Dehiscence of the sigmoid sinus and disabling pulsatile tinnitus: review of the different surgical options and proposition of a new surgical technique using a bone bankMorgane Saerens1 , Pierre Garin1,2 , Jean-Philippe Van Damme1,3

1ENT Department, CHU UCL Namur, Godinne, Belgium2Department of Anatomy, Université de Namur, Namur, Belgium3Department of Audiology, Institut Libre Marie-Haps, Bruxelles, Belgium

ABSTRACTIn this report, we describe the case of a patient presenting with right pulsatile tinnitus secondary to dehiscence of the sigmoid sinus. This abnormality of the sigmoid sinus is considered to be a rare cause of pulsating tinnitus. Different surgical approaches are described in this article. We opted for a conservative technique without skeletonization or compression of the sigmoid sinus. The isolation of the sinus was achieved with shaped cortical femur bone from our bone bank and with autologous bone pate. This treatment significantly and durably relieved the patient. Thus, we believe it is possible, despite the importance of the anatomical abnormality, to treat this pathology surgically via a transmastoid approach. We describe a new conservative and less invasive surgical technique significantly limiting the risk of complications.Keywords: Bone bank, dehiscence of the sigmoid sinus, mastoid, mastoidectomy

Introduction

Pulsatile tinnitus accounts for only a small subset, 4% to 10%, of the entire population with tinnitus (1). A precise diagnosis is crucial because in 44% to 92% of patients with pulsatile tin-nitus, structural abnormalities are found, which can be treated via surgical or endovascular intervention (1-3).

Vascular pulsatile tinnitus is attributed to turbulent blood flow caused by vascular abnormalities and is synchronous with the cardiac pulsations (1, 2, 4). This can be related to arterial ab-normalities, such as an aberrant internal carotid artery or ath-erosclerosis of the carotid artery. Venous causes of pulsatile tinnitus such as a dehiscent jugular bulb, local venous stenosis, sigmoid sinus dehiscence, or diverticulum are also possibili-ties. Finally, arteriovenous fistula is one of the arteriovenous malformations that can create pulsatile tinnitus (1, 3, 4). The dehiscence of the sigmoid sinus is a rare but treatable cause of this symptom (4, 5).

Case Presentation

In this report, we describe the case of a 50-year-old female patient complaining of permanent right tinnitus synchro-nous to cardiac pulsations for 12 years. She scored 65/80 on the Tinnitus Questionnaire evaluating the severity of the tinnitus. As relevant medical and surgical histories, we not-ed treated hypertension and chronic obstructive pulmonary disease associated with a sleep apnea syndrome. A tympa-nostomy tube was positioned three times between 1980 and 2000.

An otoscopic exam in 2016 was normal bilaterally. However, audiometry had shown a mild sensorineural hearing loss at low frequencies in the right ear (Figure 1). The cervical aus-cultation did not reveal a murmur. The Doppler ultrasound of the neck and intracranial vessels showed no abnormali-ties. The suppression of the venous signal by compression of the right jugulo-carotid axe during the exam decreased the tinnitus.

Corresponding Author: Morgane Saerens, saerensmorgane@gmail.comReceived: May 25, 2021 Accepted: April 23, 2021Available online at www.b-ent.be

DOI: 10.5152/B-ENT.2021.20149

CASE REPORTOTOLOGY

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Cite this article as: Saerens M, Garin P, Van Damme JP. Dehiscence of the sigmoid sinus and disabling pulsatile tinnitus: review of the different surgical options and proposition of a new surgical technique using a bone bank. B-ENT 2021; 17(1): 56-60.

CC BY 4.0: Copyright@Author(s), “Content of this journal is licensed under a Creative Commons Attribution 4.0 International License.”

Computer tomography showed an anatomic variation of the right sigmoid sinus, which was enlarged and protruding, caus-ing a thinning of the temporal bone (Figure 2). The middle ear and the mastoid cells were well pneumatized. Magnetic reso-

nance imaging excluded a vascular tumor or other abnormal-ities (Figure 3). An occlusive test of the right internal carotid artery excluded an arterial origin.

Surgical treatment was proposed and accepted by the patient owing to the length of the symptoms and the failure of medical

Main Points:

• Structural abnormalities are found in most patients suffering from pulsatile tinnitus.

• Dehiscence of the sigmoid sinus is a cause of pulsating tinni-tus, which is treatable surgically.

• Transmastoid sigmoid sinus wall reconstruction is a new sur-gical technique.

