9.3 Diagnosis: Peripheral Neurologic and Neurovascular Disorders

Peripheral Neurologic and Neurovascular Disorders

Peripheral neurologic disorders account for a large share of NBCE Part II NMS diagnosis items because they overlap directly with chiropractic practice — cervical and lumbar radiculopathy, upper-extremity entrapment neuropathies, and thoracic outlet complaints are daily clinical presentations. Success on the exam requires separating root-level (radicular) from nerve-level (peripheral) pathology, recognizing acute emergencies like Guillain-Barré syndrome (GBS), and knowing when neurovascular compression rather than disc disease explains the symptom pattern.

Radiculopathy vs Peripheral Neuropathy

Cervical radiculopathy most commonly affects C6 (biceps/reflex loss, thumb/index numbness) and C7 (triceps reflex loss, middle finger numbness). Lumbar radiculopathy at L5 produces foot drop (extensor hallucis longus weakness) with dorsum-of-foot numbness; S1 radiculopathy weakens plantar flexion with absent Achilles reflex and lateral foot numbness.

Upper Extremity Entrapment Neuropathies

Carpal Tunnel Syndrome (CTS)

Median nerve compression at the wrist beneath the transverse carpal ligament is the most common entrapment neuropathy.

Symptoms: Nocturnal paresthesias in the thumb, index, middle, and radial half of ring finger; thenar weakness and atrophy in chronic cases. The palmar cutaneous branch arises proximal to the carpal tunnel, so sensation over the thenar eminence is typically spared — a key distinguishing feature from proximal median neuropathy.

Diabetes, pregnancy, hypothyroidism, and repetitive hand use are common risk factors. Electrodiagnostic studies (nerve conduction velocity, EMG) confirm severity when surgical release is considered.

Cubital Tunnel Syndrome

Ulnar nerve compression at the elbow (cubital tunnel) produces paresthesias in the fourth and fifth digits, weakness of interossei and adductor pollicis (Froment sign — thumb IP flexion during pinch), and clawing of the ulnar digits in chronic cases. Tinel sign at the elbow and exacerbation with sustained elbow flexion are clinical clues.

Radial Neuropathy (Saturday Night Palsy)

Compression of the radial nerve in the spiral groove (prolonged arm compression during sleep or intoxication) causes wrist drop, weak finger extension, and sensory loss over the dorsal first web space — without triceps weakness if the lesion is distal to the spiral groove.

Pronator Teres Syndrome vs Anterior Interosseous Nerve (AIN)

Both are proximal median nerve variants. Pronator teres syndrome mimics CTS with forearm pain and median sensory symptoms but may involve palmar cutaneous branch territory. AIN syndrome is primarily motor — inability to make the "OK" sign (flexor pollicis longus and flexor digitorum profundus to index finger) with minimal sensory loss.

Lower Extremity and Lumbosacral Peripheral Nerve Lesions

Common Peroneal (Fibular) Neuropathy

The common peroneal nerve wraps around the fibular head — vulnerable to compression from crossing legs, casting, or prolonged bed rest. It produces foot drop (weak dorsiflexion and eversion), steppage gait, and sensory loss over the anterolateral leg and dorsum of foot. Reflexes: ankle jerk preserved (tibial component) unless combined root involvement.

Distinguish from L5 radiculopathy: L5 root adds hip abduction weakness (gluteus medius) and may affect the Achilles reflex if S1 co-involvement; isolated peroneal neuropathy does not weaken hip abductors.

Meralgia Paresthetica

Compression of the lateral femoral cutaneous nerve under the inguinal ligament causes burning numbness over the anterolateral thigh without motor weakness — pure sensory mononeuropathy, often in obesity, pregnancy, or tight belts.

Tarsal Tunnel Syndrome

Posterior tibial nerve compression at the medial ankle causes plantar foot paresthesias; less common than CTS but tested as a plantar analog.

