3rd Nerve Palsy Flashcards
Where does the 3rd Cranial Nerve originate?
It originates in the oculomotor nucleus in the pons, passes through the Circle of Willis, the cavernous sinus, and splits into superior and inferior divisions.
What muscles does the 3rd Cranial Nerve innervate?
Medial rectus (MR), Inferior rectus (IR), Superior rectus (SR), Inferior oblique (IO), Ciliary body, Iris sphincter.
What are the common causes of 3rd Cranial Nerve Palsy?
Posterior communicating artery aneurysm, Pressure from space-occupying lesions, Microvascular disease.
What are the features of total 3rd Cranial Nerve Palsy?
Exotropic, hypotropic, intorted eye, Dilated pupil, cycloplegia, ptosis, Limited adduction, elevation, and depression, Normal abduction.
What are the features of superior division 3rd Cranial Nerve Palsy?
Affects superior rectus and levator muscles, Hypotropic eye with ptosis, CHP: chin up, face turn to the unaffected side.
What are the muscle sequelae of superior division 3rd Cranial Nerve Palsy?
Overaction of contralateral IO, Contracture of ipsilateral IR, Secondary inhibition palsy of contralateral SO.
What are the features of inferior division 3rd Cranial Nerve Palsy?
Affects medial rectus, inferior rectus, inferior oblique, sphincter pupillae, ciliary muscle, Exotropic, intorted, hypertropic eye, Affects accommodation.
What are the muscle sequelae of inferior division 3rd Cranial Nerve Palsy?
Overaction of contralateral LR, SR, and SO.
Why does a compressive lesion like a PCA aneurysm cause pupil dilation?
The 3rd cranial nerve’s pupillary fibers are supplied by blood vessels on the pia mater, which are affected by compressive lesions.
Why does microvascular disease not cause pupil dilation in 3rd Cranial Nerve Palsy?
Microvascular conditions affect the vaso vasorum, which supplies the nerve but does not affect the pupillary fibers.
What are the signs of a complete 3rd Cranial Nerve Palsy?
Eye position: exotropic, hypotropic, intorted, Ptosis, dilated pupil, and cycloplegia.
How does the superior division of the 3rd Cranial Nerve affect eye movement?
It causes limitations in elevation and results in a hypotropic eye with ptosis.
How does the inferior division of the 3rd Cranial Nerve affect eye movement?
It causes limitations in adduction, depression, and affects accommodation.
What is CHP (compensatory head posture) in superior division 3rd Cranial Nerve Palsy?
Chin up with the face turned toward the unaffected side.
What is the management for sudden onset or worsening diplopia in 3rd Cranial Nerve Palsy?
Emergency referral.
