The present study included 18 patients with spontaneous CSF leaks. All of the patients were young adults, with a mean age of 33.3 ± 5.9 years old, which is slightly younger than reported by earlier studies (average age 45–65 years) [14,15,16].
Female patients outnumbered male patients in the present study (88.9% versus 11.1%), with a ratio of approximately 8:1. The higher prevalence of spontaneous CSF leaks in women was also reported by other studies, with a female: male ratio ranging from approximately 2:1 to 7:3 [4, 8, 14, 15, 17].
All patients in our series were obese, with their BMI ranging from 30 to 36 kg/m2, (mean=33.6 ± 1.8 kg/m2). This finding is in agreement to other studies that showed an association between spontaneous CSF leaks with obesity, with an average BMI ranging from 32 to 38 kg/m2 in such patients [4, 8, 14,15,16,17,18,19,20]. Previous studies have suggested that obesity is not a direct cause of spontaneous CSF leaks, but other conditions associated with obesity may contribute to the development of leaks, including IIH and OSA syndrome [14, 15, 21, 22].
In our series of patients, OSA syndrome was recorded in 77.8% of cases. This prevalence is analogous to that reported by a prospective study (83.3%) which assessed patients having spontaneous CSF leaks with polysomnography [22]. However, much lower prevalence rates of OSA were reported by other studies, ranging from 14 to 45% [15, 18, 23, 24]. Association between OSA and thinning of calvarium and skull base has been reported [21], though the mechanism is still not precisely known. It is postulated that transient hypercarbia during the apneic episodes in patients with OSA syndrome results in cerebral vasodilation and transient elevations in ICP [25, 26], which may on the long run lead to gradual progressive thinning of bony skull base [27]. Detection of OSA syndrome in patients with spontaneous CSF leaks is recommended using polysomnography [16].
In the present study, the majority of patients (89.9%) presented with unilateral CSF rhinorrhea as well as headache and visual symptoms; previous history of meningitis was detected in only two patients (11.1%). The incidence of meningitis was approximate to that reported by Chaaban and his colleagues [17] of 9%. However, a systematic review [7] reported a higher incidence of meningitis (23%). A wide range of incidence of meningitis was reported by other studies, from 6 [20] to 58% [28]. The presence of bone defects predisposes patients to meningitis [15].
In the present study, the radiographic imaging including thin slices (1 mm) CT scans combined with MRI of the paranasal sinuses and skull base have been done for all patients to detect the site and size of the defects and the contents of downward herniated neural structures. This was in agreement with Schuknecht and his colleagues [29]. As they stated that combination of CT scan and MRI together with intraoperative endoscopic findings will detect accurate site and size of osteodural defects. Unlike them, we did not perform CT cisternography as a routine investigation because it is an invasive technique.
We found that the most common site of leakage was the cribriform plate of the ethmoid (66.7%), followed by leakage from both cribriform and ethmoidal bone (16.7%), then sphenoid (11.1%), and only one case with leakage from ethmoidal bone fovea ethmoidalis (5.6%). Leakage of CSF is expected to occur from skull base regions that are inherently thin and pneumatized, such as the cribriform plate and the tegmen [15]. Our results are in partial accordance with previous studies reporting the cribriform plate and sphenoid as the most common sites for leakage [7, 8, 15].
Increased ICP can appear radiologically in MRI in the form of encephalocele, empty sella, and vertical tortuosity of dilated optic nerve sheaths. Thinning of skull base with multiple bone erosions can be detected by computed tomography scan [2, 5, 6, 17]. We found that encephalocele and meningocele were recorded in 61.1% and 66.7% of our cases, respectively. The radiological findings in our patients showed empty sella totalis in 66.7%, slit ventricle only in 27.8%, empty sella partialis in 5.6%, and CSF congestion around optic nerve sheath in 77.7%. These findings are supported by numerous previous studies. Encephaloceles were reported in 50 to 100% of spontaneous CSF leaks [9, 30]. Empty sella was also highly prevalent and reported in 85 to 100% of patients [17, 31].
