Definition and Overview
Peripheral neuropathy refers to damage to peripheral nerves causing numbness, tingling, weakness, and pain, most commonly in a length-dependent (stocking-glove) distribution. It affects approximately 2-7% of the general population and up to 50% of diabetic patients [1].
Causes
- Diabetes mellitus: accounts for approximately 30% of all neuropathy (most common identifiable cause)
- Idiopathic: 20-30% have no identifiable cause
- Nutritional: B12 deficiency, B1 deficiency, folate deficiency
- Toxic: alcohol, chemotherapy (vincristine, cisplatin, taxanes)
- Autoimmune: GBS, CIDP, vasculitic neuropathy
- Hereditary: Charcot-Marie-Tooth disease
- Infectious: HIV, hepatitis C, leprosy
Classification
By fiber type: large fiber (numbness, imbalance, weakness), small fiber (burning pain, temperature sensitivity, autonomic symptoms), or mixed [2].
By pathology: axonal (most common) vs demyelinating. By distribution: length-dependent (distal symmetric) vs non-length-dependent (multifocal, asymmetric).
Symptoms
Sensory: numbness, tingling, burning pain, pins-and-needles sensation starting in the feet and ascending. "Stocking-glove" distribution is characteristic [3].
Motor: distal weakness, foot drop, difficulty with fine motor tasks.
Autonomic: orthostatic hypotension, gastroparesis, bladder dysfunction, sweating abnormalities, erectile dysfunction.
Diagnosis
NCS/EMG: differentiates axonal from demyelinating neuropathy and assesses severity [4]. Blood tests: glucose/HbA1c, B12, methylmalonic acid, TSH, serum protein electrophoresis, ANA, HIV, hepatitis panel.
Skin punch biopsy: quantifies intraepidermal nerve fiber density for small fiber neuropathy diagnosis (NCS is often normal in SFN). Nerve biopsy: reserved for suspected vasculitis or amyloidosis.
Treatment
Treat underlying cause: strict glucose control (HbA1c <7%), B12 supplementation (1000 mcg/day), alcohol cessation [5].
Neuropathic pain: gabapentin, pregabalin, duloxetine, amitriptyline (see Neuropathic Pain article).
Fall prevention: appropriate footwear, home safety modifications, balance training, regular foot examinations for diabetic patients.