Objective: To report four eyelid and eye movement disorder cases misdiagnosed as seronegative ocular myasthenia gravis.

Background: Myasthenia gravis (MG) is a disorder where neurotransmission is disrupted as a result of an autonomic attack on postsynaptic antigen targets. The diagnosis of MG is made based on clinical history, neurologic examination, edrophonium and ice pack test, serologic study and electrophysiologic studies, including repetitive nerve stimulation and single fiber EMG. MG is classified into two types, ocular MG and generalized MG. Acetylcholine receptor (AChR) antibodies are present in approximately 50% of patients with ocular MG. Ocular muscle-specific protein kinase (MuSK)- MG is very rare. The patients who neither produce AChR nor MuSK antibodies are called “seronegative.” In movement disorder, there are diseases that exhibit eyelid and eye movement abnormalities. Sometimes these diseases are misdiagnosed as seronegative ocular MG by insufficient observation, examination and tests.

Methods: Four eyelid and eye movement disorder case reports and literature review.

Results: Of the four patients diagnosed with seronegative ocular MG, two were blepharospasm. Another was convergence spasm. The other was progressive supranuclear palsy (PSP). All cases were diagnosis with seronegative ocular MG by serologic study and edrophonium test. In all cases symptoms remained constant or worse despite treatment.

Conclusions: The therapeutic use of botulinum toxin is contraindicated in patients with MG. Cases of MG mimicking blepharospasm has also been reported, and the distinction between these is important. Convergence spasm (CS) refers to the abnormal persistence of this movement when the patient is not fixating on a near object. CS are often misdiagnosed as having unilateral or bilateral abducens nerve palsy. CS is the most common reported functional eye movement disorder. In neurodegeneration disorders such as PSP, the first symptom may be abnormality of eye movements. Since the diagnosis may become apparent as symptom progress, careful observation is important. It is necessary to reconsider the diagnosis of seronegative ocular MG with no definite therapeutic effect.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/four-eyelid-and-eye-movement-disorder-cases-misdiagnosed-as-seronegative-ocular-myasthenia-gravis/