Predominance of cellular edema in traumatic brain swelling in patients with severe head injuries.
OBJECTIVE
The edema associated with brain swelling after traumatic brain injury (TBI) has been thought to be vasogenic in origin, but the results of previous laboratory studies by the authors have shown that a cellular form of edema is mainly responsible for brain swelling after TBI. In this study the authors used magnetic resonance (MR) imaging techniques to identify the type of edema that occurs in patients with TBI.


METHODS
Diffusion-weighted MR imaging was used to evaluate the apparent diffusion coefficient (ADC) in 44 patients with TBI (Glasgow Coma Scale Score < 8) and in eight healthy volunteers. Higher ADC values have been associated with vasogenic edema, and lower ADC values with a predominantly cellular form of edema. Regional measurements of ADC in patients with focal and diffuse injury were computed. The water content of brain tissue was also assessed in absolute terms by using MR imaging to measure the percentage of water per gram of tissue. Cerebral blood flow (CBF) was measured using stable Xe-computerized tomography (CT) studies to rule out ischemia as a cause of cellular edema. The mean ADC value in the healthy volunteers was 0.82 +/- 0.05 x 10(-3) mm2/second. The ADC values in the patients with diffuse brain injury without swelling were close to the mean for the healthy volunteers. In contrast, the patients with brain swelling had increased brain water content and low ADC values (mean 0.74 +/- 0.05 x 10(-3) mm2/second). The ADC values correlated with CT classifications. In all patients with low ADC values, the CBF values were outside the range for ischemia.


CONCLUSIONS
The brain swelling observed in patients with TBI appears to be predominantly cellular, as signaled by low ADC values in brain tissue with high levels of water content.
Marmarou
Anthony
A
Departments of Neurosurgery and Radiology, Virginia Commonwealth University Medical College of Virginia Campus, Richmond, Virginia 23298-0508, USA. amarmaro@vcu.edu
Signoretti
Stefano
S
Fatouros
Panos P
PP
Portella
Gina
G
Aygok
Gunes A
GA
Bullock
M Ross
MR
D000293:Adolescent; D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity / Q000502:physiology; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000502:physiology; D001834:Body Water / Q000378:metabolism; D001921:Brain / Q000098:blood supply; D001929:Brain Edema / Q000175:diagnosis* / Q000503:physiopathology; D001930:Brain Injuries / Q000175:diagnosis* / Q000503:physiopathology; D002545:Brain Ischemia / Q000175:diagnosis / Q000503:physiopathology; D015170:Cerebrospinal Fluid Pressure / Q000502:physiology; D038524:Diffusion Magnetic Resonance Imaging; D045604:Extracellular Fluid / Q000378:metabolism; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007424:Intracellular Fluid / Q000378:metabolism; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology; D014057:Tomography, X-Ray Computed; D014978:Xenon
D014978:Xenon