Single-fiber electromyography of extraocular muscles in myasthenia gravis

Abstract

The jitter phenomenon of extraocular muscles (EOMs) was investigated in 11 healthy controls and 42 patients with diplopia and/or blepharoptosis using single fiber electromyography (SFEMG). The authors compared the usefulness of SFEMG of EOMs with two other diagnostic techniques (Tensilon test and the titers of anti-acetylcholine receptor antibodies: Anti-AChR ABs) in the differential diagnosis of myasthenia gravis (MG). The Tensilon test was positive in 72.7% of MG patients. Anti-AChR ABs were detected in 100% of generalized MG patients and in 63.6% of ocular MG patients. SFEMG demonstrated an abnormal jitter phenomenon in all MG patients. The authors conclude that SFEMG of EOMs is the most decisive examination in the differential diagnosis of ocular MG, and recommend its use when the etiology of fluctuating diplopia and blepharoptosis cannot otherwise be established.

Key Words:

• single fiber electromyography
• jitter phenomenon
• myasthenia gravis
• extraocular muscles
• anti-acetylcholine receptor antibody