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Year : 2019  |  Volume : 2  |  Issue : 2  |  Page : 174-178

Intramedullary arachnoid cysts – Report of three cases and literature review

Department of Neurosurgery, Grant Government Medical College and JJ Hospitals, Mumbai, Maharashtra, India

Date of Web Publication23-Jul-2019

Correspondence Address:
Dr. Anuj Arun Bhide
Department of Neurosurgery, Grant Government Medical College and JJ Hospitals, Mumbai, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/isj.isj_54_18

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Arachnoid cysts are rare lesions of the spine and occur most commonly in the extradural location. Intramedullary location is a very rare site, and only 15 cases have been reported in literature till date. We report a series of three cases with intramedullary arachnoid cysts having diverse etiopathogenesis and clinical presentations. Recurrent cyst and cyst associated with tethering of the cord are unique to our series and have not been reported previously.

Keywords: Arachnoid cyst, intramedullary tumors, tethered cord

How to cite this article:
Bhide AA, Velho VL, Mohite AG. Intramedullary arachnoid cysts – Report of three cases and literature review. Indian Spine J 2019;2:174-8

How to cite this URL:
Bhide AA, Velho VL, Mohite AG. Intramedullary arachnoid cysts – Report of three cases and literature review. Indian Spine J [serial online] 2019 [cited 2022 Aug 11];2:174-8. Available from: https://www.isjonline.com/text.asp?2019/2/2/174/263283

  Introduction Top

Intramedullary spinal lesions have a variety of differential diagnoses of which intramedullary cysts comprise of an uncommon spectrum. Arachnoid cysts of the spine can be both extradural and intradural.[1] They have been classified into three categories as follows: Type 1 – extradural not involving nerve roots; Type 2 – extradural with nerve root involvement; and Type 3 – intradural.[2] The pathogenesis of extradural arachnoid cysts is thought to be herniation through the dural defects, while the pathogenesis of intradural cysts is speculative.[3] Most intradural cysts are extramedullary, and intramedullary location is extremely rare, and only 15 cases have been reported in literature till date[1],[3] [Table 1]. The presentation of intramedullary arachnoid cysts can range from mild back pain to features of myelopathy. Most reported cases had been isolated case reports with only two reports having a series of two patients. We report a series of three cases of intramedullary arachnoid cysts, portraying spectrum epidemiology and etiopathogenesis of the disease from pediatric to adult age group and from congenital to acquired, respectively. Imaging and operative findings in all three cases were confirmed with histopathological examination.
Table 1: List of reported cases of intramedullary arachnoid cysts in literature

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  Case Reports Top

Case 1

A 7-year-old female child presented to us with a history of decrease in the power of lower limbs, ascending in pattern, and progressively increasing. On examination, the child had severe spasticity in both lower limbs and paraparesis (Power Grade 1/5), with the inability to move the limbs against gravity. There was also a distinct sensory level at D4. A magnetic resonance imaging (MRI) was performed which revealed an intramedullary cystic lesion anteriorly placed from D2 to D4 level, which was on MRI hypointense on T1-weighted and hyperintense on T2-weighted images with no contrast enhancement [Figure 1]. Considering the progressive myelopathy, the patient was operated with a D1–D4 laminotomy and the cyst location was confirmed using ultrasound. A dorsolateral myelotomy and marsupialization and partial excision of the cyst wall were performed. Complete cyst wall excision was not attempted in view of the inadequate plane between the cord parenchyma and the cyst. The cystic fluid was clear cerebrospinal fluid (CSF) and under high pressure [Figure 2]. The cyst was not in communication with the subarachnoid space or the central canal which was confirmed by Valsalva maneuver. The anterior cyst wall was perforated, and the CSF spaces were communicated anteriorly as well. The patient showed dramatic improvement in the lower limb power postoperatively (Grade 4/5) and was walking without support at 18 months of follow-up, and postoperative MRI showed complete excision [Figure 3]. The histopathology report of the cyst wall confirmed hyaline tissue lined with arachnoid cells [Figure 3].
Figure 1: Case 1: Preoperative magnetic resonance imaging showing a T1 hypointense and T2 hyperintense intramedullary cyst without contrast enhancement extending from D2 to D4 placed anteriorly

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Figure 2: Case 1: Intraoperative image after the opening of the dura, showing the enlarged cord and the cyst wall after myelotomy (top). Partial excision of the wall (bottom)

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Figure 3: Case 1: Postoperative histopathology slide confirming the wall lined by arachnoid cells with hyaline with the postoperative magnetic resonance imaging, showing complete excision at 18 months' follow-up

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Case 2

A 45-year-old male presented with a previous history of surgery on a spinal cyst 2 years back, with immediate improvement after the surgery, followed by progressive deterioration. Previous imaging and histopathology report of the patient was not available, and the operative notes mentioned an intramedullary cystic lesion which was fenestrated. After this surgery, the patient had a history of ascending weakness in both lower limbs with symptoms of hesitancy and retention of urine. On examination, there was spastic paraparesis and sensory level at D9. MRI scan showed a recurrent intramedullary cystic lesion located at D8–D9 level, at the same level as the previous laminectomy. The MRI had similar features with hypointensity on T1-weighted and hyperintensity on T2-weighted imaging with no contrast enhancement [Figure 4]. A reexploration surgery with dorsolateral myelotomy and cyst marsupialization and partial excision of the cyst wall was performed. At 1 year of follow-up, the patient's power had improved marginally; however, he could not walk without support. Follow-up MRI has shown myelomalacic changes without the recurrence of the cyst [Figure 4].
Figure 4: Case 2: Preoperative magnetic resonance imaging showing an intramedullary arachnoid cyst at D8–D9 level with evidence of previous laminectomy overlying the same site. Postoperative magnetic resonance imaging showing complete resolution of cyst at 1-year follow-up

