Peripheral nerve syndromes

Background

Nerves of the left upper extremity.

• Also known as "mononeuropathies" (i.e., conditions in which a single nerve is damaged or compressed).

Cervical Exam by Level

Radiculopathy	Motor Deficit	Sensory Deficit	Diminished Reflex
C4	Levator Scapulae & Shoulder elevation
C5	Deltoid & Biceps		Biceps
C6	Brachioradialis & Wrist extension	Thumb Paresthesia	Brachioradialis
C7	Triceps & Wrist flexion	Index/Middle/Ring Paresthesia	Triceps
C8	Index/Middle distal phlnx flexion	Small Finger Paresthesia

Clinical Features

Cutaneous innervation of the upper limb

Lower limb peripheral innervation

Peripheral nerve syndromes

• Upper extremity
  • Ulnar
    • Cause of Injury: Elbow injury.
    • Sensory changes in the 5th and medial half of 4th digits, weak wrist flexors, “claw hand”
  • Radial
    • Cause of Injury: Distal humeral shaft fracture, anterior shoulder dislocation, supra-condylar fracture, Radial neuropathy at the spiral groove, Posterior interosseous neuropathy
    • “Wrist drop,” weakness of finger extensors. +/- sensory loss over the dorsum of the hand, weak thumb adduction
  • Median, distal
    • Cause of Injury: Wrist dislocation, laceration, Carpal Tunnel Syndrome
    • Weak flexion of radial half of digits and thumb, loss of abduction and opposition of thumb. Ape hand deformity, benediction sign. Loss of sensation of lateral three and one-half digits and nail beds
  • Median, proximal
    • Cause of Injury: Supracondylar humeral fracture, Pronator teres syndrome, Anterior interosseous neuropathy, tight cast
    • See Median, distal above, loss of forearm pronation, loss of radial half digits and thumb flexion
  • Musculocutaneous
    • Cause of Injury: Anterior shoulder dislocation, entrapment due to hypertrophy
    • Elbow flexion and supination weakness, radial forearm sensory deficits
  • Axillary
    • Cause of Injury: Anterior shoulder dislocation, inferior shoulder dislocation, proximal humerus fracture
    • Weak arm abduction (from 15 to 90 degrees), weak shoulder flexion, extension and rotation of shoulder, loss of sensation of upper lateral arm
  • Suprascapular
    • Cause of Injury: Paralabral cyst, bone/soft tissue tumor, Scapular fracture, traction injury, Parsonage-Turner syndrome
    • Weak arm abduction to 90 degrees, weak shoulder flexion to 30 degrees, weak internal rotation
• Lower extremity
  • Femoral
    • Cause of Injury: Pubic rami fracture, pelvic fractures
    • Weak knee extension, anterior knee sensory deficits
  • Obturator
    • Cause of Injury: Obturator ring fracture, obturator nerve entrapment
    • Weak hip adduction, medial thigh sensory deficit
  • Posterior tibial
    • Cause of Injury: Knee dislocation
    • Weak toe flexion, plantar foot sensory deficit
  • Superficial peroneal
    • Cause of Injury: Fibular neck fracture, knee dislocation
    • Weak ankle eversion, lateral dorsal foot sensory deficits
  • Deep peroneal
    • Cause of Injury: Fibular neck fracture, compartment syndrome
    • Sensory deficit at dorsal 1st web space, weak ankle and toe dorsiflexion
  • Sciatic
    • Cause of Injury: Posterior hip dislocation
    • Lower leg weakness, foot drop, leg sensory deficits
  • Superior gluteal
    • Cause of Injury: Acetabular pelvic fracture
    • Trendelenburg’s gait, Trendelenburg’s sign
  • Inferior gluteal
    • Cause of Injury: Acetabular pelvic fracture, s/p hip replacement
    • Abnormal gait, gluteus maximus weakness resulting in gluteus maximus lurch

Differential Diagnosis

Nerve roots that supply sensation to the upper extremities.

Upper extremity peripheral nerve syndromes

Median Nerve Syndromes

• Carpal tunnel syndrome
• Pronator teres syndrome
• Anterior interosseous neuropathy

Ulnar Nerve Syndromes

• Ulnar neuropathy

Radial Nerve Syndromes

• Radial neuropathy at the spiral groove (ie. "Saturday night palsy")
• Posterior interosseous neuropathy

Proximal Neuropathies

• Suprascapular neuropathy
• Long thoracic neuropathy
• Axillary neuropathy
• Spinal accessory neuropathy
• Musculocutaneous neuropathy

Other

• Brachial plexopathy
  • Parsonage-Turner syndrome
• Cervical radiculopathy

Peripheral neuropathy

• Peripheral nerve syndromes (mononeuropathy)^
  • Acute trauma
  • Chronic nerve entrapment
• Mononeuritis multiplex^^
  • Acute
    • Diabetes mellitus
    • Polyarteritis nodosum
    • Connective tissue diseases (e.g., SLE, rheumatoid arthritis)
  • Chronic
    • Multiple compressive neuropathies
    • AIDS
    • Sarcoidosis
    • Acromegaly
    • Leprosy
    • Lyme disease
    • Idiopathic
• Associated with autonomic features
  • Alcohol use disorder
  • Amyloidosis
  • Chemotherapy-related neuropathy
  • Diabetes mellitus
  • Heavy metal toxicity
  • Porphyria
  • Primary dysautonomia
  • Vitamin B12 deficiency
• Associated with pain
  • Alcohol use disorder
  • Amyloidosis
  • Chemotherapy (heavy metal toxicity)
  • Diabetes mellitus
  • Idiopathic polyneuropathy
  • Porphyria
  • Paraneoplastic syndrome
  • Vitamin B1 or B12 deficiency
  • Arsenic toxicity
  • Thallium toxicity

^A condition in which a single nerve is damaged or compressed.
^^A condition where damage to at least two separate peripheral nerves results in a painful, asymmetric, and asynchronous presentation of sensory and motor deficits.

Extremity trauma

• Compartment syndrome
• Contusion
• Crush syndrome
• Degloving injury
  • Morel-Lavallée lesion
  • Ring avulsion injury
• Fracture
  • Open fracture
• Laceration
• Myositis ossificans
• Open joint injury
• Peripheral nerve injury
• Rhabdomyolysis
• Tendon injury
• Vascular injury

Evaluation

• Neurologic exam with focus on sensory component

See Also

• Weakness
• Focal neurologic signs