Neural tube defects and spinal dysraphism: Case

This girl has an open lumbosacral myelomeningocele with the Chiari II malformation and early hydrocephalus. The exposed neural placode with the cerebrospinal fluid leak is the classic open lesion, the lemon and banana signs on the prenatal scan are the cranial signs of the Chiari II, and the full fontanelle and the head circumference above the 97th centile point to the hydrocephalus. The motor level, around L2 to L3 given that she flexes her hips but moves nothing below the knees, predicts a significant motor deficit and a likely dependence on the wheelchair. The absent anal wink marks the sacral involvement and the neurogenic bowel and bladder. ^[1]

Clinical findings and assessment

The key findings are the open lumbosacral lesion with the neural placode, the motor level at L2 to L3, the absent sacral function, and the early hydrocephalus with the Chiari II. The pattern is unmistakable for a myelomeningocele, and the working diagnosis is confirmed by the prenatal scan. The motor level is the finding that frames the prognosis, because a lesion above L2 predicts a worse motor outcome and a lower chance of community ambulation, while a lesion at or below L3 would predict a better outcome. This girl's level is at the higher end, which means the ambulation potential is guarded. ^[1]

The differential of a newborn with a midline back lesion includes the meningocele, where the sac contains only cerebrospinal fluid and the cord is spared, and the occult dysraphic states, where the skin is intact. This girl's lesion has the neural placode exposed, so it is a myelomeningocele and not a meningocele, and the near-universal Chiari II and hydrocephalus belong to this phenotype. The meningocele carries a better prognosis because the cord and the roots are spared, but this girl's motor deficit confirms the neural tissue involvement. ^[7]