Peripheral Neuropathy Due to Vitamin Deficiency, Toxins, and Medications

Peripheral nerves are susceptible to damage by a wide array of toxins, medications, and vitamin deficiencies. It is important to consider these etiologies when approaching patients with a variety of neuropathic presentations; additionally, etiologic clues may be provided by other systemic symptoms. While length-dependent sensorimotor axonal peripheral neuropathy is the most common presentation, several examples present in a subacute severe fashion, mimicking Guillain-Barré syndrome. Nathan & Anthony, Continuum. 2014 Oct; 20(5 Peripheral Nervous System Disorders): 1293–1306.

KEY POINTS

• Acquiring a detailed history is crucial to diagnosis of neuropathies caused by toxic agents and vitamin deficiencies.
• In a neuropathy with significant asymmetry, poly radicular, or mononeuritis multiplex presentation, other aetiologies should be explored further, even in the setting of documented toxicity or vitamin deficiency.
• Causes for vitamin B₁₂ deficiency include pernicious anemia, strict veganism, gastric bypass, prolonged antacid use, atrophic gastritis, or diseases of the terminal ileum (eg, resection, Crohn disease).
• Copper deficiency may look very clinically similar to vitamin B₁₂ deficiency and should be investigated in parallel in patients with a myeloneuropathy presentation.
• Vitamin B₆ is unusual in that it is associated with peripheral neuropathy either when deficient or in excess.
• Neuropathy due to thiamine deficiency has many presentations, including length-dependent sensorimotor, cranial nerve, and motor-predominant polyneuropathy, all of which may precede cognitive and systemic symptoms.
• It has been difficult to determine whether alcohol directly causes neuropathy or if its association with neuropathy is due more to chronic malnutrition and vitamin deficiencies in alcoholics.
• Intoxication from arsenic or thallium is preceded by severe gastrointestinal illness, and the neuropathy may mimic Guillain-Barré syndrome.
• Toxic exposure from industrial agents may be more likely to occur in people using these agents for personal use or in small businesses.
• Newer chemotherapy agents approved over the past several years continue to have frequent side effects of peripheral neuropathy.
• Ingestion of toxic seafood may be associated with peripheral nerve disorders, which often present as a syndrome of gastroenteritis and perioral paresthesia.