Nerve Palsies

Question 1

What is the presentation of a third nerve palsy?

Answer 1

Ptosis (drooping upper eyelid)
A dilated non reactive pupil
Divergent strabismus (squint) in the affected eye, it causes a down and out position of the eye

Question 2

What muscles does the oculomotor nerve supply?

Answer 2

. Contains parasympathetic fibres which innervate the sphincter muscles of the iris

. Supplies the levator palpebrae superiosis

. All the extra ocular muscles

Question 3

What is the route of the oculomotor nerve?

Answer 3

It travels directly from the brainstem to the eye in a straight line, it travels through the cavernous sinus and close to the posterior communicating artery.

Question 4

What is a third nerve palsy with sparing of the pupil due to?

Answer 4

This suggests a microvascular cause as the parasympathetic fibres are spared
This may be due to:

• Diabetes
• hypertension
• ischaemia

Question 5

What is a full third nerve palsy caused by?

Answer 5

This is caused by compression of the nerve, including the parasympathetic fibres, this is called a surgical third due to the physical compression…

• idiopathic
• tumour
• trauma
• cavernous sinus thrombosis
• posterior communicating artery aneurysm
• raised ICP

Question 6

What is Horner syndrome a triad of?

Answer 6

Ptosis
Miosis
Anhidrosis (loss of sweating)

(They may also have enopthalmos which is a sunken eye)

Question 7

What is horner syndrome caused by?

Answer 7

Damage to the sympathetic nervous system supplying the face

Question 8

What is horners syndrome caused by in broad terms?

Answer 8

Damage to the sympathetic nervous system supplying the face
The journey of the sympathetic nerves to the head is relevant for the causes of horners syndrome

The causes can be remembered as the
4S= S for Sentral (pre ganglionic)
4Ts= T for torso
4Cs= C for cervical (post ganglionic)

Question 9

Specifically what are the causes of horners syndrome?

Answer 9

S= stroke
S= multiple sclerosis 
S= swelling (tumours) 
S= syringomyelia (cyst in the spinal cord) 

Pre ganglionic lesions 
T= tumour 
T= trauma 
T= thyroidectomy 
T= top rib (cervical rib growing above the first rib above the clavicle) 

Post ganglionic lesions 
C= carotid aneurysm 
C= carotid artery dissection 
C= cavernous sinus thrombosis 
C= cluster headache

Question 10

How can the location of horners syndrome be determined by anhidrosis?

Answer 10

Central lesions cause anhidrosis of the arm and trunk, as well as the face

Pre ganglionic lesions cause anhidrosis of the face whereas post ganglionic lesions do not cause anhidrosis

Question 11

How do you determine whether someone has congenital horners?

Answer 11

You can look at the colour of their pupils, if one pupil is a different colour then suspect congenital horners.

Question 12

What can be used to test for horner syndrome?

Answer 12

Cocaine eye drops

This causes a normal eye to dilate because there is more noradrenalin stimulating the dilator muscles of the iris. In Horner syndrome, the nerves are not releasing noradrenalin to start with so blocking re-uptake does not make a difference and there is no reaction of the pupil.

Alternatively, a low concentration adrenalin eye drop (0.1%) won’t dilate a normal pupil but will dilate a Horner syndrome pupil.