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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 8  |  Issue : 4  |  Page : 20-24

Split Cord Malformation: Our Experience


Department of Neurosurgery, VIMS and RC; Department of Neurosurgery, Vydehi Hospital, Bengaluru, Karnataka, India

Date of Submission03-May-2021
Date of Acceptance11-Oct-2021
Date of Web Publication24-Dec-2021

Correspondence Address:
Arjun H Dev
Department of Neurosurgery, Vydehi Hospital, #82, EPIP Area, Whitefield, Bengaluru - 560 066, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/joss.joss_2_21

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  Abstract 


Background: Split cord malformation (SCM) is a rare form of neural tube defects. It belongs to closed type of neural tube defects. SCM constitutes around one-third of cases of spinal dysraphism. In SCM, there is a division in the spinal cord into two halves which may be equal or unequal.
Objective: To analyse the clinical, radiological, intraoperative findings and surgical outcome of patients with SCM.
Materials and Methods: This was a retrospective analysis of cases of SCM operated during 3-year period (2016–2019) in our institute. The data for the study were obtained from case records, operation notes, and radiology investigations.
Results: There were 20 patients of spinal dysraphism in total, among which 6 cases were of SCM. All 6 cases were symptomatic with swelling in the back. Four had distal foot weakness, two had low backache, two had difficulty in walking, two had hypertrichosis, and one patient had foot deformity with trophic ulceration in the foot. Magnetic resonance imaging (MRI) revealed tethered cord in all 6 cases. Three had syringomyelia, three had lipomeningocele, and one case had intramedullary epidermoid. Computed tomography scan revealed bony spur in 4 cases. All patients underwent surgery.
Conclusion: MRI is the investigation of choice and surgery is the treatment of choice. We have observed detethering done at the same sitting as that of the primary surgery has improved outcome. It also avoids the dilemma in attributing the postoperative neurological deficits if any, either to surgical complication or that due to tethered cord.

Keywords: Diastematomyelia, diplomyelia, split cord malformation


How to cite this article:
Sandeep V B, Banga MS, Kishan A, Dev AH, Devabhakthuni RB, Arun Kumar A M. Split Cord Malformation: Our Experience. J Spinal Surg 2021;8:20-4

How to cite this URL:
Sandeep V B, Banga MS, Kishan A, Dev AH, Devabhakthuni RB, Arun Kumar A M. Split Cord Malformation: Our Experience. J Spinal Surg [serial online] 2021 [cited 2022 Jan 21];8:20-4. Available from: http://www.jossworld.org/text.asp?2021/8/4/20/333616


  Introduction Top


Split cord malformation (SCM) is relatively a rare form of neural tube defects. It belongs to closed type of neural tube defects. The incidence of neural tube defects has decreased in the west. However, in India and other developing countries, it is still a major problem. Majority of these cases are seen in the early childhood period. Among these, the early presenting feature is neurocutaneous stigmata.[1] Among all the cases of neural tube defects, SCM constitutes about one-third of the spectrum. In SCM, there is a division in the spinal cord into 2 halves which may be equal or unequal.[2]


  Materials and Methods Top


A retrospective analysis of patients with SCM who were treated in the Department of Neurosurgery, between 2016 and 2019, was done. The data for the study were obtained from case records, operation notes, and radiology investigations. The classification system proposed by Pang was used to classify the patients into Type I or Type II SCM.


  Results Top


There were 20 cases of neural tube defects in total, among which 6 were of SCM, which constitutes about 30% of the cases. The youngest patient was 8 months old and the oldest patient was 17 years. The mean age was 8.4 years. Two (33.4%) among the 6 cases were male. All the 6 cases presented with swelling in the back. Four cases had distal foot weakness, while 2 cases had leg pain. Two cases had hypertrichosis. Two cases presented with low back ache. One of the cases had foot deformity along with trophic ulceration in the foot [Table 1].
Table 1: The clinical presentation of patients

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All the 6 cases were evaluated with magnetic resonance Imaging (MRI) and computed tomography (CT) scan of the whole spinal column along with CT scan of the brain to rule out associated anomalies. All the 6 cases had tethered cord. Syrinx was found in 3 cases. Lipomeningocele was found in 3 cases. One case had intramedullary epidermoid. Bony spur was fund in 4 cases [Table 2].
Table 2: Radiological findings

