Hassing LT, Jiang FY, Zutt R, Arends S. Nitrous-oxide-induced polyneuropathy and subacute combined degeneration of the spine: clinical and diagnostic characteristics in 70 patients, with focus on electrodiagnostic studies.
Eur J Neurol 2024;
31:e16076. [PMID:
37754673 DOI:
10.1111/ene.16076]
[Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Revised: 09/04/2023] [Accepted: 09/11/2023] [Indexed: 09/28/2023]
Abstract
BACKGROUND AND PURPOSE
Nitrous oxide (N2 O) induced neurological symptoms are increasingly encountered. Our aim is to provide clinical and diagnostic characteristics with a focus on electrodiagnostic studies.
METHODS
Patients with neurological sequelae due to N2 O presenting in our hospital between November 2018 and December 2021 reporting clinical and diagnostic data were retrospectively reviewed.
RESULTS
Seventy patients (median 22 years) were included. Median N2 O usage was 4 kg/week during 12 months. Patients' history revealed a higher rate of sensory symptoms compared to motor (97% vs. 57%) and 77% walking difficulties. Clinical diagnosis was polyneuropathy (PNP) in 44%, subacute combined degeneration (SCD) of the spine in 19%, both in 37%. Median vitamin B12 level was low (159 pmol/L), normal in 16%. The median methylmalonic acid was increased (2.66 μmol/L). Electrodiagnostic abnormalities were observed in 91%, with 72% fulfilling axonal PNP criteria, 20% showing mild to intermediate slowing. One patient fulfilled demyelinating PNP criteria not related to N2 O abuse (Charcot-Marie-Tooth type 1a). More prominent motor nerve conduction abnormalities were found; lower limbs were more affected. In 64% with normal conduction, myography showed signs of axonal loss. Magnetic resonance imaging showed cervical myelopathy in 58% involving generally five to six segments.
CONCLUSIONS
Nitrous oxide (N2 O) leads to neurological symptoms by causing PNP and/or SCD primarily involving the legs. Distinguishing PNP and SCD clinically was shown to be insufficient. Electrodiagnostic studies showed axonal PNP. Demyelinating PNP due to N2 O abuse was not present in our cohort. Therefore, further diagnostic work-up is warranted if demyelinating features are present.
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