Midline shift after severe head injury: pathophysiologic implications.
OBJECTIVE
To investigate the mechanism of the adverse effect of midline shift after severe traumatic brain injury.


METHODS
This study compared averaged cerebral metabolic parameters of patients with midline shift > 5 mm (S) on initial computerized tomography scan to those of patients with shift < or = 5 mm (NS). The effect of an acute subdural hematoma (SDH) was determined by separating patients into those with and those without SDH and then re-examining the effect of shift in these subgroups.


RESULTS
Four hundred fifty-four patients were studied. Cerebral metabolic rate of oxygen (CMRO2, in mL/100 g per min) was always lower with shift: 1.74 for SDH-S versus 2.21 for SDH-NS (p < 0.001), and 1.80 for non-SDH-S versus 2.24 for non-SDH-NS (p < 0.001). No other major effects of shift were seen in SDH patients. Among non-SDH patients, shift was associated with higher intracranial pressure (ICP): 23.1 mm Hg versus 16.3 mm Hg (p < 0.001). Other differences between shift and nonshift patients in the non-SDH group were due at least in part to interventions to treat the elevated ICP.


CONCLUSIONS
Midline shift after severe traumatic brain injury is associated with reduced CMRo2, regardless of whether or not SDH is present. The deleterious effects of subdural blood may be related more to the mass effect of large SDHs than to the biochemical abnormalities caused by small amounts of blood in the subdural space.
Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030, USA.
A B
AB
Valadka
S P
SP
Gopinath
C S
CS
Robertson
D000328:Adult; D001794:Blood Pressure; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000378:metabolism*; D001930:Brain Injuries / Q000503:physiopathology; D005260:Female; D015600:Glasgow Coma Scale; D020199:Hematoma, Subdural, Acute / Q000503:physiopathology*; D006801:Humans; D007427:Intracranial Pressure; D008297:Male; D009460:Neurologic Examination; D011446:Prospective Studies; D012039:Regional Blood Flow; D014057:Tomography, X-Ray Computed