Cranial gun shot injuries are a form of penetrating traumatic brain injuries, which are much less common than blunt traumatic brain injuries.
Incidence of gun shot injuries to the head is increasing in some countries, due to the ease of accessibility of firearms. In the civilian population, suicide and criminal activity account for the majority of cases and young male adults remain the most at risk 4.
There are five major gun shot injuries of the head 4:
- penetrating: entry wound with no exit would
- perforating: entry and exit wound with tract through the brain parenchyma
- tangenital: strikes the head obliquely without penetrating the brain parenchyma but may result in scalp injury, skull fractures or parenchymal contusions
- ricochet: penetrating projectile that bounces off the inner table of the skull
- careening: penetrates the skull and travels with its trajectory external to the parenchyma potentially injuring the dural venous sinuses
Please see the main article "imaging of gun shot injuries" for a general description of imaging features.
The entry and exit wounds can be identified paying attention to the bone “beveling”. An inward beveling of the inner skull table is supportive of the entry wound, whereas the outward beveling of outer skull table suggests the exit wound. Often there is not an exit wound, especially in incomplete metal jacket bullets (e.g. hollow point tip) that are designed to fragment and lose kinetic energy along their path 1.
Angiographic imaging is used when there is evidence or high suspicion of intracranial vascular injury. Projectiles in or having traversed the base of skull have a high incidence of vascular injury 4. CTA may demonstrate a CTA spot sign indicating active haemorrhage at the time of the scan, as seen in non traumatic intraparenchymal haemorrhage, which correlates with a worse prognosis. Vascular injuries include be transection, pseudoaneurysm, dissection or thromboembolic occlusion.
Digital subtraction angiography
DSA is used when CTA fails to demonstrate a vascular injury and the suspicion remains high or endovascular treatment is being considered. Delayed DSA may also be performed to assess for complications such as AV fistula 4.
Treatment and prognosis
Unsurprisingly, mortality is high. In civilian shootings, approximately 20% survive the initial injury, and of those ~50% (range 30-68%) survive 2.
There are numerous complications ranging from instant to delayed 4:
- CSF leak
- vascular injury
- dural venous sinus thrombosis
- bullet migration
- 1. Forensic Sci Int. 2003 Dec 17;138(1-3):8-16. Image-guided virtual autopsy findings of gunshot victims performed with multi-slice computed tomography and magnetic resonance imaging and subsequent correlation between radiology and autopsy findings.
- 2. Traumatic Brain Injury: Methods for Clinical and Forensic Neuropsychiatric Assessment,Third Edition. CRC Press. ISBN:1466594802. Read it at Google Books - Find it at Amazon
- 3. Wilson AJ. Gunshot injuries: what does a radiologist need to know?. Radiographics. 1999;19 (5): 1358-68. doi:10.1148/radiographics.19.5.g99se171358 - Pubmed citation
- 4. Vakil MT, Singh AK. A review of penetrating brain trauma: epidemiology, pathophysiology, imaging assessment, complications, and treatment. Emergency radiology. 24 (3): 301-309. doi:10.1007/s10140-016-1477-z - Pubmed