The gold standard for the radiographic detection of skull base fractures is non contrast high resolution computed tomography. Thin-section multiplanar CT reformations, as well as 3-dimensional reconstructions, are helpful in the detection of subtle skull base fractures [4].

In the first place the SBFs are suspected in the presence of following symptoms:

• meningeal hemorrhage;
• brain contusion;
• subgaleal hemorrhage;
• pneumocephalus;
• hemorrage in mastoid cells and paranasal sinuses.

Anterior skull base fractures frequently accompany severe trauma to the frontal region or midface [1]. These frontobasal injuries lead to significant neurologic morbidity. The frontobasal region consists of the upper facial third (frontal bone/sinus and medial third of the superior orbital rim) and the anterior cranial base (nasoethmoid, cribriform plate, and planum sphenoidale) [3]. Manson et al. [3,1] analyzed 290 cadaver heads and established three distinct frontobasal fracture patterns based on impact site and force:

Type I: isolated linear anterior skull base fractures.

Type II: linear fractures of the frontal bone extending to the skull base

Type III: complex fractures that include comminution of the entire frontal bone along with comminution of the orbital roof.

Predictably, type III fractures had the highest complication rate (25 percent), with 74 percent resulting from the impure fracture combination (i.e., “cranial base crush”) [3]. Cerebrospinal fluid rhinorrhea and associated with it meningitis are the most common complications of anterior SBFs. CSF rhinorrhea complicates 4 to 48% of frontobasal fractures and pneumocephalus is seen 10 to 50% [1]. Meningitis develops in only 3% of patients if the leak lasts for less than 1 week, but it exceeds 50% if it persists for more than 2 weeks [1,3]. Approximately 80 percent of cerebrospinal fluid leaks accompanying nondisplaced or minimally displaced frontobasal fractures will close spontaneously within the first postinjury week [3]. Beyond that, anterior SBFs are associated with orbital injury and injury to cranial nerve I (anosmia).  Fig. 2

The middle cranial fossa is frequently divided into the central skull base and lateral (temporal) skull base [1]. Most fractures of the central skull base are direct extensions of frontobasal fractures and less frequently fractures of the clivus or posterior cranial fossa. Most of these fractures have either an oblique or sagittal orientation and extend through the sella and sphenoid sinus. An additional and frequently seen type is a transverse fracture orientated in a coronal plane resulting from a direct blow to the lateral skull and zygoma.  Fig. 3  Fig. 4

Temporal fractures, which are most common, are associated with carotid injury, injury to cranial nerves VII or VIII, and mastoid cerebrospinal fluid leak.

Central skull base fractures are also associated with injury to cranial nerves III, IV, V or VI and carotid injury [1,4].

Fractures involving the internal carotid artery (ICA) may result in transection, dissection, aneurysm/pseudoaneurysm, carotid cavernous fistula, or vascular entrapment in the fracture line [4].

Fractures of the posterior fossa are uncommon and usually result from a direct blow to the occiput [1]. They frequently involve the occipital bone and petrous segment of the temporal bone. Posterior skull-based fractures are associated with a cervical spine injury, vertebral artery injury, and injury to the lower cranial nerves[4]. These injuries are very serious and often the patients have hemiplegia or paraplegia. Also, the very frequent traumatic lesions of the posterior fossa are epidural hematoma and venous thrombosis.

Fig. 5 Fig. 6

Several clinical signs highly predictive of basilar skull fracture include [5]:

• Hemotympanum: Fractures that involve the petrous ridge of the temporal bone will cause blood to pool behind the tympanic membrane causing it to appear purple. This usually appears within hours of injury and may be the earliest clinical finding.
• CSF rhinorrhea or otorrhea: CSF leaks may be delayed hours to days after the initial trauma.
• Periorbital ecchymosis (raccoon eyes): pooling of blood surrounding the eyes is most commonly associated with fractures of the anterior cranial fossa. This finding is typically not present during the initial evaluation and is delayed by 1 to 3 days. If bilateral, this finding is highly predictive of a basilar skull fracture.
• Retroauricular or mastoid ecchymosis (Battle sign): pooled blood behind the ears in the mastoid region is associated with fractures to the middle cranial fossa. Like Raccoon eyes, this finding is frequently delayed by 1 to 3 days.
• Middle ear injury is seen in nearly one-third of patients and may present with hemotympanum, disruption of the ossicles, hearing loss and even CSF leak.
• Other features include dizziness, tinnitus, and nystagmus

Moreover, it is important to recognize normal anatomy findings that can mimic fractures, such as:

• vascular grooves
• skull sutures
• arachnoid granulations
• extrinsic and intrinsic fissures, bone canals.

Fig. 7: Fracture mimics

All of these structures are in predictable places, have good-seen cortical margins, are less hypodensive than fractures and have no adjoining scalp hematoma.