• Avoiding skeletonization or compression of the sigmoid sinus could be a safer option.

Figure 2. Axial computed tomography scan of the right temporal bone showing the sinus sigmoid dehiscence with a lysis of mastoid cortical bone

Figure 1. Preoperative audiometryFigure 3. Axial T1-weighted MRI showing the importance of the asy-metric venous return

Figure 4. (1) Scale of the temporal bone, (2) lysis of the cortical bone in front of the dehiscent sigmoid sinus, (3) external auditory canal, (4) mastoid tip

Figure 5. (1) Antrum, (2) allograft, (3) isolated sigmoid sinus, (4) dura mater, (5) posterior ridge of the external auditory canal

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treatments tried at other centers. During the mastoidectomy, lysis of the cortical bone was visualized in front of the dehis-cent sigmoid sinus (Figure 4). The sinus was isolated from the dura mater of the middle cerebral fossa and the posterior wall of the external auditory canal (Figure 5). Two bone flaps com-ing from the cortical bone of the femur (provided by our bone bank) (Figures 6 and 7), and autologous bone pate were placed to completely isolate the dehiscent sigmoid sinus from the dura mater, the external auditory canal, and the antrum (Figure 8). This technique was preferred to complete removal of the bone covering the sigmoid sinus with compression regarding the significance of the dehiscence. An internal jugular vein lig-ature was also rejected as a first treatment option.

Three months after the surgery, the patient was totally sat-isfied, perceiving the tinnitus lightly and only in quiet places. The TQ score was 18, which indicated that the residual tinnitus had only a minor influence on her quality of life. Hearing loss was reduced, and the audiometry showed a mild conductive hearing loss with low frequencies without any sensorineural component. The postoperative results remained stable more than four years after surgery.

Discussion

The dehiscence of the sigmoid sinus is defined as a local bone wall defect which leads to a smooth bulging of the sigmoid si-nus in direct contact with the surrounding mastoid cells (6). Of the patients suffering from pulsatile tinnitus, 4% to 23% would have an abnormality of the sigmoid sinus associated with their symptoms (5, 7, 8). These abnormalities would be more frequent in women and would have a link with idiopath-ic intracranial hypertension (5). There is a predominance of right-sided pulsatile tinnitus. The hypothesis involves the vol-ume of the right jugular foramen, which is the dominant-sided venous drainage in most individuals (5, 2, 9). It can also be ex-plained with the anatomical specificity of the right brachioce-phalic vein.

Wenjuan et al. (10) have shown that pulsatile tinnitus can potentially occur only when abnormal sigmoid sinus perfu-sion, sigmoid plate dehiscence, and normal temporal bone pneumatization coexist. Good mastoid cell pneumatization favors sound transmission to the cochlea and the middle ear. The postoperative improvement of low frequency sen-sorineural hearing loss can be attributed to the alleviation of the masking effect of pulsatile tinnitus on low-pitched sound (1).

In terms of treatment, only a surgical approach can provide a resolution of the symptoms effectively and durably. This ex-plains the number of surgical techniques described, although at this time, the most effective one has yet to be determined. Our technique, which can be called “transmastoid sigmoid si-nus wall reconstruction,” aims to fill the bone dehiscence and to reconstruct the wall of the sinus. The sinus is, therefore, iso-lated by reconstruction of a soundproof barrier, eliminating the perception of the turbulent blood flow and interrupting sound transmission through the pneumatized mastoid cells (11). Our technique was inspired by a similar case but with dehiscence of the carotid artery. The patient was treated successfully by isolation of the tinnitus generating area instead of resurfacing and compression (12).

Chong Sun Kim et al. (1) have described a surgical technique called “transmastoid sigmoid sinus reshaping surgery” where a mastoidectomy was performed, and the sigmoid sinus was ful-ly skeletonized. The reconstruction of the wall was performed by inserting a piece of harvested temporalis fascia between the sigmoid sinus and the skeletonized shell, and harvested autologous cortical bone chips were inserted between the fas-cia and the sigmoid sinus wall to compress the sigmoid sinus externally. Thereafter, the bony defect was covered by another piece of temporalis fascia and reinforced with another layer of HydroSet Injectable HA Bone Substitute (Stryker Corp.). They reported a series of eight patients in which seven showed a

Figure 6. (1) Tibial bone, (2) piece of cortical bone used for the graft

Figure 7. Piece of cortical bone used for the graft

Figure 8. 1) Isolated sigmoid sinus covered by bone pate, (2) cortical bone graft between the external auditory canal and the sigmoid sinus, (3) bone pate covering the antrum and the external auditory canal, (4) cortical bone graft between the dura mater (covered by bone) and the sigmoid sinus.

