Congenital hypomyelination neuropathy: glial bundles in cranial and spinal nerve roots.

Autopsy examination of a 3 1/4-year-old child with a severe congenital hypomyelination neuropathy showed the anterior spinal nerve roots and motor cranial nerves to be almost devoid of myelin in their subarachnoid course. The posterior spinal nerve roots and peripheral nerves were less severely affected. Onion bulb formation was minimal and was present only in the sural nerve. There was extensive glial overgrowth in cranial nerves and spinal nerve roots adjacent to the brainstem and spinal cord. The extent and severity of glial overgrowth were similar to that described in Werdnig-Hoffmann disease and morphologically appeared as glial bundles. These glial bundles are most likely secondary to chronic myelin and axonal damage.