TROCHLEAR NERVE
It is a motor nerve
It is the most slender of the cranial nerves
It supplies Superior Oblique Muscle in the orbit
FUNCTIONAL COMPONENTS
Somatic Efferent for movement of the eye ball.
General Somatic Afferent for Proprioceptive impulses from superior oblique muscle. These impulses are relayed to the mesencephalic nucleus of the trigeminal nerve.
ORIGIN
It emerges from posterior surface of the midbrain just below the inferior colliculi, then curves forward around lateral side of cerebral peduncle, runs forward in the lateral wall of cavernous sinus slightly below the occulomotor nerve. It enters the orbit through superior orbital fissure, runs forward and medially across the origin of levator palpebrae superioris and enter the superior oblique muscle.
PARALYSIS
In case of paralysis of the nerve there double vision on looking straight down. This is because the superior oblique is paralyzed and eye turns medially as well as downwards. Vision is single so long as the eye looks above the horizontal plane.
The patient will adopt a compensatory head tilt.
Isolated nerve lesions are not common.
It is the most slender of the cranial nerves
It supplies Superior Oblique Muscle in the orbit
FUNCTIONAL COMPONENTS
Somatic Efferent for movement of the eye ball.
General Somatic Afferent for Proprioceptive impulses from superior oblique muscle. These impulses are relayed to the mesencephalic nucleus of the trigeminal nerve.
ORIGIN
It emerges from posterior surface of the midbrain just below the inferior colliculi, then curves forward around lateral side of cerebral peduncle, runs forward in the lateral wall of cavernous sinus slightly below the occulomotor nerve. It enters the orbit through superior orbital fissure, runs forward and medially across the origin of levator palpebrae superioris and enter the superior oblique muscle.
PARALYSIS
In case of paralysis of the nerve there double vision on looking straight down. This is because the superior oblique is paralyzed and eye turns medially as well as downwards. Vision is single so long as the eye looks above the horizontal plane.
The patient will adopt a compensatory head tilt.
Isolated nerve lesions are not common.
ABDUCENT NERVE
It’s a small motor nerve that supplies the lateral rectus of eye ball.
FUNCTIONAL COMPONENTS
Somatic Efferent for lateral movements of the eye ball.
General Somatic Afferent for Proprioceptive impulses from the lateral rectus muscle. These impulses reach the mesencephalic nucleus of trigeminal nerve.
ORIGIN:
It emerges from the anterior surface of brain between lower border of pons and medulla oblongata. It lies first in the posterior cranial fossa then turns sharply forward crossing superior border of petrous part of temporal bone; having entered the cavernous sinus it runs forward with Internal Carotid Artery and enters the orbital cavity through superior orbital fissure. It runs forward and supplies the Lateral Rectus.
PARALYSIS
Isolated lesions are common.
In case of paralysis of this nerve eye ball cannot be turned laterally when looking straight ahead the lateral rectus is paralyzed and unopposed medial rectus pulls the eye ball medially causing INTERNAL STRABISMUS or MEDIAL SQUINT or CONVERGENT STRABISMUS
PARALYSIS
Isolated lesions are common.
In case of paralysis of this nerve eye ball cannot be turned laterally when looking straight ahead the lateral rectus is paralyzed and unopposed medial rectus pulls the eye ball medially causing INTERNAL STRABISMUS or MEDIAL SQUINT or CONVERGENT STRABISMUS
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