Case Report: Venous pulsatile tinnitus induced by enlarged oblique occipital sinus and resultant diverticulum/dehiscence of the sigmoid-jugular wall

Abstract

Pulsatile tinnitus (PT) caused by enlarged oblique occipital sinus (OOS) and resultant diverticulum/dehiscence of the sigmoid-jugular wall has not been described in previous literature. This study recruits one case of PT induced by ipsilateral enlarged OOS and sigmoid-jugular wall diverticulum (case 1) alongside one case of PT induced by ipsilateral enlarged OOS and sigmoid-jugular wall dehiscence (case 2). Various radiologic and computational techniques including computed tomography (CT), magnetic resonance (MR) imaging, Doppler ultrasound, and computational fluid dynamics (CFD) simulation were implemented. Transmastoid sinus wall reconstruction was performed on case 1 with a large sigmoid-jugular diverticulum potentially traumatizing the facial nerve canal. Contrast-enhanced CT or MR venogram images coupling with three-dimensional reconstructed are advantageous in revealing the covert route of OOS that runs under the cerebellum and drains directly into jugular bulb (JB) region. PT in case 1 was successfully eliminated after transmastoid sinus wall reconstruction surgery. Tinnitus handicap inventory score in case 1 reduced from 70 to 0. The ipsilateral jugular outflow mean velocity (V_mn) and flow volume (F_VOL) were 42.5 cm/s and 25.9 g/s (case 1 prior to surgery) and 56.6 cm/s and 41.2 g/s (case 2), respectively. Based on CFD simulation, the peak flow velocity in OOS was 1.85 m/s and 2.1 m/s, the wall pressure of the diverticular dome and dehiscence area of the SS-JB wall was 1724.7 Pa and 369.8 Pa in case 1 and 2, respectively. Enlarged OOS caries greater flow kinetic energy that possibly induces sigmoid-jugular wall diverticulum/dehiscence; transmastoid surgical method is safe and therapeutically effective against PT induced by enlarged OOS.

Keywords: dehiscence; diverticulum; oblique occipital sinus; occipital sinus; pulsatile tinnitus.

Figure 1

Radiological imaging and signs of case 1 of right-sided pulsatile tinnitus. (A) The maximum intensity projection (MIP) reconstruction of axial 2D-time-of-flight (TOF) magnetic resonance (MR) images showing an enlarged oblique occipital sinus (OOS, white arrow) anastomosing with the lower curve sigmoid sinus (SS), forming a diverticulum (red arrow) in between the SS and jugular bulb (JB). Note the abrupt transverse sinus stenosis at the middle segment. (B) Coronal MIP reconstruction of 2D-TOF MR images. The white arrow indicates the enlarged OOS. (C) Volume rendering technique reconstructed using postoperative contrast-enhanced CT images demonstrating an enlarged OOS running above the occipital bone and underneath the cerebellum to directly anastomose with SS. (D) An axial 2D-TOF MR slice showing the SS, diverticulum (Div.), JB, and OOS. (E) Coronal T2-weighted MR and T1-weighted 2D FLASH images showing the brain herniation into arachnoid granulation [(cerebrospinal fluid signal hyperintense on T2 (red arrow) and hypointense on T1 (green arrow)] that compress into the transverse sinus lumen (yellow arrow), which should be suspected of increased intracranial pressure. (F) Coronal CT image showing the relative location of the diverticulum and JB. (G) Axial CT image exhibiting a seemingly right-sided high-riding JB dehiscence/diverticulum (pseudo-JB anomalies sign) invading the mastoid cavity. The bulging vascular wall emerging at the lower SS was a diverticulum (Div.) but not JB. (H) Axial CT slice showing the SS, diverticulum (Div.), and JB. The hollow arrow indicates the facial nerve canal. The reconstructed sagittal CT slice shows the diverticulum (Div.) nearly exited the mastoid apex. SP and InE indicate the styloid process and inner ear, respectively.

