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"If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health." - Hippocrates
Cranial nerves: functions and testing of the oculomotor nerve.
on Tuesday 13 April 2010
by Robin author list
in article > Neurology
comments: 1
 10.0 - 3 votes -

The oculomotor nerve

Origin :
The oculomotor nerve arises from the anterior aspect of midbrain. There are two nuclei:
  • The oculomotor nucleus originates at the level of the superior colliculus.
  • The Edinger-Westphal nucleus supplies parasympathetic fibres to the eye
Sympathetic postganglionic fibres also join the nerve from the plexus on the internal carotid artery in the wall of the cavernous sinus and are distributed through the nerve.

  • Motor neural supply to the striated muscle in levator palpebrae superioris and all extraocular muscles except for the superior oblique muscle and the lateral rectus muscle.
  • Parasympathetic control via the ciliary ganglion of the sphincter pupillae muscle (affecting pupil constriction) and the ciliary muscle (affecting accommodation).
  • Sympathetic, to the smooth muscle of levator palpebrae superioris.

The pupils and eye movements are to be checked. The examiner instructs the patient to hold his head still and follow only with the eyes to the examiners finger or a penlight that moves in shape of a large "H" in front of the patient. The examiner observes the eye movement and eyelids and should note each of the supplied extraocular muscles and the levator palpebrae superioris muscle. Ptosis is caused by loss of motor function of levator palpabrae superioris.

The pupillary reflex should be checked, that is checking the constriction and thickening of the lens of the eye by moving a finger towards a person's face to induce accommodation, as well going cross-eyed to induce constrict.

Spillane, John A. Bickerstaff's Neurological Examination In Clinical Practice, 6th Ed. India: Wiley, 2008

Pls also mention the diagrammatic illustration to get a better overview.

Posted on 21 Jan : 08:29 AM
Maria Qaisar has Comments: 1

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