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LETTER TO EDITOR
Year : 2010  |  Volume : 58  |  Issue : 6  |  Page : 964-966

Thoracic intramedullary arachnoid cyst


Department of Neurosurgery, L.T.M.G. Hospital, Mumbai, India

Date of Acceptance22-Jul-2010
Date of Web Publication10-Dec-2010

Correspondence Address:
Batuk Diyora
Department of Neurosurgery, L.T.M.G. Hospital, Mumbai
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.73774

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How to cite this article:
Diyora B, Kamble H, Nayak N, Dugad P, Sharma A. Thoracic intramedullary arachnoid cyst. Neurol India 2010;58:964-6

How to cite this URL:
Diyora B, Kamble H, Nayak N, Dugad P, Sharma A. Thoracic intramedullary arachnoid cyst. Neurol India [serial online] 2010 [cited 2019 Aug 24];58:964-6. Available from: http://www.neurologyindia.com/text.asp?2010/58/6/964/73774


Sir,

Arachnoid cysts are benign developmental cysts that occur in the cerebrospinal axis in relation to the arachnoid membrane. A spinal arachnoid cyst is often encountered as an incidental finding and rarely causes spinal cord compression. [1] Spinal arachnoid cyst usually occurs in the pediatric population and is located in the thoracic or cervical cord. Intramedullary location of the arachnoid cyst is rare, with only a few cases reported in the literature. [2],[3],[4],[5]

A 45-year-old man presented with a history of midline thoracic back pain of 2 years' duration. Ten days prior to his presentation, he had noticed increased severity of pain and weakness in both the lower limbs, which progressed to paraplegia with urinary and fecal incontinence. Neurological examination revealed a flaccid paraplegia with absence of superficial and deep tendon reflexes. There was no muscle wasting. Below T6 level, all modalities of sensation were lost. Hematological and biochemical examinations revealed no abnormality. Lumbar cerebrospinal fluid (CSF) examination was unremarkable. Magnetic resonance imaging (MRI) of dorsal spine revealed a non-enhancing cystic intramedullary lesion at T4 to T5 level measuring 3.1×1.4 cm, which was hypointense on T1-weighted images and hyperintense on T2-weighted images [Figure 1]. Screening of the cervical and lumbar regions of the spine showed no abnormality.

He underwent a T3 to T5 laminectomy. The cyst was identified just below the cord surface after a midline myelotomy. The cyst was bluish, thin walled; and clear fluid drained out under pressure. Cyst wall was partially excised as it was adherent at places to the spinal parenchyma. No communication with the subarachnoid space or an extramedullary component was present. Microscopic examination of the cyst wall showed fibrous connective tissue lined by arachnoid cells, consistent with the diagnosis of arachnoid cyst [Figure 2]. Postoperatively, he had complete relief of pain, while his motor power improved to normal over a period of 6 weeks [Figure 3].
Figure 1: Preoperative T2-weighted sagittal (a) and axial (b) MR images of the spine revealing hyperintense intramedullary lesion at T4-5 markedly compressing the spinal cord. Preoperative T1-weighted sagittal (c) and axial (d) MR images of the spine revealing non-contrast-enhancing hypointense intramedullary lesion at T4-5

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Figure 2: Photomicrograph of a section of the cyst demonstrating the histopathological features, with thick fibrous wall with arachnoid cells, H and E, original magnification, × 50

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Figure 3: Postoperative T2-weighted sagittal (a) and axial (b) MR images of the spine showing significant decompression of hyperintense intramedullary lesion at T4-5 along with the normal-size spinal cord parenchyma. Postoperative T1-weighted sagittal (c) and axial (d) MR images of the spine revealing decompressed spinal cord

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Unlike intracranial arachnoid cysts, spinal arachnoid cysts are uncommon and may be located either intradurally or extradurally. Extradural cysts result from an extradural out-pouching of the arachnoid that is contiguous with the spinal subarachnoid space via a small dural defect. Intradural cysts are out-pouchings of arachnoid that, regardless of size, lie entirely within the dural space; these are more common than extradural cysts. Both these types may or may not communicate with the subarachnoid space. [6],[7]

Intramedullary arachnoid cysts are rare, and so far only 9 such cases have been reported. Aithala et al. reported the first case of intramedullary arachnoid cyst in a 7-year-old boy who presented with diffuse abdominal pain and progressive weakness of the lower extremities. [2] Literature review of reported cases shows that these lesions are commonly seen in the pediatric population in the first and second decades of life, more common in females as compared to males, and are located more commonly in the thoracic region than in the cervical region.

