Introductory Chapter: Penetrating Skull Base Injuries

1. Introduction

Penetrating skull base injuries (PSBI) can be caused by a range of mechanisms, and present a diagnostic and management challenge [1, 2, 3, 4, 5]. Usually, these injuries are caused by sharp objects, and these objects get entry into the skull via oro-cranial, transorbital intracranial, or transnasal routes [6, 7, 8]. While examining this group of patients, a high index of suspicion as if the entry wound is small, these lesions can be overlooked, hence, the overall incidence may get under-reported [4, 9]. A range of objects have been reported to cause PSBI raging from toilet brush handle, arrows, chopsticks, flatware, screwdrivers, keys, car antenna aerials, scissors, knives, pitchforks, crochet hooks, knitting needles, breech pins, umbrella bibs, crowbars, and iron rods [4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18]. There is an ongoing need to better understand PSBIs including associated complications, and to develop effective management protocols for these sub-groups of traumatic brain injuries [1, 19, 20, 21, 22, 23, 24].

2. Epidemiology

In view of low incidence, the overall epidemiology is largely compiled from reported cases and experiences from different institutions [4, 25, 26, 27, 28, 29]. Common causes of PSBIs include accidents, suicide attempts, and assaults [30], accounting for approximately 0.4% of all cases of head injuries [31]. The risk of injuries is higher in children who may be left unattended due to various reasons or attended by younger siblings [32]. PSBIs can be caused by low-velocity projectiles, i.e. the impact velocity < 100 m/s [33]. In cases of PSBIs, the foreign bodies can penetrate the cranial cavity via the orbital roof route as the orbital plate of the frontal bone, through face and facial bones, through the nasal cavity, or may directly penetrate the skull bones if the force is strong enough [5, 16, 18, 21, 34, 35, 36].

3. Imaging

In addition to careful and systematic clinical examination, radiological imaging has improved our approach to detect PSBIs as it will show the presence and route of foreign bodies and, extent of injury to bones and brain parenchyma [21]. The modalities of imaging include CT scan (including 3-D reconstruction) with bone window, MRI, X-ray skull, and in ocular route of entry, the ultrasound imaging of the orbit and its contents [1, 37]. The presence of radiopaque foreign bodies including metallic foreign bodies can be well visualized on CT scan and radiographs, however, organic foreign bodies including peanut, wood, or bamboo pieces may be missed [4, 5, 6, 38, 39, 40]. Non-metallic foreign bodies can be better visualized on contrast-enhanced magnetic resonance imaging (MRI) [41, 42]. CT angiogram is to assess the cerebral vasculature as well as the magnitude of bone loss or damage during these injuries [1].

4. Management

A combination of careful history, clinical examination, radiological imaging, and high index of suspicion can help in planning the comprehensive management of patients with PSBIs [40]. Once the details of the trajectory of foreign body, presence of absence including the site of CSF leak and the details and associated intracranial hematomas or vascular injuries are obtained, a strategy to treat conservatively or surgical approaches can be planned [1, 28, 35, 43, 44]. The basic principles are early removal of foreign (to reduce the risk of infection), removal of foreign body, and meticulous repair of the defect particularly of the dura to stop or prevent CSF and reduce the risk of meningitis and other catastrophic complications [6, 8, 21, 28, 40, 45, 46]. This can be followed by broad-spectrum antibiotics based on the institute policy or available guidelines, which can be changed to appropriate antibiotics after the culture and sensitivity report is available [6, 40, 47, 48, 49].

5. Complications

PSBI can be associated with various complications including intracranial infections, cerebrospinal fluid leaks, intracranial hemorrhage, pneumocephalus, and cerebral edema [2, 3, 4, 5]. Appropriate antibiotics can be selected aiming to manage the Staphylococcus aureus and Gram-negative organisms as these are the most common organisms, later can be changed to the antibiotics based on culture and sensitivity patterns [16, 30, 47, 50, 51]. It is of utmost importance to anticipate the potential risk of CSF leak and take adequate measures to repair the defects in bone and remove the foreign bodies [1, 6, 52, 53, 54]. The complications can be potentially prevented by appropriate and timely management interventions including careful and thorough irrigation of the wound to remove contaminated bone and tissue fragments and any foreign bodies [30, 35]. Post-operative imaging particularly a CT scan brain can be performed to ensure the removal of foreign bodies or any new or expanding parenchymal hematomas [55, 56].

6. Conclusions

In summary, regular follow-up with patients who have PSBIs can help recognize any infection complications or CSF leaks. If the patient has sustained subtle vascular injuries, a high index of suspicion and appropriate investigations like CT angiography can help to diagnose the formation of pseudoaneurysms or any delayed intracranial hemorrhages [30, 57, 58, 59, 60]. Patients prone to post-traumatic acute stress or adaptive disorder can be subjected to a comprehensive psychiatric assessment and can be managed if there are signs of distress [30]. Although PSBIs due to low-energy penetrating injuries are not common, knowledge and understanding of the mechanism and management of these injuries are important to achieve favorable outcomes. The management of PSBIs requires recognition of subtle external injuries, understanding of clinical approach algorithms, available management options, and the spectrum of complications, as these will help to decide the optimal treatment approach for each individual patient.