CSF Rhinorrhea and Closure by FESS Approach.
A cerebrospinal fluid rhinorrhoea (CSF leak) occurs when there is a fistula between the dura and the skull base and discharge of CSF from the nose. CSF rhinorrhea commonly occurs following head trauma (fronto-basal skull fractures), as a result of intracranial surgery, or destruction lesions. A spinal fluid leak from the intracranial space to the nasal respiratory tract is potentially very serious because of the risk of an ascending infection which could produce fulminant meningitis.
A greater proportion of the CSF leaks in the patients resolved spontaneously. CSF fistulae persisting for more than 7-10 days had a significantly increased risk of developing meningitis.
Others conditions include osteomyelitis of the adjacent bone, congenital anomalies of the brain and its coverings such as meningoceles or meningoencephaloceles, and destruction lesions along the skull base . Pituitary tumors cause erosion of the sella turcica floor and are frequently associated with CSF rhinorrhea.
Detection of glucose in the sample fluid has been a traditional method for detection of the presence of CSF in nasal and ear discharge. Glucose detection is not recommended as a confirmatory test due to its lack of specificity and sensitivity . Interpretation of the results is confounded by various factors such as contamination from glucose-containing fluid (tears, nasal mucus, blood in nasal mucus) or relatively low CSF glucose levels (meningitis) . Studies have shown that glucose can be detected in airways secretions from people with diabetes mellitus, stress hyperglycaemia and people with nasal epithelial inflammation due to viral colds.
Diagnosis through nasal inspection by Nasal Endoscopy must be done.
Beta-2 Transferrine test
The beta-2 transferrin assay is the test of choice because of its high sensitivity and specificity.
In some cases, there is contamination of the material with blood or other secretions, so the test with beta-2 transferrine becomes mandatory.
Beta-2 transferrin is a carbohydrate-free (desialated) isoform of transferrin, which is almost exclusively found in the CSF and blood or nasal secretion does not disturb the test . Beta-2 transferrin is not present in blood, nasal mucus, tears or mucosal discharge.
Beta-2 transferrin was reported to have a sensitivity of near 100% .
The most reliable methods of distinguishing between a traumatic or neoplastic lesion and a spontaneous CSF rhinorrhea are high-resolution computed tomography (CT) and magnetic resonance (MR) tomography .MR imaging is reserved for defining the nature of soft tissue i.e. inflammatory tissue, meningoencephalocele or tumor . In MR images we can find brain herniation into the ethmoid or frontal sinuses .
Patients with CSF leaks that persist greater than 7-10 days are at risk for meningitis, and maybe require surgical intervention. Prophylactic antibiotics may be effective and should be considered in this group of patients .
Most of CSF leaks close spontaneously within 7 to 10 days Although most trauma-related CSF leaks resolve without intervention, conservative treatment of CSF leaks may lead to bacterial meningitis, therefore surgical closure of leaks or defects at the skull base should be considered treatment of choice to prevent ascending meningitis.
Conservative management consists of a 7-10 day trial of bed rest with the patient in a head-up position with antibiotics.
The goal of surgical therapy is repair of the dural defect contributing to the CSF leak .
The surgical management of CSF leak has changed significantly after the introduction of functional endoscopic sinus surgery (FESS) in the management of sinusitis.
The clear anatomical exposure of the roof of the nasal and the sinus cavities by the endoscope offers the surgeon an opportunity to identify the area of the CSF leak, which enables one to adequately plan the treatment .
It is currently accepted that endoscopic intranasal management of CSF rhinorrhea is the preferred method of surgical repair, with higher success rates and less morbidity than intracranial surgical repair in selected cases .
Endonasal endoscopic approach can be preferred for the closure of uncomplicated CSF fistula, located at the anterior or posterior ethmoid roof and in the sphenoid sinus, due to its minimal postoperative morbidity.
Compared with external techniques, endoscopic techniques have several advantages, including better field visualization with enhanced illumination and magnified-angle visualization. Other advantages include the ability to clean the mucosa off the adjacent bone without increasing the size of the defect and accurate positioning of the graft. Multiple studies demonstrate a 90-95% success rate with closure of skull base defects using the endoscopic approach.
Uncomplicated CSF fistula, located at the posterior wall of frontal sinuses can be repaired extradurally with osteoplastic frontal sinusotomy.
Intracranial approaches should be reserved for more complicated CSF rhinorrhea which results from extensive comminuted fractures of the anterior cranial base and is accompanied with intracranial complications .
Anosmia is the most frequent permanent complication mentioned.
Role of Antibiotic-Prophylaxis
The value of antibiotic prophylaxis in patients with CSF leakage is debatable. The question of the use of prophylactic antibiotics in patients with CSF rhinorrhea stems from the reasonable assumption that a communication between a sterile environment (intracranial vault) and a nonsterile environment (sinonasal cavity) will ultimately result in infection of the sterile compartment.
The use of prophylactic antibiotics in patients incurring skull base injuries during endoscopic sinus surgery has not been studied in a randomized controlled fashion. However, administering antibiotics in this setting is reasonable because the skull base injury occurred during surgery for chronic inflammatory/infectious sinusitis and implantation of bacteria into the sterile compartment may have occurred.