Congenital myelomeningocele containing two hemicords with placodes in a patient with complex split spinal cord...

The unified theory of split spinal cord malformation (SCM) comprises type I, with each one of the hemicords in one own dural tube, separated by a bone spur, and type II, with two hemicords in one dural tube, separated by a nonrigid septum. This classification is still evolving, with denominations SCM type 0.5 proposed for incomplete forms, SCM type 1.5 for lesions combining features of SCM types I and II, and SCM type III for the composite lesions occurring on different spinal levels.

A newborn male patient presented with a complex SCM with two placodes, one in each hemicord, contained in one myelomeningocele (MMC) sac. In addition, caudal regression of the lumbosacral spine, hydrocephalus, and herniation of cerebellar tonsils down to thoracic levels were detected.

This complex case of two asymmetrical nonneurulated hemicords attached to a single MMC sac, opening on different levels of the bone spur and on the right side covered by a rudimentary hemilamina, illustrates the difficulties in classifying SCMs. Since up to 15% of MMC patients additionally have SCM, the case description underlines the role of preoperative MRI in newborns before neurosurgical MMC closure. https://thejns.org/doi/10.3171/CASE251036.