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significant improvement in their tinnitus and hearing. One pa-tient experienced increased intracranial pressure postoper-atively requiring revision surgery for partial decompression of the sigmoid sinus (1).

P. Raghavan et al. (11) and Eisenman et al. (9) have reported the surgical results of 40 and 13 patients, respectively, using simi-lar surgical procedures as Chong sun Kim et al. All the patients were successfully treated in the study of Eisenman et al. Nev-ertheless, two patients had major postoperative complications with one presenting with visual loss associated with intracra-nial hypertension, and the other suffering from headache with ipsilateral sinus thrombosis.

The resolution of pulsatile tinnitus postoperatively occurred in 38/40 patients in the study of P Raghavan et al.; however, they described nine patients with surgical complications. Rong Zeng et al. (6) have reported a series of 27 patients operated with a similar technique but with a different type of graft and without inserting the grafts between the dura and the posterior fossa bony plate. Seven patients reported no change, and pulsatile tinnitus was aggravated in one patient but no serious com-plications were noted following surgery. P L Santa Maria et al. (5) have described a case of resurfacing using only soft tissue with one of the layers packed tightly into the intervening space between the mastoid and the sigmoid sinus. The patient re-mained asymptomatic postoperatively; however, the follow-up was only three months.

Jae-Jin Song et al. (3) described a case series of four patients presenting with sigmoid sinus diverticulum treated surgical-ly with transmastoid resurfacing and reconstruction of the bony defect with the extraluminal placement of covering materials. In all the patients, pulsating tinnitus disappeared completely immediately after the surgical procedure; howev-er, one patient experienced pulsating tinnitus 4.5 years later. Two patients had preoperative low-frequency hearing loss and experienced an immediate postoperative improvement in hearing loss.

Internal jugular vein ligature is to be proposed only after fail-ure of the sigmoid sinus reshaping surgery because of a high-er risk of complications with this technique, such as hydro-cephalus (4). In a systematic review where 139 patients were reported to present with either sigmoid sinus diverticulum or sigmoid wall dehiscence, sigmoid sinus wall reconstruction/resurfacing was used in 91.4% and endovascular procedures in 7.9% of the patients. Bone pate, unspecified soft-tissue graft, and bone cement had the highest rates of pulsatile tin-nitus resolution. Although temporalis fascia and autologous bone chips were the materials most commonly used, they had significantly lower rates of pulsatile tinnitus resolution than other materials, except for auricular cartilage and bone cement (5).

To the best of our knowledge, this case report is the first one describing the combined use of cortical bone coming from a bone bank and bone pate. This technique was chosen owing to the importance of the dehiscence and the large surface to cover. It did not involve any risks for the approach of the sigmoid sinus, which was not skeletonized. Only the mastoid cells in contact with the sinus were open; however, there

was no burring on direct contact with the sinus. We also did not cauterize the surface of the sigmoid sinus, which limited the risk of bleeding. Finally, we did not exert any compres-sion on the sinus, which avoided the risk of intracranial hy-pertension.

The main limitation of this technique was access to a bone bank and thus reserved to tertiary centers. We also noted that there are a lot of studies pointing the use of a bony graft for the maxillary alveolar ridge reconstruction. Histological analy-sis has shown reduction in the size of grafts ranging from 9% to 50%, three to eight months after the surgery and also the presence of new bone formation in the grafted area (13, 14).

This is the first case described with this technique, but the in-nocuousness of this treatment calls to spread this technique for publishing a bigger series.

Informed Consent: Verbal informed consent was obtained from the patients who agreed to take part in the study.

Peer-review: Externally peer-reviewed.

Author Contributions: Supervision – J-P.V.D., P.G.; Design – M.S., J-P.V.D.; Resources – J-P.V.D., P.G.; Materials – J-P.V.D.; Data Collection and/or Processing – M.S., J-P.V.D.; Analysis and/or Interpretation – M.S., J-P.V D.; Literature Search – M.S.; Writing Manuscript – J-P.V.D., P.G.; Critical Review – J-P.V.D., P.G

Conflict of Interest: The authors have no conflict of interest to de-clare.

Financial Disclosure: The authors declared that this study has re-ceived no financial support.

Acknowledgements: Dr J-P. Van Damme provided peroperative pic-tures, precious for describing the surgical technique.

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