Attending Rochester Regional Health Rochester, New York, United States
Case Diagnosis: Subacute combined degeneration
Case Description: Patient presented to the emergency department with progressive bilateral lower extremity sensory changes, weakness, and gait difficulty over a 3 week period in context of 3 months of daily Whippets abuse. 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 was noted to have bilateral lower extremity weakness and impaired proprioception and vibration in bilateral upper and lower extremities. He had pronounced 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. His symptoms improved within 1 week of starting supplementation.
Discussions: Whippets abuse induces N2O toxicity which leads to subacute combined degeneration (SCD) via B12 depletion. It typically presents with impaired proprioception, weakness, and paresthesias. 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.
