Evaluation and Diagnosis of Painful Conditions
History and red flags
Begin with the pain history (onset, quality, radiation, aggravating/relieving factors, timing, severity) plus functional impact. Red flags mandate urgent action: saddle anesthesia or bowel/bladder dysfunction (cauda equina), fever with spinal pain (infection), night pain with weight loss or cancer history (malignancy), significant trauma or osteoporosis (fracture), and progressive neurologic deficit. Trap: red-flag questions usually test whether you escalate and image urgently, not whether you order a specific test first.
Physical examination
Dermatomes are sensory, myotomes motor. Key myotomes: C5 deltoid, C6 biceps/brachioradialis, C7 triceps, C8 finger flexors, L4 tibialis anterior, L5 extensor hallucis longus, S1 gastrocnemius. Reflexes: biceps C5–6, triceps C7, patellar L4, Achilles S1. Trap: L5 has no reliably named reflex; Achilles is S1. Provocative tests include straight leg raise (L4–S1), Slump, Spurling for cervical root, and sacroiliac provocation clusters. Waddell signs are non-organic findings, not proof of malingering.
Diagnostic tools
EMG/NCS separates radiculopathy from plexopathy or peripheral neuropathy. In radiculopathy, sensory nerve action potentials remain normal because the lesion is proximal to the dorsal root ganglion, while EMG shows fibrillations in a myotomal and paraspinal distribution. Diagnostic blocks can confirm a pain generator but have false positives; dual blocks improve specificity. Imaging correlates poorly with symptoms-disc bulges are common in asymptomatic adults.
Worked example
A patient has great-toe dorsiflexion weakness, numbness over the dorsum of the foot, and normal reflexes. NCS shows normal superficial peroneal and sural SNAPs, but EMG shows fibrillations in the tibialis anterior and lumbar paraspinals. This localizes to the L5 root, not the peroneal nerve at the fibular head, because paraspinal muscles are innervated by the posterior ramus and are spared in distal nerve lesions.
Rule of thumb: normal SNAPs plus abnormal EMG in a myotomal and paraspinal pattern means root.