Figure 2

Intraoperative photographs and detailed description of the transmastoid surgery of case 1. (A) Localizing the SS-JB diverticulum by adopting a lower mastoid bone incision site with the upper and lower bonds leveling with the base of the external canal and the mastoid apex, respectively. Note the absence of osseous wall and dura mater covering the surface of the diverticulum upon initial exposure. SS, sigmoid sinus; Div., diverticulum; A, anterior; P, posterior; T, top; B, bottom. (B) Skeletonization of the posterior semi-circular canal (PSC), facial nerve (FN), and the diverticulum (Div.) in sequential order. Notably, the diverticulum abuts the posterior digastric muscle (PDM) and nearly exits the mastoid apex. (C) A 45-degree knife curette was used to separate the diverticular wall from the surrounding osseous walls. To prevent excessive hemorrhage, a ribbon gauze was placed topically over the diverticulum to protect its fragile surface. (D) Rupture of the diverticular wall can be inevitable during the separation procedure, which the high blood flow velocity and pressure render the process of hemostasis arduous. Therefore, we harvested and customized the hemostatic material (a robust yet pliable artificial dura mater-temporalis fascia complex) that also serves as the sinus wall repairing material. (1) Topical fixation of a tough solidified artificial dura mater smeared with surgical glue to compress and reduce the diverticulum. (2) Robust yet pliable hardened/dried temporalis fascia providing a petticoat-like supporting structure to fit and laminate with the surrounding osseous structures. (3) Prior to holistic and surgical glue fixation of the repairing materials, the suture was sewn at the caudal portion of the temporalis fascia to prevent suction of the operative filler into the vascular laceration and into the sigmoid sinus. (E) Surgical glue fixation of the repairing materials covering the diverticulum. The thickness of repairing materials should be prudently controlled to avoid total collapse of the sigmoid sinus wall. (F) and (G) Bone wax-solidified gelatin sponge complex is applied topically to reconstruct the sound-proof barrier. (H) Postoperative contrast-enhanced CT and magnetic-resonance venogram demonstrating complete reduction of the diverticulum. The yellow arrow exhibiting the befitted extraluminal compression over the sigmoid sinus.

Figure 3

Radiological images of the patient in case 2 of right-sided pulsatile tinnitus (PT). (A) The maximum intensity projection (MIP) reconstruction of axial 2D-time-of-flight (TOF) magnetic resonance (MR) images showing an enlarged oblique occipital sinus (OOS) with distal stenosis (yellow arrow) anastomosing with the ipsilateral jugular bulb (JB). (B) (1) Coronal and (2) sagittal maximum intensity projection (MIP) reconstruction of 2D-time-of-flight (TOF) magnetic resonance (MR) images demonstrating the enlarged OOS (white arrows) running under the cerebellum. SS, sigmoid sinus; IJV, internal jugular vein. (C) Coronal contrast-enhanced T1-weighted gradient echo (2D FLASH) MR slice showing the relative locations of OOS and JB. (D) An axial 2D-TOF MR slice showing the SS, diverticulum (Div.), JB, and OOS. (E) Coronal CT image demonstrating dehiscence at the top of the SS-JB wall. (F) The notch of the OOS cuts through the edge of the foramen magnum of the occipital bone (red arrow). (G) Axial CT image showing SS-JB wall dehiscence and intrasinus flow pattern exhibited using the corresponding 2D-time-of-flight (TOF) magnetic resonance slice. (H) Reconstructed sagittal CT image exhibiting SS-JB wall dehiscence and locations of the SS, JB, and inner ear (InE).

Figure 4

Flow field analysis of the enlarged oblique occipital sinus. (A) Velocity flow field in case 1. (B) Velocity flow field in case 2. (C) Flow pressure field of case 1. Note the pressure increase at the diverticular dome (yellow arrow). (D) Flow pressure field of case 2. Note the large trans-stenotic pressure gradient caused by OOS stenosis. Blue and red arrows indicate flow inlet and outlet, respectively. SSS, superior sagittal sinus; Str.S, straight sinus; TS, transverse sinus; OOS, oblique occipital sinus; SS, sigmoid sinus; Div., diverticulum; PCV, posterior condylar vein; IJV, internal jugular vein.