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|LETTER TO EDITOR
|Year : 2014 | Volume
| Issue : 6 | Page : 704-708
Non-terminal cervical myelocystocele: Unusual cause of spastic quadriparesis in an adult
Amol Raheja1, Deepak Kumar Gupta1, Aasma Nalwa2, Vaishali Suri2, Bhawani Shankar Sharma1
1 Department of Neurosurgery and Gamma Knife, All India Institute of Medical Sciences, New Delhi, India
2 Department of Pathology, All India Institute of Medical Sciences, New Delhi, India
|Date of Submission||06-Jul-2014|
|Date of Decision||12-Aug-2014|
|Date of Acceptance||03-Oct-2014|
|Date of Web Publication||16-Jan-2015|
Deepak Kumar Gupta
Department of Neurosurgery and Gamma Knife, All India Institute of Medical Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Raheja A, Gupta DK, Nalwa A, Suri V, Sharma BS. Non-terminal cervical myelocystocele: Unusual cause of spastic quadriparesis in an adult. Neurol India 2014;62:704-8
Terminal and non-terminal variants of myelocystocele are divided on anatomic location and postulated hypothesis of origin. , Former is a disorder of retrogressive differentiation (secondary neurulation) compared to limited dorsal myeloschisis (primary neurulation) in latter. , To the best of author's knowledge, till date only 38 cases of non-terminal myelocystocele (NTM or equivalent pathology) ,,,,,,,,,,,, have been published in literature [Table 1] with most common age of presentation being neonates and infants.
|Table 1: Summary of non-terminal myelocystocele: Patient profile, surgical modality and outcome|
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We present a unique case of cervical NTM in a 42-year-old male who presented with progressive spastic ascending quadriparesis (power 4/5 below C6 myotome), decreased sensation (below C6 dermatome) for two years, and upper motor neuron type bowel and bladder dysfunction for eight months. Local examination revealed 5 × 4 × 3 cm midline non-tender cystic saccular skin covered lesion with dysplastic skin in midline along with hypertrichosis and positive fluctuation test [Figure 1]a. Magnetic resonance imaging (MRI) of craniospinal axis revealed arrested hydrocephalus, mild type I Arnold- Chiari malformation More Details More Details II  (ACM II) with cerebellar tissue pegging through foramen magnum, fused C6/7 and D1/2 vertebrae, spina bifida defect at C6-C7 level, tenting of open-book configuration spinal cord at C6-C7 level with posteriorly tethered cystic dilation continuous with hydromyelic cavity, attached to dome of cystic meningocele lying below intact skin [Figure 1]b-d. Abnormal cerebrospinal fluid (CSF) flow dynamics are seen in dilated sub-arachnoid space ventral to cord at the level of cord tethering along with syrinx cranially. Dorsally central canal is open and continuous with ependymal lined cyst tethered to dysplastic skin dorsally. Radiological diagnosis of NTM (Rossi type B)  was made. Intra-operatively fused posterior elements of C6/7 with a midline spina bifida defect was seen with dural sac meningocele containing ependymal lined and extending intra-spinally to invest on dorsal aspect of spinal cord and communicating with dilated central canal [Figure 2]. Complete excision of tethering band and intra-spinal adhesiolysis was done to release cord adequately. Histopathological examination revealed microscopic nests of glial tissue along with adipose tissue in a fibro-collagenous background confirming the diagnosis of myelocystocele [Figure 3]. Patient had a clinical improvement from neurological grade three to two post-operatively (as classified by Pang et al.),  which remained stable till last follow up at six months. Interval MRI done after three months was suggestive of stable ventricular size, reduction of CSF space ventral to cord with improved flow dynamics and evidence of detethered spinal cord with non-progression of syrinx and ACM II [Figure 4].
