Cribriform Plate Fractures

Etiology

The most common cause of cribriform plate fractures is blunt force trauma to the face, which makes up 80%-90% of cases.[1] A fracture of the cribriform plate requires a heavy frontal impact and a significant mechanism of injury. This fracture rarely occurs in isolation and is generally associated with other facial bone fractures. As such, data on specific causes of cribriform plate fracture alone is lacking. Overall, the most common cause of midface fracture in adults is traffic accidents, which comprise nearly two-thirds of cases.[2] The next most common cause is assault at 21%, followed by falls at 9%.[2] Occupational injuries and sports-related injuries make up a smaller percentage.

In young children, fractures of the midface are more commonly due to falls. In children aged 11 to 14 years, sports-related injuries predominate, and by age 15 to 18, assault becomes most common. The remaining causes of cribriform plate fractures include penetrating trauma, such as gunshot wounds, and iatrogenic complications. Unlike in cases of blunt trauma, cribriform plate fractures do occur in isolation as a complication of endoscopic sinus surgery. The rate of CSF leak secondary to the iatrogenic complication is reported to be less than 1%.[3]

Epidemiology

Naso-ethmoid fractures comprise about 5%-15% of facial fractures.[1] Midface fractures are more frequently seen in males than females, at a rate of 3 to 1. The peak incidence is seen in ages 21 to 30 years.[2] Cultural and socioeconomic differences influence these rates.[2] 

Traffic accidents are the most common cause of cribriform plate fractures overall, and motorcycle accidents pose a particularly high risk.[2] Alcohol consumption is strongly associated with midface fractures. A study of 200 patients with midface fractures found 33% were under the influence of alcohol at the time of their injury.[2]

History and Physical

A patient presenting with significant trauma to the face requires extensive evaluation and should be managed in accordance with the Advanced Trauma Life Support guidelines.[4] A primary survey must be completed immediately to assess and treat life-threatening injuries. The survey consists of assessing the patency of the airway, breathing, and circulation with hemorrhage control. Appropriate cervical spinal precautions should be implemented. Facial fractures can lead to altered facial anatomy, airway compromise, and aspiration risk. Clinicians should have a low threshold for intubation if current or impending airway compromise is suspected.[5] A rapid neurologic assessment should be completed, and all patients with a Glasgow coma scale (GCS) score of 8 or below require emergent intubation. 

After addressing acute life threats, a secondary head-to-toe trauma evaluation should be completed. The head should be examined for scalp hematomas, lacerations, and depressed skull fractures. Assess for signs of a basilar skull fracture, including peri-orbital ecchymosis, known as "raccoon eyes," and retro-auricular ecchymosis, also known as "Battle sign" and hemotympanum.[4] Clear or bloody fluid draining from the nose or ear is concerning for a basilar skull fracture with a CSF leak. Specifically, clear rhinorrhea is highly suspicious for a cribriform plate fracture with a dural fistula. 

Attempt to obtain all available history from the patient, medics, family, and bystanders. Determine the mechanism of injury and the patient's past medical history. In cases of a motor vehicle collision, determine seat belt use, airbag deployment, steering wheel deformity, and condition of the vehicle. Perform a review of systems in patients that are responsive. Headache, nausea, vomiting, and alterations in consciousness are concerning for acute intracranial injury.

Stable patients with a cribriform plate fracture will likely present with post-traumatic midface pain and epistaxis. All such patients require thorough exams of the head, neck, face, ears, nose, and throat. If the epistaxis resolves but clear rhinorrhea persists, this is highly concerning for a post-traumatic CSF leak.

Evaluation

The preferred imaging modality for the diagnosis of cribriform plate fractures is head and maxillofacial computed tomography (CT). Ideally, this will be high resolution with 1 mm cuts, including sagittal, coronal, and axial views that should be performed.[6]

The filter test has been used to aid in identifying CSF in bloody secretions. When placed on the filter paper, CSF moves outward while blood moves inward, showing a "double halo" sign. This test, while quick and easy to perform, has not been shown to be significantly sensitive nor specific in detecting CSF; thus, further diagnostic studies are warranted. If present, nasal and/or otic secretions samples should be obtained and evaluated for beta trace protein and beta-2-transferrin. Beta trace protein is found in high concentrations in CSF. Beta-2-transferrin is found in CSF, aqueous humor, and perilymph. Positive tests of these two substances are highly indicative of a CSF leak.[7][8][9]

