Penetrating cerebral (craniocerebral or orbitocerebral) injuries can be divided between missile and nonmissile injuries. The missile injuries are caused by shrapnel or bullets, which carry a high incidence of morbidity and mortality5,12
and are associated with shock waves, cavitations,13
and additional concentric zones of injury related to blast effect.14
The nonmissile (stabbing) injuries are, by comparison, relatively rare and usually caused by objects such as knives, with an impact velocity of less than 100 m/s and pathophysiology related to tissue laceration and maceration restricted to the wound tract.15
They are, therefore, more amenable to treatment and carry a better prognosis than missile injuries.
The adult calvarium in most instances provides an effective barrier of protection against stab wounds. However, there are specific areas of weakness, such as the orbit, skull base foramina, anterior fossa floor, and temporal squama where the skull is more penetrable.1,11
The amount of force needed to penetrate the skull in the temporal region is estimated to be 5 times greater than that of the skin, as compared with 11 times that of the skin in the parietal region.16
Transorbital skull penetration follows two main pathways: either medially into the superior orbital fissure through the cavernous sinus and toward the brain stem (as seen in case 2) or superiorly through the thin orbital plate into the frontal lobe. In one report, the orbital roof was observed as the entry point in 89% of cases and could be explained by the tendency of the victims to extend their heads at the time of the injury, exposing the orbital roof to the direction of the penetrating object.13
A third, least common transorbital route includes the optic canal.17
Early recognition of these injuries is essential to ensure the best possible outcome. This can sometimes be challenging in cases of nonretained objects where the entry point may appear trivial or be hidden by hair (as seen in case 3). Additionally, the patients may present with good initial Glasgow coma scale (GCS) presentation in many cases, making it difficult to appreciate the extent of the injury, especially in children.13,18,19
A high index of suspicion is needed in patients presenting with scalp injuries because the actual amount of injury may be more extensive than what appear on the surface. A meticulous examination of the scalp and thorough neurological and radiological assessment are required to evaluate the extent of the damage.18
An initial head CT is the most effective tool for initial investigation of penetrating injuries to the brain, but it fails to identify plastic, wood, or soil.18
Given the high association of vascular abnormalities with such injuries, a CT angiogram is recommended in all cases, although the presence of metallic artifacts from the retained foreign body may limit visualization of intracranial contents.20
Therefore, when a high index of suspicion for a vascular injury exists, an angiogram should be performed. For the same reason, a second head CT should be considered after removing the foreign body to look for missed brain contusion or hemorrhage obscured by artifact in the original scan.
Situations in which cerebral angiography is indicated in the literature, given very high likelihood of associated vascular injury, include: orbitofacial or pterional entry point, presence of intracranial hematoma on CT, injuries with fragments crossing two or more dural compartments, delayed or unexplained subarachnoid hemorrhage, or delayed intraparenchymal hematoma.20
The treatment goals are to treat and prevent both short- and long-term complications associated with these injuries. In the short term, the objective is to remove the foreign object, avoiding further neurological injury, hemorrhage, and possibly death. Long-term management includes prevention and treatment of vascular abnormalities, persistent CSF leakage, infection, and seizures.
The literature is inconsistent in respect to the safety of blindly removing retained objects from the skull. Some authors suggest that blind removal of a retained blade is acceptable,21
others claim that the safety of blind removal is unknown due to the lack of evidence-based studies,5
and some authors suggest that blind removal is unacceptable.22
In our experience, we feel blind removal is unacceptable, and removing the retained blade prior to obtaining high-resolution imaging imposes undue risk on the patient, including possibly death. We routinely use high-resolution CT scan, CT angiogram, and formal four-vessel cerebral angiogram to assess both brain parenchyma injury as well as potential vascular injury prior to surgical planning. As we reported in our first and second cases, the high-resolution imaging protocol was critical to understanding the relationship of the knife blades to intracranial vascular structures, allowing us to successfully remove the retained blades without causing further injury and to plan the necessary craniotomies to visualize the removal of the offending object around the vascular structures at risk under direct vision with proximal control.