|Figure 1: (a) Pre - operative clinical photograph demonstrating midline cystic cervical lesion covered with dysplastic skin suggestive of non - terminal myelocystocele (MCC). (b) Axial T2W magnetic resonance image (MRI) demonstrating "open - book" configuration of cord with hydromyelic cavity continuing as myelocele (MYC) through spina-bifida (SB) bony defect and investing on outer cystic cavity of dural meningocele (MC) below intact skin. (c) and (d) Saggital T2W MRI showing C6/7 and D1/2 block vertebrae (BV), mild chiari II malformation (ACM) features with cerebellar pegging through foramen magnum. Cord is tented dorsally to meningocele (MC) sac with resultant increased sub - arachnoidal space along with abnormal cerebrospinal fluid flow dynamics ventrally creating flow voids (FV)|
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|Figure 2: Intra - operative photograph (a) demonstrating myelocele (MYC) sac tethered dorsally to meningocele (MC) sac and its relation to normal cord. (b) After detethering, small part of residual myelocele sac seen with thinned out distal cord (DC) and proximal cord (PC) owing to release of syringomyelic cavity communicating with myelocele|
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|Figure 3: HPE findings - (a) Photomicrograph showing fibro - collagenous tissue and fibro - adipose tissue (H and E x100). (b) Photomicrograph shows small islands of glial tissue along with neuro - melanin (arrow) admixed in a fibro - collagenous background (H and E x100)|
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|Figure 4: Follow up (a) aggital, (b) and (c) - axial magnetic resonance images after six months demonstrating completely untethered cord (UC) with remnant hydromyelic cavity (HC) and reduced ventral sub - arachnoidal space along with no evidence of flow voids (NFV) attributing to laminar cerebrospinal fluid flow pattern after procedure. There is evidence of non - progression of chiari II malformation compared to pre - operative imaging|
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Myelocystocele is a rare variant of closed spinal dysraphism characterized by skin covered mass located posteriorly in midline, narrow spina bifida defect, cerebrospinal fluid cyst, expanded dural sheath with varying amounts of dorsal fat continuous with sub-cutaneous fat.  Though no proven genetic basis exists, it has been associated with intrauterine exposure to retinoic acid,  loperamide  and hydantoin.  Developmental origin of NTM is hypothesized by limited dorsal myeloschisis leading to delayed disjunction of ectoderm and neuro-ectoderm in final stages of primary neurulation, thereby leaving small defect in midline. , Surrounding mesenchyme and ectodermal elements overgrow and cover this small defect, leaving on small part of dorsal cord tissue connected to skin in form of either well formed myelocystocele (complete variant, Rossi type B, myelocystocele, limited dorsal myeloschisis with saccular myelocystocele and myelocystocele consisting of a second ependymal lined cyst herniated inside a meningocele) or neuro-fibro-vascular band (abortive variant, Rossi type A, fibroneurovascular stalk, limited dorsal myeloschisis with stalk and cystic spinal dysraphism with neuro-glial stalk) based on classification given by Rossi et al.,  Habibi et al.,  Pang et al.  and Salamao et al.,  respectively.
Severity of symptoms is unrelated to location of lesion but probably increases with increasing age.  Surgical strategy aims at excision, intra-dural exploration and complete detethering for optimal outcome, with poor neurological outcome associated when only extra-dural excision is undertaken.  The index case ponders us to acknowledge that such lesions may remain asymptomatic for major part of adult life but eventually are bound to cause symptoms due to tethering of cord posteriorly, affirming an important proposition in natural history of such lesions. Intra-dural exploration with release of arachnoidal bands and fibrous adhesions between two split cords along with excision of sac was associated with radiological non-progression of syrinx, improved CSF flow dynamics ventrally and optimal outcome in short-term follow up, confirming the cause-effect relationship and emphasizing on the same as the primary surgical strategy. Oldest age of NTM at presentation is unique to the present study, with only other adulthood presentations of cervical cystic closed spinal dysraphisms being either CSF containing meningocele or rudimentary meningocele with absence of true ependymal-lined myelocele. ,,,
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]