In the present study, the sites of leakage during endoscopic repair was depended mainly on the pre-operative CT and MRI finding combined with endoscopic exploration without the use of intrathecal injection of fluorescein dye. As US FDA (United States Food and Drug Administration) had received 136 case reports (1969–2003) with 13 patients died as a result of adverse drug reactions. Furthermore, seizures, headaches, pulmonary edema, and lower extremities numbness have been reported Javadi and his colleagues [32]. For this reason, we excluded this technique from our protocol of management of CSF rhinorrhea.
The normal pressure range of CSF is from 5 to 15 cm H2O, as detected on opening measurement via lumbar puncture [11]. All patients in our series had elevated CSF pressure. Their preoperative CSF pressure ranged from 35 to 40 mm H2O (average of 36.5 ± 1.7 mm H2O). Elevated ICP over a period of years is suggested to cause bone thinning in the skull base that end in the formation of bone defects, through which “spontaneous” CSF leaks occur [4, 14, 21].
Elevated CSF pressure was reported in 10–66% of patients with spontaneous CSF leaks [33]. A recent systematic review by Teachey and his colleagues [34] reviewed 56 articles and concluded that 43.5% of patients in the included studies had signs of CSF hypertension on radiological imaging or through lumbar tap. However, the true prevalence of CSF hypertension in patients with spontaneous leaks cannot be estimated precisely, as many studies did not measure CSF pressure in those patients. The reported mean preoperative opening pressure of CSF in patients with anterior skull base defects was 33 cm H2O [35]. Management of intracranial hypertension seems mandatory, as ICP has been shown to increase significantly after repair of skull base defects [11]. Although temporary use of lumbar drainage will decrease this pressure, ICP will remain elevated if no intervention is performed, subjecting the patient to both early and late failures.
Control of elevated ICP may be achieved by various methods, treatments with acetazolamide, permanent CSF diversion via a ventriculo-peritoneal shunt, decreased body weight by diet or bariatric surgery, or serial lumbar punctures [11, 36,37,38].
Lumbo-peritoneal shunting is an effective, safe procedure that has been used to treat IIH. The efficacy of this kind of shunting is maintained as long as the shunt remains patent [12]. Therefore, all patients in our series underwent lumbo-peritoneal shunt insertion.
In the current study, patients were followed-up after repair for a period ranging from 6 to 60 months, with a median follow-up period of 24.5 months (Table 3). Follow-up of the studied patients showed that the repair failed in only two cases (11.1%). The reported success rates in previous studies vary widely, ranging from 33 to 100% [17, 36, 39]. Higher success rates have been associated with management of increased ICP, such as ventriculo-peritoneal shunting, acetazolamide, and weight loss [4, 11, 34, 36]. However, there is still some debate considering management of elevated ICP in patients with spontaneous CSF leaks [15]. The main concerns that may hinder the inclusion of ICP management techniques into routine care are adverse effects associated with these treatments, in addition to lack of evidence of their efficacy. Acetazolamide is a carbonic anhydrase inhibitor that may cause electrolyte and metabolic disturbances. Permanent CSF diversion by ventriculo-peritoneal shunt is an invasive cranial procedure that carries the risk of surgical site infections, meningitis and blockage, and migration of distal catheter. Moreover, overshunting leading to low pressure headaches and chronic subdural collections and hence shunt failure [15, 40]. Lower complication and revision rate of 11% has been reported in the study of Bjornson and his colleagues [40] on 28 patients. Image guidance with electromagnetic (EM) navigation was mandatory for ventricular catheter insertion for their patients, whereas in 2014, Menger and his colleagues [41] published a retrospective cohort study, in which 4480 patients was diagnosed as idiopathic intracranial hypertension, with 2505 undergoing first-time VP shunt insertion and 1754 undergoing initial LP shunt, ventriculo-peritoneal shunts proven to be superior to lumbo-peritoneal shunts secondary to IIH regarding rate of revision surgery and average hospital stay period.
In current study, unfortunately image guidance (neuro-navigation) was not available in our institution for shunting of small sized ventricles.
