Fast Five Quiz: Refresh and Test Your Knowledge of Myasthenia Gravis

Amy Kao, MD

Disclosures

July 06, 2021

Patients with MG present with painless, specific muscle weakness, and not usually generalized fatigue. Myasthenic weakness typically affects the extraocular, bulbar, or proximal limb muscles. Droopy eyelids or double vision is the most common symptom at initial presentation of MG, in more than 75% of patients. These symptoms progress from mild to more severe disease over weeks to months. Difficulty in swallowing; slurred or nasal speech; difficulty chewing; and facial, neck, and extremity weakness occur.

Patients with MG who have difficulty chewing may demonstrate weakness of jaw closure due to masseter and temporalis muscle weakness. Weakness of jaw opening due to pterygoid muscle weakness, on the other hand, is rarely seen. This pattern of weak jaw closure and relatively strong jaw opening is quite typical of MG.

Certain limb muscles are involved more commonly than others. In the upper limbs, deltoids and extensors of the wrist and fingers are affected most. The triceps is more likely to be affected than the biceps. In the lower extremities, commonly involved muscles include hip flexors, quadriceps, and hamstrings, with rare involvement of foot dorsiflexors or plantar flexors.

Cognition, coordination, sensation, and muscle stretch reflexes are normal in the myasthenic patient.

Learn more about the presentation of MG.

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