Synopsis
Distinguish true loss of strength or sensation from pain, fatigue and impaired motor planning, then map the deficit to central, peripheral, junctional, muscular or functional mechanisms.
- Clarify what 'weak' means: loss of force, fatigability, heaviness, pain-limited effort, stiffness, incoordination, breathlessness, low endurance and impaired initiation describe different physiology.
- Establish onset, maximum severity and trajectory before detailed examination. Sudden focal weakness is vascular until assessed; progression over hours to days raises inflammatory, compressive, toxic, metabolic and neuromuscular emergencies.
- Map function through tasks—buttons, jars, overhead activity, rising, stairs, foot clearance and falls—then test the individual movements that reproduce the reported limitation.
Key red flags
Sudden unilateral face, arm or leg weakness with language, neglect, gaze or field disturbance is a cerebral vascular syndrome until proven otherwise. Pure motor stroke remains possible without cortical features and early CT can be normal.
Investigation priorities
Identify immediate metabolic mimics or causes and complications of profound weakness.
Management branches
Abrupt face or limb power loss, drift or loss of function, whether persistent, improving or discovered on waking.
- Perform ABCDE, glucose and a concise stroke examination; establish last known well, functional impact, seizure activity, headache, trauma, anticoagulants and pre-event disability.
- Activate urgent stroke imaging and specialist assessment rather than waiting for routine blood results or symptom resolution; include posterior-circulation and dissection clues.