Vector analysis correlating bullet trajectory to outcome after civilian through-and-through gunshot wound to the head: using imaging cues to predict fatal outcome.

OBJECTIVE

We identify radiographic imaging similarities found on head computed tomographic (CT) scans of patients with through-and-through gunshot wounds to the head with fatal outcomes.

METHODS

A retrospective analysis was conducted over an 18-month period from June 2001 through December 2002. Two hundred seventeen gunshot wound patients were evaluated. Exclusion criteria included any patient with cardiopulmonary injury and instability, airway compromise, or extracranial injuries affecting prognosis. Thirty-seven patients with isolated gunshot wounds to the head were included, 10 of which were fatal. Vital signs, examination results, Glasgow coma scale (GCS) score, intracranial pressure monitoring, surgical data, days in the intensive care unit, and CT scan appearance were collected. A Cartesian xyz coordinate system was created centered on the dorsum sella. Bullet pathways on CT scans were plotted and graphed onto a standardized magnetic resonance imaging scan.

RESULTS

Ten patients progressed to brain death. GCS score and pupil irregularity were associated with fatal outcome (P < 0.0001). CT scans showed that brain shift was more common in survivors. Seventy percent of nonsurvivors had minimal brain shift. A tram-track sign on CT scans correlated with fatal outcome (P = 0.005). Vector analysis of nonsurvivors showed an area of the brain approximately 4 cm above the dorsum sella that, when penetrated through the midline, led to brain death (P = 0.0006). This zone was coined the zona fatalis.

CONCLUSION

We confirm that GCS score and diabetes insipidus correlated with fatal outcome. In the setting of low-velocity gunshot wounds, fatal outcome and low GCS score were associated with a tram-track sign on CT scans. Bullet passage through a particular supra-dorsum sellar transventricular zone was associated with fatal outcome.