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Neuropathy

Nicholas Mallett

Background

  • Peripheral neuropathy is damage to peripheral nerves. Classical polyneuropathy is slow, chronic, progressive sensory loss in length-dependent fashion

  • Common etiologies of polyneuropathy: Diabetes, chronic EtOH use, Vitamin Deficiencies/Toxicities, chronic HIV/HBV/HCV, Amyloidosis, Monoclonal Gammopathies, Hypothyroidism, autoimmune, Medication, and Critical Illness

  • Mononeuropathy: sensory ± motor symptoms in single peripheral nerve distribution (ie carpel tunnel). Can be from local trauma, compression, entrapment

  • Radiculopathy is from spine nerve root localization (ie L4), polyradiculopathy if multiple, plexopathy is process affecting multiple nerves in brachial or lumbosacral plexus

  • Large Fiber Neuropathy: loss of vibration sense/proprioception

  • Small Fiber Neuropathy: loss of pain/temperature sensation – cannot be dx by EMG/NCS!

Evaluation

  • Usually diagnosed clinically based on examination and history

  • Polyneuropathy presents with slow, progressive sensory loss in the classic “stocking and glove” distribution, usually beginning in the lower extremities.

  • Many patients don’t realize numbness until very symptomatic (can’t feel car pedals, burning pain, gait disturbances, etc). Can have +Romberg, falls in dark due to poor proprioception

  • Reduced reflexes on examination

  • In cases where exam is not sufficient, EMG/NCS can aid in diagnosis

  • Important to determine etiology behind neuropathy to attempt to stop/slow progression

  • Basic lab work: A1c, B12 (<400 can cause symptoms), SPEP+IFE

Management

  • No treatment to reverse numbness, aim to treat pain if needed

  • Address underlying etiology to prevent progression

  • If rapidly progressive, consider referral to Neurology for evaluation

  • Neuropathic pain management

  • Gabapentin/Pregabalin – PROS: antiseizure benefits, headache treatment; CONS: dizziness, drowsiness -
  • Duloxetine – PROS: anxiety/depression effect, migraine prophylaxis; CONS: risk of Serotonin Syndrome/Mania
  • Amitriptyline – PROS: depression treatment, headache prophylaxis; CONS: anticholinergic effects
  • Alpha Lipoic Acid – relatively benign OTC supplement with antioxidant properties shown to reduce nerve hypoxia with diabetic neuropathy
  • Topicals: Lidocaine, Capsaicin
  • DO NOT PRESCRIBE OPIOIDS FOR NEUROPATHIC PAIN AS THEY HAVE LITTLE BENEFIT