Simpson test is a clinical test used in neurology to determine ocular
myasthenia gravis
Myasthenia gravis (MG) is a long-term neuromuscular junction disease that leads to varying degrees of skeletal muscle weakness. The most commonly affected muscles are those of the eyes, face, and swallowing. It can result in double vision, dro ...
. It was first described by the Scottish neurologist
John Alexander Simpson.
Procedure
In myasthenia gravis, there is a variable weakness of skeletal muscles, which is exacerbated by repeated contraction. To cause sustained contraction of
levator palpebrae superioris muscle, the patient is asked to gaze upward for an extended period of time, without lifting the head. After a few minutes, the patient with myasthenia gravis starts to show drooping of upper eyelids, while normal individuals do not show any drooping.
Thus, this test can be used to clinically differentiate between ocular myasthenia gravis and normal individuals. Since myasthenia gravis affects all skeletal muscles, eyelid drooping is often bilateral. It is sometimes done in conjunction with
tensilon test
A tensilon test, also called an edrophonium test, is a pharmacological test used for the diagnosis of certain neural diseases, especially myasthenia gravis. It is also used to distinguish a myasthenic crisis from a cholinergic crisis in individual ...
, where
edrophonium is injected to look for reversibility of eyelid drooping. In myaesthenia gravis, eyelid drooping is no longer detectable after tensilon test.
This test is less sensitive than
anti-AChR antibody titers and
electromyography
Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyog ...
, and hence is used only as a screening test in clinical setup.
References
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Diagnostic neurology