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Cerebrospinal fluid rhinorrhea from the lateral recess of sphenoid sinus: More to it than meets the eye
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.253634
Keywords: Cerebrospinal fluid rhinorrhea, extended endonasal approach, lateral recess, sphenoid sinus, transpterygoid approach
Cerebrospinal fluid (CSF) rhinorrhea from the lateral recess of the sphenoid sinus is rare; the incidence of occurrence of lateral recess leaks reported in the literature is 7.7%.[1] Endoscopic endonasal repair of CSF rhinorrhea has rapidly superseded the transcranial repair. In most reported series, the success rate of the procedure is around 90%.[2] Based on etiology, these leaks may be classified as congenital, neoplastic, traumatic (including iatrogenic), and idiopathic.[2] These leaks may present clinically with meningitis, which may often be life-threatening. The location of the skull-base defect dictates the endoscopic approach and techniques necessary for surgical treatment. When present in the lateral recess of the sphenoid sinus, an EEA (expanded endonasal approach) with an additional transpterygoid extension of the approach is useful for complete exposure and repair of the skull-base defect. The transpterygoid extension facilitates adequate visualization and optimal manipulation of instruments within this corridor.[3]
This is a retrospective review of patients who underwent endoscopic endonasal repair of CSF rhinorrhea from the lateral wall of the sphenoid sinus between June 2015 and June 2018. Institutional ethical committee clearance was obtained prior to commencement of the study. Patients with a history of trauma and previous endoscopic endonasal surgery for tumors were excluded. The patient demographic characteristics, duration of presenting symptoms, and history of previous procedures were reviewed. Perioperative variables, including complications and postoperative outcomes at most recent follow-up, were used as the main outcome measures. Major complications were defined as vascular injury, neural injury, postoperative recurrence of CSF leak, and postoperative meningitis. Technique The approach was performed using 0° and 30°, 4-mm sinus endoscope (Karl Storz, Tuttlingen, Germany). The technique we use for repair of lateral recess leaks is as follows. A lumbar drain is inserted before surgery, and 10% fluorescein in a dilution of 1 in 1000 (maximum of 25 mg) is instilled into the subarachnoid space (50 mL/h) in an infusion. A wide anterior sphenoidotomy with ipsilateral posterior ethmoidectomy is done. A maxillary antrostomy is performed on the side of the encephalocoele, and the mucosa over the posterior maxillary wall is elevated. The perpendicular plate of the palatine bone harbours a raised bony crest called the ethmoidal crest, and the sphenopalatine artery (SPA) can be identified arising from behind the crest. The perpendicular plate of the palatine bone is removed and the SPA is coagulated and cut. Further removal of the palatine bone behind the sphenopalatine foramen exposes the pterygopalatine ganglion, which is retracted laterally. The base of the pteryogoid process is then drilled to allow visualization and manipulation of instruments within the lateral recess of the sphenoid. During surgery, active leak of fluorescein-stained CSF is used to identify the defect. Once the site of the defect is located, the mucosa is removed from its surface. If a meningoencephalocele is present, it is coagulated and resected. Dissection is continued till the bone defect is delineated circumferentially. The defect is then sealed with inlay fat and fascia lata. Cartilage harvested from the nasal septum may also be used for the repair. The nasoseptal flap was used in cases of very large defects. The absence of fluorescein at the end of the procedure helps to assess the completeness of repair. The repair is then reinforced using a tissue sealant [Figure 1].
During the study period of January 2015–June 2018, a total of 48 patients underwent endoscopic endonasal repair for CSF rhinorrhea. Of these, we found seven patients (four females and three males) with CSF rhinorrhea from the lateral wall of the sphenoid sinus [Table 1].
Role of ICP Five patients had features of raised intracranial pressure [(ICP); idiopathic intracranial hypertension [IIH] – two, obstructive hydrocephalus – two, and dural arteriovenous fistula (DAVF) – one], which preceded the occurrence of CSF rhinorrhea. Other radiological features of raised ICP including the presence of an empty sella was seen in five patients, and the transverse sinus narrowing was seen in two patients [Table 2].
BMI The mean body mass index in this group was 24.00 kg/m 2 (range 20.8–27.9 kg/m 2). Two of the seven patients were overweight. All patients underwent an endoscopic endonasal transpterygoid approach for identification and repair of the skull-base defect. Techniques of repair In four of the seven cases, the repair was completed with a pedicled nasoseptal flap harvested from the opposite side. This was done when the defect was large or in the case of bilateral defects in the sphenoid sinus wall. In three patients, cartilage inlay graft was reinforced with a free mucosal graft taken from the ipsilateral middle turbinate. Five patients underwent measurement of the CSF opening pressure 3 weeks following endonasal repair of the CSF leak. Four of five patients were found to have opening pressure more than 15 mmHg (mean = 17 mmHg, range 12–21 mmHg). CSF diversion was performed in 3 patients [ventriculoperitoneal shunt (VP) shunt – 2, thecoperitoneal (TP) shunt – 1]. In the patient with a DAVF, CSF pressures normalized after endovascular embolization of the DAVF. All patients continue to remain on follow-up (mean 16.5 months, range 6–30 months). No patient has developed recurrence of CSF rhinorrhea. Both patients with intracranial tumors underwent definitive surgery for their respective tumors (vestibular schwannoma – one, trigeminal schwannoma – one) [Table 1]. Cases Patient 2 had undergone two previous operations at another center for a left vestibular schwannoma. The surgeries were done through a retrosigmoid approach. She presented with worsening ataxia and profuse left-sided CSF rhinorrhea, due to a defect in the left lateral recess of the sphenoid sinus [Figure 2]. Incidentally, a second arachnoid pouch was seen at the cribriform plate on the right side; the patient had no CSF leak from the right side.
