Neurology: Case of the Month

Factors complicating the diagnosis of myasthenia gravis in elderly patients include:

Which of the following features is MOST supportive of a diagnosis of myasthenia gravis over that of ALS (amyotrophic lateral sclerosis)?

Which of the following statements about diagnostic testing for myasthenia gravis is NOT true?

[ A ] Single fiber EMG is the most sensitive test for generalized and primary ocular forms of myasthenia gravis.
[ B ] In myasthenia gravis, acetylcholine receptor antibody titers do not predict the severity of disease.
[ C ] Acetylcholine receptor antibodies are present in generalized myasthenia gravis 80-90% of the time.
[ D ] Improvement on the Tensilon (edrophonium) test is diagnostic of myasthenia gravis.
[ E ] Denervation can be seen on electromyography of patients with myasthenia gravis.

All of the following statements about repetitive nerve stimulation (RNS) testing for myasthenia gravis are true EXCEPT:

[ A ] Repetitive nerve stimulation at high rates of stimulation, producing a CMAP decrement of at least 10%, is supportive of myasthenia gravis.
[ B ] Repetitive nerve testing should be done on proximal muscles to increase the yield for generalized myasthenia gravis.
[ C ] Low amplitude complex motor action potentials (CMAPs) or decrement in RNS in distal hand muscles may raise the possibility of Lambert-Eaton myasthenic syndrome.
[ D ] Normal RNS testing does not rule out the presence of myasthenia gravis.

Which of the following patterns of weakness is UNLIKELY to be a presentation of myasthenia gravis?

Test Yourself — Patient 63