Severe Isolated Peripheral Polyneuropathy without Myelopathy after Nitrous Oxide Abuse: A Case Report

Abstract

Nitrous oxide (N2O) abuse induces vitamin B12 deficiency, resulting in complications in the central and peripheral nervous systems. Some cases related to subacute combined degeneration or myeloneuropathy after N2O abuse have been reported. However, isolated peripheral polyneuropathy without spinal cord involvement has rarely been reported in South Korea. We describe a 29-year-old woman who had inhaled “happy balloons” daily (1,000 balloons/day) for recreational purposes over 3-month period, and presented with acute symmetrical hypoesthesia, paresthesia, and motor weakness on the bilateral lower limbs. Serologic tests showed megaloblastic anemia and vitamin B12 deficiency. Magnetic resonance imaging of the brain and spine showed no abnormalities. An electrodiagnostic study confirmed lower limb-dominant axonal sensorimotor polyneuropathy due to vitamin B12 deficiency from N2O abuse. The patient was treated with intramuscular vitamin B12 replacement. A follow-up electrodiagnostic study 4 months after the initial study showed only partial improvement. Despite the legal efforts of the Korean government to ban the use of N2O other than for medical purposes, cases of complications from its abuse are on the rise, especially among young adults. Physicians should recognize the strong possibility of N2O abuse as an underlying cause of vitamin B12 responsive polyneuropathy with or without spinal cord involvement.