H&E stained sections prepared from individual cranial nerves (R1-R12 and L1-L12), revealed scattered enlarged cells with brightly eosinophilic cytoplasmic inclusions or large eosinophilic nuclear inclusions in most cranial nerves (L3, L5-L12, and R6-R12) with occasional necrosis. The inclusion bearing cells were located within the endoneurium, epineurium, perineurium and the leptomeninges. The olfactory bulbs and tracks, as well as R4, did not show any pathologic changes. The optic nerves and R5, showed only leptomeningeal inclusion-bearing cells. Sections of R4 and L4 showed only perineurial involvement.
A low power view of the left 5th cranial nerve (Image-04) demonstrates multiple intranuclear and intracytoplasmic eosinophilic bodies. A higher power view of the 5th cranial nerve demonstrates a typical "Cowdry A" inclusion body (Image-05)within the endoneurial region. Note that there is no significant inflammation in any of the sections.
Sections of the upper cervical cord showed similar inclusion bearing cells within the leptomeninges and adjacent spinal nerve roots. Due to the restricted autopsy the lower part of the spinal cord and nerve roots were not available for examination.
Examination of the brain revealed extensive necrosis (Image-06) in periventricular areas including the ependymal and subependymal layers. In these areas, enlarged cells with abundant cytoplasm and intranuclear and cytoplasmic inclusion bodies (Image-07) were seen. The involved regions with ventriculo-encephalitis included the cingulate gyrus and corpus callosum, fornix, mammilary bodies and hypothalamus, cuadate and internal capsule, rostral pons, caudal pons, cerebellar peduncles and dorsal caudal pons, as well as deep cerebellar white matter. Immunohistochemical stain (Image-08) confirmed the diagnosis.