Nitrous oxide induced myeloneuropathy
History of tingling sensation in all extremities and burning sensation in bilateral soles; weakness and difficulty walking for 1 week. Exam reveals decreased light touch and pinprick sensation in all extremities with distal to proximal gradient. Decreased vibration sense in both feet. Hyporeflexia in upper limbs and absent reflexes in both lower limbs. Rhomberg weakly positive. No bladder or bowel incontinence.
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Patchy increased signal intensity from C1-C4 affecting dorsal column. Axial T2 mid-cervical better demonstrates hyperintensity in posterior column.No cord compression or edema seen.
Further investigations revealed:
- Vitamin B12 : 279pg/mL
- Homocysteine : 58 nmol/mL
- MMA :1.59 nmol/mL
Her social history was significant for nitrous oxide abuse, she used about 5-10 canisters of nitrous oxide a week. Also patient tested negative for HIV. Other investigations were unremarkable.
A clinical diagnosis of myelopathy due to nitrous oxide toxicity was made.