Ophthalmoplegia - CNIII Palsy

 

Thank you for asking to examine Harry who presented with eye abnormalities.

 

The salient findings one examination was right/left sided ptosis, with a fixed, dilated pupil and divergent strabismus with the eye in a ‘down and out’ position, indicative of a third cranial nerve palsy. I could/could not appreciate the underlying aetiology today.

 

I will now comment on my findings in full.

 

On general inspection, there was right sided complete ptosis. There was/was not evidence of scars, indicating a previous resection.

 

Visual acuity was ___.

 

Visual fields were normal/other

 

Colour saturation was normal.

 

There was a left/right dilated pupil unreactive to direct or consensual light, and unreactive to accommodation. There was direct and consensual response in the other eye.

 

On eye movements, there was restriction in all movements of the right/left eye except for abduction. The other eye showed no restriction. There was intorsion of the affected eye with head tilt, suggesting the fourth nerve is intact.

 

On further examination beyond the eyes, the 5th cranial nerve was intact with normal sensation, and masseter strength. Jaw reflex was normal.

 

The 7th cranial nerve was intact with normal symmetry and power.

 

Hearing was normal on screening.

 

Cranial nerves 9 and 10 were normal.

 

Cranial nerve 11 was intact with normal power in the sternocleidomastoid muscles and shrugging of the shoulders.

 

Cranial nerve 12 was intact with normal tongue movements, and no wasting or fasciculations.

 

In terms of an aetiology:

• Central (midbrain lesions):

  • Scars suggesting tumour resection

  • Vascular (e.g. brainstem) - any other infarct signs

  • Demyelination

  • Trauma

• Peripheral:

  • Diabetes - any features of diabetes

  • Compression along its course:

    • Posterior communicating artery aneurysm

    • Tumour causing raised ICP

    • Nasopharyngeal carcinoma

    • Orbital lesions

  • Trauma

  • Cavernous sinus lesions (cranial nerve IV, V1, V2 and VI associated)

 

Anatomy of the 3rd nerve:

• The third nerve begins as a nucleus in the midbrain that consists of several subnuclei that innervate the individual extraocular muscles, the eyelids, and the pupils. The levator palpebrae superioris muscles are controlled by a single central subnucleus. Thus, in patients with nuclear lesions, if ptosis is present, it is bilateral.

• The third nerve fascicle leaves the nucleus and passes ventrally near important structures in the midbrain (eg, red nucleus, corticospinal tract).

• The third nerve then enters the subarachnoid space, passes into the lateral wall of the cavernous sinus, and finally divides into superior and inferior branches as it enters the superior orbital fissure in the orbit to innervate the extraocular muscles