High velocity pTBI is often associated with significant cerebral injury. Initial presentation may be characterized best by the wounding trajectory. If the patient survives, significant cerebral edema and swelling can be anticipated over the early days following the initial injury secondary to the primary and secondary ballistics cavities74,75. For the purposes of this algorithm, the term "multiple lobes" is defined as a penetrating injury with trajectory that traverses more than one lobe or cerebral compartment. Cerebral injury of this type can be associated with a mass lesion, usually defined as a hematoma, midline shift, and cerebral edema. As with all trauma evaluations, the initial physical examination is crucial. Localization of the entry, and if applicable, exit wound(s) is critical as this will inform understanding of possible missile/fragment primary trajectories. Rapid CT and CTA should be obtained as soon as safe and feasible in order to determine additional extent of injury, including any secondary trajectories, skull base injury, and CTA detectable vascular injury (traumatic aneurysms, arterial occlusions)10,76-79. It is worth noting that injury to the skull base and cerebral vasculature may accompany severe cerebral injury, and therefore the Skull Base Injury and Traumatic Vascular Injury Toolkits may require consultation.

Pending a Futility Assessment, injury of this type will almost certainly require surgical intervention. If surgery is deemed necessary, there is little benefit to delay (VII-1 Urgency of Neurosurgery, Level IV and expert consensus)44,53-57. One report recommends surgery within 5 hours if possible to improve outcomes80. Resuscitation consisting of PRBC:FFP:Plt in a 1:1:1 ratio or whole blood should begin en route to or immediately upon arrival to the operating room in anticipation of significant blood loss81,82. The goals of surgery depend largely on the location and extent of injury, and include cerebral decompression, debridement of local bone/foreign bodies/hair, etc., and control of hemorrhage (Section VII-3, Extent of Debridement). The surgical plan depends heavily on the wounding pattern. For example, a unilateral supratentorial GSW to the brain with retained missile may be best addressed with a unilateral exposure. A bifrontal injury may be best addressed with a bifrontal exposure. In any case, the approach should account for a large decompression with planned craniectomy if cerebral swelling or edema is present or anticipated (Section VII-1, Urgency of Neurosurgery, Level IV). The decision to save or discard the bone may depend heavily on the degree of foreign body contamination or disruption seen at the initial surgery. Debridement of locally indriven bone, foreign bodies, and hair is appropriate, and this can be facilitated by irrigation of the missile/fragment tract. It is not necessary, and may be detrimental, to search for and remove deeply indriven fragments and bone (Section VII-3, Extent of Debridement, Level III)23,25,30,37,60,61,63,66,83-92. Following decompression, control of hemorrhage, and local debridement, dural and skin closure is necessary. Every effort should be made to avoid cerebrospinal fluid leak from the skin in order to prevent infection (Section VII-4, Prevention and Management of Cerebrospinal Fluid Leaks, Level II, Consensus)53,59-72,93. It is often not possible to obtain a watertight dural closure. Dural onlay with either synthetic dural replacements, pericranium or other tissue substitutes (fascia lata, etc), and/or dural sealants will likely be necessary. Subgaleal and, if possible, ventricular drain placement may facilitate and maintain the necessary multilayer, water tight skin closure.

Certain circumstances require additional guidance and explanation. The presence of skull base injury, protruding foreign bodies, and cerebrovascular arterial injury will be addressed in specific Toolkits/Algorithms. Occasionally, the penetrating trajectory will include one or more dural venous sinuses. This will present with noticeable transcutaneous blood loss from the entry and/or exit wound, sinus disruption on CT/CTA, or in the operation room following exposure and decompression. There are numerous published and well-established techniques addressing the management of venous sinus injury and/or violation (Section VII-8, Management of Penetrating Venous Sinus Injuries, Level IV, Consensus)66,67,94-98. In general, significant blood loss should be anticipated, with blood product transfusions initiated prior to surgical repair. Standard techniques including elevating the sinus injury above the heart, but with irrigation and covering the area of injury with a wet sponge to reduce the risk of air embolism should be employed. Direct insertion of balloon catheters (foley, etc.) proximal and distal to the area of sinus laceration may help control catastrophic hemorrhage and facilitate repair94. Injuries to the anterior third of the superior sagittal sinus may be addressed with sinus ligation if direct repair is not possible. Efforts including direct repair, tissue patch (pericranium, muscle, other tissue), dural inversion, or, less commonly, venous graft, should be made to preserve and maintain the middle to posterior third of the superior sagittal sinus if possible. Repair and preservation of the dominant transverse sinus, if known, is preferable, though ligation may also be necessary. Endovascular interventions in this setting may include delayed thrombectomy should malignant edema and cerebral infarction present in a delayed fashion97.

While it is not necessary to remove deeply indriven missile or metallic fragments at the time of initial surgical decompression (see above), delayed removal may be necessary if the fragment becomes infected or migratory99. Migration patterns include intraventricular, subarachnoid, within the missile/fragment tract, within a developing abscess or infection, and intravascular. Follow up imaging is necessary to ensure missile/fragment stability. A mobile fragment, depending on location and eloquence of surrounding brain, may require delayed removal.

If decompressive craniectomy is performed at the first operation, delayed cranial reconstruction will be necessary. It may be necessary, given significant contamination or fragmentation, to discard the removed autologous bone. Use of synthetic cranioplasty materials may be necessary at the time of reconstruction. The literature currently does not support optimal timing for cranial reconstruction in the setting of closed and penetrating brain injury (Section VII-9, Timing of Cranioplasty, Consensus)100-103. Prudence and judgement should be exercised with respect to timing to reduce the risk of infection while simultaneously reducing the risk of post-craniectomy syndrome of the trephined.