Dual retrotympanic aural mass

Abstract

High-riding jugular bulb (HRJB), although rare, may pose a challenge as it may be mistaken for other non-alarming condition, such as middle ear effusion. Patients with HRJB classically present with pulsatile tinnitus. We report a unique case of a 26-year-old patient with underlying beta thalassaemia who presented with a 2-month history of intermittent epistaxis and rhinorrhoea. Otoscopic examinations revealed a pulsatile bluish mass behind the right tympanic membrane and a dull left tympanic membrane. Imaging performed revealed a finding of dual retrotympanic pathology, which consisted of a right dehiscent HRJB and left cholesterol granuloma. We highlight a rare case of dual retrotympanic mass as well as its management.

Background

The jugular bulb (JB) is the dilated upper portion of the jugular vein (JV), located at the junction between the sigmoid sinus and the internal JV (IJV). Despite the varying location of this structure within the temporal bone, it commonly lies below the hypotympanum of the middle ear cavity.^{1 2} Atypical presentation of JB, termed as JB abnormalities includes high-riding JB (HRJB) and JB diverticulum, are often encountered in clinical practice.^3–5 HRJB is an upward extension of the bulb into the middle ear cavity, invading the hypotympanum and has been traditionally subclassified as ‘with dehiscence’ or ‘without dehiscence’. A dehiscent HRJB (DHRJB) occurs when a high JB has absent or non-existent bony septum within the middle ear. Incidence of HRJB and DHRJB has been reported to be between 3.5% and 22.6% and 0.5% and 1.7%, respectively.^{6 7}

Patients with HRJB may typically present with pulsatile tinnitus, aural fullness or hearing loss, although approximately half of the patients with HRJB are asymptomatic.^{8 9} Otoscopic examination typically confirms a bluish mass behind an intact tympanic membrane. Herein, we present a case of dual retrotympanic pathology whereby the patient presented with a right DHRJB and left cholesterol granuloma (CG), which was incidentally found during outpatient clinic review.

Case presentation

A 26-year-old woman with underlying beta thalassaemia presented with a 2-month history of intermittent epistaxis, rhinorrhoea and unilateral aural fullness. According to the patient, the epistaxis was spontaneous, painless, with no triggering factor and resolving spontaneously. Similarly, rhinorrhoea was also intermittent with no triggering factor identified. There was no history of atopy, nose itchiness, sneezing or facial tenderness. As for the aural fullness, the patient described it to be intermittent, right-sided and resolving spontaneously. She denied any other ear symptoms, such as tinnitus, vertigo, otalgia or otorrhoea. There was also no other bleeding tendency or history of recent fall or trauma.

On examination, the patient was comfortable under room air. No external facial or nose deformity was seen. A 0° rigid nasendoscopy was unremarkable. Interestingly, otoscopic examination revealed a pulsatile bluish mass behind an intact right tympanic membrane (figure 1) and a dull left tympanic membrane (figure 2). Cervical and cranial examinations as well as other systemic examinations were unremarkable.

Figure 1.

Right otoscopic image showing red-bluish retrotympanic mass occupying the posterior inferior quadrant of the tympanic membrane with some tympanosclerosis.

Figure 2.

Otoscopic image of the left ear showing a dull tympanic membrane.

Investigations

Hearing assessment performed with pure tone audiometry revealed right-sided mild conductive hearing loss (CHL) with normal hearing over the left ear (figure 3). Tympanometry showed type A tympanogram bilaterally. High-resolution CT (HRCT) of temporal bone demonstrated dual pathology: a right DHRJB protruding into the right mesotympanum and hypotympanum of the middle ear cavity with absence of sigmoid plate between the JB and the middle ear cavity (figure 4). MRI with gadolinium showed hyperintensity in T1-weighted (T1W) soft tissue lesion in the left mastoid and hypotympanum (figure 5).

Figure 3.

Pure tone audiogram of the right ear showed 10–20 dB conductive hearing loss.

Figure 4.

High-resolution CT denotes high, dehiscent right jugular bulb projecting into the right middle ear cavity. Black arrowhead signify Right jugular bulb.

Figure 5.

MRI denotes hyperintensity in the T1-weighted soft tissue lesion in the left mastoid and hypotympanum. Black arrowhead signify Left cholesterol granuloma.

Differential diagnosis

Differential diagnosis of bluish tympanic membrane besides HRJB is CG, haemotympanum, middle ear effusion, aberrant internal carotid artery and persistent stapedial artery.

Treatment

Surgical options were explained to the patient along with the risks and benefits. Treatment options were discussed with the patient, including conservative, hearing amplification, serial imaging and surgery. As the patient was asymptomatic, conservative option was jointly decided.

Outcome and follow-up

The patient is currently under yearly follow-up with no complications.

Discussion

JB anomalies described within the temporal bone include HRJB, DHRJB and diverticulum associated with the JB.^3–5 The most common vascular anomaly of the petrous temporal bone is HRJB, defined as upward extension of JB to the middle ear cavity separated by an intact sigmoid plate, where the incidence is reported as 3.5%–22.6%.^{6 7} If the sigmoid plate is absent, the bulb may protrude into the middle ear cavity and is then known as DHRJB.

