An unusual case of 4 level spinal dysraphism: Multiple composite type 1 and type 2 split cord malformation, dorsal myelocystocele and hydrocephalous.

The authors here have reported a rare case of a child with a complex spina bifida with two different levels of split cord malformation (SCM) type 1 and single level type 2, a non terminal myelocystocele, coccygeal dermal sinus, bifid fatty filum and hydrocephalus, which substantiates the neuroenteric canal theory and have further tried to highlight the importance of complete Magnetic resonance imaging (MRI) screening of the whole spine and brain with SCM to rule out other associated conditions. The patient was admitted with a leaking myelocystocele with bilateral lower limb weakness. MRI of whole spine with screening of brain was done. Patient underwent 5 operations in the same sitting- (According to classification given by Mahapatra et al.) removal of SCM type 1a at D7-8; removal of SCM type1c at L2-3; removal of SCM type 2 at D10; repair of non terminal myelocystocele at D6-D10; low pressure ventriculoperitoneal shunt on right side with excision of dermal coccygeal sinus; and, excision of bifid fatty filum. The clinicoradiological findings in our patient further substantiate the multiple accessory neuroenteric canal theory in the development of composite type of SCM. The physical and neurological signs of SCM and nonterminal myelocystocele should prompt the neurosurgeon to consider performing the screening MRI of whole spine with brain to rule out other composite types of SCM and hydrocephalus.

Introduction

The term “Split cord malformation” (SCM) has been used since 1992 to describe diastematomyelia and diplomyelia. SCM is a part of occult spinal dysraphism,[1] which is defined as a skin covered lesion that has no exposed neural tissue with no visible cystic mass,[2] barring few cutaneous anomalies, which are indicators of underlying spinal pathology.[3] They constitute about one third of the cases of spinal dysraphism, where the spinal cord is divided over a portion of its length into two equal or unequal proportions.[3]

SCM is divided into two types- type 1 consisting of two hemicords, each of which has its own dural sheathed tube while being separated by a median bony spur; and type 2 that consists of two hemicords housed in a single dural tube separated by a fibrous median septum.[4] Of late, with slight modification of Pang's classification by Kumar et al., and Mahapatra et al., it is now obvious that SCM is not always occult and may coexist with open spinal dysraphism, like meningomyelocele (complex spina bifida) in a significant number of cases.[5] It is also surprising that about 40.8% cases of all SCM present with meningomyelocele, suggesting that open and closed form of spinal dysraphism can coexist.[3] Composite type SCM is very rare and results from two separate foci of ectoendodermal adhesions and endomesenchymal tracts,[6] leading to development of different SCM types with intervening normal cord in the same patient.

Only a few cases of composite type SCM have been reported in literature.[6-10] In this report, we present a case of composite type of SCM with a dorsal non terminal myelocystocele, two level SCM type 1 and single level SCM type 2, hydrocephalus and coccygeal dermal sinus. To our knowledge, this is the first reported case of composite type of SCM with a non terminal myelocystocele, hydrocephalus and dermal sinus, operated at 5 different sites during the same surgery.

Clinical Presentation

A 4-year-old-female child, with a swelling in the upper back since birth associated with difficulty in standing and walking, came to our institute. There was a positive history of cerebrospinal fluid (CSF) leak from the swelling, with no history of high grade fever, delayed developmental milestones or bowel or bladder incontinence. On physical examination, the swelling was in the mid thoracic region and was measuring 8 × 6 cm [Figure 1], with a dermal sinus at coccygeal level. Muscle tone was decreased bilaterally in the lower limbs with the power in lower limbs being 4/5, and deep tendon reflexes diminished. Imaging of whole spine showed a thoracic non terminal myelocystocele present from D6-10 level, [Figures 2 and 3] with bony spur at D7-D8 and L2-L3 level and fibrous spur at D10 in computed tomography scan (Computed Tomography Scan in Figure 4) and hydrocephalus.