Magnetic resonance imaging (MRI) also revealed a large recurrence of the vestibular schwannoma, with hydrocephalus. She underwent an endoscopic endonasal transpterygoid approach repair of the skull-base defect. The cribriform plate defect was also repaired. She underwent a VP shunt and tumor excision in a staged manner. At her most recent follow up, 5 months after surgery, she remains asymptomatic. Patient 6, a 46-year-old female patient, presented with complaints of constant headache and a sudden worsening of vision in the left eye. Her examination was unremarkable, except for the presence of primary optic atrophy in both eyes. An MRI study done at that time had shown an empty sella and left transverse sinus stenosis. The diagnosis of IIH was made and medical management with acetazolamide was started. After 3 months of treatment, she suddenly developed CSF rhinorrhea through the right nostril. MRI with a cisternogram revealed a right-sided temporal encephalocoele through a right lateral recess defect [Figure 3]. She underwent an endoscopic endonasal transpterygoid approach for repair of the skull-base defect. During the procedure, a 2-cm defect in the sphenoid bone with a temporal encephalocoele was found. The temporal encephalocoele was excised, and the defect was closed with inlay fat and fascia reinforced by a left-sided nasoseptal flap. Her postoperative course was uneventful. She then underwent CSF pressure study 3 weeks later and the opening pressure was 21 mmHg. She was managed with a thecoperitoneal (TP) shunt and remains symptom-free 12 months following surgery.
CSF leaks from the lateral recess of the sphenoid sinus are rare. The leaks have been postulated to arise as a result of a congenital craniopharyngeal canal. We first reported a case of bilateral meningoencephalocoele, where the evolution of the meningoencephalocoeles of the lateral wall was observed over a period of 4 years. This was noted in the background of raised ICP caused by a DAVF, which resolved following endovascular treatment.[4] This raised a very pertinent question- Is the anatomical configuration alone responsible for CSF rhinorrhea or does the anatomical configuration along with elevated ICP predispose to the development of CSF rhinorrhea? The lateral recess of the sphenoid sinus is never seen at birth; it forms with progressive pneumatization of the sphenoid sinus.[5] The pneumatization is rarely symmetrical and it is not unusual to see patients with a recess only on one side. The incidence of the lateral recess in adults is around 37.5%.[6] The presence of the recess itself is not a prerequisite for developing a leak from the lateral wall and encephalocoeles may be seen coming directly from the lateral wall of the sphenoid sinus. This lends further strength to the possibility that factors other than the anatomical configuration alone can contribute to the development of these leaks. The most important factor involved in the causation of these leaks is elevated ICP.[2],[7] In our series, five of seven patients had features of raised ICP (idiopathic intracranial hypertension – one, obstructive hydrocephalus – two, DAVF – 1) which preceded the occurrence of CSF rhinorrhea. Another interesting finding that we noted in two patients with raised ICP was the presence of multiple defects in the skull-base (bilateral sphenoid sinus – 1, sphenoid sinus and right cribriform – 1). Illing et al., also noted a very high incidence of raised ICP in patients with CSF rhinorrhea from the lateral recess [Table 3].[5] In our series, associated findings such as the presence of arachnoid pits eroding the inner table of the skull were also noted. In one patient, the evolution of the defect in the bone and progressive enlargement of the meningoencephalocoele could be observed on sequential MRI images. The endoscopic endonasal approach is a minimally invasive approach to the lateral wall of the sphenoid sinus. The approach allows for direct visualization of the lateral wall of the sphenoid sinus and the defect in the bone.[3] The use of this trajectory obviates a craniotomy, brain retraction, or resection of the temporal lobe. None of our patients needed antiepileptics following surgery.
CSF leaks from the lateral recess of the sphenoid sinus have for long been misattributed to a congenitally occurring lateral recess or the Sternberg's canal.[5],[8] Our findings as well as previously published articles, however, now support the possibility that the leaks are precipitated by raised ICP.[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21] In the setting of raised ICP, CSF pulsations over a period of a few years result in defects in the bone through which arachnoid and brain tissue pouches out and causes CSF rhinorrhea.[11] The presence of an empty sella (five/seven) and transverse sinus narrowing (two/five) lends greater credence to this hypothesis. To verify this hypothesis, we started measuring the opening pressures in these patients 3 weeks following the endonasal repair of the leak. Four patients were found to have pressures more than 15 mmHg (mean = 17 mmHg, range 12–21 mmHg). Therefore, we advocate monitoring of CSF pressure in these patients by a lumbar puncture 3 weeks following the repair of CSF leak. Patients with elevated pressure need to be counselled regarding the need for CSF diversion. Those with normal pressures need to be kept on close follow-up to recognize the clinical signs of benign intracranial hypertension.[22],[23] We do not have any experience with transverse sinus stenting in this subset of individuals.
CSF rhinorrhea occurring from defects in the lateral recess of the sphenoid sinus is rare. The predisposing factor for occurrence of these leaks appears to be raised ICP. Endoscopic endonasal transpterygoid approach provides excellent visualization of the skull-base defect and facilitates adequate instrument manipulation within the corridor allowing successful repair of the defect with low rates of recurrence. CSF diversion in patients with elevated ICP is needed for long-term durability of the repair and to avoid leaks from other sites. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]
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