The most common vascular complications that can result from these injuries are usually traumatic pseudoaneursym formation or carotid-cavernous fistula.23
Traumatic aneurysms comprise less than 1% of intracranial aneurysms.24,25
The most common aneurysm associated with penetrating brain injuries is actually a false or pseudoaneurysm, rather than a true aneurysm. These lesions usually do not have a neck, are irregularly shaped, and have delayed filling and emptying.26
Kieck and de Villiers reviewed vascular lesions secondary to penetrating trauma and found abnormalities in 26 of 74 patients, with the largest proportion of lesions being aneurysm formation (42%).27
Traumatic aneurysms may occur in a delayed fashion and carry a 50% mortality rate if left untreated.26,27,28,29
Not all these lesions are visible on initial angiography and therefore a second angiogram should be performed 2 to 3 weeks later in all patients with penetrating brain injuries. Our third case exemplifies this phenomenon. In Kieck and de Villiers' series, 80% of the untreated aneurysms ruptured with subsequent death of the patient, and 100% of the aneurysms that were treated had good outcomes.27
Pseudoaneurysms following transcranial or transorbital stab wounds have a tendency to form in the peripheral vessels—sylvian candelabra and median hemispheric vessels—as opposed to the circle of Willis. They are usually found along the course of the arteries as opposed to vascular bifurcations. Haddad et al30
found that these lesions range in size from 2 mm to 15 mm and are multiple in 20% of the patients. Their natural history is more malignant than congenital aneurysms, with greater propensity for intraoperative rupture. Surgical mortality of these lesions varies from 15 to 20%.31
Therefore, aggressive management of traumatic pseudoaneurysms associated with penetrating brain injuries is warranted to prevent life-threatening hemorrhage and/or thromboembolic phenomenon. Oftentimes, these aneurysms cannot be safely clipped, and therefore trapping or occlusion of the parent vessel may be necessary. Preliminary results suggest that placement of stent grafts through endovascular techniques associated with appropriate antiplatelet therapy may be a safe and effective method to treat such traumatic ICA pseudoaneurysms.32
The main question still unanswered is the long-term efficacy of stenting in this setting.
Infectious complications, such as brain abscesses and meningitis, are also associated with penetrating brain injury, being found in 48 to 64% of cases7
; however, in 20% of cases, microbiological culture remains sterile,33
and this also happened to our case 3. Due to the incidence and potential severity of this complication, it is essential to use broad-spectrum antibiotic prophylaxis in these patients for at least 7 to 14 days.23,34
Other factors associated with higher likelihood of infectious complications include CSF leaks, air sinus wounds, transventricular injuries, or wounds crossing the midline.19
Whenever an intracranial abscess occurs, presence of a retained foreign body should be suspected and investigated.13
About 30 to 50% of patients suffering penetrating brain injuries will develop seizures, with up to 10% of them appearing early (first 7 days after trauma). Prophylactic antiseizure drugs are recommended during the first week after injury to reduce the incidence of early posttraumatic seizures.19
Stabbing injuries to the brain are more frequently seen as a cause of emergent neurosurgical admissions in South Africa. The largest report in the literature regarding nonmissile penetrating injury is from a neurosurgical group in South Africa where cranial stab wounds are a frequent cause of emergent admission. In this study, the presenting GCS score was identified as the most indicative prognostic factor of long-term outcome.35
Other predictive factors included presence of intraventricular hemorrhage, intracranial hemorrhage, and number of surgical procedures.35
Additionally, there was a marked association between vascular abnormalities (41% cases) and mortality (76.5% cases), especially when brain stem injury was involved.
Other reports confirmed the presenting GCS score as the strongest prognostic indicator of outcome after penetrating brain injury.16,19
Such injuries in the vast majority of the Western world remain uncommon among civilians and are usually related to violence, accidents, or suicide attempts in association with mental disorders.19