Hereditary Neuropathy With Liability to Pressure Palsy Detected During the Use of Recreational Drugs.

Background: Nitrous oxide (N2O) has been an increasingly popular recreational drug over the past few years. Abuse is associated with severe neurological complications and even fatal outcomes. Purpose: Here we present a case of chronic nitric oxide abuse in a teenager presenting with rapidly progressive mixed sensory and motor polyneuropathy. Results: The initial diagnostic workup excluded electrolyte derangement, heavy metal intoxication, autoimmune neuropathy, myopathy, hematological disorders, and thyroid disease. On further questioning, patient reported 8-months of inhalation of nitrous oxide, commonly known as "whippets". Subsequent tests revealed low Vitamin B12 and elevated homocysteine level. Eventual genetic test demonstrated a heterozygous deletion in the gene that encodes the peripheral myelin protein 22 (PMP22), consistent with a diagnosis of Hereditary Neuropathy with Liability to Pressure Palsies (HNPP). Conclusion: The association of neurologic and genetic findings with the timeline of nitrous oxide inhalation suggests a multifactorial etiology of her symptoms, with the N2O acting as a trigger to the axonal degeneration and demyelination detected on electrodiagnostic studies.

Yield of Neurodiagnostic Testing in Children Presenting to a Pediatric Emergency Department With Altered Mental Status.

BACKGROUND: Emergency department (ED) visits for altered mental status (AMS) in children are common. Neuroimaging is often performed to ascertain etiology, but its utility has not been well studied. Our objective is to describe the yield of neuroimaging studies in children who present to an ED with AMS. METHODS: We performed a retrospective chart review of children 0-18 years of age, presenting to our PED between 2018 and 2021 with AMS. We abstracted patient demographics, physical examination, neuroimaging and EEG results, and final diagnosis. Neuroimaging and EEG studies were classified as normal or abnormal. Abnormal studies were categorized as clinically important and contributory: abnormalities that were clinically important and contributed to the etiology, clinically important but noncontributory: abnormalities that were clinically significant but did not explain the etiology, and incidental: abnormalities that were not clinically significant. RESULTS: We analyzed 371 patients. The most common etiology of AMS was toxicologic (188, 51%) with neurologic causes (n = 50, 13.5%) accounting for a minority. Neuroimaging was performed in one-half (169, 45.5%) and abnormalities were noted in 44 (26%) studies. Abnormalities were clinically important and contributed to the etiologic diagnosis of AMS in 15/169 (8.9%), clinically important and noncontributory in 18/169 (10.7%), and incidental in 11/169 (6.5%). EEG was performed in 65 patients (17.5%), of which 17 (26%) were abnormal with only one being clinically important and contributory. CONCLUSIONS: Though neuroimaging was performed in approximately one half of the cohort, it was contributory in a minority. Similarly, diagnostic utility of EEG in children with AMS was low.