(Kiosk 5) Cervical Myelopathy Involving Posterior and Central Cord Secondary to Whippet’s Use: A Case Report

Case Diagnosis: Subacute combined degeneration secondary to nitrous oxide toxicity

Case Description or Program Description: 33 year old male with history of polysubstance abuse, anxiety, depression, and thyroid disease presented to the emergency department with progressive bilateral lower extremity sensory changes, weakness, and gait difficulty over a 3 week period in context of Whippets abuse.

Setting: Tertiary Care Academic Hospital

Assessment/Results: MRI of the Cervical Spine with and without contrast was significant for T2 hyperintensity involving C2-6 dorsal column and central cord. Labs significant for decreased B12 level < 200 (normal 232-1245), elevated Homocysteine 71 (normal 0-15) and methylmalonic acid 0.75 (normal 0.00-0.40), normal levels of folate, TSH, fT4. On exam, he had bilateral lower extremity weakness and impaired proprioception and vibration in bilateral upper and lower extremities. He had proximal weakness, graded 2/5 in hip flexors and knee extensors upon initial evaluation. He received B12 2000 mcg, methionine 3000 mg, and folic acid 1 mg the day after admission and continued daily supplementation. Symptoms improved within 1 week of starting supplementation with strength improving to 4/5 in hip flexors bilaterally upon discharge to acute inpatient rehab.

Discussion (relevance): Whippets abuse induces N2O toxicity which leads to subacute combined degeneration (SCD) via B12 depletion. It typically presents with impaired proprioception, weakness, and paresthesia. SCD is associated with multiple causes with Whippets rising in popularity due to recreational use. B12 supplementation along with folic acid and methionine have been shown to improve prognosis in this context.

Conclusions: Symptoms like bilateral weakness, impaired sensation and proprioception should raise suspicion for SCD. Recreational N2O use has been rising in popularity and should be a differential diagnosis. There are no current screening tests for N2O use and limited studies on treatment, so it is essential to obtain a complete history. It is important to consider this as an etiology for better treatment outcomes and prognosis.