Superior Oblique Myokymia

Question 1

What are some characteristics of Superior Oblique Myokymia?

Answer 1

• Recurrent
• Monocular
• High frequency, low amplitude torsional contractions of the SO muscle
• Involuntary

Symptoms – oscillopsia and diplopia, patients often describe a “funny” sensation in their eye

Question 2

What are the symptoms of Superior Oblique Myokymia?

Answer 2

• Recurrent episodes of fine rapid eye movement causing vertical and torsional eye movements

This microtremor an intorsion - best observed on slit-lamp
Hypotropia

• May be triggered by reading, fatigue, stress or occur spontaneously

Question 3

What is the aetiology of Superior Oblique Myokymia?

Answer 3

There is no universal underlying cause but can follow a traumatic SO palsy and may present following head or ocular trauma or after a brainstem tumour (rare)

Linked to neurovascular compression syndromes

Low incidence of associated tumours so MRI is usually normal and so not often requested. However, magnetic resonance angiography may be requested to look for vascular compression of the root of the trochlear nerve or signs of prior trauma

Question 4

Who does Superior Oblique Myokymia most commonly affect?

Answer 4

Affects M/F equally and can present at any age, most commonly between 30 & 50 years old

Question 5

What do we request in Superior Oblique Myokymia? MRI or magnetic resonance angiography?

Answer 5

Low incidence of associated tumours so MRI is usually normal and so not often requested. However, magnetic resonance angiography may be requested to look for vascular compression of the root of the trochlear nerve or signs of prior trauma

Question 6

What medication can we give in Superior Oblique Myokymia?

Answer 6

• Oral Beta Blockers
  Propranolol or Levobunolol (Zhang et al., 2018)
• Topical Betablockers such as timolol, levobunolol or betaxolol
• Carbamazepine (improves/resolves symptoms in 80% of patients; Joosten et al., 2018)
• Memantine (has a lot of side effects)

Question 7

What did Xhang et al. (2018) find out about Levobunolo?

Answer 7

That in 2 patients with Superior Oblique Myokymia there were no side effects of levobunolo as a treatment

Question 8

What’s the most common medication to use in Superior Oblique Myokymia?

Answer 8

Topical Betablockers

Question 9

What did Joosten et al. (2018) find out about Carbamazepine?

Answer 9

That carbamazepine improves/resolves symptoms of Superior Oblique Myokymia in 80% of patients

Question 10

What surgery is recommended in Superior Oblique Myokymia?

Answer 10

• Superior oblique tenectomy/ tenotomy
  Can cause iatrogenic SO palsy and require additional ipsilateral IR recession
  Symptoms can recur
• SO tenotomy & IO myectomy
• Partial weakening of SO tendon (reverse Harado-Ito)
  Weaken anterior fibres of SO tendon, preserving SO function
• Botulinum Toxin injection (Superior oblique) – often affect other EOM’s as well therefore not recommended

Question 11

What did Ruttum & Harris (2009) find about Superior Oblique Myokymia?

Answer 11

53 year old female
Several years history of episodic twitching of her RE

Observation: Rhythmic downbeating and intorting movements

Diagnosis: Superior Oblique Myokymia

Treatment: Carbamazepine 800mg daily reduced symptoms by 50% but unacceptable side effects
Over several years alternative drug therapies tried without success and resorted to wearing a patch most of the time

7 years after initial presentation she requested surgery

Underwent surgical excision of proximal portion of her right superior oblique tendon, the trochlea and 10mm of SO muscle.

Post-op: fusion with 2∆ BD RE 2∆ BU LE and slight head tilt left.

Not requested surgery for iatrogenic palsy of her SO