Case 5: Carmen Shellinger - Hand Pain/Numbness

Peripheral Nerves: Layers

Endoneurium

Perineurium

Epineurium

Peripheral Nerves: Endoneurium

Inner layer

Thin

Connective tissue around 1 nerve fibre

Peripheral Nerves: Perineurium

Middle layer

Connective tissue around nerve fascicles (bundle of fibres)

Contain blood-nerve barrier

Peripheral Nerves: Epineurium

Outer layer

Dense connective tissue around nerve

Contain:

• Nerve fascicles

• Blood vessels

Peripheral Nerves: Parts

Soma

Axon

Dendrites

Myelin sheath

Peripheral Nerves: Soma

Cell body

Contain:

• Nucleus + organelles

• Nissl Substance: Produced by rough ER proteins

• Cytoskeleton: Microfilaments

Peripheral Nerves: Axon

Projection from soma

Conduct AP

• From axon hillock (connection to soma) → Synapse

Contain:

• Cytoskeleton: Microtubules

  • Transport cargo (organelles, proteins)

  • Kinesine: Anterograde transport (- → +)

  • Dynein: Retrograde transport (+ → -)

• Neurofilaments: Structural support

Peripheral Nerves: Dendrites

Branching projections from soma

Receive input from other neurons

• Transmit to cell body

Contain:

• Spines: Increase synapses to other neurons

• Nissl substance

• Cytoskeleton: Microfilaments

Peripheral Nerves: Myelin Sheath

Lipid-rich insulating layer around axons

Increase signal conduction velocity

Produced by Schwann cells

• 1 cell/internodal segment in 1 axon

• Phagocytose debris after injury + promote injury repair (guide nerve regeneration)

Nodes of Ranvier: Signal conduction

Myelin Sheath: Nodes of Ranvier

Unmyelinated regions between myelinated segments

Increased Na+ channels = Saltatory conduction

• Gaps in myelin = Signal jump between gaps = Increase AP velocity

Approach to Hand Pain + Numbness: DDX

Nerve entrapment

Ulnar:

• Cubital tunnel syndrome: At elbow

• Guyon canal syndrome: At wrist

Median:

• Carpal tunnel syndrome

Radial:

• Elbow: Radial tunnel syndrome

• Deep: Forearm

• Superficial: Forearm + wrist

Ulnar Nerve Entrapment: Clinical Presentation

Ulnar claw: Clawed digits 4 + 5

Tinel sign: Tapping humerus medial epicondyle = Paresthesias in digits 4 + 5

Cubital Tunnel + Guyon Canal Syndrome:

• Motor: Muscle atrophy + weakness

  • Decreased dexterity + grip strength

  • Difficulty lifting

• Sensory: Paresthesias + sensory loss of…

  • Medial hand

  • Digit 5

  • Ulnar side of ring finger

Median Nerve Entrapment: Clinical Presentation

Bottle sign: Cannot hold cylindrical object

Tinel’s sign: Tapping over carpal tunnel = Paresthesias in thumb + digits 2,3,4

Phalens’s sign: Flex wrists (press back of hands together) = Paresthesias in thumb + digits 2,3,4

Carpal Tunnel Syndrome:

• Motor:

  • Impaired digits 1,2,3 flexion

  • Thenar muscle atrophy

• Sensory: Paresthesias + sensory loss of…

  • Thumb

  • Digits 2 + 3

  • Radial side of ring finger

Radial Nerve Entrapment: Clinical Presentation

Radial Tunnel Syndrome:

• Motor: Weakness during extension + supination

• Sensory: Pain + tenderness from…

  • Extension

  • Repeated pronation/supination

Deep:

• Motor: Finger extensor paralysis

• Sensory: None

Superficial:

• Motor: None

• Sensory: Paresthesias + loss of sensation of radial hand dorsum

Nerve Entrapment: Investigations

Sensation exam

Nerve conduction study

EMG

Nerve Entrapment Investigations: Sensation Exam

Follow dermatomes

Tactile

• Sharp/pain: Spinothalamic

• Dull: Dorsal

• Light touch: Dorsal

Pallesthesia (vibration): Dorsal

Proprioception: Dorsal + spinocerebellar

Temperature: Spinothalamic

Nerve Entrapment: Treatment

Conservative therapy

Surgery

Nerve Entrapment Treatment: Conservative Therapy

Physical therapy + exercise

Analgesics

• NSAIDs

• Glucocorticoid injections

Immobilization

• Night brace

Nerve Entrapment Treatment: Surgery

Decompression

Indications:

• Severe + persistent symptoms

• Worsening symptoms with conservative therapy

Nerve Entrapment: Complications

Nerve trauma

Seddon Classification:

• Neurapraxia: Transient function block

  • Local demyelination

  • No anatomical damage

• Axonotmesis: Axon + myelin sheath disruption

  • Intact connective tissue layers

• Neurotmesis: Complete nerve axon, myelin, and connective tissue layers disruption

Nerve Trauma: Clinical Presentation

Sensory loss

• Numbness

• Paresthesias

• Tingling

• Loss of sensation

• Neuropathic pain

Motor loss

• Muscle weakness + atrophy

• Fasciculations

• Loss of tendon reflexes

Autonomic dysfunction

• Sweating abnormalities

• Orthostatic hypotension

• Bowel/bladder dysfunction

• Dry eyes + mouth