Treatment / Management

All basilar skull fractures warrant admission for observation and potential surgical treatment. The level of consciousness and additional intracranial injury play a large factor in the treatment of cribriform plate fracture. Conservative treatment tends to be chosen for those who initially present with a GCS >8. Most traumatic CSF leaks resolve spontaneously within the first seven days, and a lumbar drain may be employed to decrease intracranial pressure and facilitate spontaneous resolution[10]. A small percentage of post-traumatic CSF leaks may persist for several months. Surgical closure is more likely to be the chosen treatment for patients who initially present with a GCS of <8 or have a persistent leak for greater than 7 days. Leaks persistent for more than 7 days have an increased risk for the development of bacterial meningitis.[11][12] (B2)

An endoscopic repair has been shown to be highly effective, with a resolution rate of greater than 95%, and requires no additional treatment. If fractures are in the extreme anterior cribriform, sufficient access may not be possible endoscopically, and an open surgical approach may be required. If an open approach is used, minimizing retraction of the frontal lobes is important to optimize the olfactory function and decrease the chance of postoperative frontal lobe syndrome[13]. An anterior subcranial approach can be employed to minimize frontal lobe retraction in many cases. However, a formal anterior craniotomy may be required in rare instances.[14] Prophylactic antibiotic use is not currently supported for cribriform plate fractures due to a lack of research, though patients with an active CSF leak will be treated with antibiotics in many centers.[15](A1)

Differential Diagnosis

Given the severe mechanism of injury involved with cribriform plate fracture, these patients should be evaluated for concomitant traumatic brain injuries (TBI), intracranial hemorrhage, and other facial fractures.

Treatment Planning

Initial, conservative treatment involves bed rest and avoidance of Valsalva or other maneuvers that can increase intracranial pressure. Acetazolamide can be used to decrease CSF pressure, and a lumbar drain can be placed to measure opening pressures and maintain a lower intracranial pressure and facilitate spontaneous resolution of the leak.[16]

If the leak persists for more than 1 week, surgical repair can be entertained. High-resolution CT scans with 1 mm cuts are the preferred imaging modality to plan repair and image-guidance protocols can be used to facilitate intraoperative navigation. This imaging can also identify post-traumatic encephalocele that will need management also. All but most anterior cribriform fracture-related leaks can be managed endoscopically, and fascial or bone grafts, vascularized mucosal flaps, or allogenic materials have all been used successfully in repairs. It is important to confidently identify the leak site intraoperatively, and this typically requires a total ethmoidectomy and possible sphenoidotomy. If the leak can still not be identified, an intraoperative intrathecal fluorescein injection can help locate it. [17]

Prognosis

The prognosis of a cribriform plate fracture is variable and highly dependent upon initial presentation and concomitant injuries. For those patients who initially present with a GCS of greater than 8 and do not require surgical intervention, the prognosis is good, and CSF leaks generally resolve spontaneously. The prognosis of cribriform plate fracture alone is good, and complications, morbidity, and mortality are most often tied to concomitant injuries rather than due to the cribriform plate fracture itself.[18]

Complications

Anosmia, or a loss of smell, is a common complication of cribriform plate fracture. The injury is due to the damage of olfactory nerves or injury to the olfactory bulb itself. Anosmia can be partial or complete. If neurosurgical repair is indicated, an approach done without lifting the frontal lobes has been shown to decrease the risk of detaching olfactory elements and subsequent anosmia.[19]

Patients with a history of cribriform plate fractures have an increased risk of ascending infections and bacterial meningitis. The probability of developing meningitis is higher with a documented CSF leak. Higher rates of meningitis were noted, with fractures occurring more than one year ago. [20]

One study showed the majority of meningitis cases post cribriform plate fractures in the pediatric population were caused by S. pneumoniae and recommended the pneumococcal vaccination for those who displayed CSF leak.[21]

Cribriform plate fracture with persistent CSF leak can lead to a headache syndrome. The headaches are exacerbated by being upright and resolve when supine. This syndrome is similar to post-dural puncture headache, and the etiology (decreased intracranial pressure) is the same.  

Clinicians must evaluate for nasal septal hematoma in patients with cribriform plate fractures and midface trauma. An undiagnosed nasal septal hematoma can result in avascular necrosis of the septal cartilage and subsequent saddle nose deformity.[22]

Nasotracheal intubation and nasogastric tube placement are contraindicated in patients with midface trauma due to the possibility of tubes being passed into the cranial vault via a fractured cribriform plate.