Abstract
Background Recreational Nitrous oxide (N2O) use has seen a rise in Australia in recent years. Chronic N2O misuse leading to adverse neurological sequelae such as myeloneuropathy are well described in literature. We report a case of chronic N2O inhalation causing cognitive dysfunction and thalamic changes on MRI-Brain along with concurrent acute myeloneuropathy.
Objective To describe a case of chronic N2O use induced cognitive dysfunction with thalamic changes on MRI-Brain.
Case A 24-year-old male with no past medical history presented with 2 weeks of progressive lower limb weakness, paraesthesia, ataxia, forgetfulness, and low mood on a background of heavy N2O (8g) and cocaine (0.5–2g) inhalation every day for 4 months.
Neurological examination showed mild short term memory loss, hyporeflexia and sensorimotor impairment predominantly affecting bilateral distal lower limbs.
Investigations revealed an elevated methylmalonic acid level of 23umol/L. CSF studies showed mildly elevated proteins (564mg/L) with no oligoclonal bands. Nerve Conduction Studies showed evidence of a motor predominant axonal polyneuropathy. MRI-Spine showed cervical myelopathic changes from C2-C7 vertebral level. MRI-Brain showed right thalamic hyperintensity on FLAIR images without corresponding contrast enhancement or diffusion abnormality.
Patient was treated with intramuscular hydroxocobalamin and improved with neurorehabilitation.
Conclusion N2O can cause cognitive dysfunction in addition to myeloneuropathy. N2O related neurotoxicity to the brain has not been well documented. Clinicians should be vigilant in the search of clinical and radiological features in patients with suspected N2O misuse.
