Entrapment Neuropathies: Causes and Etiology

10 Questions

What is the primary cause of entrapment neuropathies?

Compression and/or irritation of peripheral nerves

What is the consequence of prolonged ischemia in entrapment neuropathies?

Demyelination and axon degeneration

What is the result of extraneural pressures on intraneural venous circulation?

Disruption of intraneural venous circulation

Which of the following is a complication of entrapment neuropathies?

Focal demyelination

What is the role of neuroinflammation in entrapment neuropathies?

Contributing to neuropathic pain

Which of the following nerve entrapments is most commonly associated with foot drop?

Common Peroneal Nerve Entrapment

What is the primary purpose of anesthetics in diagnosing nerve entrapment?

To confirm symptoms by temporarily relieving compression

Which of the following is a common symptom of chronic nerve entrapment?

Muscle weakness and wasting

What is the primary role of electrodiagnostic testing in diagnosing nerve entrapment?

To diagnose nerve entrapment, although early normal results do not rule out compressive neuropathy

Which of the following types of nerve entrapment affects the supraspinatus fossa?

Suprascapular Nerve Entrapment

Study Notes

Entrapment Neuropathies

Caused by compression and/or irritation of peripheral nerves as they travel through narrow anatomical spaces
Common causes include: repetitive motion, inflammation, anatomical abnormalities, prior fractures or dislocations, scar tissue or myofascial tension, bone spurs, arthritis, swelling, edema, cysts, repetitive or prolonged activities, and systemic conditions like diabetes

Pathophysiology

Ischaemia, Oedema & Intraneural Fibrosis: mild entrapment neuropathies cause intraneural ischemia, disrupting intraneural venous circulation
Demyelination & Axon Degeneration: prolonged ischemia causes demyelination and axon degeneration, affecting large myelinated fibers
Neuroinflammation: activation of immune cells releases inflammatory mediators, contributing to neuropathic pain
Changes to Axonal Transport: compression and inflammation impair retrograde and anterograde axonal transport, increasing nerve mechanosensitivity
Central Nervous System Contributions: peripheral nerve injuries can cause central changes, including bilateral sensory deficits, widespread hypersensitivity, and impaired pain modulation

Clinical Symptoms

Sensory abnormalities, pain, paresthesia, and motor paralysis
Localized or referred pain, numbness, tingling, electric shock sensation
Muscle weakness and wasting, dry, thin skin in chronic cases

Common Types of Nerve Entrapments

Carpal Tunnel Syndrome (CTS): affects the median nerve
Cubital Tunnel Syndrome: affects the ulnar nerve
Thoracic Outlet Syndrome (TOS): affects the lower trunk
Suprascapular Nerve Entrapment: affects the supraspinatus fossa
Axillary Nerve Entrapment: affects the quadrilateral space
Radial Nerve Entrapments: includes PIN syndrome, radial tunnel syndrome, and Wartenberg’s syndrome
Sciatic Neuropathy: can result from various conditions like piriformis syndrome
Common Peroneal Nerve Entrapment: causes foot drop
Tibial Nerve Entrapment: includes tarsal tunnel syndrome
Interdigital Neuroma (Morton's Neuroma): affects the interdigital nerves

Diagnosis

Visual Inspections: focus on limb asymmetry, muscular atrophy, and abnormal posture
Palpation: attempt to reproduce symptoms by pressing or scratching the affected area
Nerve Tension Tests: Straight Leg Raise (SLR), Slump Test, Neural Thomas Test, Upper Limb Tension Tests (ULTT)
Anesthetics and Electrodiagnostic Testing: local anesthetic administration can confirm symptoms, and electrodiagnostic testing (EDS) helps diagnose nerve entrapment
Imaging and Nerve Conduction Studies: MRI and ultrasound provide detailed anatomical information, and nerve conduction studies help diagnose distal neuropathy