2), and showed T2 signal change in the brainstem, cerebellar peduncles
and cerebellum associated with variable enhancement on contrasted T1-weighted images.
1) This appearance is a result of absence or hypoplasia of the cerebellar vermis, lack of normal dorsal decussation and consequent enlargement of the superior cerebellar peduncles
which follow a more horizontal course as they extend perpendicularly to the brainstem between the midbrain and the cerebellum.
1-4) While hypertrophic olivary degeneration can occur with any focal lesion that involves the dentato-rubro-olivary pathway, it is typically associated with lesions that involve the superior cerebellar peduncle
(dentatorubral tract), the dentate nucleus, or the central tegmental tract.
This patient also demonstrated a similar diffusion signal abnormality involving the left superior cerebellar peduncle
Magnetic resonance imaging (MRI) demonstrated that intradural extension resulted in brainstem compression and created an intimate relationship between the lesion and both the vertebral artery and the cervicomedullary junction (figure 1, B); the tumor also extended rostrally to the middle cerebellar peduncle
(figure 1, C).
The fibers then course deep through the pons and exit from the central nervous system between the olive and the inferior cerebellar peduncle