Back & Leg Neuropathies

Back and leg neuropathies include conditions affecting the lumbar and sacral nerve roots, lumbosacral plexus, and peripheral nerves of the lower extremities.

What is involved?

Multiple nerves and nerve roots of the lower extremity:

• Lumbar and Sacral nerve roots (L2-S2)
• Lumbosacral plexus
• Peripheral nerves (Sciatic, Femoral, Peroneal, Tibial, Lateral Femoral Cutaneous)

Location

• Lumbar/Sacral Spine: nerve root compression at neural foramen or central canal
• Lumbosacral Plexus: in the pelvis and retroperitoneum
• Lower Extremity: various entrapment sites along peripheral nerves

Common symptoms

Symptoms vary by location and nerve involved:

Lumbar Radiculopathy

• Low back pain radiating to leg (sciatica)
• Dermatomal numbness and tingling
• Weakness in specific muscle groups
• Pain often worse with sitting, bending, coughing

Lumbosacral Plexopathy

• Hip, thigh, and leg weakness
• Diffuse leg numbness
• May be associated with diabetes, tumors, or trauma

Peripheral Nerve Entrapments

• Peroneal Neuropathy: foot drop; numbness over dorsum of foot
• Tarsal Tunnel: burning foot pain; numbness of sole
• Meralgia Paresthetica: lateral thigh burning and numbness
• Femoral Neuropathy: thigh weakness and numbness

Onset

• Radiculopathy: can be sudden (disc herniation) or gradual (stenosis)
• Plexopathy: variable depending on cause
• Entrapments: usually gradual over weeks to months

Risk factors

• Lumbar spondylosis (degenerative disc disease)
• Disc herniation
• Spinal stenosis
• Trauma
• Diabetes mellitus (diabetic amyotrophy)
• Leg crossing (peroneal neuropathy)
• Obesity (meralgia paresthetica)
• Surgery or hip replacement
• Tumors (especially for plexopathy)

Exam

General Assessment

• Gait assessment (look for foot drop, limp)
• Lumbar range of motion
• Straight leg raise test (radiculopathy)
• Lower extremity strength testing by myotome
• Sensory examination by dermatome
• Deep tendon reflexes (patellar L3-4, Achilles S1)

Key Muscle Groups by Root

• L2-L3: Hip flexors (Iliopsoas)
• L3-L4: Knee extensors (Quadriceps)
• L4: Ankle dorsiflexion (Tibialis Anterior)
• L5: Great toe extension (EHL), Hip abduction
• S1: Ankle plantarflexion (Gastrocnemius), Knee flexion

Specific Tests

• Tinel’s sign at fibular head (peroneal)
• Tinel’s sign behind medial malleolus (tarsal tunnel)
• Palpation over lateral thigh (meralgia paresthetica)

EMG

EMG is essential for localization and determining severity.

For Lumbar Radiculopathy

• Paraspinal muscle involvement helps confirm root level
• Look for denervation in muscles from same root but different peripheral nerves
• Sensory nerve studies normal (lesion proximal to dorsal root ganglion)
• H-reflex may be prolonged or absent in S1 radiculopathy

For Lumbosacral Plexopathy

• Abnormalities span multiple nerve territories
• Sensory potentials affected (lesion distal to DRG)
• Paraspinal muscles spared
• Localize to lumbar or sacral plexus

For Peripheral Entrapments

• Focal slowing or conduction block at entrapment site
• Denervation limited to muscles distal to lesion
• Compare side-to-side

Findings by Condition

Condition	Motor NCS	Sensory NCS	Needle EMG
Radiculopathy	Usually normal	Normal	Denervation in myotome + paraspinals
Plexopathy	Abnormal	Abnormal	Denervation across plexus distribution
Peroneal neuropathy	Focal slowing at fibula	May be abnormal	Denervation in peroneal muscles

Recommendations

Lumbar Radiculopathy

• Conservative treatment initially (physical therapy, NSAIDs)
• Activity modification, proper lifting mechanics
• Epidural steroid injections
• Surgery for severe weakness, cauda equina syndrome, or failed conservative treatment

Lumbosacral Plexopathy

• Treat underlying cause (glucose control for diabetic amyotrophy)
• Physical therapy
• Pain management
• Prognosis depends on etiology

Peripheral Entrapments

• Activity modification (stop leg crossing for peroneal)
• Weight loss (meralgia paresthetica)
• AFO brace for foot drop
• Surgical release for severe or progressive cases

What else could it be?

• Motor Neuron Disease (ALS): if weakness without sensory loss in multiple regions
• Peripheral Neuropathy: if bilateral and symmetric, length-dependent
• Cauda Equina Syndrome: if bowel/bladder involvement - surgical emergency
• Myopathy: proximal weakness, elevated CK
• Hip Pathology: for groin and thigh pain
• Vascular Claudication: leg pain with walking, relieved by standing still
• Neurogenic Claudication: leg pain with walking, relieved by sitting or bending forward