Peripheral Nerve Disorders

Question 1

Carpal Tunnel Syndrome

Answer 1

• Definition:
  
  • median nerve entrapment & compression at the carpal tunnel
• Risks:
  
  • women, DM, pregnancy, hypothyroidism, RA, occupations with repetitive extension & flexion of the wrist (typing)
• S/sxs:
  
  • Paresthesias or pain of the palmar aspect of the 1st 3 digits % radial aspect of the 4th digit
  • -Nighttimewaking d/t pain
• PE:
  
  • Tinel test: percussion (Tapping) of median nerve reproduces sxs
  • Phalen test: flexion (Phlat against each other) of both wrists for 30-60 seconds reproduces sxs
  • -Atrophy (if advanced)
• Dx:
  
  • Nerve conduction velocity
• Tx:
  
  • Conservative: night splint, NSAIDs, avoid repetitive wrist movements
  • -Corticosteroid injections
  • -Refractory: carpal tunnel surgery

Question 2

Complex Regional Pain Syndrome

Answer 2

• Definition:
  
  • chronic neurological condition resulting from a traumatic injury. Unknown pathogenesis. Involves a body region (most of often the distal limbs)
• Subtypes:
  
  • CRPS Type I: absence of major nerve injury
  • -CRPS Type II: presence of major nerve injury
• Risks:
  
  • female, Upper extremity injury, high-energy trauma.
• S/sxs:
  
  • Pain that is:
  • -burning, tearing, or stinging
  • -Continuous
  • -Regional (not in one dermatome or nerve)
  • -Usually distal
  • -Out of proportion in time or intensity
  • -Variably progressive & often worse at night
• PE:
  
  • hyperalgesia
  • Autonomic: differences in skin temp, color, sweat or edema
• Dx:
  
  • Budapest Criteria for Dx:
    
    • -Continuing pain which is disproportionate to any inciting event AND at least 1 symptom in ¾ categories: sensory, vasomotor, sudomotor/edema, motor/trophic
• Tx:
  
  • -PT & OT
  • -Psychosocial assessment
  • -Symptomatic pain management: NSAIDs, gabapentin, pregabalin, or a TCA; topical lidocaine or capsaicin cream
  • -Bisphosphonates in pts with abnormal bone uptake on scan

Question 3

Guillain-Barre Syndrome

Answer 3

• Definition:
  
  • acquired autoimmune demyelinating polyradiculopathy of the peripheral nervous system
• Pathophys:
  
  • autoantibody attacks the myelin sheath of the peripheral nerves after an infection; two subtypes: 1. demyelination that interferes with nerve conduction & 2. direct attack on axon that blocks nerve conduction
• Etiology:
  
  • Onset of sxs 1-3 weeks post infection; Campylobacter jejuni, Epstein barr virus, cytomegalovirus, HIV, hepatitis E, Zika, Mycoplasma pneumoniae, COVID-19, trauma, surgery, bone marrow transplant, vax
• Epidemiology:
  
  • ~5000 cases/year in the US, M>F, adults > children
• S/sxs:
  
  • *Acute, rapidly evolving
  • -Progressive ascending motor paralysis: weakness, paresthesias, pain (legs affected more than arms)
  • -Areflexic (absent or depressed DTRs)
  • -Back & extremity pain
  • -Facial nerve palsies
  • -Oropharyngeal weakness
  • -Autonomic dysfunction: bradycardia or tachycardia, hyponatremia, GI sxs, urinary retention, reversible cardiomyopathy +/- sensory deficits
• PE:
  
  • 50% of cases involve the lower CNs → bulbar weakness (swallow), facial paralysis, difficulty managing secretions & problems maintaining an airway
• Dx:
  
  • CSF analysis: albuminocytologic dissociation (very high protein) with normal WBC
  • -EMG: acute polyneuropathy or axonal dysfunction
  • -Spinal MRI: thickening of spinal nerve root
  • -Antibody testing: useful in diagnosing Miller Fisher variant
• Tx:
  
  • *Supportive Care
  • -Hospitalization: symptoms can progress & worsen rapidly
  • -Respiratory failure requires intubation & mechanical ventilation
  • -Management of autonomic dysfunction & CV involvement
  • -Pain medication
  • -Bladder & bowel care
  • -DVT prevention
  • -Disease-modifying tx: IV immune globulin (IVIG), plasmapheresis
  • -May need PT & rehab afterwards to regain strength

Question 4

Peripheral Neuropathy

Answer 4

• Definition:
  
  • injury to nerves
• Pathophys:
  
  • large nerve fibers mediate motor, sensory, vibration & proprioception; small nerve fibers mediate pain, temperature & autonomic functions.
• Etiologies:
  
  • DM, nerve compression or injury, alcohol use, toxin exposure, hereditary disease, nutritional deficiencies
• S/sxs:
  
  • Symmetrical distal numbness, tingling, pain, & burning sensation in a “stocking & glove” pattern
  • -Later stages: proximal numbness, weakness, and atrophy
• PE:
  
  • Neuro: CN, fundoscopy, reflexes, symmetry of sensation & motor strength, 128 Hz tuning fork, monofilament testing
  • -Assess muscle bulk & tone
• Dx:
  
  • R/o CNS involvement before making dx of peripheral neuropathy
  • -CBC
  • -CMP with fasting BG
  • -TSH
  • -Vitamin B12 levels
  • -serum protein electrophoresis
  • -Imaging not usually done
• Tx:
  
  • Non-pharmacologic: good foot hygiene & wearing appropriate footwear, weight loss, PT, gait training
  • -Pharmacologic: Gabapentinoids (gabapentin, pregabalin), Antidepressants (amitriptyline, nortriptyline, venlafaxine, duloxetine, bupropion), topical meds (capsaicin, lidocaine)
  • -Opioids NOT RECOMMENDED

Question 5

Erb-Duchenne Palsy

Answer 5

• Definition:
  
  • obstetric brachial plexus palsy due to injury at birth (C5 & C6 nerve roots)
• Pathophys:
  
  • loss of the lateral rotators of the shoulder, arm flexors, and hand extensors
• S/sxs:
  
  • Arm will hang by side and be medially rotated
  • -Forearm extended & pronated
  • -Wrist in flexion

Question 6

Klumpke’s Palsy

Answer 6

• Definition:
  
  • low brachial plexus injury that results from stretching/hyperextension injury of the arm or pulling on arm during birth (C8 & T1 nerve roots).
• S/sxs:
  
  • “Claw hand”
  • -loss of sensation along C8 dermatome
  • -Ptosis (rare)