NO, or laughing gas, is generally used for anesthesia, especially in stomatology and pediatrics but is also commonly used recreationally. Cognitive dysfunction induced by the recreational use of NO is rare. Here, we present the case of an 18-year-old female with a history of having used NO recreationally for 5 months who suffered from encephalatrophy and severe cognitive dysfunction. All of the symptoms gradually subsided with ~20 days of treatment by hyperbaric oxygenation. We hypothesize that the long-term use of NO may have induced a chronic state of systemic hypoxia that further induced cerebral atrophy with impaired cognitive function. Hyperbaric oxygen therapy (HBOT) is reported here for the first time as an important therapeutic element for treating NO toxicity due to recreational use.
Simple reaction time (SRT) and procedural reaction time (PRT) are speed-of-processing tasks in the Automated Neuropsychological Assessment Metrics (ANAM) that may be sensitive to mild traumatic brain injury (mTBI). The investigators measured SRT and PRT throughput (correct responses per minute) at baseline, 6 weeks, and 13 weeks in military personnel with mTBI randomized to local care or 40 chamber sessions (sham-1.2 atmospheres absolute [ATA] air, hyperbaric oxygen-1.5 ATA O2). Scores were assessed at baseline using univariate analysis of variance and across time with repeated measures methods. Data reported as throughput standard scores (mean = 100, SD = 15). Seventy-two participants with ongoing symptoms after mTBI enrolled in the study (three female, median age 31 years, mean three lifetime concussion events, most recent mTBI 23 months prior). Sixty-four had Automated Neuropsychological Assessment Metrics data at 13 weeks. SRT and PRT throughput standard scores were comparable across groups at baseline. Over time, SRT scores did not change in the hyperbaric oxygen or sham groups and decreased in the local care group. PRT throughput standard scores increased from baseline to mid-intervention and decreased from mid-intervention to postintervention in all groups. Repeated measures change over time in SRT (p = 0.23), and PRT (p = 0.17) scores were not different among groups. This study may be underpowered to detect statistically significant change.