Figure 1

Clinical photograph showing incision marks at mid dorsal, lumbar and coccygeal area

Figure 2

MRI sagittal T2 weighted image showing myelocystocele with hydromyelia in mid dorsal area with SCM Type1 at D7-8, D10, L2-3

Figure 3

MRI Axial T2 weighted image shows myelocystocele and hydromyelia

Figure 4

CT scan of spine axial view showing Bony spur SCM type 1 at L2-3 level

Intervention

Right sided low pressure ventriculoperitoneal shunting was done in supine position, following which the patient was made prone, and excision with repair of thoracic non terminal myelocystocele arising from left hemicord at D7-D8 level, with excision of a bony spur at same level was carried out. SCM type 2 present at D10 level, and SCM type 1c spur at L2-3 (as per the classification given by Mahapatra and D Gupta),[1112] was removed. Split conus medullaris and filum terminale were present, and resection of fatty filum terminale was done. Dermal sinus present in coccygeal region was removed.

Patient received IV methyl prednisolone intra operatively. Surgery took 8 hours and patient was reversed from anaesthesia post operatively. In immediate post operative period, patient developed mild weakness of right lower limb (power 3/5) but the power gradually improved. She received methyle prednisolone for 3 days, cloxacilline and amikacin for 8 days. She was discharged on post operative day 10 with the same muscle power as in the pre operative period.

Discussion

SCM includes the rare congenital anomalies of the spinal cord and its covering. It was first termed as “diastematomyelia” by Ollivier[13] in 1837, who described the condition as an abnormality of the spinal cord in which the dura is separated by a bony spur, or by rigid fibrous bands, which creates two different sleeves, each containing a portion of the spinal cord, divided into two parts sagittally. Bruce et al.,[14] used the term “diastematomyelia” to describe a spinal cord split by a midline bony spur, and reserved the term “diplomyelia” for a true doubling of the spinal cord without a spur. Feller and Stenberg[15] were the first to implicate a notochordal cleft caused by persistence of a midline cell rest as the cause of diastematomyelia.

Pang[16] in 1992 gave a new classification recommending the term “SCM” for all double spinal cord malformations. He also described the unified theory, which explains the embryologic mechanism of development of all variants of SCM. According to the theory, the formation of an “accessory neuroenteric canal” between the yolk sac and amnion through the midline embryonic disc was the main cause of the defects. This canal gets subsequently invested with the mesenchyme to form an endomesenchymal tract, which causes the splitting between the notocord and neural plate. The location of this abnormal fistula is variable, but it must be rostral to the primitive neuroenteric canal, because the primitive pit into which the latter normally opens, ultimately comes to lie opposite the coccyx. If the precursor cells within the endomesenchymal tract form a bony septum, it is called Type 1 SCM. In case the mesenchymal tract forms a fibrous band that divides the hemicords in one dural sac, it is called as Type 2 SCM.

Thus the accessory neuroenteric canal can be regarded as the key point in the development of this type of malformation. The canal maybe single or multiple, and the presence of multiple accessory neuroenteric canals results in two or more septae that divide the spinal cord into hemicords; hence, one or more types of SCM may develop in these patients at different levels. Pang in 1992[16] reported about two such cases of composite type of SCM, out of total 39 case studies, and Ersahin et al.[7] reported on 4 such cases out of 74 cases of SCM in their study. The frequency of composite type SCM was reported as less than 1% by Harwood – Nash and McHugh.[9] Vaishya and Kumarajain[10] also reported about three cases of composite type of SCM. Kamil and Yusuf[17] reported a rare composite type of SCM of two different types at three different levels in the same patient. Myelocystocele has been described in literature from a long time; however, the term “non terminal myelocystocele” has been only recently added by Rossi et al.[18] Our patient is unique than the cases previously presented in literature in having three different levels of spur at D7-8, D10 and L2-L3 level, non terminal myelocystocele arising from the left hemicord at D7-D8 level, bifid fatty filum, coccygeal dermal sinus and hydrocephalus. What makes it all the more unique is that, all the different lesions were managed in a one-stage operation over a period of 8 hours. Prolonged surgery at multiple sites can have various complications like severe blood loss, and can cause hypothermia especially in children, and thus cause post operative morbidity. Our patient withstood the surgery well; however, had post-operative pyrexia for 5 days. Though the culture results were negative, antibiotics were continued for 8 days due to the fever.

Conclusion

The clinicoradiological findings in our patient further substantiate the multiple accessory neuroenteric canal theory in the development of composite type of SCM. Physical and neurological signs of SCM and nonterminal myelocystocele in a patient should prompt the neurosurgeon to consider performing the screening MRI of whole spine with brain to rule out other composite type SCM and hydrocephalus.

Competing Interests

The authors have no personal financial or institutional interest in any of the drugs, materials, or devices described in this article.