CN - Upper limb mononeuropathies Flashcards
What are upper limb mononeuropathies?
Conditions in which a single nerve is affected, leading to dysfunction in the corresponding muscle(s) or sensory areas.
Describe a median nerve mononeuropathy
Common Cause: Carpal tunnel syndrome, compression at the wrist, or trauma to the forearm.
Motor Symptoms: Weakness or atrophy of the thenar eminence (muscles at the base of the thumb), causing difficulty with thumb opposition and grasping (i.e., “ape hand”).
Sensory Symptoms: Numbness or tingling in the palmar surface of the thumb, index, middle, and part of the ring fingers, often worse at night.
Test: Positive Tinel’s sign (tapping over the median nerve at the wrist causes tingling) and Phalen’s maneuver (wrist flexion for 30–60 seconds causes symptoms).
Describe an ulnar nerve mononeuropathy
Common Cause: Compression at the elbow (cubital tunnel syndrome) or at the wrist (Guyon’s canal syndrome).
Motor Symptoms: Weakness or atrophy of the hypothenar eminence, interossei muscles, and lumbricals, leading to difficulty with fine motor tasks, such as gripping, and problems with finger abduction/adduction (e.g., claw hand deformity).
Sensory Symptoms: Numbness or tingling in the pinky and half of the ring finger.
Test: Positive Tinel’s sign at the elbow or wrist, and Froment’s sign (a pinch test that demonstrates weakness in the adductor pollicis muscle).
Describe a radial nerve mononeuropathy
Common Cause: Compression or injury (e.g., “Saturday night palsy,” where the arm is draped over a chair or the use of crutches).
Motor Symptoms: Weakness of the extensor muscles of the wrist and fingers, leading to wrist drop (inability to extend the wrist and fingers).
Sensory Symptoms: Numbness or tingling along the dorsal surface of the forearm, hand, and thumb.
Test: Wrist drop is often observed, and tapping over the radial nerve may reproduce symptoms.
Describe an axillary nerve mononeuropathy
Common Cause: Dislocations of the shoulder, trauma, or compression from prolonged pressure (e.g., from crutches).
Motor Symptoms: Weakness of the deltoid muscle, which results in difficulty with shoulder abduction (raising the arm).
Sensory Symptoms: Numbness or tingling over the lateral shoulder (also known as the “regimental badge” area).
Test: Difficulty with shoulder abduction and weakness of the deltoid on examination.
Describe a musculocutaneous nerve mononeuropathy
Common Cause: Rare, but can be due to trauma or compression.
Motor Symptoms: Weakness of the biceps and brachialis muscles, causing difficulty with elbow flexion.
Sensory Symptoms: Numbness or tingling along the lateral forearm.
Test: Weakness with elbow flexion and forearm supination.
Describe a long thoracic nerve mononeuropathy
Common Cause: Trauma, repetitive motion, or viral infection.
Motor Symptoms: Weakness of the serratus anterior muscle, leading to winged scapula, where the scapula protrudes from the back, particularly when pushing against a wall or raising the arm.
Sensory Symptoms: Usually none, as the long thoracic nerve is a motor nerve.
Test: Winged scapula is the characteristic sign, often revealed when the patient presses against a wall.
Describe a spinal accessory nerve mononeuropathy
Common Cause: Surgical injury (e.g., neck surgeries), trauma, or compression.
Motor Symptoms: Weakness or atrophy of the trapezius and sternocleidomastoid muscles, resulting in difficulty elevating the shoulder (shoulder shrug) and turning the head.
Sensory Symptoms: None.
Test: Difficulty with shoulder shrugging, weakness in head turning.
