Third Nerve Palsy

Question 1

What type of deviation do you expect in a third nerve palsy?

Answer 1

Exotropia + Hypotropia in complete 3rd + ptosis (ptosis, and maybe dilation of pupil and accommodation palsy)

Superior division 3rd = hypotropia + ptosis (LP)

Inferior Division 3rd = depends what muscles are affected ;

• Isolated IR palsy = hypertropia
• Isolated MR palsy = Exotropia
• Isolated IO = hypotropia with possible slight eso.
  Ciliary ganglion - pupil dilated

Question 2

Pathway of third nerve

Answer 2

1. Begins in the oculomotor nucleus is a cluster of individual muscle subnuclei and Edinger-Westphal nuclei in the dorsal midbrain
2. The neuron axons traverse anteriorly within the third nerve fascicle and exit midbrain near medial aspect of the cerebral peduncle.
3. It enters the subarachnoid space, where it travels between the superior cerebellar artery and the posterior cerebral artery, and
   travels medially along the posterior communicating artery and lateral to the internal carotid artery (susceptible to aneurism).
4. Runs anterior through the cavernous sinus where enclosed within lateral wall, above 4th nerve.
5. Enters orbit through the superior orbital fissure then divides into 2 (inferior and superior division) at annulus of zinn.

Question 3

Aetiology of 3rd nerve palsy

Answer 3

• Microvascular
• Trauma
• Secondary to space occupying lesion / tumour
• Aneurysm (if pupil blown, indicates aneurysm, might result in subarachnoid haemorrhage)
• Myasthenia Gravis
• Congenital 3rd
• Inflammatory/viral infection
• Ophthalmic Migraine

Question 4

What blood tests should be carried out in a px over 50 y/o and the pupil IS involved ?

Answer 4

• BP
• Blood Glucose
• ESR - erythrocyte sedimentation rate (Sign of inflammation/infection)
• MRI with MRA (MR angiography)(angiography = check vessels through circle of Willis + all vessels)

Question 5

What blood tests should be carried out in a patient over 50 y/o WITHOUT pupil involvement?

Answer 5

• BP
• Blood Glucose
• ESR - erythrocyte sedimentation rate (Sign of inflammation/infection = MS, Rheumatoid Arthritis)
• They should be reviewed closely and if the pupil becomes involved Immediate Scan looking for compressive lesion

Question 6

How long does it take for a microvascular 3rd to resolve?

Answer 6

• Approx 3-4 months
• If not starting to resolve then MRI/MRA
• Ptosis first to recover = will get diplopia

Question 7

What do you get with a traumatic or compressive 3rd nerve palsy ?

Answer 7

Pupil involvement
Abberent regeneration (because nerves are damaged and when they regrow, they attach to new muscles)

Question 8

What are the signs of aberrant regeneration?

Answer 8

Elevation of upper eyelid on down-gaze or attempted adduction (pseudo-von Graefe phenomenon).
Adduction of the eye on attempted up-gaze and sometimes on attempted down-gaze.
Retraction of the globe on up-gaze or down-gaze.
Constriction of the pupil on attempted adduction.
“Pseudo-Argyll Robertson pupil”: greater constriction of pupil to convergence than to light and gaze-evoked pupillary constriction

Question 9

Why does the pupil become involved in a third nerve palsy?

Answer 9

pupillary fibres run on the outside of the nerve therefore when PCA aneurysm (abnormal swelling or bulge in the wall of an artery) will compress on the third nerve

NEED SCAN ASAP if pupil involved, could have a subarachnoid haemorrhage

Question 10

what are the signs of an aneurysm?

Answer 10

• Severe headache with sudden onset, will wake up with very sore head (might feel nauseous/being sick)

Loss of consciousness

Pain in or around the eye

Question 11

if just one nerve affected where is the lesion likely?

Answer 11

At the nucleus

Question 12

Bilateral Ptosis and Superior Rectus Paresis:
Where is the lesion in 3rd?

