What are examples of radicular symptoms in an older adult with chronic back pain and do changes appear on electromyography (EMG)?

Radicular Symptoms: Clinical Presentation and EMG Findings

Examples of Radicular Symptoms

Radicular symptoms result from nerve root impingement and present as lower extremity pain, paresthesia, and/or weakness in a specific dermatomal and myotomal distribution. 1

Lumbar Radiculopathy Presentations

• Pain radiation: Radiates from the back into the leg following specific nerve root distributions (e.g., L5 radiculopathy causes pain down the lateral leg to the dorsum of the foot; S1 radiculopathy causes pain down the posterior leg to the heel) 2
• Sensory changes: Numbness, tingling, or burning sensations in dermatomal patterns corresponding to the affected nerve root 1, 2
• Motor deficits: Weakness in specific muscle groups (e.g., gastrocnemius weakness with grade I strength and absent Achilles reflex in S1 radiculopathy) 3
• Positive provocative testing: Straight leg raise test is specific for nerve root tension in lumbar radiculopathy 3

Cervical Radiculopathy Presentations

• Neck pain with arm radiation: Combination of neck pain with unilateral arm pain in a dermatomal distribution 1
• Sensory or motor deficits: Varying degrees of sensory loss or motor weakness in the affected nerve root distribution 1
• Radicular pain patterns: Pain follows specific cervical nerve root distributions (e.g., C6 radiculopathy causes pain radiating to the thumb and index finger; C7 affects the middle finger) 1

Thoracic Radiculopathy

• Band-like pain: Pain wrapping around the chest wall in a dermatomal distribution 1
• Less common presentation: Thoracic radiculopathy is far less common than cervical or lumbar presentations 1

EMG Changes in Radiculopathy

Yes, EMG demonstrates characteristic changes in radiculopathy, with modest sensitivity but high specificity, making it the most important electrodiagnostic test for confirming nerve root pathology. 4, 5

Specific EMG Findings

• Spontaneous activity (SA): Fibrillation potentials and positive sharp waves appear in muscles innervated by the affected nerve root, indicating denervation 6, 4
• Motor unit recruitment abnormalities: Reduced recruitment or altered interference pattern (IP/MUR) in affected myotomes 6, 5
• Paraspinal muscle involvement: Abnormalities in paraspinal muscles are particularly specific for radiculopathy, as these muscles are innervated proximal to peripheral nerve entrapment sites 4, 5
• Multisegmental pattern: Abnormalities in multiple muscles sharing the same nerve root but different peripheral nerve innervations confirm radicular pathology 4

Timing of EMG Changes

• Acute phase limitations: EMG changes may not appear immediately after symptom onset, as denervation changes require 2-3 weeks to develop 4
• Optimal timing: EMG is most sensitive when performed at least 3-4 weeks after symptom onset 5
• Chronic changes: In long-standing radiculopathy, chronic neurogenic changes (large amplitude, long duration motor units) may be present 5

Clinical Correlation with EMG

• Improved outcomes with positive EMG: Patients with disc herniation showing EMG improvement (MUR/SA) after epidural steroid injections demonstrate better clinical outcomes, particularly in the first 6 months 6
• Prognostic value: EMG findings (MUR and SA) have significant prognostic value for pain improvement (R² = 0.287 and 0.277 respectively) 6
• Complementary to imaging: EMG has high specificity and complements MRI findings, helping distinguish true radiculopathy from imaging abnormalities that may be incidental 4, 5

Streamlined EMG Protocol

• Six-muscle examination: A focused examination of 6 muscles (including 1 paraspinal muscle) provides high diagnostic yield while minimizing patient discomfort 4
• Nerve conduction studies: Should be performed concurrently to exclude peripheral nerve entrapment (carpal tunnel, ulnar neuropathy) and polyneuropathy, which frequently mimic radicular symptoms 4, 5

Common Pitfalls

• False negatives: EMG has modest sensitivity, so normal EMG does not exclude radiculopathy, especially in mild or very acute cases 4, 5
• Asymptomatic imaging findings: MRI abnormalities (disc protrusions, stenosis) are common in asymptomatic individuals and increase with age, so clinical correlation with EMG findings is essential 1
• Timing errors: Performing EMG too early (before denervation changes develop) reduces sensitivity 5