An Adopted 42-Year-Old With Slurred Speech and Memory Loss

Catherine Divingian, MD, PhD; Beena Stanley, MD; Jeffrey Jordan, MD

Disclosures

September 15, 2021

Discussion

This patient presented with myasthenia gravis (MG) and was most likely in myasthenic crisis. In MG, the neuromuscular junction becomes less responsive as the day progresses, leading to fatigue. Thus, the symptoms of MG worsen throughout the day. Some patients may demonstrate bulbar weakness, and others exhibit overall weakness. Bulbar weakness is associated with more severe presentations of myasthenic crisis.[1,2]

MG is typically caused by an autoimmune condition in which antibodies attack the acetylcholine receptors (AChRs) embedded in the sarcoplasm of the postsynaptic muscle cells. Another subtype of MG is an autoimmune condition involving anti–muscle-specific tyrosine kinase (MuSK) antibodies. These two subtypes can be distinguished from the seronegative subtype, which is characterized by a lack of antibodies to either AChR or MuSK.

MG can be diagnosed by the following methods[1]:

  • Tests for AChR or MuSK antibodies

  • Assessment of recovery by using ice packs

  • Use of edrophonium to prevent the breakdown of acetylcholine in the synaptic cleft

  • Electromyography to determine responses from neuromuscular stimulation

MG may be difficult to distinguish from other conditions that present with similar symptoms. Patients with Lambert-Eaton myasthenic syndrome (LEMS) have more proximal extremity weakness than those with MG; ptosis may occur. The symptoms of LEMS exhibit the opposite circadian influence: worsening in the morning and improving in the afternoon. In addition, LEMS is a paraneoplastic syndrome associated with small cell lung or prostate cancer.[3]

Multiple sclerosis is thought to exemplify central fatigue, which includes sleep disruption, generalized weakness, and mood disorders as part of a poorly understood process. In contrast, patients with MG have peripheral fatigue, owing to the pathology at the level of the AChRs.[4] Patients who are MuSK antibody–positive may appear similar to those with amyotrophic lateral sclerosis (ALS), particularly if they have bulbar symptoms; they can be distinguished by their positive response to the immunotherapies for MG discussed below.[5] MG often presents with ptosis, which is not typically seen in ALS. ALS is also exemplified by both upper and lower motor neuron signs, which is not seen in MG.

The most frequently used treatments for patients with MG who are not in crisis include medical symptomatic therapies, glucocorticoids, immune modulators, plasma exchange, intravenous immunoglobulin (IVIG), and surgical intervention. Various medications and other therapies may be tried until the patient shows a positive response via a decrease in symptoms, such as reduced afternoon fatigability and dyspnea.[6,7]

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