Ocular Neuromyotonia

Question 1

What are some characteristics of Ocular Neuromyotonia?

Answer 1

A rare disorder causing involuntary, transient spasms of EOM’s that is typically induced by sustained gaze and can cause intermittent diplopia.

It can be CNIII, IV or VI and is usually unilateral

Can be painful or painless with episodes lasting a few seconds to several minutes occurring every 10 - 40 minutes

Question 2

What is the aetiology of Ocular Neuromyotonia?

Answer 2

• Assumed to be caused by nerve damage leading to delayed muscle relaxation and inappropriate neural firing
• Majority have history of parasellar tumour and undergone radiation therapy – late side effect of this
• Nerve compression
• May be more common in patients with autoimmune disorders (MG / TED)
• May be linked to vitamin B12 or vitamin D deficiency
• Remainder no known cause

Question 3

What treatment is there for Ocular Neuromyotonia?

Answer 3

Membrane stabilising medications usually reduce / control frequency of attacks

• Carbamazepine 200mg
• Oxcarbazepine
• Lamotrigine

Question 4

What did Ezra et al. (1996) find out about Ocular Neuromyotonia?

Answer 4

3 patients
Two III cranial nerve affected
1 due to compression of internal carotid artery aneurysm
1 following radiotherapy for a pituitary tumour
One IV cranial nerve affected
Induced by alcohol

Cases (on slides) highlight the need for careful history taking, especially around history of radiotherapy in parasellar area (even if a long time ago). Careful examination with prolonged eccentric gaze and most patients will have MRI scan to exclude a sinister cause