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The most common level of the split cord was in the lumbar level. The longest length of the split cord was for 8 levels. All these patients were classified based on the classification system proposed by Pang.[3] Four patients (66.6%) belonged to SCM Type I (Diastematomyelia) and two patients (33.3%) belonged to SCM Type II (Diplomyelia) [Table 3].
Table 3: Classification of patients into types of split cord malformation

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All the six patients underwent surgical treatment. The surgery performed was laminectomy along with excision of either the bony spur or the fibrous band, removal of lipomemingocele, detethering of cord and unification of the dural tube. Intra-operatively tethered cord was present in all 6 cases. Fibrous band was present in 3 cases and the bony spur was found in 4 cases. Lipoma of the filum terminale was present in 2 cases. There was a posteriorly located bony spur in 1 case [Table 4].
Table 4: Intra-operative findings

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All the patients had good post op recovery in terms of wound healing a symptomatic relief of pain. There was no cerebrospinal fluid leak noted in any of the post op cases. The foot weakness also gradually improved during the course of the hospital stay. In one patient the tethering was found at a different level. Two staged surgery was planned for this patient; first to excise the lipomeningocele and release the fibrous band and later to do a detethering in the second sitting. This patient developed weakness of the foot in the postoperative period after 3 days. Hence she immediately underwent the second surgery to detether the cord. The weakness improved following the detethering.


  Discussion Top


SCM is an uncommon spinal developmental anomaly. Here, there is a division of the spinal cord into two by the fibrous septum or bony ridge.

Such hemicords which are separated by a septum or spur may be present in their individual dural tubes (Type I) or in a single dural sheath (Type II). This classification was proposed by Pang.[3] Earlier they were termed diastematomyelia and diplomyelia respectively. Diastematomyelia means split spinal cord and diplomyelia means double spinal cord.[4] Type II SCM are more common than Type I SCM. Type II SCM constitute around 50%–60% of all SCM.[4]

The location of the split cord can be present anywhere along the spinal cord however, it is most common at the lower dorsal or upper lumbar level.[4],[5],[6] It is also three times more common in females as compared to males.[7] These are usually diagnosed in the young age and rarely in the adults.[6],[8],[9] The average age at diagnosis is 5 year. The symptomatology differs in children and adults differ at the time of presentation.[6] Secondary anomalies of the spine are commonly associated features in SCM.[10] These abnormalities arise from various remnants of ectoderm or endoderm. These abnormalities can be neurenteric cysts,[4] hemivertebrae, tethering of the spinal cord, a dermal sinus tract, spina-bifida, butterfly vertebrae, kyphoscoliosis, congenital lipoma of filum terminale, dermoids, scoliosis,[11] teratoma, and spondylolisthesis.[12]

Because of the associated anomalies, the classification system proposed by Pang is not sufficient to classify all the SCM under 2 types. A more detailed classification system considering the associated anomalies is needed. Mahapatra and Gupta gave a new classification system for bony spur in SCM Type I. They were classified into a-d types, depending on where the bony spur was located. Whether in between the proximal and distal part where the cord is split, or at the space superior or inferior to the spur.[13]

Type Ia-Bony spur is located in the center with the duplicated spinal cord distributed equally superior and inferior to it.

Type Ib-Bony spur is located at the upper pole without any space superiorly and a large duplicated cord lying inferiorly.

Type Ic-Bony spur is located at the lower pole with a split cord superiorly.

Type Id-Bony spur is located straddling the bifurcation of the split cord with no space superior or inferior to the spur.

This classification helps in planning the surgical approach and also in predicting the risk of deterioration in the postoperative period.

Multiple theories have been postulated for the development of SCM. Herren and Edwards[14] based on his observations made in the embryos of chick in 1940, stated that SCM is a result of exaggerated neural plate folding. Gardner[15] postulated that the two neural tubes were a result of hydromyelic distension of the neural tube and its secondary rupture both on its ventral and dorsal aspect. Later the space between the neural tubes is penetrated by the fibrous or bony tissue which is of mesodermal origin. This tissue would form the bony spur or the fibrous septum.

