Central Nervous System- Basic Neuropathology
Photomicrograph is courtesy of Dr. Kar-Ming Fung.
Question No. 8. The Answer is: (A). The followings are true:
1. Segmental hypertrophy of the inferior olivary nuclei is illustrated here.
2. Enlarged neuron with bizarre morphology is associated with this situation.
3. These changes can be produced by damage to the central tegmental tract.
Discussion: The inferior olivary nucleus is being illustrated here. One arm of it is expanded, less curvy, and less well demarcated from the surrounding white matter. These features are compatible with segmental hypertrophy of the inferior olivary nuclei. In other cases, the entire nucleus can be hypertrophic. Hypertrophy is a misnomer as the expansion is featured by neuronal loss and gliosis. Pseudohypertrophy is a better tem. Pathologically, there is neuronal loss accompanied by the presence of bizarre and enlarged neurons with cytoplasmic vacuoles. There is also proliferation of reactive astrocytes that lead to expansion of the olivary nuclei. Astrocytosis are usually fibrillary, increased in number and size and have prominent, thick processes and large bizarre nuclei. Multinucleated astrocytes are common. There is also demyelination of periolivary and hilar fibers. Pseudohypertrophy (hypertrophy) of the inferior olive can be caused by the destruction of the central tegmental tract in the pons with pontine hemorrhage due to hypertensive crisis or cavernous hemangioma bleeding. Clinically, the manifestation is characterized by symptomatic palatal myoclonus.