Korean J Neuromuscul Disord.  2023 Dec;15(2):42-45. 10.46518/kjnmd.2023.15.2.42.

Unhappy Balloon, Nitrous Oxide-induced Subacute Combined Degeneration of the Spinal Cord: A Review of Case Series

• Park SH
• Jang SI
• Kim P
• Yoon HS
• Kim NH

• KMID: 2550215
• DOI: http://doi.org/10.46518/kjnmd.2023.15.2.42

Abstract

Background
The younger generation in Korea easily exposed to nitrous oxide (N₂O) under the name “Happy Balloon” may abuse it. N₂O can irreversibly oxidize vitamin B₁₂ and cause abnormal hematopoiesis or nervous system toxicity such as subacute combined degeneration (SCD). The objective of this study was to assist in early diagnosis of N₂O-induced SCD of spinal cord by characterizing its clinical manifestations.
Methods
Four patients with myelopathy after abusing N₂O were enrolled. To characterize N₂O-induced myelopathy, previously reported cases of N₂O-induced SCD were searched through PubMed and KoreaMed. Collected cases and our four patients were analyzed.
Results
A total of 30 patients with N₂O-induced myelopathy (26 males and 4 females with mean age of 24 years) were analyzed. These patients took a median dose of 650 canisters for a median duration of 3.5 months. All patients presented sensory disturbances, which involved the lower extremities more frequently (100%) than the upper extremities (63.3%). Gait ataxia (76.7%), weakness in the upper (23.3%) and lower (36.7%) extremities, bladder symptoms (26.7%), Rhomberg sign (43.3%), and Lhermitte’s phenomenon (10.0%) were observed. Serum vitamin B12 levels were decreased in many (63.3%) patients and homocysteine levels were elevated in all. Of 20 patients who underwent magnetic resonance imaging (MRI) of the spine, 19 had abnormal findings. Three patients presented with contrast enhancement in lesions.
Conclusions
We strongly recommend that history of N₂O abuse should be asked for young patients with suspected myelopathy, especially those presenting with gait ataxia and sensory disturbances suggesting posterior column dysfunction and those presenting long-segment lesion involving the upper cervical cord on MRI.

Keyword

Myelopathy; Subacute combined degeneration; Spinal cord; Myeloneuropathy; Laughing gas