Neurosurgery Bullet Review: Gunshot Penetrating Brain Injury

• Penetrating brain injury can be classified as (Youman ed.7)
  • low velocity (eg.knife)
  • high velocity
    • subsonic (<300 m/s)
    • hypersonic (>300m/sec)
• Civilian VS wartime penetrating injury
• Projectiles with high kinetic energy eg. machine guns 
  • direct tissue damage along the missile path
  • cavitation 
• low velocity projectiles eg.handguns, knives, or nails 
  • localized tissue damage along the trajectory 
• close range projectiles produce the greatest degree of injury 
• Wound types (Vakil, Emerg Radiol, 2017)
  • Penetrating: entry wound with no exit wound
  • Perforating: entry and exit wound with tract through the brain parenchyma
  • Tangential: strikes the head obliquely without penetrating the brain tissue but may result in scalp lacerations, skull fractures, or cerebral contusions
  • Ricochet: penetrating bullet that may bounce off the inner table of the skull one or more times
  • Careening: penetrates the skulls and travels along the periphery of the cortex without entering parenchyma but has the potential to damage the dural venous sinuses

• 

Evaluation, Possible complications and Management (Loggini, Journal of Critical Care, 56, 2020)

• 

• Initial treatment of penetrating brain injury should focus on immediate resuscitation with control of bleeding and elevated intracranial pressure
• Cervical spine immobilization
  • incidence of cervical spine injury was 0.49% (all suffered direct spinal injury from bullet passage)
  • Evidences do not support routine cervical spine immobilization in penetrating gunshot wound injury
    • ยกเว้นพบมี penetrating injury บริเวณคอ หรือมีสถานการณ์อื่นๆที่ทำให้สงสัย C-spine injury
• Seizure prophylaxis
  • not able to identify reliable data on the incidence of early versus late seizures in this population
  • early seizures may be high in cvPBI.
  • the rate of late seizures does not appear to be different from non- penetrating mechanisms

• intraparenchymal retention of bone plus metal fragments could represent a significant risk factor for development of seizures. (Englander, Arch Phys Med Rehabil, 2003)
  • guidelines for “Management and Prognosis of Penetrating Brain Injury” recommend prophylactic antiseizure medications for the first week after PBI, but not beyond that. 
• Antibiotic prophylaxis
  • there is no robust data supporting the use, type, or duration of prophylactic antibiotics in cvPBI. 
    • In a prospective cohort of 160 surgically treated patients low–velocity (civilian) firearm projectiles, 40/160 patients were confirmed to have a CNS infection, 95% of which occurred during the first 30 days(Jimenez, World Neurosurgery, 2013)
      • pre-surgical prophylactic antibiotics was not associated with a reduction in CNS infection 
      • Injury through paranasal sinuses or oral cavity, persistence of osseous or metallic fragments on CT scan, and prolonged hospitalization were associated with infection regardless of prophylactic antibiotic administration (p = .03, p = .0001, p = .006 respectively) 
  • The most common prophylaxis was a third-generation cephalosporin (Youman, ed 7)

• Coagulopathy
  • the prevalence of coagulopathy ranges from 44 to 52% 
  • is an predictor of poor outcome (Folkerson, Am J Emerg Med, 2018)
  • coagulopathy ought to be early investigated
• Vascular complications (Bodanapally, J Neurosurg,2015)
  • incidence of vascular injury in cvPBI ranges between 38% and 50%. 
  • risk is higher when 
    • a projectile penetrates the cranium in the fronto-basal region 
    • the projectile traverses both hemispheres 
    • close proximity to the circle of Willis 
    • intraventricular or subarachnoid hemorrhage is present 
  • types of vascular complications
    • traumatic intracranial aneurysms are the most common (39%), 
    • arterial dissections (29%)
    • arterial occlusion (21%)
    • arterio-venous fistulas (11%)
  • 96% of the injuries are limited to the anterior circulation, namely the MCA and ICA 
    • intracavernous and infraclinoid ICA and vertebrobasilar arteries are particularly susceptible to injury from skull base fractures 
  • traumatic intracerebral aneurysm
    • may develop within the first several hours following initial trauma 
    • or as a delayed complication often presenting as delayed subarachnoid hemorrhage or hematoma 
    • associated with a 50% mortality and are therefore treated aggressively 
  • The incidence of cerebral vasospasm following cvPBI can be as high as 42%
    • presence of subarachnoid blood being the strongest risk factor(Kordestani, Neurosurgery 1997 
    • Subarachnoid hemorrhage in cvPBI is correlated with poor outcome
  • Conventional angiography is superior to CTA for detecting overall arterial injury
    • Gold standard
    • the clinical utility in the acute setting remains ambiguous. 
  • CTA has limited overall sensitivity in detecting arterial injuries in cvPBI (72.7% sensitivity and 93.5% specificity)
    • It is reliable in identifying traumatic aneurysms in this patient population (100% sensitivity and specificity)
  • Patients who are at risk of developing a traumatic aneurysm should be evaluated with angiography or CT angiography early.
  • Because the time frame for development of traumatic pseudoaneurysms is uncertain, a repeat examination in approximately 2 weeks is recommended (Ambrosi, Neurosurg Rev, 2012),(Ecklund, WNEU, 2014)

