Fig 1.
Criteria for EH-grading of the cochlea and vestibule in MRI performed 4 h after intravenous and 24 h after intratympanic administration of Gd-based contrast media (IV-Gd + IT-Gd MRI).
(A) The criterion for cEH was the dislocation of the Reissner’s membrane. (B) The decisive factor for vEH is the EVVR. EH, endolymphatic hydrops; MRI, magnetic resonance imaging; Gd, gadolinium; IV-Gd, intravenous injection of gadopentetate dimeglumine; IT-Gd, intratympanic injection of gadopentetate dimeglumine; cEH, cochlear EH; vEH, vestibular EH; EVVR, endolymph to vestibule-volume.
Fig 2.
For the EH-grading of the vEH, the overall EVVR was calculated by measuring the area of the xn and yn in every section plane showing the vestibule, and then using the average of those values. The volume of both endolymphatic and perilymphatic space was calculated by multiplying the measured x or y, by the uniform layer thickness of 0.8 mm (a). EVVR, endolymph to vestibule-volume; EH, endolymphatic hydrops; vEH, vestibular EH; xn, endolymph; yn, perilymph; x or y, surface area.
Fig 3.
(A) Left ear mastoidectomy and endolymphatic sac dissection showing the intraosseous portion of sac (white arrow), extraosseous portion of sac (black arrow) and posterior fossa dura (arrow head). (B) Two titanium clips (white arrow) blocking the endolymphatic duct behind the posterior semicircular canal (PSCC).
Table 1.
Clinical profiles in all 22 patients prior to and following surgery.
Fig 4.
3D-real IR MRI scans of patient no. 14 (Table 1) with right MD.
(A) prior to surgery, (B) 2 weeks, (C) 10 months and (D) 16 months after surgery, as well as changes of the hearing threshold and -SP/AP ratio of EcochG prior to and following surgery. (A) Axial IT-Gd + IV-Gd MRI scan of the right ear showing a significant EH in the vestibule (red arrow) and cochlea (white arrow) and no pathological finding in the left unaffected ear. (B) A significant EH in the vestibule (red arrow) and cochlea (white arrow) remained unchanged 2 weeks after surgery in the right ear. (C) Downgrading of vestibular EH from grade II to none (EVVR, 24.25%) and a remaining grade II EH in the cochlea 10 months after surgery. (D) Axial IT-Gd + IV-Gd MRI showing downgrading of EH from grade II to none (EVVR, 13.89%) in the vestibule (red arrow) and from grade II to I (white arrow) in the cochlea 16 months after surgery in the right ear in the same section plane as in parts A-C. Axial IV-Gd MRI scan of the left unaffected ear showing insufficient contrast in the basal turn of the cochlea. (E) Audiogram showing that the mean hearing threshold of air conduction (0.25, 0.5, 1.0 and 2.0 KHz) decreased from 55 dB before to 26.3 dB after surgery. (F) A negative conversion of EcochG was detected as the -SP/AP ratio decreased from 0.95 before to 0.22 (Table 1) after surgery. LSCC, lateral semicircular canal; 3D-real IR, three-dimensional real inversion recovery; MRI, magnetic resonance imaging; -SP/AP, summating potential/action potential ratio; Gd, gadolinium; EcochG, electrocochleography; EH, endolymphatic hydrops; EVVR, endolymph to vestibule-volume; MD, Meniere’s disease; IT-Gd, intratympanic injection of gadopentetate dimeglumine; IV-Gd, intravenous injection of gadopentetate dimeglumine.
Fig 5.
3D-real IR serial MRI scans of patient no. 14 (Table 1) with right MD.
(A1-3) prior to surgery, and (B1-3) 2 weeks, (C1-3) 10 months and (D1-3) 16 months after surgery. (A1-3) Serial MRI scans showing a significant EH in the vestibule (red arrow) and cochlea (white arrow) before surgery. (B1-3) Unchanged EH in the vestibule (red arrow) and cochlea (white arrow) 2 weeks after surgery. (C1-3) Reversal of vestibular hydrops and remaining grade II EH in the cochlea 10 months after surgery. (D1-3) Serial MRI scans showing a disappearance of vestibular EH (red arrow) and the reduction of cochlear EH (white arrow) 16 months after surgery. LSCC, lateral semicircular canal; 3D-real IR, three-dimensional real inversion recovery; MRI, magnetic resonance imaging; EH, endolymphatic hydrops; MD, Meniere’s disease.
Fig 6.
Correlation between the difference value of the hearing threshold, -SP/AP ratio of EcochG, EVVR and grading of cochlear hydrops prior to and following surgery.
(A)The difference value of the hearing threshold had a significant positive correlation with the difference value of the EVVR (P = 0.000, r = 0.739). (B) A significant positive correlation was observed between the difference value of the hearing threshold and grading of cochlear hydrops (P = 0.000, r = 0.562). (C) The difference value of the -SP/AP ratio was significantly correlated with the difference value of the EVVR (P = 0.000, r = 0.690). (D) A significant positive correlation was identified between the difference value of the -SP/AP ratio and grading of cochlear hydrops (P = 0.001, r = 0.467). -SP/AP, summating potential/action potential ratio; EVVR, endolymph to vestibule-volume; EcochG, electrocochleography.
Fig 7.
Changes in the average hearing threshold and -SP/AP ratio of EcochG.
Among patients with a decreased EVVR, the (A) average hearing threshold (43.27±15.60) and (B) -SP/AP ratio (0.45±0.32) decreased significantly following surgery, as compared with the value prior to surgery (56.06±11.33, P = 0.005 and 0.78±0.41, P = 0.049, respectively). Among patients with an increased EVVR, the (A) average hearing threshold (57.64±11.40) and (B) -SP/AP ratio (0.67±0.33) tended to increase following EDB, as compared with the value prior to it (54.16±11.40 and 0.56±0.26, respectively), but there was no significant difference between the two groups (P = 0.115 and P = 0.105, respectively). -SP/AP, summating potential/action potential ratio; EcochG, electrocochleography; EVVR, endolymph to vestibule-volume; EDB, endolymphatic duct blockage; **P < 0.01, paired t-test; *P < 0.05, paired t-test; NS, not significant, paired t-test.