of the cyst to allow for full visualization of the cyst. In case of mutiple large cysts, such an extensive surgery carries an increased risk of infection and instability due to spinal deformity. As laminectomy increases the risk of future kyphotic deformity, especially in the pediatric age group, some surgeons advocate a tailored laminoplasty with cyst fenestration and dural defect repair.[11] The predominant postoperative complication remains cyst recurrence, and, hence, serial clinicoradiological surveillance is necessary. The SAC can be satisfactorily treated surgically with good recovery of neurological function.
| Conclusion | | |
The SACs are infrequent mass lesions in the spine that can cause neurologic dysfunction requiring surgical intervention. Extensive involvement of the spine by multiple EAC as described in the present case is not previously reported in literature. The MR imaging with CT myelography defines the cyst number, size, location, and site of communication with spinal subarachnoid space. In multiple cysts, marsupialization at the level where the cyst size and cord compression are maximum offers satisfactory neurological recovery. However, long-term follow-up is required with clinical and radiological monitoring in such cases.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/ have given his/ her/ their consent for his/ her/ their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| References | | |
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[Figure 1], [Figure 2], [Figure 3]
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