Episode 194: Nitrous Oxide Toxicity

We review Nitrous Oxide Toxicity: Symptoms, diagnosis, and treatment overview Hosts: Stefanie Biondi, MD Brian Gilberti, MD https://media.blubrry.com/coreem/content.blubrry.com/coreem/Nitrous_Oxide_Toxicity.mp3 Download Leave a Comment Tags: Toxicology Show Notes Patient Case Illustration * Hypothetical case: 21-year-old male with no previous medical history, experiencing a month of progressively worsening numbness, tingling, and weakness. Initially starting in his toes and spreading to his hips, and later involving his hands, the symptoms eventually escalated to the point of immobilization. Despite initially denying drug use, the patient admitted to using 40-60 canisters of nitrous oxide (whippets) every weekend for the last three months. Background and Recreational Use of Nitrous Oxide * Nitrous oxide, a colorless, odorless gas with anesthetic properties. * Synthesized in the 18th century. * Its initial medical purpose expanded into recreational use due to its euphoric effects. * Resurgence as a recreational drug during the COVID-19 lockdowns. * Accessibility and legal status. Public Misconceptions and Health Consequences * There are widespread misconceptions about nitrous oxide * Particularly the belief in its safety and lack of long-term health risks. * Contrary to popular belief, frequent use of nitrous oxide can lead to significant, sometimes irreversible, health issues. Neurological Examination and Diagnosis * Key components of the examination include assessing strength, sensation, cranial nerves, and proprioception, with specific abnormalities such as symmetrically decreased strength in a stocking-glove pattern, upgoing Babinski reflex, and positive Romberg sign being indicative of potential toxicity.  Physical Exam Findings: Upper vs Lower Motor Neuron Lesions Localize the Lesion- Differential Diagnoses for Extremity Weakness  Localize the Lesion- Differential Diagnoses for Extremity Weakness Localize the Lesion- Differential Diagnoses for Extremity Weakness MRI Findings and Subacute Combined Degeneration * The MRI displayed symmetric high signal intensity in the dorsal columns, a diagnostic feature identified as the inverted V sign or inverted rabbit ear sign. * Significance of the Inverted V Sign: This MRI sign is pathognomonic for subacute combined degeneration, indicating it is a distinct marker for this condition. * T2 Weighted Axial Images: The inverted V sign is observed in T2 weighted axial MRI images, which are used to evaluate the presence and extent of demyelination within the spinal cord. * Interpretation of Hyperintense Signals: Hyperintense signals on T2 weighted images generally indicate demyelination, where the protective myelin sheath around nerve fibers is damaged or destroyed. * Anatomical Location: The dorsal columns,