Fraktur Basis Kranii

01Pathophysiology

The cranial base (skull base) is formed by five bones arranged into three distinct fossae. The anterior cranial fossa is composed of the orbital plates of the frontal bone, the cribriform plate of the ethmoid, and the lesser wings of the sphenoid. The middle cranial fossa is formed by the greater wings of the sphenoid and the petrous portion of the temporal bone. The posterior cranial fossa consists of the occipital bone and the posterior surface of the petrous temporal bone.

When a high-energy impact strikes the skull, forces are transmitted inward and concentrate at the thinnest, weakest points of the skull base. The cribriform plate and the tegmen tympani (roof of the middle ear) are among the most fragile regions and therefore fracture most readily. Foramina and suture lines serve as additional stress concentration points.

The pathology of the clinical signs follows directly from the anatomy. When the cribriform plate fractures, the overlying dura tears, creating a direct communication between the subarachnoid space and the nasal cavity. CSF then leaks through this defect, producing CSF rhinorrhea. Likewise, a fracture through the petrous temporal bone disrupts the tegmen tympani and the dura, allowing CSF to drain into the middle ear and out through the external auditory canal as CSF otorrhea. If the tympanic membrane is intact, fluid accumulates behind it, resulting in hemotympanum (blood visible behind the drum on otoscopy).

Raccoon eyes (bilateral periorbital ecchymosis) develop because blood from an anterior fossa fracture dissects along the loose areolar tissue of the periorbital region. Battle sign (ecchymosis over the mastoid process) occurs when blood from a middle or posterior fossa fracture tracks posteriorly along the fascial planes to the retroauricular area. Both of these signs are delayed findings, typically appearing 12 to 72 hours after injury; their delayed onset is the reason they are not useful for initial diagnosis but are highly suggestive once present.

Cranial nerves traversing the skull base are vulnerable to direct transection, stretching, or compression. CN I (olfactory) passes through the cribriform plate and is commonly injured in anterior fossa fractures, leading to anosmia. CN VII (facial) and CN VIII (vestibulocochlear) travel through the internal auditory canal within the petrous temporal bone, and temporal bone fractures frequently damage one or both, producing facial paralysis and hearing loss or vertigo. CN VI (abducens) has a long intracranial course anchored at the petrous apex (Dorello canal) and is susceptible to stretching injury from any skull base fracture that shifts intracranial contents.

Pneumocephalus (air within the cranial cavity) occurs when a fracture creates a pathway between an air-filled sinus or the middle ear and the intracranial space. In most cases, a small amount of intracranial air resorbs on its own. However, a tension pneumocephalus can develop if a one-way valve mechanism allows air to enter but not exit the cranial vault. This is a neurosurgical emergency because the expanding air mass causes direct compression of brain parenchyma.

02Classification and Clinical Manifestation

By Cranial Fossa Location

Temporal Bone Fracture Classification

When a patient presents with immediate-onset facial nerve paralysis after temporal bone trauma, the prognosis is poor and surgical exploration is often indicated.

Delayed-onset facial palsy (appearing hours to days later) carries a much better prognosis and is usually managed conservatively with observation and corticosteroids.

03Diagnostic Workup

CT head without contrast is the best initial test and the imaging study of choice in any patient with head trauma and suspected skull base fracture. It is fast, widely available, and can simultaneously identify fracture lines through the skull base, the presence and extent of pneumocephalus, and any associated intracranial hemorrhage (epidural, subdural, subarachnoid, or intraparenchymal). Fracture lines through the skull base can be subtle on standard axial images, so bone window settings and coronal reformats are important for visualization.

If a temporal bone fracture is suspected based on clinical signs (hemotympanum, hearing loss, facial nerve palsy, CSF otorrhea), a high-resolution CT of the temporal bones with thin-cut (0.5 to 1 mm) axial and coronal reconstructions should be obtained. This study delineates the fracture orientation, determines whether the otic capsule is violated (which correlates with sensorineural hearing loss and vestibular injury), and evaluates the ossicular chain.

The halo sign is a quick bedside test performed by placing a drop of the suspected fluid on filter paper, gauze, or a white sheet. If CSF is mixed with blood, the blood collects centrally while the CSF diffuses outward, forming a clear ring (halo) around the blood. While this test is easy to perform, it is not highly reliable because other fluids (saline, mucus) can produce a similar ring pattern.

Beta-2 transferrin is the gold standard for confirming that a fluid is CSF. This protein isoform is found almost exclusively in CSF (and in small amounts in perilymph and aqueous humor). It is not present in blood, nasal secretions, tears, or saliva. The test has a sensitivity and a value approaching the high 90s for percentage, making it the most accurate confirmatory study. Glucose testing of the fluid (CSF contains glucose whereas nasal mucus does not) is a less reliable alternative and is not recommended as a standalone confirmatory method.

