[UW Anatomy |
Contents]
Function:
This tiny nucleus contains cells that directly innervate the CONTRA.
superior oblique muscle.
Pathway:
The trochlear nucleus sits on top of the M.L.F. in the caudal
midbrain (level #9) and at the junction of the pons and midbrain
(level #8). Neurons in this nucleus send axons dorsally around the
cerebral aqueduct to exit from the dorsal surface of the midbrain.
These fibers decussate just caudal to the inferior colliculus, course
ventrally adjacent to the cerebral peduncle, enter the superior
orbital fissure and innervate the superior oblique muscle.
Deficits:
Lesion of the trochlear nucleus or nerve prior the decussation
results atrophy of the CONTRA. superior oblique muscle. Patient will
TILT and slightly flex their head TOWARDS or IPSI. to the lesion in
order to ameliorate the double vision. A lesion of the trochlear
nerve AFTER the decussation results in atrophy of the IPSI. superior
oblique (ipsi. to the lesion) and the patient will TILT and slightly
flex their head AWAY (CONTRA.) from the lesion (compare with lesion
of C.N. VI).
Other Note:
Lesions result in difficulty going down stairs. Trochlear nerve is
only C.N. to be completely CROSSED and to exit DORSALLY from the
brainstem.