Disorders• 5 SECTIONMuscle Extraocular
98
Orbital Myositis
Key Facts
•Subacute, usually monocular, non-infectious inflammation of one or more of the extraocular muscles
•Usually orbital congestion
•Diplopia
•May be associated with systemic connective tissue or vasculitic disorder
•Orbital imaging (CT or MRI) usually shows enlargement and enhancement of affected extraocular muscles
•Biopsy not necessary at outset unless orbital imaging is not diagnostic
Clinical Findings
•Ductional deficits in affected eye
•Diplopia
•Tenderness to palpation, eyelid edema, conjunctival congestion, proptosis, increased resistance to retropulsion of eye
•Incomitant ocular misalignment
•Forced ductions may show impaired eye movement
•In very indolent cases, increased resistance to retropulsion of the globe may be the only clue to diagnosis
Ancillary Testing
•Orbital imaging (CT or MRI) usually shows enlargement and enhancement of affected extraocular muscles and their tendons and higher signal within intraconal fat (fat stranding)
•Laboratory studies related to systemic autoimmune condition are indicated if the ophthalmic manifestations linger or there are suggestive systemic symptoms
•Orbital biopsy necessary only if clinical and imaging features are not diagnostic or the ophthalmic manifestations remain active despite medical treatment
Differential Diagnosis
•Graves disease
•Primary or metastatic orbital tumor
•Orbital cellulitis
•Sino-orbital aspergillosis or mucormycosis
•Carotid–cavernous fistula
Treatment
•Prednisone 0.5–1 mg/kg per day
•If this medical regimen is not effective or imaging is not diagnostic, consider biopsy
•Corticosteroid-sparing agent may be necessary if long-term treatment required
•Orbital radiation reserved for refractory cases
•Spectacle prisms may provide relief from diplopia in active and chronic phases
•Eye muscle surgery indicated for bothersome diplopia once disease no longer active and misalignment is stable for at least 6 months
Prognosis
•Usually very responsive to prednisone but often recurs if prednisone tapered
•Usually becomes inactive after months but often recurs
•Systemic autoimmune condition may appear later
•In diplopia refractory to prism or eye muscle surgery, spectacle or contact lens occluder useful to relieve diplopia
•Eye muscle surgery may restore a useful zone of single binocular vision
Fig. 5.1 Right orbital myositis. Abduction and supraduction are reduced in the right eye. Caution: orbital myositis may produce any ductional deficit. It more commonly affects one eye but may involve both; it differs from Graves disease (see Fig. 5.2) in being of more rapid onset and producing periocular pain on the involved side.
Myositis Orbital
99
Disorders• 5 SECTIONMuscle Extraocular
Graves Disease
Key Facts
•Subacute or chronic but self-limited inflammation of extraocular muscles and other orbital soft tissues associated with autoimmune reaction to thyroid gland
•Usually binocular but may be markedly asymmetric
•Periocular discomfort but no pain
•Lid edema, lid retraction, and lid lag in most patients
•Conjunctival edema (chemosis), tearing, proptosis, and hyperemia over insertion of extraocular muscles
•Reduced ocular ductions, especially in upgaze, causing diplopia
•Imaging often shows swelling of extraocular muscles with sparing of tendons
•In active phase, treatment usually palliative but some clinicians use short-term oral corticosteroids
•Orbital wall removal recommended only for optic neuropathy
Clinical Findings
•Hyperthyroidism or hypothyroidism and goitrous neck mass may be present, but patients may also be euthyroid
•Lid retraction and lag, eyelid edema, conjunctival congestion, proptosis
•Limited ocular ductions owing to swelling or scarring of extraocular muscles
Ancillary Testing
•Thyroid function tests may show hyperthyroidism, hypothyroidism, or euthyroidism
•Orbital imaging (CT or MRI) usually shows enlargement and enhancement of affected extraocular muscles with sparing of their tendons
•Forced ductions (passive ductions) testing may be positive but is not necessary for diagnosis—should be avoided because often causes pain and unsightly subconjunctival hemorrhage
Differential Diagnosis
• Orbital myositis
•Primary or metastatic orbital tumor
•Orbital cellulitis
•Sino-orbital aspergillosis or mucormycosis
•Carotid–cavernous fistula
Treatment
•In active phase, raise head of bed, use systemic diuretics and/or vasoconstrictor eyedrops
•Short-term oral corticosteroids may provide palliative relief of periocular discomfort and diplopia, but long-term use is associated with dangerous side effects
•Surgical orbital wall decompression recommended for optic neuropathy if imaging shows clear evidence of compression (see Graves optic neuropathy)
•Spectacle prisms or monocular occlusion may eliminate bothersome diplopia
•Once disease becomes inactive, extraocular muscle surgery, spectacle prisms, or monocular occlusion may eliminate bothersome diplopia
Prognosis
• Eyelid, extraocular muscle, and conjunctival inflammation eventually burn out after several years but often leave eyelid retraction, proptosis, and scarred muscles, causing ocular misalignment and diplopia
• Prisms and/or extraocular muscle surgery are often successful in palliating
diplopia
100
Fig. 5.2 Graves disease. Left hypertropia in primary gaze position. Supraduction is reduced in both eyes, more in the right eye. Any ocular motility disturbance may be seen in Graves disease, but reduced supraduction is most common as the result of restriction of ocular movement by a scarred and shortened inferior rectus muscle.
Disease Graves
101