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A 26-year-old woman with no past medical history presents to the emergency department with several days of fatigue, difficulty climbing stairs, and double vision. She has one-word dyspnea and appears to be retracting. Her chest x-ray is normal, as are all her initial laboratory studies. She mentions having had an upper respiratory infection 1 week before. She does not take any medications and has not traveled recently. Vital signs: heart rate, 105 bpm; sinus tachycardia; blood pressure, 145/90 mm Hg; respiration rate, 30 breaths per minute; temperature, 37.2°C. She is in moderate respiratory distress and is using accessory muscles of respiration. She has no rashes. She is drooling and has difficulty clearing her secretions. Her oropharynx is clear. Her neurological examination is notable for ptosis, bilateral 6th nerve palsy, bilateral facial weakness, and neck flexion, 3/5; deltoids, 3/5; biceps, 3/5; triceps, 3/5; wrist extensors and intrinsic hand muscles, 5/5; ileopsoas, 4+/5; quadriceps, 4+/5; hamstrings, 5/5; tibialis anterior, 5/5; and gastrocnemius, 5/5. Her sensory examination is normal, as are her reflexes.

What is the differential diagnosis for this patient?

Acute bilateral weakness can be due to either central or peripheral lesions. When approaching such a patient, it is advisable to develop a methodology beginning with brain and spinal cord etiologies and moving peripherally, ruling out possibilities based on examination, imaging, and laboratory findings. The acuity of the presentation and the symmetry and pattern of weakness can be helpful. Generalized fatigue due to cardiopulmonary disease, anemia, malignancy, depression, and fibromyalgia, for example, can overlay objective muscle weakness. Similarly, pain can limit the motor examination. A broad overview of possibilities using the mnemonic VINDICATE is shown in Table 6-1.

Table 6-1.Acute Motor and Sensory Weakness Differential Diagnosis

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