Point: 18. Superior cerebellar peduncle
Principle efferent (out of) pathway of the cerebellum. Plays
a major role in the coordination of the IPSI. arm and leg.
Cells in the deep cerebellar nuclei (esp. globose,
emboliform and dentate) possess axons that pass rostrally
(towards the midbrain), dorsal and lateral to the fourth
ventricle. These fibers, which comprise the superior
cerebellar peduncle (or brachium conjunctivum), eventually
CROSS in the caudal midbrain (inferior colliculus; level
#9). After crossing, some fibers terminate in the red
nucleus, but most past through and around the red nucleus to
eventually reach the "motor" thalamic nuclei, the ventral
lateral (V.L.) and ventral anterior. (V.A.) The V.L. and
V.A. contain cells that project to the motor cortex (cells
of origin of the corticospinal tract, which influences the
CONTRA. side of the body). YOU MUST UNDERSTAND THIS!!!!!!!!
Lesion of the superior cerebellar peduncle CAUDAL to the
decussation will result in motor incoordination on the IPSI.
side of the body, whereas a lesion that occurs ROSTRAL to
the decussation results in CONTRA. motor incoordination of
the arm and leg.
REMEMBER THAT CEREBELLAR LESIONS RESULT IN IPSI. DEFICITS.
THE SAME IS TRUE OF SUPERIOR CEREBELLAR PEDUNCLE LESIONS
BEFORE ITS DECUSSATION.