Sudden Onset Proximal Arm and Distal Leg Weakness: Differential Diagnosis

Life-Threatening Causes Requiring Immediate Evaluation

Immediate brain imaging (CT or MRI) must be completed within 24 hours for any sudden unilateral weakness, according to the International Journal of Stroke guidelines 1
The American Heart Association recommends looking for sudden onset (minutes to hours), unilateral distribution, associated facial weakness, speech disturbance, or sensory changes in patients with suspected stroke 1

Idiopathic Inflammatory Myopathy can present acutely in 4.6% of cases, with atypical patterns of proximal arm with distal leg weakness, as reported by the European League Against Rheumatism 3
The American College of Rheumatology suggests assessing immediately for respiratory muscle weakness, dysphagia, or dysarthria, which represent medical emergencies requiring ICU admission 5
Elevated creatine kinase (CK) levels (>10x normal) suggest inflammatory myopathy, according to the American Association for Clinical Chemistry 5

If symptom onset is within 48 hours with unilateral weakness, the American Heart Association recommends immediately sending the patient to the emergency department 1
Obtain urgent brain imaging (CT or MRI) and vascular imaging (CTA/MRA from aortic arch to vertex) within 24 hours, as suggested by the International Journal of Stroke guidelines 1
The American Thoracic Society recommends checking vital capacity, negative inspiratory force, and oxygen saturation immediately to assess for respiratory emergency 5
Bulbar symptoms (dysphagia, dysarthria, dysphonia) indicate severe disease requiring urgent high-dose methylprednisolone, according to the American Academy of Neurology 2