Pontine tegmental cap dysplasia (PTCD) is a newly described hindbrain malformation characterized by hypoplasia of the ventral pons and vaulting of the pontine tegmentum into the IVth ventricle. Approximately 20 cases have been reported but descriptions have been limited to clinical and radiologic findings. We report the first autopsy findings in PTCD.

The mother is a healthy 35-year-old G2P1 who elected to terminate pregnancy at 22 weeks gestational age due to radiologic findings of severe hindbrain abnormalities. General autopsy revealed a vertebral segmentation defect. Pertinent central nervous system findings included cerebellar hypoplasia and architectural disarray of the brainstem tegmentum. In the rostral pons, the midline tegmentum was occupied by a wedge of neurons, splaying the normal elements laterally and partially filling the ventral IVth ventricle. The nucleus basis pontis was absent, with apparent caudal displacement into the medulla. In the dorsal and caudal pons, the tegmentum was obscured by tracts of unmyelinated axons of uncertain destination running tangentially, obscuring the floor of the IVth ventricle. The inferior olivary nuclear complex was severely hypoplastic.

Our report provides the first pathologic description of PTCD and supports the radiological descriptions. In addition to the current hypothesis that PTCD represents a defect of axon guidance, our findings demonstrate abnormal neuronal migration as fundamental.

Conflictsof Interest:

None.