Traumatic CSF Fistula

Traumatic cerebrospinal fluid (CSF) fistulas result from a tear in the dura and arachnoid and are often found with a fracture of the skull base that is in communication with the nasal cavity, paranasal sinuses, or middle ear. In general, the most common causes of CSF fistulas are motor vehicle accidents, falls, and assaults. The reported incidence of skull base fractures after nonpenetrating head injury ranges from 7% to 24% and that of associated CSF fistulas from 2% to 20.8% after head injury.

CSF fistulas usually occur with fractures of the anterior and middle cranial fossae of note you can divide the timing of CSF leak into early, delayed and very late for early CSF leak causes include torn dural margins, extensive loss of bone, high intracranial pressure secondary to insult and endocrine dysfunction. Causes of delayed CSF leak include shrinking of blood clot that was previously acting as a scaffolding to prevent leak, maturation of scar, necrosis of bone. Very late causes include normal atrophy of brain previously plugging dural defect, encephalocele that formed and grew to a point allowing for drainage. When investigating Pts for potential CSF leak there are a multitude of bedside laboratory and radiographic images that can be performed. While at the bed side clear fluid from drainage site can be procured on white napkin CSF will migrate further then blood and mucus creating in essence what appears to be a halo. Glucose test strips can also be used to determine likelihood of CSF since these are positive at levels of CSF as low as 2 meg and CSF has glucose concentration roughly 60 percent that of serum glucose, a negative glucose test strip can eliminate likelihood of CSF. Regarding laboratory data b2 transferin test is the most sensitive indicator for likelihood of CSF leak since this is found only in CSF, lymph, and vitreous humor. Fluid can be analyzed for chloride and a concentration greater then 110meq suspicious for CSF. Regarding radiographic findings A CT scan is the most useful investigation for determining the possible site of a CSF fistula and predicting the likelihood of spontaneous healing. Adding thin cuts to the skull base allows better visualization of fracture lines. Using MRI to assess for CSF leak On T2-weighted images, CSF will appear white and perimucosal discharge and nasal disease will be darker. Mucosal disease can be highlighted by the administration of gadolinium. MRI signs indicative of a CSF fistula include a CSF signal in the perinasal sinuses that is continuous with intracranial CSF. If suspicion for CSF leak is still high tracer studies can be performed using flourescein or ct cisternography

In regards to treatment there is conservative verse surgical care. Conservative care can be tried if fractures are nondisplaced and linear. Treatment includes bed rest with hob elevated to 30 degrees. Avoidance of maneuvers that can increase pts intracranial pressure including blowing nose, coughing, sneezing. If Pts continue to leak after three days lumbar drainage can be employed in attempt to increase CSF outflow allowing fistula to scar down. If conservative management fails or is not a option surgical intervention then becomes mandatory, at this point the decision becomes whether to take patient to or in expedited or delayed fashion. Indications for early surgery include penetrating injury, meningitis, intended surgery for another intracranial lesion with pathology adjacent to fistula, parenchyma herniation through nose. Indications for delayed surgery include failed conservative management beyond 10 days continued intracranial air after 10 days, meningitis.

Antibiotic prophylaxis continues to be debated with multiple studies failing to definitively state whether abx is indicated. Arguments against antibiotic prophylaxis include antibiotics usually have poor penetrance into CSF, antibiotic use may allow super infection as they select out against common bacteria and finally there is no known time at which antibiotic treatment is mandatory.

As surgical procedures continue to evolve we will continue to see a paradigm shift from routinely performing open craniotomy for repair to endonasal approach.