Neuromuscular and Nervous System
Localizing the lesion
Neurologic questions often ask where the problem is. Upper motor neuron lesions (stroke, MS, SCI above the conus) produce spasticity, hyperreflexia, and a Babinski sign; lower motor neuron lesions (radiculopathy, peripheral nerve injury) produce flaccidity, atrophy, fasciculations, and hyporeflexia. Map findings to dermatomes, myotomes, and cranial nerves to localize.
Concepts to name
- Stroke: contralateral deficits, middle cerebral artery patterns, neglect, aphasia.
- Spinal cord injury: ASIA level, complete versus incomplete, spinal shock, autonomic dysreflexia (hypertension, bradycardia, headache - a medical emergency).
- Parkinson disease: rigidity, bradykinesia, resting tremor, festination; cueing and large-amplitude training.
- Multiple sclerosis: fatigue, heat sensitivity, variable course.
- Guillain-Barré: ascending weakness, areflexia, respiratory monitoring.
- Balance and vestibular systems; neuroplasticity principles (task specificity, repetition, salience).
Traps
Candidates label all weakness as UMN, forget that spinal shock causes flaccidity early, or miss autonomic dysreflexia. Cranial nerve questions demand knowing that a peripheral CN VII lesion causes ipsilateral facial weakness, while a central lesion spares the forehead.
Worked rule
For any patient with SCI at T6 or above, a sudden headache with hypertension and bradycardia is autonomic dysreflexia until proven otherwise: sit the patient up, loosen tight clothing, check for bladder or bowel distension, and get medical help.