Answer 12

Nuclear lesions e.g. R 3rd nucleus palsy causes bilateral ptosis (drooping eyelids) and bilateral paresis (weakness) of the superior rectus muscles, and ipsilateral RMR, RIO, RIR + R pupil!)
The levator is supplied by a common single caudal nucleus; the superior rectus is supplied by the contralateral nucleus; and the medial rectus, inferior rectus and inferior oblique muscles are supplied from the ipsilateral nucleus.
In this setting the bilateral superior rectus weakness can only be confirmed to be of nuclear origin by demonstrating a deficient vestibular input by means of the doll’s head manoeuvre, where neither eye will elevate.

Question 13

what are fasicular syndromes associated with 3rd np?

Answer 13

Weber’s syndrome: Combination of ipsilateral third nerve palsy and contralateral hemiparesis (weakness to the opposite side of the body) due to damage to the cerebral peduncle and the third nerve (also port-wine stain (red mark on face) and glaucoma).

Benedikt’s syndrome: Combination of ipsilateral third nerve palsy, contralateral hemiparesis, and contralateral ataxia with intention tremor (occurs during voluntary movement towards a target) due to damage to the cerebral peduncle, third nerve, and red nucleus (coordination of movements and the integration of sensory and motor information to facilitate smooth and precise motor control).

Question 14

how to test if other nerves affected (4th, 5th and 6th)

Answer 14

4th: Confirming the integrity of the fourth nerve can be difficult. The main action of the superior oblique is depression when the eye is adducted. This function cannot be tested properly when adduction is limited. Instead, the patient should be instructed to abduct the eye and then try to look down, when intorsion should be seen if the fourth nerve is intact. Observation of an iris landmark or a conjunctival vessel can aid detection of intorsion.
6th : Even when the eye is very exotropic, it is possible to demonstrate lateral rectus function by observing the saccadic velocity or performing a force generation test.
5th: Reduced corneal sensitivity in association with a third nerve palsy suggests a lesion in the orbit or cavernous sinus

Question 15

management non surgical in 3rd np

Answer 15

Spontaneous recovery is high in microvascular 3rd nerve palsies. Traumatic 3rds show some improvement but is rarely complete and frequently complicated by aberrant regeneration.

Nonsurgical Treatment:
Prisms are of limited use in complete palsy due to reversibility of diplopia in different positions of gaze or too large deviation, and torsional image. Partial palsy = better chance of BSV with prism.
Occlusion may be used to manage diplopia.
Some px find can easily ignore second image, or some with long-standing can supress.
Tint glasses can help with photophobia from dilated pupil; pilocarpine drops may constrict pupil if necessary. Can also paint CL with small pupil.
Ptosis crutches fitted to spectacles can support ptosis (watch for dry eye)
Botulinum toxin may be used to improve alignment and in investigating BSV potential. It is occasionally effective in restoring long-term alignment of the visual axes when injected into the LR or a vertical rectus in a partial palsy.; repeated injections may be necessary for long-term alignment in partial 3rd. Unlikely to bring about a significant change in alignment in a total palsy.

Question 16

when is surgery inidcated in 3rd np

Answer 16

Only considered once deviation is stable. In the absence of any residual muscle function, a transposition or globe fixation procedure is necessary.
For total palsy, surgery aims to improve appearance and move eye into primary position.
Transposition procedures or globe fixation techniques can be considered for total palsy.
Surgery for the ptosis should only be considered if diplopia is acceptable to the patient (complete)

Question 17

Abberent regen definiton and when does it occur?

Answer 17

Definition:
Aberrant regeneration, or oculomotor synkinesis, occurs when neurological signals destined for one group of muscles are redirected to another group due to injury, the axons enter the wrong myelin tubes to supply inappropriate muscles. If no history of trauma, need to investigate compressive lesion!!
Aetiology and Incidence:
Common in acquired third nerve palsies due to trauma or space-occupying lesions.
Rare in congenital third nerve palsy; does not occur in microvascular conditions.
Aberrant regeneration can take place as early as 6 weeks after the onset of the palsy but more commonly develops after 8–12 weeks have elapsed. Infants who have sustained birth trauma resulting in an oculomotor palsy will show aberrant regeneration in 4–6 weeks

Question 18

management for abberent regen

Answer 18

Aberrant regeneration causing upper eyelid elevation during adduction can temporarily improve partial ptosis.
Surgery on the horizontal recti of the contralateral eye for associated exotropia increases stimulus to the lateral rectus and the medial rectus, improving ptosis and abnormal lid movement.

