Acute nitrous oxide-induced neuropathy mimicking Guillain-Barré syndrome.

The early clinical features of nitrous oxide (N2 O)-induced neuropathy were mimicking that of Guillain-Barré syndrome (GBS). We aimed to explore clinical and laboratory characteristics of N2 O-induced neuropathy in comparison with GBS. We retrospectively reviewed data of 15 patients with N2 O-induced neuropathy and compared them with 15 GBS patients. The age of the N2 O-induced neuropathy group was significantly younger than that in the GBS group (22 ± 5 vs 45 ± 17). Paresthesia was more common in N2 O-induced neuropathy group (100% vs 53.3%). The proportion of distal upper limbs weakness was lower than that in GBS group (20.0% vs 93.3%). There was no significant difference in the distal weakness of the lower limbs (100% vs 80.0%). The incidence of motor conduction block and compound muscle action potential amplitude reduction in upper limbs was lower than that in GBS group (6.7% vs 60.0%; 26.7% vs 80.0%). The sensory nerve action potential amplitude drop in the lower limbs was more severe than that in GBS group (53.3% vs 0). The increase of Mean corpuscular volume (MCV) was more pronounced compared to GBS group (96.97 ± 6.00 vs 88.55 ± 5.41). High homocysteine levels were more common in N2 O-related group [29.80(11.60, 70.50) vs 14.35(9.22, 19.30)]. Typical clinical features of the acute N2 O neuropathy appears to be a myeloneuropathy, affecting the lower limbs more than the upper limbs, mixed axonal-demyelinating electrophysiological performance, higher homocysteine level, and larger MCV and common posterior spinal cord involvement in cervical segment.