'Unified theory of embryogenesis' initially proposed by Bremer and later modified by Pang is the most widely accepted theory about the embryological origin of SCM.[3]

In 1952, Bremer postulated a theory taking into consideration a dorsal intestinal fistula. From the archenteron that forms the gut, a diverticulum develops. This expands to separate the notochord and the neural plate into two separate parts. Dorsal enteric fistula is formed when the diverticulum opens at the level of the skin, an open form of split notochord syndrome. When the endodermal elements totally disappear, the fibrous or bony septum is left behind between the two-split cord.[16]

Pang et al.,[3] described a theory called the “Unified theory.” This was based on an endo-mesenchymatous tract and this applies to the cases with both bony septum with associated malformation of the vertebra (Type I SCM) and cases with just a fibrous septum between the two split cords without any associated malformations of the vertebra (Type II SCM). The endomesenchymal tract that determines Type II SCM is only constituted by meninx primitiva which does not contains precursors of bone cells.

SCM also presents with a variety of clinical features, ranging from being asymptomatic to symptoms like autonomic dysfunction, gait disturbance, pain, and motor and/or sensory deficits.[13],[17],[18],[19] In our series all 6 cases were symptomatic. In total we had 6 cases of SCM among 20 cases of neural tube defects. This amounts to 30% of the cases as compared to the reported 20% in various Indian studies. All 6 cases presented with swelling in the back. Two cases had hypertrichosis [Figure 1]. Four cases had presented with distal foot weakness while 1 case had foot deformity. The same patient had trophic ulceration in the foot due to deformity if the foot. All the 6 patients underwent CT and MRI of the whole spine. All six patients had tethered cord. Four patients had Type 1 SCM which amounts to 67% and 2 patients had Type II SCM. Three patients had syrinx [Figure 2]. One patient had intramedullary epidermoid tumour. The longest level of the split cord involved was 8 levels. Four patients had bony spur [Figure 3]. One of the patients with Type II SCM had a partial bony spur arising from the dorsal aspect attached to the lamina [Figure 4]. This is a rare occurrence as reported by Borkar and Mahapatra.[1]
Figure 1: Clinical photograph of patient with hypertrichosis in the lumbar region

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Figure 2: (a) Sagittal magnetic resonance imaging of a patient showing syrinx in the dorso-lumbar region with tethered cord. (b) Axial magnetic resonance imaging of the same patient showing syrinx

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Figure 3: Axial computed tomography scan of a patient showing complete bony spur within the spinal canal

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Figure 4: Axial computed tomography scan of a patient showing partial bony spur within the spinal canal

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Even though the Pang et al.'s unified theory[3] resolves the pathogenetic classification and clinical importance of these SCM, it does not explain the other variants like posteriorly placed bone spur and complex SCM (associated with epidermoid, dermoid, lipoma, etc). We had two cases with Type I SCM, having bone spur located dorsally and running ventrally. Chandra et al.,[20] in their case report of dorsal bony spur in a lumbar SCM postulated 2 theories for such rare occurrence: (1) an abnormal population of cells passes posteriorly and loose contact with their anteriorly located counterparts subsequently and (2) movement of these cells between in an antero-posterior direction and around the split cords.

The treatment of choice for all the cases of SCM is surgery.[1],[13],[17]

The steps can be summarized as follows

  1. Through a posterior midline incision the area is exposed
  2. The lipomatous tissue and the fibrous band encountered initially is excised
  3. The fibrous band separating the dura is carefully excised
  4. Laminectomy is done one above and below the level of the deformity
  5. Where ever there was a bony spur, care is taken while excising the spur so that it did not cause any further damage to the dural sac or the cord. The initial drilling of the bony septum was carried out using an electric drill and the remaining part was removed using Kerrison punches
  6. The spinal cord is exposed by opening the dura in the traditional vertical manner. The dural opening is extended 1 level above and below the level of the incision to get adequate closure [Figure 5]
  7. The tethered cord encountered is released during the time of primary surgery
  8. In our series, tethered cord was released in 5 patients during primary surgery
  9. In one case, the deformity was at a higher level and the tethering of the cord could not be tackled with the same incision. Hence, the detethering surgery was planned as a staged procedure at a later date. She started having weakness in the lower limbs in the post operative day 2. She was operated for the tethered cord on post operative day 3. The weakness improved following detethering. Filum terminale lipoma was found in two patients
  10. The dural closure is done using 4'0 vicryl in a watertight manner. Rest of the layers are closed.
Figure 5: Intra-operative photograph showing durotomy and split cord within the dural sac

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  Conclusion Top


SCMs are not so very common, complex conditions of closed neural tube defects. Posteriorly located bone spur is of very rare occurrence. MRI is the investigation of choice, and CT scan completes the radiological evaluation. Especially in cases of low-lying conus and syringomyelia, other co-occurring anomies have to be investigated for. MRI screening of the entire spine is always mandatory to identify other co-occurring anomalies as well as split cord deformities at other site, which is rare but a known entity. Removal of the spur by surgery along with detethering of filum should be done in the same sitting as that of the primary surgery. New classification system is needed which can take the associate anomalies into consideration.



