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A 26-year-old woman with no past medical history presents to the emergency department (ED) with several days of fatigue, difficulty climbing stairs, and double vision. She has one-word dyspnea and appears to be using accessory muscles of respiration. Her chest radiograph is normal as are all her initial laboratory studies. She mentions having an upper respiratory infection 1 week ago. She does not take any medications and does not have any recent travel. Vital signs: HR 105 bpm, sinus tachycardia, BP 145/90 mm Hg, RR 30 breaths/min, temperature 37.2°C. Examination: The patient is in moderate respiratory distress and using accessory muscles of respiration. She has no rashes. She is drooling and has difficulty clearing her secretions. Her oropharynx is clear. Her neurologic examination is notable for ptosis, bilateral sixth nerve palsy, bilateral facial weakness, neck flexion 3/5, deltoids 3/5, biceps 3/5, triceps 3/5, wrist extensors and intrinsic hand muscles 5/5, iliopsoas 4+/5, quadriceps 4+/5, hamstrings 5/5, tibialis anterior 5/5, 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 a central or peripheral lesion. 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, 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 listed in Table 6-1.

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

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