Disclosures: Alexa Ryder: No financial relationships or conflicts of interest

Case Diagnosis: Spinal Cord Damage to Dorsal Columns from Chronic Nitrous Oxide Abuse

Case Description: 51-year-old male with history of Klinefelter syndrome and polysubstance abuse presented with shortness of breath, back pain, and bilateral upper and lower extremity numbness, weakness, and paresthesia.

Setting: Acute inpatient rehabilitationAssessment/

Results: MSK exam significant for bilateral upper and lower extremity weakness. Sensation, proprioception, and vibration were decreased in bilateral lower extremities. There was dysmetria on finger-to-nose testing. Patient endorsed inhaling nitrous oxide (whippet form) as a teenager and daily over the past two months. Imaging findings were consistent with subacute combined degeneration of the spinal cord and cervical spine pathology. The patient was placed on vitamin B12 supplementation and referred for intensive inpatient rehabilitation. Neurosurgery was consulted and did not propose surgical intervention but recommended a cervical collar. Gabapentin was prescribed for neuropathic pain.

Discussion: Nitrous oxide, also known as laughing gas, is a substance notoriously abused in the form of “whippets.” Abuse of nitrous oxide interferes with the transmethylation of cobalamin I by oxidizing it to its inactive form. Repeated exposure leads to depletion of vitamin B12 stores resulting in a decrease of the pathways end products methionine and tetrahydrofolate. Reduction of methionine causing decreases S-adeosylmethionine can lead to the demyelination in B12 deficiency. These effects ultimately lead to the development of subacute combined degermation of the spinal cord.

Conclusion: Patients can frequently present with parasthesias and weakness. Of the spinal cord syndromes for incomplete injuries, posterior cord syndrome is the most uncommon. Upper motor neuron signs, loss of vibratory sense and proprioception are pathognomic for PCS. Social history and drug use history can be important identifiers in the work-up and should be considered with patients presenting with dorsal column degeneration.

Level of Evidence: Level IV

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/posterior-cord-syndrome-secondary-to-nitrous-oxide-abuse/