• Intracranial infection
  • 5 to 23% including intracranial and extracranial infections 
    • osteomyelitis of the skull, superficial wound infections, epidural and subdural empyema, meningitis, ventriculitis cerebritis, and cerebral abscess.
  • commonly associated with CSF leaks, transventicular and bihemispheric injuries, air sinus wounds, and retained fragments 
  • Staphylococcus epidermidis, Staphylococcus aureus, and gram-negative bacteria are the most common 
  • Brain abscess
    • Incidence 2-3%, mortality 50%
    • More likely to form around retained fragment, 2-4 wk after injury, may be years if the organism is low virulence
    • Adequate debridement of contaminat- ed tissue and treatment of CSF leak 
• Intraventricular hemorrhage and hydrocephalus
• Venous sinus thrombosis and venous infarction
  • may result from direct dural penetration by bullet fragments or skull fractures overlying the dural venous sinuses. 
  • 80%superior sagittal sinus
• Venous sinus injury with air embolism (Brune, BMJ Case Rep,2018)

• Bullet migration
  • Intracranial bullet migration is an uncommon
  • potentially significant complication
  • may result in change in a patient’s neurologic examination:seizures, hematomas, and obstructive hydrocephalous 
  • Depending on the location of the fragment, surgery may be indicated for migrated fragments 

Surgical Management: highly controversial 

• Criteria for surgical intervention
  • No consensus on criteria for surgical intervention
• Timing for surgical intervention (Helling, J Trauma 1992)
  • no clear benefit of early intervention was demonstrated 
• Types of surgical intervention
  • Current surgical practice focuses on aggressive intracranial decompression with wide decompressive craniectomy performed for patients with significant cerebral swelling
  • Surgeons are often less aggressive with deeply-seated fragment and bone retrieval given increased risk of morbidity associated with deep exploration (Rosenfeld, World J Surg, 2015)
  • Exceptions include bullet fragments that have migrated, located near a vascular structure, or CSF communication in a cistern or ventricle 
  • The approaches range from decompressive craniectomy with evacuation of mass lesions to procedures limited to superficial wound debridement,dural repair to prevent CSF fistulas, and ICP monitor placement
  • some literature suggests that retention of foreign bodies post-surgery may increase seizure risk 

• no studies addressed whether surgical debridement of necrotic tissue and removal of surgically accessible bone and bullet fragments has a role in decreasing seizure or infection risk (Englander, Arch Phys Med Rehabil,2003)

Clinical Outcomes

• Surgery seems to be associated with decreased mortality
  • Mortality in surgical groups ranges from 13 to 33% while mortality in non-surgical cohort ranges from 66 to 83% 
    • patients with GCS 3–5, <1% survived without surgery, while 38% survive with surgical intervention (p b .0001) (Levy, Neurosurgery,1994)
    • patients with GCS 6–8, no patients survived without surgery, while 83% survive with surgery (Levy, Neurosurg Focus,2000)
  • higher GCS is associated with better clinical outcome at discharge. 
    • surgical intervention was associated with better outcome only in the patients whose GCS was 3–8 (p <.05)
• CT findings that are associated with poor prognosis
  • brainstem, bilateral hemispheric, multilobar, or transventricular injuries
  • injury to eloquent brain
  • subarachnoid hemorrhage
  • large intracerebral hemorrhage
  • midline shift
  • tram-track sign hemorrhage on either side of a dark center track in a perforating injury