Article

Myasthenia gravis is a rare, auto-immune disorder of the neuromuscular junction.
Onset signs frequently involve ocular muscles, accounting for ptosis and/or
diplopia in more than 75% of cases. Among the cases with purely ocular muscle
involvement, less than one half will never progress towards a more general form
of myasthenia. However, even if they do not share the potentially
life-threatening course of generalized myasthenia, purely ocular forms are often
responsible for severe impairment in everyday life. The diagnosis is essentially
based on fluctuations in the time and topography of the ocular muscle weakness.
It still remains uneasy, as investigations such as electromyography, search for
antiacetycholine receptor antibodies (positive in 50% of cases of purely ocular
myasthenia), and edrophonium chloride test sometimes yield false negative
results. Whereas some patients get better while on anticholinesterasic drugs
alone, most of them will experience insufficient improvement and need steroids
and/or immunosuppressant drugs. There is no indication for plasma exchanges,
intravenous immunoglobulin or thymectomy (except in the presence of thymoma).
This treatment could well decrease the risk of an evolution towards generalized
myasthenia. The reasons underlying the vulnerability of ocular motor muscles in
myasthenia are complex and several factors (linked to immunology, anatomy and
function) may combine to bring about their specific involvement. In the future,
randomized, controlled trials will be necessary, in order to determine a more
rational approach of the treatment of ocular myasthenia, which currently lies
mostly on retrospective data and the expertise of reference centers implicated in
the management of the disease.
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Langue : FRANCAIS