|Year : 2014 | Volume
| Issue : 3 | Page : 129-131
High-riding jugular bulb: A rare entity
Vivek Sasindran1, Antony Joseph1, Shobin S Abraham1, Shivaprakash B Hiremath2
1 Department of Otorhinolaryngology, Pushpagiri Institute of Medical Sciences and Research Centre, Tiruvalla, Kerala, India
2 Department of Radiodiagnosis, Pushpagiri Institute of Medical Sciences and Research Centre, Tiruvalla, Kerala, India
|Date of Web Publication||16-Jul-2014|
Department of Otorhinolaryngology, Pushpagiri Institute of Medical Sciences and Research Centre, Tiruvalla - 689 101, Kerala
Source of Support: None, Conflict of Interest: None
We present a case of high-riding jugular bulb that obscured the round window niche causing gradual hearing loss. Encounters with the jugular bulb in ear surgery are uncommon.
Keywords: Conductive hearing loss, High-riding jugular bulb, Tinnitus
|How to cite this article:|
Sasindran V, Joseph A, Abraham SS, Hiremath SB. High-riding jugular bulb: A rare entity. Indian J Otol 2014;20:129-31
| Introduction|| |
The superior border of the jugular bulb normally lies below the hypotympanum of the middle-ear cavity. However, in rare cases the jugular bulb may extend upwards, elevating the floor of the hypotympanum and presenting in the middle-ear space with a thin or absent bony septum. This anomaly is known as a high-riding jugular bulb. A jugular bulb is also considered high-riding if it extends superior to the level of tympanic annulus, or encroaches within 2mm of the internal auditory canal (IAC). Symptoms of a high-riding jugular bulb include tinnitus and conductive hearing loss, which may be ascribed to turbulent blood flow through the aberrant anatomy resulting in unwanted sound transmission through the middle-ear apparatus.  Furthermore, symptomatology may be enhanced with conditions that increase cardiac-output.
| Case Report|| |
A 43-year-old male operated for chronic otitis media-squamosal type in the right ear presented with progressive hearing loss 7 months later in the other ear (left ear). [Figure 1] shows the Audiometry findings of the left ear of the patient when he presented to us before the surgery of his right ear Otoscopy showed a normal tympanic membrane on the left side, and the graft was intact in the right ear. Audiometry revealed a bilateral moderate mixed hearing loss (65 dB). as shown in [Figure 2]. Tympanometry showed type A tympanogram with absent reflexes bilaterally. Given these findings, with a probable diagnosis of otosclerosis, we elected to proceed with an exploratory tympanotomy.
|Figure 2: Pure tone audiogram showing moderately severe hearing loss in left ear 7 months later|
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Upon elevation of the left tympanomeatal flap, the prominence of the jugular bulb could be appreciated in the middle-ear cavity, as shown in [Figure 3]. Ossicles were intact and mobile. The jugular bulb was found to be obscuring the round window niche. Given the nature of the middle-ear finding, the procedure was abandoned. Follow-up examination showed satisfactory healing of the tympanomeatal flap in the left ear. A high resolution computed tomography (HRCT) scan of the temporal bone was taken 2 weeks after the surgery, [Figure 4] and [Figure 5] which confirmed our intra-operative findings. We gave our patient, the option of using a hearing aid in the left ear, and to undergo an ossicular reconstruction with a prosthesis (total ossicular replacement prosthesis) in the right ear as a second-stage procedure.
|Figure 3: Intra-operative image. 1-high-riding jugular bulb, 2-incudostapedial joint, 3-promontory|
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|Figure 4: High resolution computed tomography temporal bone. Axial computed tomography in bone window showing dehiscent jugular bulb abutting round window niche|
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|Figure 5: High resolution computed tomography temporal bone. Coronal computed tomography in bone window showing high lying jugular bulb indenting the round window|
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| Discussion|| |
A "high-riding jugular bulb" is defined as an extension of the most cephalad portion of the jugular bulb superior to the floor of the IAC. Otoscopically, this is seen as a blue mass behind an intact tympanic membrane, which may become distended on valsalva or ipsilateral jugular compression. A high-riding jugular bulb has an intact sigmoid plate - a thin plate of bone separating the jugular bulb from the middle-ear cavity. This can only be appreciated on a thin slice bone algorithm computed tomography, and is too thin to appreciate on magnetic resonance imaging. If the sigmoid plate is deficient, the bulb is free to protrude into the middle-ear cavity, and is then known as a dehiscent jugular bulb. A high jugular bulb is often discovered as an incidental finding that is asymptomatic.  Conductive hearing loss in association with this anomaly may occur, but has been reported infrequently in the literature.  Mechanisms to explain the conductive hearing loss include contact of the jugular bulb with the tympanic membrane, interference with the ossicular chain, and obstruction of the round window niche. 
Despite potential implications of a high-riding jugular bulb, management is generally conservative. HRCT is the imaging modality of choice for evaluating the Jugular bulb, and some recommend periodic follow-up with serial imaging studies every few years to identify any progression.  Surgical management of patients with intolerable symptoms should be analyzed on a case-by-case basis. Jugular-vein ligation has been reported to relieve symptomatology in certain cases; however, this carries the potential neurological risk of pseudotumor cerebri. Patients with high cardiac-output states may benefit from a simple reduction in blood pressure. Great care should be taken by the surgeon if a high- riding jugular bulb is preoperatively identified because patients with this anatomical anomaly are predisposed to surgical complications during myringotomy or middle-ear surgery. In these cases, a middle-ear exploration may be warranted in order to definitively diagnose the lesion; however, once a high-riding jugular bulb has been found to be impinging on the ossicles or round window niche, it is prudent to abort the operation and discuss the options further with the patient and his or her family.
| Conclusion|| |
A high-riding jugular bulb is a relatively uncommon entity. Failure to recognize it; however, can have dramatic implications. The management is typically conservative, although surgical management has been reported. In this present case, a high-riding jugular bulb impinging on the round window niche caused the gradual hearing loss in the left ear. High jugular bulb is not a contraindication for middle-ear surgery. Awareness of this pitfall may lessen the operation risk.  HRCT is the imaging modality of choice for evaluating the jugular bulb. 
| References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]