a 3-month - old girl child presented to us with a history of swelling on back since birth .
she had a history of full term normal vaginal delivery with no significant family history .
there was complete flaccid paralysis of right lower extremity with normal anal tone . on local examination ,
an initial diagnosis of a myelomeningocele was made and patient was referred for magnetic resonance imaging ( mri ) of neuraxis .
mri spine revealed a bony spur at d11 level dividing the spinal cord into two halves suggesting pang type 1 split cord malformation ( scm ) or diastematomyelia .
right hemicord , along with meninges and cerebrospinal fluid was herniating through the defect in posterior element of same vertebra forming a large hemimeningomyelocele [ figures 1 and 2 ] .
t2-weighted sagittal ( a ) and coronal ( b ) magnetic resonance imaging of dorso - lumbar spine shows a hemivertebrae from d10 to d12 level along with a bony spur at d11 .
continuation of left hemicord is appreciable in coronal view ( b ) t2 weighted axial image shows a bony spur dividing the cord into two halves ( a and b ) .
herniation of right hemicord , meninges and cerebrospinal fluid is noted through the defect in posterior element , forming a large hemi - meningomyelocele ( c ) .
two hemicords are visible below the level of herniation ( d ) which reunites at d12 level to form a single cord ( e ) based on clinical examination and mri a final diagnosis of scm type 1 with right hemimyelomeningocele ( hmm ) was made and patient was prepared for surgery .
excision of bony spur along with microneurosurgical dissection and meticulous layered closure of myelomeningocele was achieved .
according to pang 's unified theory of embryogenesis , the whole spectrum of split cord syndrome originates from one basic ontogenic error occurring around the time of primitive neurenteric canal closure .
this basic error is the formation of  accessory neurenteric canal  between the amniotic cavity and the yolk sac .
this abnormal fistulous connection bisects the notochord and the neural plate on approximately postovulatory day 18 .
final appearance of matured scm depends on the ability of the embryo to heal around this abnormal fistulous connection aka endomesenchymal tract . according to pang et al . ,
formation of endomesenchymal tract before postovulatory day 21 gives rise to scm type 2 or diplomyelia , whereas formation of this tract after postovulatory day 30 gives rise to scm type 1 or distematomyelia .
the formation of this tract between postovulatory day 21 and 30 gives rise to composite / mixed scm .
each hemineural plate undergoes neurulation in which , the neural folds converge and fuse each other in relation to their respective hemi - notochords .
this process of primary neurulation occurs between postovulatory days 2228 . in case of neurulation defect on one side , hmm or hemimeningocele
myelomeningocele are frequently associated with chiari malformation diastematomyelia ( up to 45% in some reported series ) and other congenital vertebral defects such as spondylocostal dysostosis , jarcho - levin syndrome , klippel - feil anomaly and a wide range of syndromic malformation complexes , but true hemimeningocele , where a single hemicord fails to neurulate is rare .
the neurological deficit in children with hmm is less severe than compared to myelomeningocele patients and is limited only to the side of exposed hemicord .
this case report highlights the importance of detailed imaging of complete neuraxis in cases of spinal dysraphism for optimal neurosurgical management .
second the rarity of this condition suggests that formation of the endomesenchymal tract and neurulation defect are two separate embryological events , and their coexistence at the same level is only by chance though more inputs are warranted in this regard .
 variations in split cord malformation ( scm ) have been described earlier . however , a true hemimyelomeningocele ( hmm ) as only congenital malformation is extremely rare and is reported infrequently in published literature . 
 we are reporting the case of a 3-month - old girl child who presented with a swelling on the lower back since birth . 
 magnetic resonance imaging revealed a type 1 scm with right hemicord forming a hmm . precise diagnosis and thorough anatomical detail of dysraphism is essential for optimal , individualized neurosurgical management . 
Case Report
Discussion
Conclusion
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