CT cisternography is reserved for patients with confirmed CSF leak who are being considered for surgical repair. Intrathecal contrast is injected via lumbar puncture, and CT images are obtained to identify the exact site where contrast exits the subarachnoid space. MRI can be used as a non-invasive alternative to locate dural defects and meningoceles, using heavily T2-weighted sequences (e.g., constructive interference in steady state, or CISS).

04Management and Treatment

Immediate stabilization follows standard Advanced Trauma Life Support principles. Airway, breathing, and circulation take precedence. The cervical spine must be immobilized until injury is excluded, because the mechanism capable of fracturing the skull base carries a significant risk of associated cervical spine injury.

The most tested management point is the contraindication to nasogastric tube and nasal airway placement. In patients with anterior cranial fossa fractures (or suspected basilar skull fractures in general), a tube introduced through the nose can pass through the fractured cribriform plate directly into the cranial vault. If gastric decompression is required, an orogastric tube must be used instead. If endotracheal intubation is needed, the oral route is mandatory.

CSF leak management is primarily conservative. The head of the bed is elevated to 30 degrees to reduce intracranial pressure at the fracture site and promote dural healing. The patient is instructed to avoid any activity that raises intracranial pressure, including nose blowing, straining during bowel movements (stool softeners are prescribed), vigorous coughing, and bending forward. Under these conservative measures, approximately 85% of traumatic CSF leaks resolve within 7 to 10 days.

If the leak persists beyond 7 to 14 days, a lumbar drain is placed. This continuously diverts CSF from the lumbar cistern, reducing CSF pressure at the dural defect and allowing the tear to seal. Lumbar drainage is maintained for 3 to 5 days, and the drain is then clamped and the patient observed for recurrence.

Surgical repair (craniotomy with direct dural repair or grafting) is indicated in the following situations:

• Persistent CSF leak despite lumbar drainage

• Recurrent meningitis

• Expanding or tension pneumocephalus

• Depressed skull base fracture with mass effect

• Significant vascular injury (e.g., carotid artery dissection or carotid-cavernous fistula) requiring intervention

Prophylactic antibiotics for CSF leak are a classic exam topic. Despite the intuitive concern about meningitis risk from an open communication between the subarachnoid space and the external environment, evidence does not support routine prophylactic antibiotics. Systematic reviews, including a Cochrane review, have found no significant reduction in meningitis incidence with prophylactic antibiotics in basilar skull fracture with CSF leak. In fact, their use may select for resistant organisms. The correct management is vigilant monitoring for signs of meningitis (fever, worsening headache, nuchal rigidity, altered mental status) rather than empirical antibiotic coverage.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The single most common way students lose points on this topic is by selecting nasogastric tube placement as a management step in a trauma patient who has signs of a basilar skull fracture. The vignette will describe a patient with head trauma, raccoon eyes or CSF rhinorrhea, and then ask for the next step in management or which intervention to avoid. Students who do not recognize the constellation of basilar skull fracture signs will choose NGT placement for gastric decompression without hesitation, which is the intended trap. The correct answer is always an orogastric tube.

A second common trap involves prophylactic antibiotics. The vignette may describe a patient with a confirmed CSF leak and then offer "start prophylactic antibiotics" as one of the answer choices. This is a strong distractor because the clinical reasoning seems sound (open communication with the environment should logically increase infection risk). However, the evidence-based answer is that prophylactic antibiotics are not indicated and that the patient should be monitored for signs of meningitis instead.

A third testing angle is the timing of physical exam signs. A vignette may present a patient immediately after head trauma and ask whether raccoon eyes or Battle sign are expected. At the time of initial presentation, these signs are typically absent because they take 12 to 72 hours to develop. The correct best initial test is CT head, not reliance on these delayed physical examination findings.

Finally, students must distinguish between immediate and delayed facial nerve palsy after temporal bone fracture. Immediate, complete paralysis suggests nerve transection or severe compression and warrants surgical exploration. Delayed palsy suggests edema or hematoma and is managed conservatively with corticosteroids and observation. The exam expects you to match the timing of onset to the correct management approach.

The core competency being tested across all of these question stems is the ability to recognize the clinical pattern of basilar skull fracture from indirect signs (periorbital and mastoid ecchymosis, CSF leak, cranial nerve deficits) and to know the absolute contraindications (no nasal intubation, no nasogastric tube) and the evidence-based nuances (no prophylactic antibiotics, conservative CSF leak management) that differentiate a well-prepared student from one relying on intuition alone.