Glaucoma of the Inner Ear Vis-a-Vis Endolymphatic Hydrops: an Updated Imaging Algorithm

Menières disease is a highly stressful and personally restricting disorder of the inner ear [1]. Diagnosis is made by clinical characteristics and clinical/physiological testings, but in many cases a definite diagnosis of Menières disease is not possible [2,3]. The recently established Endolymphatic Hydrops MRI (EH-MRI) by use of i.v.-application of Gadolinium-based contrast agents allows the in-vivo diagnosis of Menières disease Naganawa et al. [4]. The already prevalent analysis done semi-quantitatively, objective grading systems may be inaccurate in lieu of therapy monitoring and have recently shown lacunae.


Introduction
Menières disease is a highly stressful and personally restricting disorder of the inner ear [1]. Diagnosis is made by clinical characteristics and clinical/physiological testings, but in many cases a definite diagnosis of Menières disease -is not possible [2,3]. The recently established Endolymphatic Hydrops MRI (EH-MRI) by use of i.v.-application of Gadolinium-based contrast agents allows the in-vivo diagnosis of Menières disease Naganawa et al. [4]. The already prevalent analysis done semi-quantitatively, objective grading systems may be inaccurate in lieu of therapy monitoring and have recently shown lacunae.

Materials & Methods
This prospective clinical study was conducted at the Prince Bijey Singh Memorial Hospital, Bikaner, Rajasthan including n = 10 patients with definite and n = 1 patient with possible diagnosis of Menière's disease. As negative control an asymptomatic subject was examined the same way. The patient's mean age was 35 to 75 years (54.91 ± 14.2 years), 7 patients were female and 4 male. 4 hours before MR measurements intravenous application of a single dose Omniscan® (0.2 ml/kg or 0.1 mmol/kg body weight) was performed ( Figure 1). The imaging was performed on a 1.5tesla MR imaging unit (Philips Achieva) using a 12-channel array head and neck coil. Endolymphatic hydrops was graded by two different radiologists in consensus-procedure according to the criteria of Nakashima, Naganawa et al. [5]. After the examination, a survey consisting of 8 questions was conducted for evaluation of patient acceptance and satisfaction. Institutional review board approval was obtained for this study.

Results
MRI was carried out on average 4 hours after intravenous-injection of a standard-dose Omniscan (0.2 ml/kg or 0.1 mmol/kg body weight). The measurements done quantitatively of the endolymph showed a mean volume of the cochlear labyrinth of 104 µl and a mean volume of the vestibular labyrinth of 165 µl. The total labyrinth volume was 265µl. The difference was statistically significant p = 0.025; (Figure 2). The affected Cancer Therapy & Oncology International Journal inner ears showed this accentuated volume increase as well as the side without endolymphatic hydrops. Symptoms occurred on the left ear in 5 cases (right ear 4 cases) and in one case both ears were affected [6]. Semi-quantitative analysis for the total of n = 20 cochlear structures in 12 inner ears no cochlear hydrops was detected, n = 4 inner ear presented with a minimal degree of cochlear hydrops and n = 6 inner ears were effected with significant degree by cochlear endolymphatic hydrops. The semi quantitative analysis of the endolymphatic sac delivered 3 inner ears with mild cochlear hydrops, n = 6 with significant degree of cochlear hydrops and 13 patients had no relevantly dilated endolymphatic cul-de-sac. The correlation coefficient r between both methods was r = 1 for the right ear and r = 0.95 for the left ear.

Cancer Therapy & Oncology International Journal
The evaluated analysis semiquantitavely of the vestibule showed the following results: n = 7 inner ears showed a mild degree of vestibular endolymphatic hydrops, n = 7 a significant vestibular EH and 8 inner ears showed no relevant EH Correlation coefficients between semi-quantitative and quantitative analysis were r = 1 for the right and r = 0.73 for the left vestibular structures (Figure 3). We detected no statistical significant difference between both methods. 8 from 11 patients participated in the survey. Due to the ongoing stress and strain of the examination undertaken a mean value of 3 (in a scale of 1 to 10 with 1 = nonstressful, 5=mid range and 10 = extremely stressful) was made, no patient had any problems with the intravenous -application of the contrast agent. The personal benefit for the patients was high. All patients felt confident that the results of the examination have an impact on therapy and course of the disease. Moreover, all of the included subjects would recommend Endolymphatic Hydrops MRI to other patients ( Figure 4).

Conclusion
MRI is a highly efficient diagnostic tool to evaluate hydrops in Menière's disease. Our study shows that the already compliant quantitative analyses are highly accurate, but certain necessary conditions (e.g., schwannoma) should be additionally evaluated by semiquantitative post-procedural methods. The importance of patient satisfaction and accessability and the high acceptance of CE MRI-examinations should be taken into account in the upcoming years to succor our fellow otologists.