Question 19

total 3rd np sx?

Answer 19

• Poor prognosis for establishing a small field of BSV.
• Surgery aims to treat exotropia or improve appearance. Postoperative diplopia expected (botox not successful + prisms don’t work). Some don’t experience post-op dip possibly due to supp’n.
• Horizontal muscle surgery with traction sutures: Uses extensive LR recession and MR resection, combines horizontal rectus surgery with traction sutures under insertion site of SR and IR to the upper and lower lids, to anchor the eye in adduction.
• Postoperative problems: limited eye movement therefore extensive use of head movement, overaction of contralateral synergist muscles.
• Other Procedures: Superior oblique anterior transposition, medial transposition of the vertical recti, medial fixation of the globe using nonabsorbable sutures, and inferior nasal transposition of the lateral rectus.

Question 20

superior division surgery for 3rd np

Answer 20

• Hypotropic affected eye with partial ptosis. Overaction of contralateral inferior oblique and ipsilateral inferior rectus. Inhibitional palsy of the contralateral superior oblique is also seen.
• Head posture: elevated head, tilt, and turn towards the affected side.
• Nonsurgical: No treatment if diplopia not bothering px in PP. Prisms in long-standing cases. Sector occlusion can relieve diplopia on up-gaze.
• Surgical: Strabismus surgery before ptosis repair; procedures depend on residual superior rectus muscle function;
  -Mild SR weakness: contralateral inferior oblique muscle weakning if Incomitant and overacing. Concomitant = If the deviation is < 15 prism Δ in PP , we recommend recession of the contralateral superior rectus. If the deviation is > 15 Δ, then the ipsilateral inferior rectus should also be recessed. An alternative approach is to perform an ipsilateral inferior rectus recession and superior rectus resection
  -Marked SR weakness: The first procedure should be a forced duction test (FDT) to confirm that the ipsilateral inferior rectus is not causing mechanical restriction. In the presence of a negative FDT we recommend performing an ipsilateral Knapp procedure. A subclinical paresis of the ipsilateral inferior rectus may be uncovered by this procedure, resulting in diplopia in down-gaze; the patient should be warned of this risk before proceeding with surgery. The Knapp procedure can be enhanced with the posterior fixation suture (PFS).
• Poor prognosis for establishing a small field of BSV.
• Surgery aims to treat exotropia or improve appearance. Postoperative diplopia expected (botox not successful + prisms don’t work). Some don’t experience post-op dip possibly due to supp’n.
• Horizontal muscle surgery with traction sutures: Uses extensive LR recession and MR resection, combines horizontal rectus surgery with traction sutures under insertion site of SR and IR to the upper and lower lids, to anchor the eye in adduction.
• Postoperative problems: limited eye movement therefore extensive use of head movement, overaction of contralateral synergist muscles.
• Other Procedures: Superior oblique anterior transposition, medial transposition of the vertical recti, medial fixation of the globe using nonabsorbable sutures, and inferior nasal transposition of the lateral rectus.

Question 21

surgery for inferior division 3rd np

Answer 21

• Affected eye is exotropic, intorted, and hypertropic with pupil dilation. Overaction of contralateral lateral rectus, superior rectus, and superior oblique muscles. + Accom Insuff
• Unlikely to have a field of BSV; hence, no need for a head posture.
• Nonsurgical: Prisms and sector occlusion may help restore useful BSV, bu unlikely because insuprible diplopia torsion if dev size big.
• Surgical: Partial palsies: lateral rectus recession and medial rectus resection with infroplacement (moving the insertion points of the muscles downward on the eye).
  Total palsies: medial transposition of the superior rectus and inferior transposition of the lateral rectus, nasal tenotomy (weakening, surgically cut near the nasal (inner) side of the eye) of the ipsilateral superior oblique tendon.

Question 22

DIFF between S O and SR palsy

Answer 22

Dev in PP : 4th = increases on depression and 3rd increases on elevation
Hess charts show UA of SR in 3rd and u/a of SO in 4th
AHP: 3rd = elevated, 4th = depressed
ptosis in 3rd, not likely in 4th
Hypertropia increases at nr in 4th whereas dev will remain same in SR palsy