FIG 6.

Intraoperative photographs show posterior fossa decompression in a patient with CM-1. A, After a midline incision in the occipitocervical region, the occipital bone, the atlanto-occipital membrane, and the C1 lamina are exposed. B, A suboccipital craniectomy and removal of the posterior arch of C1 has been performed, and the dura mater will be opened in a Y-shaped fashion. C, After opening of the dura mater and the arachnoid overlying the cisterna magna, the 2 cerebellar hemispheres with their respective cerebellar tonsils can be visualized. D, A duraplasty has been performed, wherein a dural graft has been inserted and sutured in a watertight fashion to enlarge the cistern.