Traumatic CSF leakage occurs in 2% of head trauma patients, and accounts for 12–30% of all skull base fractures. Persistent CSF leaks often require surgical repair. Following repair, early recurrence can occur whereas the occurrence of delayed fistula is less common.
The qualitative diagnosis of CSF rhinorrhea is relatively simple,compared with the determination of sugar content[2, 3], the determination of beta-transferrin , is more sensitive and specific. However, the difficulty lies in the determination of the location of CSF leakage, which is of great significance to clinical decision-making. The detction of bony defect is not difficult, and dural defect may be indicated by indirect signs. In most cases, the defects are contiguous. The most significant displacement of fracture slices are mostly the location of the fistula . Patients with chronic traumatic CSF leakage can be inferred from the presence of meningeal encephalocele on MRI T2 images and abnormal accumulation of CSF. CT cisternography is a good method to show the fistula. However, it has been noted that no imaging techniques are particularly useful.In this case, CT cisternography suggests that the bony defect is in the frontal sinus. However, this method is static and does not dynamically show CSF flow,that is, the dural defect cannot be clearly shown. In this case, the dural defect was found to be non-contiguous with the bone fracture.
Delayed post-traumatic CSF rhinorrhea is more inclined to surgical treatment to reduce the risk of intracranial infection. There are two kinds of surgical repair methods: craniotomy and transnasal approach[10, 11]. Common craniotomy incisions include unilateral frontal incision and bilateral frontal coronal incision. It is suitable for patients with large skull base defects and extensive repairs, and for patients with frontal sinus opening. The transnasal approach is more suitable for those leakages in the sphenoid sinus, planum sphenoidale, tuberculum sellae, and the cribriform plate. These defects are generally small . Therefore, identifying the fistula, including dural and bony defects is the most important task.
In this case, the fistula was considered to be in the frontal sinus. Considering that the blood supply of the pedicle could have been compromised if the original incision had been taken. Hence,we chose the transeyebrow incision to expose the defects. This minimally invasive approach is widely used in the resection of lesions in the anterior skull base[14–17], including tumors and aneurysms. It can effectively expose the bone and the dura of the anterior skull base, and is feasible for the exploration and repair of the bony and dural defects.Unexpectedly, the dural and bony defects are discontinous, and the choice of transnasal repair may lead to the failure of the operation. To analyze the causes of inconsistent fistula,we infer that the anterior skull base was covered with pedicled temporoparietal fascial flaps in the first operation, thus the bony defect was repaired, while the dural defect perhaps remained patent. Delayed CSF leakage may occur when the frontal sinus was not closed properly or when the bone wax contracted and displaced. This case also suggests that the sealing of the frontal sinus may not be sufficient with bone wax alone, but pedicled periosteal flaps may be required.Since there is no pedicled vascular tissue available for the second operation, we chose free fat and fascia for multilayer repair, which proved to be reliable.