Neuromusculoskeletal Diagnosis
Core concepts
Neuromusculoskeletal diagnosis combines regional orthopedics with neurologic localization. Know dermatomes, myotomes, deep tendon reflexes, and peripheral nerve territories. Cervical root patterns include C5 shoulder abduction and biceps reflex, C6 wrist extension and brachioradialis reflex, C7 elbow extension and triceps reflex, C8 finger flexion, and T1 finger abduction. Lumbar patterns include L4 knee extension and patellar reflex, L5 great toe extension and foot dorsiflexion, and S1 plantar flexion and Achilles reflex. Distinguish upper motor neuron signs, such as hyperreflexia, spasticity, and Babinski sign, from lower motor neuron signs, such as atrophy, fasciculations, and hyporeflexia. Orthopedic special tests are meaningful only when combined with history and neurologic findings.
Traps
L5 and S1 are commonly confused: L5 drives great toe extension and ankle dorsiflexion; S1 drives plantar flexion and ankle jerk. C6 and C7 are also confused: C6 drives wrist extension and brachioradialis; C7 drives elbow extension and triceps. A positive straight leg raise supports lumbosacral root irritation but is not specific for a single level. Radiculopathy is not the same as myelopathy.
Worked example and rule of thumb
A patient has weak great toe extension, sensory loss over the dorsum of the foot, and no reflex change. Localize to L5. If ankle plantar flexion is weak and the Achilles reflex is diminished, localize to S1. Rule: match the weakest movement and the reflex to the root; L5 often has no routine reflex.
Exam focus
Localize before naming a diagnosis. Use myotome, dermatome, and reflex together.