Radiculopathy and Plexopathy

Adam Chen

David Chad

RADICULOPATHY

CERVICAL RADICULOPATHY

Definition: Caused by spinal nerve root compression or irritation. Structural causes most common: Spondylosis (e.g., degenerative arthritis, osteophyte) or disc herniation. Incidence: C6, C7 > C8 >> C5 (Amato AA, Russell JA. Neuromuscular Disorders. McGraw Hill, 2008). Nonstructural causes less common: Infection (HSV, VZV, Lyme), immune-mediated neuropathy (focal demyelination in CIDP), neoplasia (leptomeningeal infiltration), sarcoidosis (granulomatous involvement).

Si/sx: Numbness & paresthesias in fingers in dermatomal distribution; lancinating or deep aching pain radiating into scapula, shoulder/arm; weakness depending on cervical roots involved. H/o trauma or exertion in only 15% (Brain 1994;117:325-335).

Exam: Weakness and/or sensory loss in upper extremities depending on affected roots (see chart below). Provocative maneuvers: Spurling (passive cervical extension w/lateral flexion toward the affected side), vertical traction (N Engl J Med 2005;353:392-399). Be careful in performing maneuvers if spinal instability, trauma, RA.

Dx: MRI C-spine. EMG/NCS: Most useful >3 wk after symptom onset, less informative in first 2-3 wk. LP: Consider when investigating nonstructural radiculopathy.

NCS: Sensory responses are normal; motor responses typically normal except if severe axon loss (e.g., ulnar motor responses may be reduced in severe C8 radiculopathy). NCS useful to exclude other dx (e.g., mononeuropathy, brachial plexopathy, polyneuropathy).
EMG: Day 1: Only reduced recruitment. Weeks 2-3: Fibrillation potentials & positive sharp waves. Months 3-4: Abnormal motor unit potentials (i.e., long duration, high amplitude). Test 2 muscles supplied by same root but different peripheral nerves & 1 paraspinal muscle (to confirm preganglionic site of lesion). Paraspinals may be normal due to multisegmental innervation (Preston DC, Shapiro BE. Electromyography and Neuromuscular Disorders. Elsevier, 2013).

Rx: Often self-limited if structural cause (Brain 1994;117:325-335). Urgent surgical evaluation if C-spine instability, progressive root deficit, myelopathy, or intractable pain (N Engl J Med 2005;353:392-399). Otherwise conservative Rx 3-6 wk (e.g., ice/heating pad, muscle relaxants, NSAIDs, short course [10 days] of oral steroids [Phys Med Rehabil Clin N Am 2011;22:127-137], gentle massage, stretching, PT). Consider cervical epidural steroid injections. If conservative Rx fails, consider surgery (pain responds well; myelopathy can be arrested; long-term benefit for radicular weakness likely but not clearly established) (Spine 2002;27:736-747).

LUMBOSACRAL RADICULOPATHY

Definition: Caused by nerve root compression or irritation. Structural causes most common: Spondylosis (e.g., foraminal/spinal stenosis, ligamentous hypertrophy) or disc herniation. Incidence: L5, S1 > L4 > L3 (Neurol Clin 2007;25:387-405). Nonstructural causes less common: Diabetes (see Diabetic Amyotrophy), infection (Lyme, HSV, VZV, CMV, Mycoplasma), immune-mediated neuropathy (AIDP, CIDP), neoplasia (leptomeningeal infiltration), inflammatory processes (sarcoidosis, vasculitis).

Si/sx: Lancinating or deep aching radiating pain, often worse w/standing. Weakness, numbness in distribution of affected root. L3-L4: Back pain, radiates to anterior thigh & medial calf. L5: Back pain, radiates to posterior thigh & lateral calf. S1: Buttock pain, radiates to posterior thigh/calf & heel (Preston & Shapiro 2013).

Exam: Weakness and/or sensory loss in lower extremities depending on affected nerves (see chart below). Rectal tone to evaluate sphincter tone if concern for cauda equina syndrome. Straight leg raise: Good sensitivity, low specificity for disc herniation (Phys Med Rehabil Clin N Am 2011;22:7-40).

Dx: MRI L-/S-spine. EMG/NCS: See Cervical Radiculopathy for findings. LP: Consider if nonstructural cause.

H-reflex: Assess afferent/efferent S1 fibers (akin to ankle reflex). Abnormal in S1 radiculopathy.

Rx: Often self-limited (Spine 1983;8:131-140). Urgent surgical evaluation if rapidly progressive motor deficits, cauda equina syndrome, or intractable pain. Otherwise, conservative rx initially (e.g., ice/heating pad, NSAIDs, muscle relaxants, massage, PT, TENS). May consider epidural steroid injections. Surgery if conservative rx fails (Phys Med Rehabil Clin N Am 2011;22:161-177).