Two-third of HRJB has a right-sided predominance, with a much smaller incidence of bilateral HRJB.³ This is due to the larger size of right lateral venous sinuses and more dominant venous system draining the head,^9–12 as demonstrated in our case. Several classifications of HRJB have been described in the literature by several authors ranging from protrusion into the middle ear,⁶ through extension above the inferior rim of the bony annulus,¹³ to rising above the round window and basal turn of the cochlea.^{3 13}

A new CT scan-based classification was proposed for JB location, which consists of: (1) type 1: no bulb; (2) type 2: below the inferior margin of the posterior semicircular canal (SCC); (3) type 3: between the inferior margin of the posterior SCC and inferior margin of the internal auditory canal (IAC); (4) type 4: above the inferior margin of IAC; and (5) type 5: combination of dehiscences.⁵ JB anomalies can manifest with varying clinical symptoms, including pulsatile tinnitus, hearing loss and vertigo, depending on their impact on the neighbouring structures. However, almost half of the patients with JB anomalies may be asymptomatic.⁹ Our patient presented with vague nasal symptoms with occasional aural fullness.

Among the varying symptoms, pulsatile tinnitus is the most common symptom (50.4%),¹⁴ which may be attributed to the turbulent venous flow in the JB, resulting in direct unwanted sound transmission to the middle ear apparatus.⁸ Whereas perceived hearing loss is relatively rare, which only accounts for 1.9%.¹⁴

Acccording to the literature, the CHL demonstrated in our patient could be caused by the following three mechanisms: close contact between the JB and tympanic membrane, ossicular chain interference and round window niche obstruction.^{15 16} Round window niche obstruction was considered the most likely mechanism of CHL in view of its proximity to the floor of middle ear cavity,^{12 15 16} which was not evident in our patient’s CT scan. Parallel to that, other symptoms, such as sensorineural hearing loss, facial weakness and vertigo, may be attributed to the compression effect on vestibular aqueduct, followed by facial nerve and posterior SCC.

CG of the temporal bone is normally found incidentally during imaging, ear surgeries and otoscopic examination and no true incidence has been reported. CG, also termed as giant cholesterol cyst, is a histological term used to describe tissue response in the temporal bone following the presence of foreign body called ‘cholesterol crystal’. CG develops following a reaction to longstanding retention of secretion or haemorrhage associated with poor or obstructed ventilation in a usually pneumatised mastoid space, leading to negative pressure, air resorption and mucosal oedema. Catabolism of haemoglobin or breakdown of local tissue forms cholesterol, which eventually causes foreign body reaction, leading to the formation of CG.¹⁷ CG are usually associated with eustachian tube dysfunction, chronic otitis media with or without cholesteatoma, otological surgery or local trauma.¹⁷ As they expand, they can become symptomatic as they come in contact with surrounding structure, but this is relatively rare.

HRCT temporal bone is usually the preferred diagnostic modality for investigating retrotympanic mass, instead of myringotomy and middle ear exploration. HRCT is more sensitive for JB anomalies to detect presence of bony dehiscence as compared with MRI,^{1 9} and some literature recommends serial imaging to monitor the progression if the mass. Yet, MRI is superior in differentiating between a vascular and non-vascular mass in the middle ear such glomus tumour, haemagioma, cholesteatoma and CG. CG appears as smooth, well-circumscribed mass, which are hyperintense in T1W and T2-weighted images in the MRI.

Treatment for both HRJB and CG is generally conservative with regular follow-up and serial imaging, in addition to reassuring patient regarding the benign nature of this disease. Surgical intervention is reserved for patients with intolerable symptoms, such as persistent loud pulsatile tinnitus, cranial nerve palsy or in the event of massive bleeding complication. In the event of severe bleeding, the patient should be place in a head down position to minimise the risk of air embolism,² and haemostasis can be achieved by packing the ear with petrolatum-impregnated gauze strips¹⁸ or Gelfoam application backed by pressure with cottonoid.¹⁹ Surgical interventions reported include IJV ligation,⁸ endovascular embolisation and reconstruction using fascia, perichondrium, autologous cartilage and bone dust,⁷ or Gelfoam application to separate the JB and tympanic membrane.

Learning points.

• Bluish mass behind an intact tympanic membrane needs to be investigated thoroughly as there is a wide range of differential diagnosis from middle ear effusion, haemotympanum to glomus tumour and high-riding jugular bulb (HRJB).

• Presence of retrotympanic pulsatile mass requires investigation, notably imaging, as procedures, such as myringotomy and grommet, may be devastating.

• HRJB and cholesterol granuloma (CG) can be managed conservatively through regular follow-up and serial imaging.

• Surgical intervention of HRJB and CG should be reserved for patients with intolerable and debilitating symptoms such as tinnitus, vertigo, worsening hearing loss or in the event of massive bleeding as a result of surgery.