Regarding the etiology of these lesions, several theories exist, suggesting that the occurrence of these lesions is attributed to congenital defect, or to arachnoid adhesion due to inflammation because of various causes. [6],[7],[8] The hypothesis proposed by Hyndman and Gerber is that the cyst arises from misplaced cellular remnants as a result of the embryonic malformation. [9] Ball valve mechanism and fluid shifts as a result of pathological distribution of the arachnoid trabaculae have been postulated for increase in the size of extramedullary cyst. However, the cause for increase in the size of the intramedullary cyst needs to be established.

MRI plays a vital role in diagnosis and treatment planning of these lesions. The differential diagnoses of intramedullary cystic lesions include primary and secondary syrinx, tumor (astrocytoma, ependymoma, teratoma, ganglioglioma)-associated syrinx, epidermoid cyst and synovial cyst. With the widespread availability of MRI, more cases of asymptomatic intramedullary cyst are likely to be reported. However, a wait-and-watch policy appears to be justified for these cases.

Although percutaneous drainage of the cyst and shunting procedure have been reported in the management of spinal extramedullary arachnoid cysts, surgical excision is the treatment of choice for intramedullary cysts.

 
  References Top

1.Gimeno A. Arachnoid neurenteric and other cyst. In: Vinkeri PJ, Bruyn GW, editors. Handbook of Clinical Neurology. Vol. 32. Congenital malformation of the spine and spinal cord. Amsterdam: North Holland; 1978. p. 393-448.  Back to cited text no. 1
    
2.Aithala GR, Sztriha L, Amirlak I, Devadas K, Ohlsson I. Spinal arachnoid cyst with weakness in the limbs and abdominal pain. Pediatr Neurol 1999;20:155-6.  Back to cited text no. 2
[PUBMED]  [FULLTEXT]  
3.Sharma A, Sayal P, Badhe P, Pandey A, Diyora B, Ingale H. Spinal intramedullary arachnoid cyst. Indian J Pediatr 2004;71:65-7.   Back to cited text no. 3
    
4.Guzel A, Tatli M, Yilmaz F, Bavbek M. Unusual presentation of cervical spinal intramedullary arachnoid cyst in childhood: Case report and review of the literature. Pediatr Neurosurg 2007;43:50-3.  Back to cited text no. 4
[PUBMED]  [FULLTEXT]  
5.Medved F, Seiz M, Baur M, Neumaier-Probst E, Tuettenberg J. Thoracic intramedullary arachnoid cyst in an infant. J Neurosurg Pediatrics 2009;3:132-6.  Back to cited text no. 5
    
6.Choi JY, Kim SH, Lee WS, Sung KH. Spinal extradural arachnoid cyst. Acta Neurochir (Wien) 2006;148:579-85.  Back to cited text no. 6
[PUBMED]  [FULLTEXT]  
7.Kumar K, Malik S, Schulte PA. Symptomatic spinal arachnoid cysts: Report of two cases with review of the literature. Spine 2003;28:E25-9.  Back to cited text no. 7
[PUBMED]  [FULLTEXT]  
8.Holly LT, Batzdorf U. Syringomyelia associated with intradural arachnoid cysts. J Neurosurg Spine 2006;5:111-6.  Back to cited text no. 8
[PUBMED]  [FULLTEXT]  
9.Hyndman OR, Gerber WF. Spinal extradural cysts, congenital and acquired. Report of cases. J Neurosurgery 1946;3:474-86.  Back to cited text no. 9
    


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