Orbital Myositis

Question 1

Ocular myositis defintion

Answer 1

A subgroup of idiopathic orbital inflammatory syndrome characterized by inflammatory swelling of one or more of the extraocular muscles.
Pseudo tumour

Question 2

Ocular myositis types

Answer 2

Unilateral or bilateral.
Acute or chronic.

Question 3

Ocular myositis potential cause

Answer 3

Previous history of an upper respiratory tract infection.
History of ocular or systemic autoimmune disease.

Question 4

Ocular myositis symptoms

Answer 4

Main symptom is painful on OM + diplopia.
Usually MR
Lid swelling.
Chemosis (Oedema – periorbital/chemosis)
Proptosis in severe cases.
Underlying Inflammatory disease/Autoimmune disorder(MS) /sinusitis/cellulitis

Question 5

Ocular myositis limitation of movement

Answer 5

Paresis in the direction of the involved muscle’s action (one muscle).
Mechanical in the opposite direction due to the inflammatory process.

Question 6

Ocular myositis tests

Answer 6

Hess chart, saccadic velocity measurements, and forced duction testing to confirm signs.
Orbital neuroimaging shows marked swelling of the affected muscles.

Question 7

Ocular myositis Differential Diagnosis:

Answer 7

Graves’ Orbitopathy: Differentiation is based on absence of lid retraction and lid-lag, and more severe pain, thyroid function, more acute onset in myositis and CT scan shows tendon involvement in myositis (not in graves).
Idiopathic Orbital Inflammatory Syndrome: Orbital myositis is a subgroup of this condition. Most commonly involved are the lacrimal gland, orbital fat and extraocular muscles. Neuroimaging shows enlargement of those structures involved and enhancement of the orbital fat
Orbital Cellulitis: Infective disease associated with systemic symptoms and secondary to adjacent sinus infection.
Orbital Rhabdomyosarcoma: Typically occurs in childhood and is rare in orbital myositis cases. Highly malignant.

Question 8

Ocular myositis: Management
Systemic Treatment:

Answer 8

Orbital myositis may occasionally be self-limiting
Corticosteroids lead to swift improvement within days or weeks in most cases. However, in some cases of acute orbital myositis the condition can become chronic. The early use of systemic steroids may reduce the risk of acute orbital myositis recurring and possibly becoming chronic.
Mild restriction of ocular motility only requires treatment if it is symptom producing. Some patients can be managed with prisms.
Botulinum toxin may be used for patients failing conservative management.

Question 9

Ocular myositis sx tx

Answer 9

Should be delayed until the condition stabilizes and the patient is off systemic treatment. Even then, the patient should be warned about the risk of further attacks.

Question 10

Ocular myositis diff between TED

Answer 10

GRAVES = lid lag/retraction
GRAVES = dull pain (OM severe)
TED BIL/asymmetrical (OM typically UNI)
TED = swelling of more than one muscle sparing tendon, OM = swelling of one muscle + tendon