ABSTRACTCaret
-Ocular myasthenia gravis is a not uncommon autoimmune disorder causing diplopia,
ptosis, and weakness of lid closure. The predilection of myasthenia for the ocular
muscles may be related to differences between limb and extraocular muscles in either
physiological function or antigenicity. Clinically, ocular myasthenia can mimic any
form of pupil-sparing ocular motility disorder. Dynamic abnormalities of myasthenic
eye movements may reflect the primary hallmarks of the disease, which are fatigability
and variability in strength, or secondary adaptive effects by the central nervous
system. Tests to confirm the diagnosis include edrophonium challenge, repetitive nerve
stimulation, single-fiber electromyography (EMG) of the frontalis, and assays for
antibody directed against the acetylcholine receptor: all are less sensitive for ocular
myasthenia than for generalized myasthenia. There is a higher incidence of other autoimmune
conditions in myasthenia, notably thymoma and thyroid dysfunction. The differential
diagnosis includes other diseases of the neuromuscular junction, such as Lambert-Eaton
syndrome and botulism. Treatment consists of symptomatic use of acetylcholinesterase
inhibitors and immunosuppression with steroids or azathioprine. Between 50 and 70%
of patients with ocular myasthenia will eventually develop generalized disease: there
is some retrospective data that steroids or azathioprine may reduce this by about
75%. The role of thymectomy in ocular myasthenia remains unclear.
KEYWORD
Ocular myasthenia - autoimmune disorder - diplopia - ptosis
