Brain Magnetic Resonance Imaging Anomalies in U-2 Pilots with Neurological Decompression Sickness

Abstract

This was a retrospective observational study of imaging used to evaluate and treat 13 U-2 pilots with neurological decompression sickness (DCS). Magnetic resonance imaging (MRI) and computed tomography (CT) provided data for screening, diagnosis, and determinations of fitness to fly after recovery. While small series and case reports described the role of imaging in diving DCS, none addressed radiology's role in aviation DCS. We performed a literature review of altitude DCS radiology studies. We then reviewed radiology images at our institution on U-2 pilots with neurological DCS between January 2002 and August 2010. We retrospectively analyzed MRI data for white matter hyper-intensities (WMHs), defined as hyperintense lesions > or = 3 mm on T2 and FLAIR. All studies occurred after hyperbaric oxygen (HBO) treatment. There were 17 pilots who reported 20 neurological DCS incidents. Of these 17 pilots, 13 underwent imaging. Two (15%) demonstrated acute subcortical lesions on MRI, seven (54%) had asymptomatic WMHs, and six (46%) were normal. The clinical significance of the lesions is unknown. Consistent with diving DCS, imaging played no role in acute diagnosis. However, imaging was vital for determining fitness for return to flying. Additionally, CT identified a potentially predisposing sinus condition in one pilot which may enable return to flying after treatment. Modern imaging has unique findings for altitude DCS patients. The high incidence of WMHs in this series is a matter of ongoing research to determine potential clinical consequences. Emerging techniques such as functional MRI may play important roles in future aeromedical decisions.