Brain magnetic resonance imaging anomalies in U-2 pilots with neurological decompression sickness.

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 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. 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), defined as hyperintense lesions > or = 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 fitness for return to flying. Additionally, CT identified a potentially predisposing sinus condition in one pilot which may enable return to flying after treatment. CONCLUSIONS: 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.

Altitude decompression sickness incidence among U-2 pilots: 1994-2010.

INTRODUCTION: The U-2 aircraft exposes its pilots to cabin pressures equivalent to 29,500 ft (8992 m) during flight, placing them at risk for decompression sickness (DCS). Historical data documenting DCS in the U-2 pilot community is lacking. This study assesses how rates and types of DCS have changed temporally in the U-2 flight program. METHODS: We created a database of all DCS cases among U-2 pilots from 1994 through 2010. Cases were analyzed by date of occurrence and symptoms experienced. Flight data were collected to calculate DCS incidence rates. RESULTS: From 1994-2010, there were 73 documented DCS cases in U-2 pilots. Between 1994 and 2005, the number of annual cases ranged from 0-5; between 2006 and 2010, the number of annual cases increased to 6-10. Additionally, there was a trend toward more severe (neurologic and pulmonary) cases between 2006 and 2010 with 22 cases compared to 10 cases the preceding 12 yr. The most common presentations of U-2 DCS were joint pain (59%), mainly involving large joints, and generalized neurologic symptoms (44%). From 2006-2010, there was an increase in the average annual flight hours per pilot to meet wartime operational needs that correlated temporally with the increase in number and severity of DCS cases. The DCS risk per flight was 0.076% from 1994-2005 but increased to 0.23% from 2006-2010. CONCLUSIONS: 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.

Neurological altitude decompression sickness among U-2 pilots: 2002-2009.

INTRODUCTION: Compared to the previous 47 yr, U-2 pilots reported an increased number of altitude decompression sickness (DCS) incidents with central nervous system (CNS) manifestations during 2002-2009. Due to increasing incident severity during military operations, the U.S. Air Force initiated an investigation to prevent future mishaps. METHODS: We retrospectively examined all neurological DCS cases observed among U-2 pilots during 2002-2009. Urgency to prevent further pilot losses limited this study to using existing, often incomplete data sources. RESULTS: During 2002-2009, 16 confirmed incidents of CNS DCS occurred with 13 pilots, plus 4 possible incidents with 4 pilots. Significantly, 12 of 16 confirmed incidents occurred at 1 operating location, including 4 of 5 life-threatening cases. This series of cases were of a type and severity rarely found in flight operations and correlated temporally with increased sortie frequency/duration associated with combat operations. Multiple investigations confirmed no defects in aircraft, support equipment, or oxygen supplies. Nor were significant trends observed with age, habitus, environmental exposure, medication use, or cardiac defects. In 11 cases, symptom recognition occurred well after the 4-h point where clinical experience indicated risk should stabilize. Symptoms also recurred days later and responded to repeat hyperbaric oxygen therapy in three of four cases. Finally, neuropsychiatric symptoms persisted in six pilots for years and may represent permanent injury. CONCLUSIONS: 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.

Severe neurological decompression sickness in a U-2 pilot.

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.

Conventional radiography of the shoulder.

Conventional radiography is a useful tool in the evaluation of shoulder pain whether in the setting of acute trauma or chronic pain and in most clinical situations should be the first imaging modality performed. Knowledge of the various projections and radiographic findings described above will ensure an optimal evaluation of the shoulder regardless of the suspected etiology of the shoulder pain.