This study aimed to determine the distribution and subcellular localisation of aquaporin 2 and vasopressin type 2 receptor in the human endolymphatic sac.

Ten samples of human endolymphatic sac were collected during acoustic neurinoma removal using the translabyrinthine approach. Immunohistochemistry and immunofluorescence were performed using aquaporin 2 and vasopressin type 2 receptor monoclonal antibodies.

Confocal microscopy demonstrated that vasopressin type 2 receptor labelling was expressed in both the apical and basolateral plasma membranes, and in the cytoplasm of the endolymphatic sac epithelium, whereas aquaporin 2 was strongly expressed at the basolateral site of the endolymphatic sac epithelium, in both the intraosseous and extraosseous parts of the endolymphatic sac.

Both aquaporin 2 and vasopressin type 2 receptor were detected in the epithelial cells of the human endolymphatic sac, suggesting that this channel may be involved in inner-ear fluid homeostasis. However, strong basolateral expression of aquaporin 2 in endolymphatic sac epithelium suggested that the function of aquaporin 2 may differ between the endolymphatic sac and kidney.

To highlight a case from 1960 connecting endolymphatic sac tumour and von Hippel–Lindau disease.

In 1960, a 24-year-old woman presented with unilateral hearing loss, pulsatile tinnitus and a mass visible on otoscopy. The patient underwent surgical biopsy, which was complicated by haemorrhage, and ultimately resulted in death. At autopsy, a destructive temporal bone neoplasm with cystic and papillary architecture was observed that had eroded into the otic capsule. Intra-abdominal lesions consistent with von Hippel–Lindau disease were also observed, and the surgeon postulated a connection between endolymphatic sac tumour and von Hippel–Lindau disease.

A review of the literature was carried out using PubMed.

Endolymphatic sac tumours are rare neoplasms of the temporal bone that can occur sporadically or as part of von Hippel–Lindau disease. The connection between endolymphatic sac tumour and von Hippel–Lindau disease was first proposed in 1988 and formalised in 1997. We believe that this case represents the first documented connection between endolymphatic sac tumour and von Hippel–Lindau disease.

To describe the results obtained with endolymphatic sac drainage in patients with Ménière's disease.

A retrospective case review study was conducted of 95 Ménière's disease patients who underwent endolymphatic sac drainage in a tertiary care referral centre, after failing a long course of medical management. The main outcome measures were vertigo control and hearing preservation.

In patients with unilateral disease, vertigo control was obtained in 94.3 per cent of patients. A significant improvement in cochlear function was seen in 14 per cent of patients, and hearing was preserved or improved in 88 per cent. For the bilateral group, vertigo control was obtained in 85.7 per cent of patients and cochlear function improved in 28 per cent. Hearing preservation was attained in 71 per cent of these patients.

Endolymphatic sac drainage is a good surgical option for patients with incapacitating endolymphatic hydrops, providing a high percentage of vertigo control and hearing preservation.

Decompression of the endolymphatic sac for Ménière's disease gives unpredictable results. This may be because the sac is difficult to identify and decompress accurately without causing surgical trauma.

In order to test this idea, transmastoid decompression was simulated in 5 cadaver half heads and the anatomy of the endolymphatic sac was reviewed in a further 14 specimens.

The endolymphatic sac was found and confirmed by histology in all five simulated decompressions. A newly described feature, a trapezoid thickening of dura, was a useful guide. The review showed that the sac was constant proximally, but variable distally. The posterior semicircular canal, posterior fossa dura and sigmoid sinus are at risk during dissection.

The endolymphatic sac may be identified on inspection by an overlying patch of dura, thereby reducing exploratory dissection. It is best to decompress the sac as far proximally as possible, whilst protecting the posterior semicircular canal.

To increase awareness of the presentation, diagnostic difficulties and management of endolymphatic sac tumours.

A 79-year-old man with a 6-month history of unilateral hearing loss, tinnitus and vertigo, who was suspected to have an endolymphatic sac tumour on imaging, underwent successful transmastoid-translabyrinthine resection. A 53-year-old man with unilateral hearing loss and pulsatile tinnitus underwent subtotal resection of a suspected paraganglioma, which was identified histologically. Due to interval growth, gamma knife radiosurgery was performed followed by subtotal petrosectomy, at which juncture an endolymphatic sac tumour was reported.

A review of the world literature was carried out using Medline, which identified less than 150 reported cases of endolymphatic sac tumour.

Endolymphatic sac tumours are rare lesions of the petrous temporal bone. Although benign, they can be locally destructive. At present, there is no consensus regarding the management and long-term follow up of these tumours. Surgical resection is usually favoured, although treatment with radiotherapy and gamma knife surgery has also been reported.