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Case 3

A 33-year-old male child presented to us with a history of hairy patch with swelling over the lower back since birth. The mother had also noticed continuous dribbling of urine with decreased movements of the lower limbs of the child since birth. On examination, the child had paraparesis and incontinence with a cutaneous marker over the lumbosacral region with a soft subcutaneous base with a nondischarging dermal pit. A bifid spinous process was palpable through the surface. The MRI scan of the baby revealed a low lying cord at L3 level with a cystic intramedullary swelling extending from D10 to D12 levels, which was hypointense on T1-weighted and hyperintense on T2-weighted images. The patient also had a dermal sinus just below the cyst [Figure 5]. The patient was operated with a D10–L3 laminotomy with dorsolateral myelotomy and marsupialization of the cyst with partial cyst wall excision and detethering of the cord and primary dural closure. The intraoperative diagnosis of the arachnoid cyst was confirmed with histopathological analysis. The postoperative course of the child was uneventful, and the child could stand with support at 6 months of follow-up. Urinary incontinence was persistent; however, the dry periods had increased in duration.
Figure 5: Preopertive magnetic resonance imaging showing a D10–D12 intramedullary arachnoid cyst in a case of low-lying tethered cord with dermal sinus and lipomeningocele

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  Discussion Top

Spinal arachnoid cysts are rare, benign, mostly asymptomatic lesions. Most common sites for these lesions are extradural, while the intramedullary location is very rare. The first intramedullary lesion was described by Aithala et al.[4] Ten out of the 15 reported intramedullary arachnoid cysts have been in the pediatric age group, and they may or may not be associated with other neural tube defects.[5],[6],[7] Although the exact causes are not clear for the formation of these cysts, various hypothesis have been suggested which include sequestration of misplaced arachnoid cells,[8] congenital, inflammatory, and traumatic.[1] The clinical presentation of intramedullary arachnoid cysts depends on the spinal level of the lesion and the extent of compression. All reported cases have had some form of myelopathy and motor involvement [Table 1]. Classical MRI findings of these lesions include homogeneously hyperintense well-circumscribed lesions on T2-weighted imaging and hypointensity without contrast enhancement on T1-weighted imaging.[9] The main differential diagnosis of these cysts is mainly neuroenteric cysts and neuroepithelial cysts.[9] Neuroenteric cysts are lined by cells of endothelial origin, while neuroepithelial cysts are lined by ependymal cells. The contents of these two cysts are mucinous while the arachnoid cysts contain CSF.[9] The classical histopathological finding of cyst wall lined with meningothelial cells differentiates arachnoid cysts from these two differentials.[1] The management of all intramedullary cysts remains identical which includes a dorsomedian or dorsolateral myelotomy with cyst decompression and marsupialization or a cyst fenestration with wall biopsy.[3] The location of myelotomy depends on the exact location of the cyst and the thinning of the parenchyma. All reported cases have shown improvement in symptoms after decompression. Case 2 and Case 3 of our series are the only reported cases of recurrent intramedullary arachnoid cyst and intramedullary arachnoid cyst associated with tethering of the cord, respectively, to the best of our knowledge.

  Conclusions Top

Although intramedullary arachnoid cysts are a very rare entity, this diagnosis should be kept in mind as surgical decompression affords the best chance of improvement in symptomatic patients. Cyst decompression and adequate marsupialization are the treatment of choice, and complete wall excision is neither necessary nor recommended.

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.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Alugolu R, Arradi V, Sahu BP. Intramedullary arachnoid cyst in an adult: Case report and review. Asian J Neurosurg 2016;11:70.  Back to cited text no. 1
[PUBMED]  [Full text]  
Nabors MW, Pait TG, Byrd EB, Karim NO, Davis DO, Kobrine AI, et al. Updated assessment and current classification of spinal meningeal cysts. J Neurosurg 1988;68:366-77.  Back to cited text no. 2
Novegno F, Umana G, Di Muro L, Fraioli B, Fraioli MF. Spinal intramedullary arachnoid cyst: Case report and literature review. Spine J 2014;14:e9-15.  Back to cited text no. 3
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. 4
Voss O. Rückenmarkskompression durch eine intradurale cyste. Langenbecks Arch Surg 1937;248:341-5.  Back to cited text no. 5
Rabb CH, McComb JG, Raffel C, Kennedy JG. Spinal arachnoid cysts in the pediatric age group: An association with neural tube defects. J Neurosurg 1992;77:369-72.  Back to cited text no. 6
Gelabert-González M, Cutrín-Prieto JM, García-Allut A. Spinal arachnoid cyst without neural tube defect. Childs Nerv Syst 2001;17:179-81.  Back to cited text no. 7
Hyndman OR, Gerber WF. Spinal extradural cysts, congenital and acquired; report of cases. J Neurosurg 1946;3:474-86.  Back to cited text no. 8
Fortuna A, Mercuri S. Intradural spinal cysts. Acta Neurochir (Wien) 1983;68:289-314.  Back to cited text no. 9


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1]


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