Before naming a neurological disease, localise the lesion anatomically. Decide whether the syndrome is cortical, subcortical, brainstem, cerebellar, spinal cord, nerve root, peripheral nerve, neuromuscular junction or muscle.
Use onset and tempo first: seconds-minutes suggests vascular/seizure; hours-days inflammatory/infectious/toxic; weeks-months neoplastic/degenerative. Look for cortical signs (aphasia, neglect, seizures), crossed brainstem findings, sensory level, dermatomal or length-dependent patterns, fatigability and proximal myopathy.
Perform mental status, cranial nerves, tone, power, reflexes, plantar responses, sensory modalities, coordination and gait in a fixed sequence. Pattern matters more than isolated weakness.
Select tests after localisation: CT/MRI brain, MRI spine, EEG, CSF, nerve-conduction/EMG or targeted laboratory testing. Avoid shotgun testing before deciding the likely anatomical level.
Treat emergencies before completing localisation: airway compromise, status epilepticus, acute stroke, spinal cord compression, meningitis/encephalitis and impending herniation.
Exam pearl: UMN weakness = increased tone/reflexes and extensor plantar response; LMN weakness = wasting, fasciculation and reduced reflexes.