(1) To study the prevalence and characteristics of large endolymphatic sac internal compartments on thin-section T2- and T2*-weighted magnetic resonance imaging, and to relate these to other large endolymphatic sac magnetic resonance imaging features, and (2) to correlate the compartment imaging features, endolymphatic sac size and labyrinthine anomalies with the patients' clinical and audiological data.

Magnetic resonance imaging studies for 38 patients with large endolymphatic sac anomalies were retrospectively reviewed in a tertiary referral centre. Endolymphatic sac compartment presence, morphology and imaging signal were assessed. Endolymphatic sac size and labyrinthine anomalies were also recorded. Endolymphatic sac compartments and other imaging features were correlated with clinical and audiological data.

Compartments were present in 57 per cent of the imaged endolymphatic sacs, but their presence alone did not correlate with other imaging features or clinical data. The endolymphatic sac : internal auditory meatus signal ratio was associated with a history of sudden or fluctuating hearing loss. Hearing loss correlated with opercular and extraosseous endolymphatic sac size measurements. A larger midpoint intraosseous endolymphatic sac size was associated with clear fluid loss at cochlear implantation.

The magnetic resonance imaging characteristics of large endolymphatic sac compartments have been defined. The endolymphatic sac size and distal compartment signal should be recorded, as these provide prognostic information and assist the planning of appropriate interventions.

Allergic rhinitis is associated with excess specific immunoglobulin E. Inner ear involvement (via both cellular and humoral immunity) is poorly understood, but appears to arise from the endolymphatic sac and duct.

To assess the otological and audiological status of patients with allergic rhinitis.

Thirty allergic rhinitis patients (14 men, 16 women; age 17–45 years, mean 31 years) and 20 controls (12 men, eight women; age 21–42 years, mean 27 years) underwent audiological investigation.

All study group patients had sensorineural (rather than conductive) hearing loss, worse at high frequencies. All had abnormal transient evoked otoacoustic emissions and 27 had abnormal distortion product otoacoustic emissions. All had a statistically significantly prolonged wave I latency, and shortened absolute wave I–III and I–V interpeak latencies, compared with controls.

Allergic rhinitis patients had a higher prevalence of hearing loss and otoacoustic emission abnormalities than controls. The endolymphatic sac can process antigens and produce its own local antibody response; the resulting inflammatory mediators and toxic products may interfere with hair cell function. Additional research is needed to determine the clinical value of audiometry and otoacoustic emission testing in allergic rhinitis.

We describe a case of endolymphatic sac tumour confined to the middle ear, which radiologically mimicked a glomus tympanicum, in a 58-year-old woman with tinnitus.

A 58-year-old woman presented with a one-year history of right-sided tinnitus. The clinical, radiological and surgical features were felt to be in keeping with a glomus tympanicum. However, the histopathological picture was that of a low grade papillary carcinoma of the endolymphatic sac, i.e. an endolymphatic sac tumour.

Endolymphatic sac tumours are classically locally aggressive and centred around the petrous temporal bone. Further growth results in complete replacement of the mastoid and petrous pyramid by tumour. To the best of our knowledge, there have been no previous reports of an endolymphatic sac tumour located solely within the hypo- and epitympanum of the middle ear.

To evaluate the vestibular aqueduct in patients with sudden sensorineural hearing loss.

We evaluated 19 patients (12 men and seven women; age range, 22−79 years) with unilateral sudden sensorineural hearing loss, using computed tomography and magnetic resonance imaging. All these patients had unilateral sudden sensorineural hearing loss. We also evaluated 47 control subjects (22 men and 25 women; age range, 22–79 years).

In sensorineural hearing loss affected ears, the width of the vestibular aqueduct at the midpoint and at the operculum was significantly greater than that in contralateral ears or in control ears. The width of the vestibular aqueduct at the midpoint and the operculum did not correlate with the audiometric threshold or the audiogram configuration. Contrast enhancement of the ipsilateral endolymphatic sac was observed in 17 of 19 patients with sudden sensorineural hearing loss (89 per cent). Eleven of these 17 patients also showed enhancement on the contralateral side, but no patient showed enhancement only on the contralateral side. In sensorineural hearing loss affected ears, the width of the vestibular aqueduct did not differ significantly between those patients with and without enhancement.

The vestibular aqueducts of sudden sensorineural hearing loss affected ears are wider than those of controls. Precise imaging and evaluation of the inner ear is essential when investigating the pathological conditions responsible for sudden sensorineural hearing loss.