No abstract

Severe neurological decompression sickness (DCS) has been a rare entity in the U.S. Air Force, including the U-2 community. In over 50 yr of operation, few U-2 pilots reported severe neurological DCS in flight despite the extreme altitudes at which they operate. This article describes a near-fatal case of neurological DCS that occurred during a combat mission. The injury left the pilot with permanent cognitive deficits that correlated with focal lesions present on magnetic resonance imaging of his brain. To our knowledge, the images presented herein are the first to show radiological evidence of brain injury induced by altitude DCS. Though only a single case, the objective and clinical findings in the case pilot are similar to results documented in divers suffering DCS with central nervous system injury and victims of traumatic brain injury. DCS will remain a potentially serious threat to current and future air and space operations.

An increase in U-2 CNS DCS cases probably resulted from more cockpit activity combined with longer, more frequent high-altitude exposures. Adjustments in preoxygenation, cabin altitude, exercise at altitude, and frequency of flights may reduce incidence.

DCS remains prevalent among U-2 pilots. An increase in number and severity of cases correlated temporally with increased operational tempo of the U-2 squadron. Changes in cockpit pressurization and limiting the length and frequency of hypobaric exposure may reduce future incidence.

P. Brain magnetic resonance imaging anomalies in U-2 pilots with neurological decompression sickness.Aviat Space Environ Med 2013; 84:3-11.Introduction: 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 fi tness to fl y after recovery. While small series and case reports described the role of imaging in diving DCS, none addressed radiology ' s role in aviation DCS. Methods: 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), defi ned as hyperintense lesions Ն 3 mm on T2 and FLAIR. All studies occurred after hyperbaric oxygen (HBO) treatment. Results: 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 fi tness for return to fl ying. Additionally, CT identifi ed a potentially predisposing sinus condition in one pilot which may enable return to fl ying after treatment. Conclusions: Modern imaging has unique fi ndings 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.