2.3 Spine Pathology, Radiculopathy & Myelopathy

2.3 Spine Pathology, Radiculopathy & Myelopathy

Spinal disorders represent a cornerstone of PM&R board examination content. Distinguishing between root compression, spinal cord pathology, and non-neurological vascular conditions is critical for electrodiagnosis and non-operative management.

Cervical Radiculopathy

Cervical radiculopathy stems from neuroforaminal narrowing caused by uncovertebral/facet joint hypertrophy in older individuals or posterolateral disc herniation in younger patients.

Level-Specific Neurological Examination

• C5 Radiculopathy: Motor weakness in deltoid and biceps; sensory deficit over lateral arm; diminished biceps reflex.
• C6 Radiculopathy: Motor weakness in wrist extensors and biceps; sensory loss over lateral forearm, thumb, and index finger; diminished brachioradialis reflex.
• C7 Radiculopathy (Most common ~60%): Motor weakness in triceps, wrist flexors, and finger extensors; sensory loss over middle finger; diminished triceps reflex.
• C8 Radiculopathy: Motor weakness in finger flexors and intrinsic hand muscles; sensory loss over medial forearm, ring, and little fingers; no deep tendon reflex.
• T1 Radiculopathy: Motor weakness in intrinsic hand muscles; sensory loss over medial arm.

Diagnostic Provocative Maneuvers

• Spurling Test (Neck Compression Test): Patient extends neck and laterally flexes toward affected side while examiner applies axial compression. Reproduction of dermatomal radicular pain down arm is highly specific (~92–100%).
• Cervical Distraction Test: Examiner applies upward traction to patient's head. Relief of radicular neck and arm symptoms indicates nerve root decompression.
• Shoulder Abduction (Bakody) Sign: Patient places hand of affected arm on top of head. Relief of arm pain suggests cervical radiculopathy by reducing nerve root tension.

Lumbar Radiculopathy

Lumbar radiculopathy results from mechanical nerve root compression or inflammatory cascade secondary to herniated nucleus pulposus or lumbar spondylosis.

Level-Specific Physical Examination Findings

• L4 Radiculopathy: Motor weakness in tibialis anterior and quadriceps; sensory loss over medial lower leg and foot; diminished patellar reflex.
• L5 Radiculopathy (Most common): Motor weakness in extensor hallucis longus (EHL), extensor digitorum longus, and gluteus medius; sensory loss over lateral calf and dorsum of foot; no reliable reflex.
• S1 Radiculopathy: Motor weakness in gastrocnemius-soleus, gluteus maximus, and hamstrings; sensory loss over lateral border of foot and sole; diminished Achilles (ankle jerk) reflex.

Specialized Clinical Nerve Tension Tests

• Straight Leg Raise (SLR / Lasegue Sign): Patient supine; passive elevation of symptomatic leg with knee extended. Reproduction of radicular pain below knee between 35° and 70° elevation indicates lower lumbar (L4-S1) nerve root irritation (high sensitivity ~80-90%).
• Crossed Straight Leg Raise (Well SLR): Passive elevation of asymptomatic leg reproduces radicular symptoms in affected leg. Highly specific (>90%) for herniated disc.
• Femoral Nerve Stretch Test (Reverse SLR): Patient prone; knee flexed and hip passively extended. Pain over anterior thigh indicates upper lumbar (L2-L4) radiculopathy.

Disc Herniation vs. Lumbar Spinal Stenosis

Distinguishing disc herniation from lumbar spinal stenosis (LSS) is fundamental to spine triage.

Mechanical Exacerbating and Relieving Factors

• Lumbar Disc Herniation: Exacerbated by lumbar flexion, sitting, coughing, sneezing, and Valsalva maneuvers (increases intradiscal pressure). Relieved by standing or spinal extension.
• Lumbar Spinal Stenosis: Central canal, lateral recess, or neuroforaminal narrowing. Exacerbated by lumbar extension and prolonged walking/standing erect (causes ligamentum flavum buckling and decreases canal cross-sectional area). Relieved by lumbar flexion ("shopping cart sign", sitting, stooping).

Neurogenic vs. Vascular Claudication

Neurogenic claudication (pseudoclaudication) caused by LSS must be differentiated from vascular claudication secondary to peripheral artery disease (PAD).

Cervical Spondylotic Myelopathy (CSM)

Cervical Spondylotic Myelopathy (CSM) is the leading cause of spinal cord dysfunction in adults over age 55. It results from chronic mechanical compression and ischemia of the cervical spinal cord due to disc-osteophyte complexes, ossification of posterior longitudinal ligament (OPLL), and ligamentum flavum hypertrophy.

Clinical Presentation

Insidious onset of gait instability (wide-based, spastic ataxia), loss of hand dexterity ("clumsy hands", difficulty buttoning shirts), upper motor neuron (UMN) signs below lesion, and lower motor neuron (LMN) signs at level of lesion.

Physical Examination Pathologic Signs

• Hoffmann Sign: Examiner flicks distal phalanx of middle finger into flexion. Involuntary reflex flexion of thumb interphalangeal joint and index finger DIP joint indicates corticospinal tract lesion.
• Inverted Brachioradialis Reflex: Tapping brachioradialis tendon produces finger flexion without brachioradialis contraction.
• Babinski Sign & Clonus: Upward extensor plantar response and >3 beats of ankle clonus.
• Lhermitte Sign: Electric shock-like sensation radiating down spine into limbs upon neck flexion.
• Finger Escape Sign: Inability to maintain adduction and extension of 4th and 5th digits for 30 seconds.

Spondylolysis and Spondylolisthesis

Spondylolysis

Defect or stress fracture of the pars interarticularis. Most common at L5 (90%). Prevalent in adolescent athletes undergoing repetitive lumbar extension (gymnasts, figure skaters, football linemen).

• Radiography: Oblique radiographs reveal a break in the neck of the "Scotty dog".
• Stork Test (Single-Leg Hyperextension Test): Patient stands on one leg and extends spine. Focal low back pain on stance side confirms symptomatic spondylolysis.

Spondylolisthesis

Anterior displacement of one vertebra relative to adjacent caudal vertebra. Classified by Meyerding Grading System based on percentage slip: Grade I (<25%), Grade II (25–50%), Grade III (50–75%), Grade IV (75–100%), Spondyloptosis (>100%).

• Etiologic Types (Wiltse-Newman):
  1. Type I (Dysplastic): Congenital sacral/arch dysplasia.
  2. Type II (Isthmic): Pars interarticularis defect (lytic stress fracture).
  3. Type III (Degenerative): Long-standing facet/disc osteoarthritis; most common at L4-L5; intact pars interarticularis.