Guillain-Barré Syndrome (GBS)

Guillain-Barré syndrome is an acute immune-mediated polyradiculoneuropathy, often following Campylobacter jejuni gastroenteritis, cytomegalovirus, or recent vaccination/surgery by one to three weeks.

Classic presentation:

• Ascending symmetric weakness starting in the legs
• Areflexia or hyporeflexia (LMN pattern)
• Mild sensory symptoms (back pain common)
• Respiratory failure risk from diaphragmatic weakness — monitor vital capacity

Miller Fisher variant: ophthalmoplegia, ataxia, areflexia — associated with anti-GQ1b antibodies.

GBS is a medical emergency. Chiropractic manipulation is contraindicated during acute progression. Plasmapheresis and IV immunoglobulin are standard treatments.

Chronic inflammatory demyelinating polyneuropathy (CIDP) resembles GBS but progresses or relapses over more than eight weeks.

Diabetic and Other Polyneuropathies

Diabetic peripheral neuropathy is the most common polyneuropathy: symmetric distal numbness, burning pain, ankle reflex loss, and ulcer risk from unrecognized trauma. Monofilament testing at standard plantar sites screens for loss of protective sensation.

Other causes tested on boards: alcohol-related (thiamine deficiency), B12 deficiency (subacute combined degeneration — proprioception loss + UMN signs), chemotherapy-induced, and uremic neuropathy in renal failure.

Complex Regional Pain Syndrome (CRPS)

CRPS (types I and II) follows injury or surgery with pain disproportionate to the inciting event. Budapest clinical criteria require continuing pain plus at least one symptom and one sign in three of four categories: sensory, vasomotor (temperature/color asymmetry), sudomotor/edema, and motor/trophic (weakness, hair/nail changes).

CRPS is not explained by a single nerve entrapment; early graded motor imagery, physical therapy, and pain management improve outcomes. Long-term opioids are discouraged.

Neurovascular Compression Syndromes

Thoracic Outlet Syndrome (TOS)

Compression of the brachial plexus and/or subclavian vessels between the scalenes and first rib or at the pectoralis minor produces:

• Neurogenic TOS (most common): medial arm and ulnar hand paresthesias, hand intrinsic weakness, symptoms worsened by overhead activity
• Vascular TOS (rare): arm pallor, coolness, pulse deficit, thrombosis (Paget-Schroetter in effort thrombosis)

Cervical rib or anomalous first rib may be present on imaging. Differentiate from C8–T1 radiculopathy with Spurling test, reflex examination, and vascular assessment.

Raynaud Phenomenon

Raynaud phenomenon is episodic digital vasospasm triggered by cold or stress: triphasic color change (white → blue → red) with numbness or pain. Primary Raynaud is benign; secondary Raynaud associates with connective tissue disease (scleroderma, lupus) and may cause digital ulcers.

Compartment Syndrome (Acute Recognition)

Acute compartment syndrome after fracture or crush injury produces severe pain out of proportion, pain with passive stretch, tense compartments, and pallor/pulselessness late. This is a surgical emergency (fasciotomy) — not a chiropractic presentation, but board vignettes test recognition.

Clinical Integration for Chiropractic Practice

When a patient presents with extremity paresthesias, work through a structured differential:

1. Map the symptoms — dermatomal (root) vs nerve territory (entrapment) vs stocking-glove (polyneuropathy).
2. Examine reflexes and strength — segmental pattern vs distal symmetric loss.
3. Perform appropriate provocative tests — Spurling, SLR, Phalen, Tinel, Adson — and document bilateral comparison.
4. Screen for red flags — progressive weakness, bilateral symptoms, bowel/bladder change, fever, acute ascending paralysis (GBS), or vascular compromise.
5. Refer for electrodiagnostics or imaging when surgical candidates, progressive deficits, or diagnostic uncertainty exist.

Conservative chiropractic care — manipulation, mobilization, nerve gliding, ergonomics — is appropriate for many entrapment and radicular conditions when red flags are absent and progression is not rapid. Document neurologic baselines so worsening triggers timely referral.