Our study is in a partial accordance with the study of Woodworth and his colleagues [8]; as they managed 56 patients presented with initial spontaneous CSF rhinorrhea combined with increased intracranial tension through a 10-year study. They stated that the treatment of the underlying intracranial hypertension coupled with endoscopic repair in cases of spontaneous CSF leak carried a high success rate of (95%) reaching that of other etiologies of CSF leaks. Intracranial pressures averaged 27 cm H2O. Patients were treated with acetazolamide. Meanwhile, in severe cases, with a ventriculo-peritoneal shunt, unlike our patients, all of them had recurrent CSF rhinorrhea with previous attempts to repair it whereas permanent CSF lumboperitoneal diversions were adopted for all of them.
In contrast to our study, Ahmed and his colleagues [42] proposed that the transvers venous sinus stenting (VSS) is a procedure with a favorable outcomes and lower complication rates. Their cost analysis showed that over 100 procedures performed, VSS weigh less than CSF shunting in the long term, not due to the average cost of the procedure itself but a relatively lower revision rate, fewer total revisions per patient, and less infections. This technique is not well established or familiar in our institute. Furthermore, in our study, the lumbo-peritoneal shunts were not coasty and of lower revision rate (11.1%) as well.
Our data was partially in accordance with Locatelli and his colleagues [43], as they managed 135 patients over 9 years, 91% of them was purely endoscopic repair but all of them had normal intracranial tension with success rate 93.3% [43]. Unlike our data, all patients were presented with a considerable increased ICP (35 to 40 mm H2O) and underwent purely endoscopic repair with success rate 89.9%.
Our technique for repairing and reconstructions of the defects was as follows: small circular defects up to 5mm were plugged with a single piece of fat and may be overlayed with mucoperichondrial. Defects more than 5 mm combined application of underlay fascia lata graft between brain and dura matter with fat plugs through osseous defect was done and then stabilized with layers of Surgicel and absorbable Gelatin.
There are various techniques for endoscopic skull base reconstruction, for example, Hadad and his colleagues [44] applied either vascularized flaps or non-vascularized grafts: vascularized flaps carried a high success rate like pedicled naso-septal flap which had been described for reconstruction of defects of the anterior, middle, clival, and parasellar skull base, while non-vascularized grafts like fat plugs and mucoperichondrial grafts were considered in skull base defects reconstruction [44]. In our study, we applied both techniques for reconstruction either vascularized naso-septal flaps or non-vascularized grafts.
Another study of Kassam and his colleagues [45] stated that the applied pressure for example the balloon of foly’s catheter 12mm reduce the risk of migration of the underlying grafts. Collagen matrix can be used as inlay graft between brain and dura matter. Fibrin sealants are no longer used between the inlay and onlay grafts. However, the application of lumbar drains no longer routinely used by Kassam et al. because it potentially creates negative pressure with the hazards of separation of the initial subdural inlay graft from the dural edges according to their experience [45]. We believe that lumbar drains might be accepted in primary cases of CSF leaks; in our study, we did not consider it as we had synchronously inserted lumbo-peritoneal shunt at the same sitting.
Another technique described by Cavallo and his colleagues [46] 3F (fat, flap, and flash) technique used with high success rate 96%. After extended endoscopic endo-nasal approaches for achieving watertight skull base reconstruction, the 3F strategy involves autologous fat grafting, naso-septal flap coverage, and flash mobilization out of the bed following the operation. This technique can be used in reconstruction of various skull base defects. We recommend this technique for further upcoming research work.
The repair of skull base defects is achieved either via endoscopic or open craniotomy, whereas open repairs are through a bifrontal craniotomy approach which provides a direct access to the dural defect, the option to directly deal with nearby tissue injury, and the ability to apply a vascularized pericranial flap for grafting the anterior skull base. However, the hazards of brain retraction, anosmia, and morbidity associated with craniotomy are the main disadvantages of this approach [47]. For these reasons, we adopted the repair of the defects purely via endonasal endoscopic.
The limitations of the current study attributed mainly to relative rarity of recurrent spontaneous CSF rhinorrhea, rendering it with insufficient cohort sizes to perform a statistical analysis. However, operative techniques and perioperative protocols were the mainstay determinants of outcome.
