Introduction
Subacute combined degeneration (SCD) is a myelopathy caused by demyelination of dorsal and lateral spinal cord. The most common cause of SCD is vitamin B12 deficiency, which is usually associated with pernicious anemia or severe malnutrition. Nitrous oxide (N2O), better known as “Laughing gas” or “Happy Balloon gas”, is commonly used as sedative agents by pediatric dentists, which allows a feeling of euphoria. However, massive inhalation of N2O can cause SCD. The aim of this study is to report the prognosis of SCD due to N2O inhalation.
Case Reports
This study was conducted on 3 patients who were diagnosed with subacute combined degeneration from with laughing gas inhalation history. The “inverted V sign”, bilateral high-intensity T2 signal within the posterior column of spinal cord, was found in magnetic resonance imaging (MRI) of C-spine MRI in all three patients. Patient 1 was a 30-year-old woman who presented with progressive paresthesia and weakness in her legs. She inhaled “laughing gas” more than 100 times for 1 year. A neurological examination revealed decreased proprioception and bilateral weakness of both lower extremities. When she was transferred to department of rehabilitation, she couldn’t stand or walk independently. After 4 weeks of rehabilitation, she is still unable to walk without holding bar. Patient 2 was a 24-year-old woman who presented with progressive paresthesia and weakness in her arms and legs. She inhaled N2O gas for once but she ate only one meal for weight reduction about 3 months. A neurological examination revealed decreased proprioception. When she was transferred to department of rehabilitation, she was able to stand alone and walk with one hand support. After 10 months, she still requires assistance for walking. Patient 3 was 22 years old when she started to inhale N2O gas. She felt weakness in bilateral legs after using it every weekend for 2 months. When she was transferred to department of rehabilitation, she could not stand alone and required wheelchair to move. She recovered rapidly during rehabilitative therapy and independent standing was available after 1 week. Now she walks independently after 1–year follow–up but she still shows impaired standing balance.
Discussion
N2O gas is a safe analgesic substance, however, massive consumption of N2O gas could be hazardous to cause SCD. In addition, it is necessary to mention that only one time exposure to N2O gas can cause SCD if someone has a predisposing factor such as anorexia nervosa, pernicious anemia or chronic vitamin B deficiency. Early differential diagnosis of SCD and proper treatment including medication and rehabilitation could be crucial to a favorable outcome. It is recommended not to be exposed to N2O gas since full recovery may not be achieved. |
