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Case report
Encephalitis secondary to nitrous oxide and vitamin B12 deficiency
  1. Gareth Hughes,
  2. Ed Moran and
  3. Martin J Dedicoat
  1. Department of Infectious Diseases and Tropical Medicine, Birmingham Heartlands Hospital, University Hospitals Birmingham, Birmingham, UK
  1. Correspondence to Dr Gareth Hughes; g.hughes3{at}


A 27-year-old woman presented with confusion, agitation and fever. Having initially been treated as an infective encephalitis case her initial and subsequent lumbar punctures revealed cerebrospinal fluid with a worsening pleocytosis and elevated protein. It was initially felt she had been suffering from tuberculous meningitis and started on treatment it later became apparent that she had a severe vitamin B12 deficiency related to recreational nitrous oxide use. She also was noted to have a peripheral neuropathy. After replacing her vitamin B12 and later stopping her tuberculous medication once cultures were negative her cognition and peripheral neuropathy continued to improve.

  • Drug misuse (including addiction)
  • TB and other respiratory infections

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  • Contributors GH: created the initial case report concept and design and gathered the data. Reviewed final manuscript before submission. EM: analysis and interpretation of data along with rationale for B12 deficiency causing fever and reference for this. He also reviewed and commented on the final version before submission. MJD: analysis and interpretation of data along with review and commenting on final version before submission.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.