Prevalence of Neurologic Decompression Sickness and Necrotic Brain Lesions in High-Altitude Pilots (S08.005)

Abstract

Objective: To determine the prevalence of NDCS and necrotic brain lesions in a cohort of high-altitude pilots and to discover predictive factors. Background The U.S. Air Force U-2 community has experienced an increase in neurologic decompression sickness (NDCS). This is the first nonanonymous aircrew study combining clinical and neuroimaging findings. Design/Methods: Fifty pilots underwent flight and NDCS history questionnaires as well as 3T brain magnetic resonance imaging at the Research Imaging Center. To date, 29 images have been analyzed for the presence of necrotic lesions. Results: Eleven pilots (22%) were treated for NDCS. Data were compared between pilots with and without NDCS, respectively: total U-2 hours – 500±330 to 745±417; number of missions – 65±51 to 107±71; operational tempo (OT) between high-flights (in days) – 3.1±0.7 to 2.9±0.9. Six pilots developed NDCS within their first three flights, while five developed it near the end of their deployment. Analyzed images of 4 of 7 pilots with NDCS displayed necrotic lesions compared to 10 of 22 pilots without NDCS. Comparative data for pilots with necrotic lesions versus pilots without necrotic lesions were not significantly different (total U-2 hours – 648±371 to 684±399; missions – 69±48 to 105±66; and OT – 2.8±0.5 to 3.0±0.6). Conclusions: The prevalence of NDCS in this sample was 11/50. There is no statistical difference in total hours, missions, and operational tempo between those with and without NDCS. An early and late group among NDCS was identified. Fifty-five percent of NDCS cases occurred earlier in pilots with fewer flight hours and missions, suggesting susceptibility to NDCS in pilot subpopulations. Necrotic lesions were found in 57% of NDCS pilots analyzed and, surprisingly, 45% of non-NDCS pilots analyzed. Research is ongoing to study the clinical and operational significance of these findings. Supported by: USAF AFMSA/SG9 study grant I-11-10 and AFMSA/SG9 study grant I-11-44. Disclosure: Dr. Robinson has nothing to disclose. Dr. Sherman has nothing to disclose. Dr. Kochumov has nothing to disclose. Dr. Grogan has received personal compensation for activities with Pfizer Inc. and US Worldmeds as a speaker. Dr. McGuire has nothing to disclose.