Ballistic lobar trajectory outcomes in civilian firearm penetrating brain injury

Penetrating brain injury (PBI) is the most lethal of all firearm injuries, with reported survival rates of less than 20%. The projectile trajectory (PT) has been shown to impact mortality, but the significant lobar tracks have not been defined. The aim of this retrospective case-control study was to test for associations between distinct ballistic trajectories, missile types, and patient outcomes.

A total of 243 patients who presented with a PBI to the Saint Louis University emergency department from 2008 through 2019 were identified from the hospital registry. Conventional CT scans combined with 3D CT reconstructions and medical records were reviewed for each patient to identify distinct PTs.

A total of 65 ballistic lobar trajectories were identified. Multivariable regression models were used, and the results were compared with those in the literature. Penetrating and perforating types of PBI associated with bitemporal (t-statistic = -2.283, p = 0.023) or frontal-to-contralateral parietal (t-statistic = -2.311, p = 0.025) projectile paths were universally found to be fatal. In the group in which the Glasgow Coma Scale (GCS) score at presentation was lower than 8, a favorable penetrating missile trajectory was one that involved a single frontal lobe (adjusted OR 0.02 [95% CI 0.00-0.38], p = 0.022) or parietal lobe (adjusted OR 0.15 [95% CI 0.02-0.97], p = 0.048). Expanding or fragmenting types of projectiles carry higher mortality rates (OR 2.53 [95% CI 1.32-4.83], p < 0.001) than do nondeformable missiles. Patient age was not associated with worse outcomes when controlled by other significant predictive factors.

Patients with penetrating or perforating types of PBI associated with bitemporal or frontal-to-contralateral parietal PTs should be considered as potential donor candidates. Trauma patients with penetrating missile trajectories involving a single frontal or parietal lobe should be considered for early neurosurgical intervention, especially in the circumstances of a low GCS score (< 8). Surgeons should not base their decision-making solely on advanced patient age to defer further treatment. Patients with PBIs caused by nondeformable types of projectiles can survive multiple simultaneous intracranial missile trajectories.