Download THIRD NERVE PALSY

I.
The Unique Anatomy of the Third Nerve
A. The Third Nerve Nucleus
1. Consists of subnuclei
2. Contralateral innervation to the superior rectus
B. The Neighborhood
1. Located in the midbrain, at level of superior colliculus
2. Pass between the posterior cerebral and superior cerebellar
arteries
a) Subject to compression from posterior communicating
artery (PCA) aneurysm
3. Cavernous sinus (lateral wall)
a) Splits into superior (levator and superior rectus) and
inferior
(medial rectus, inferior rectus and oblique) divisions
b) Parasympathetic fibers travel with inferior division until
enters ciliary ganglion
II. Third Nerve Palsy: Presentations
A. General Considerations
1. Eye won’t go in, up, down. Has intorsion
2. Pupil may be dilated
a) If pupil spared with compressive lesion, ophthalmoplegia is
incomplete
3. Ptosis
a) May result in masking the motility dysfunction and diplopia
4. Accommodation reduced
B. Nuclear Third Nerve Palsy
1. In addition to above, contralateral superior rectus palsy,
partial bilateral ptosis
2. If caudal area spared, levator may be spared
3. Very rare to have individual subnucleus affected
4. Usual causes are infarcts (vertebrobasilar), demylinating
disease or metastasis
C. Lesions of the Nerve Bundle
1. Presentation depends on nerve portion affected
2. Often surrounding midbrain structures contribute clinical signs
3. Sudden onset with pupil involved – think: aneurysm
4. Sudden onset with pupil spared – think: microvascular
((Diabetes)
5. Slow, progressive onset with pupil spared – think: cavernous
sinus mass
6. Divisional palsies
a) Consider cavernous sinus
b) All deserve workups
1) CT or MRI (with gadolinium)
2) Possible MRA
7. Congenital palsy
a) Relatively rare
b) Usually benign with respect to neurologic disease
c) Amblyopia in 3/4 of these patients
d) May have aberrant regeneration
III. Aberrant Regeneration
A. Follows axonal damage
1. Does not occur following microvascular insult (Diabetes)
B. Misdirection during regrowth to wrong IIIN site
C. Consider evaluation for aneurysm if no history of trauma
IV. Selected Systemic Conditions to Consider in Third Nerve Palsy
A. Vascular or Ischemic
1. Diabetes Melitus
2) Hypertension
3) Atherosclerosis
4) Pupil usually spared due to peripheral location of fibers
5) Recovery in 3 to 6 months
B. Myasthenia Gravis
1) May mimic any EOM dysfunction
C. Acquired Third Nerve Palsy in children usually blunt trauma or
infection
V. Iatrogenic Causes
V. Treatment Options
A.
B.
C.
D.
Tinture of Time
Motility Training
BoTox
Surgical Options and Limitations
a. Goals
b. Muscle Transposition
E. Prescription Pitfalls
a. Avoid multifocals
F. Monocular Prism To Permit Better head Position