 
  References Top

1.
Borkar SA, Mahapatra AK. Split cord malformations: A two-year experience at AIIMS. Asian J Neurosurg 2012;7:56-60.  Back to cited text no. 1
[PUBMED]  [Full text]  
2.
Kumar R, Singh V, Singh SN. Split cord malformation in children undergoing neurological intervention in India: A descriptive study. J Pediatr Neurol 2004;2:21-7.  Back to cited text no. 2
    
3.
Pang D, Dias MS, Ahab-Barmada M. Split cord malformation: Part I: A unified theory of embryogenesis for double spinal cord malformations. Neurosurgery 1992;31:451-60.  Back to cited text no. 3
    
4.
Hung PC, Wang HS, Lui TN, Wong AM. Sonographic findings in a neonate with diastematomyelia and a tethered spinal cord. J Ultrasound Med 2010;29:1357-60.  Back to cited text no. 4
    
5.
Mahapatra AK. Split cord malformation – A study of 300 cases at AIIMS 1990-2006. J Pediatr Neurosci 2011;6:S41-5.  Back to cited text no. 5
    
6.
Kumar DS, Concepcion LA. Adult with progressive foot deformity. Br J Radiol 2007;80:384-7.  Back to cited text no. 6
    
7.
Gan YC, Sgouros S, Walsh AR, Hockley AD. Diastematomyelia in children: Treatment outcome and natural history of associated syringomyelia. Childs Nerv Syst 2007;23:515-9.  Back to cited text no. 7
    
8.
Kaminker R, Fabry J, Midha R, Finkelstein JA. Split cord malformation with diastematomyelia presenting as neurogenic claudication in an adult: A case report. Spine (Phila Pa 1976) 2000;25:2269-71.  Back to cited text no. 8
    
9.
Uzüm N, Dursun A, Baykaner K, Kurt G. Split-cord malformation and tethered cord associated with immature teratoma. Childs Nerv Syst 2005;21:77-80.  Back to cited text no. 9
    
10.
Proctor MR, Scott RM. Long-term outcome for patients with split cord malformation. Neurosurg Focus 2001;10:1-5.  Back to cited text no. 10
    
11.
Qureshi MA, Asad A, Pasha IF, Malik AS, Arlet V. Staged corrective surgery for complex congenital scoliosis and split cord malformation. Eur Spine J 2009;18:1249-54.  Back to cited text no. 11
    
12.
König M, Boszczyk B. Limited access surgery for 360 degrees in-situ fusion in a dysraphic patient with high-grade spondylolisthesis. Eur Spine J 2012;21:390-5.  Back to cited text no. 12
    
13.
Mahapatra AK, Gupta DK. Split cord malformations: A clinical study of 254 patients and a proposal for a new clinico-imaging classification. J Neurosurg Pediatr 2005;103:531-6.  Back to cited text no. 13
    
14.
Herren RY, Edwards JE. Diplomyelia (duplication of the spinal cord). Arch Pathol 1940;30:1203-14.  Back to cited text no. 14
    
15.
Gardner WJ. The Dysraphic States from Syringomyelia to Anencephaly. Amsterdam: Excerpta Medica; 1973. p. 127-43.  Back to cited text no. 15
    
16.
Bremer JL. Dorsal intestinal fistula; accessory neurenteric canal; diastematomyelia. AMA Arch Pathol 1952;54:132-8.  Back to cited text no. 16
    
17.
Sinha S, Agarwal D, Mahapatra AK. Split cord malformations: An experience of 203 cases. Childs Nerv Syst 2006;22:3-7.  Back to cited text no. 17
    
18.
Kumar R, Bansal KK, Chhabra DK. Split cord malformation in pediatric patients. Neurol India 2001;49:128-33.  Back to cited text no. 18
[PUBMED]    
19.
Kumar R, Singh SN. Spinal dysraphism – Trend in northern India. Pediatr Neurosurg 2003;38:133-45.  Back to cited text no. 19
    
20.
Chandra PS, Kamal R, Mahapatra AK. An unusual case of dorsally situated bony spur in a lumbar split cord malformation. Pediatr Neurosurg 1999;31:49-52.  Back to cited text no. 20
    


    Figures

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

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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