Factors affecting hearing deterioration in vestibular schwannoma patients treated with gamma knife radiosurgery: the Asan Medical Center experience

<p><b>Objectives:</b> To investigate the changes in hearing and to determine factors predicting hearing deterioration in patients with vestibular schwannoma (VS) who undergo gamma knife radiosurgery (GKRS).</p> <p><b>Design:</b> A retrospective review of medical records in patients diagnosed with VS and initially treated with GKRS at a tertiary care medical center between 1995 and 2015 was performed. Tumor factors (location, volume), parameters related to irradiation to the tumor and cochlea, and distance between the tumor and cochlea were reviewed.</p> <p><b>Results:</b> Fifty-six patients were included in the final analysis with a mean observation period following GKRS as 24.4 ± 27.8 months. Prior to GKRS, the average pure tone threshold at 500, 1k, 2k, and 4k Hz (PTA₄) was 51.0 ± 29.7 dB HL. After GKRS, the mean PTA₄ was 71.6 ± 33.3 dB HL. Significant independent odds ratios for hearing deterioration were 8.5 for extracanalicular tumors, 18.8 for more than 10 shots in GKRS, and 12.2 for a distance between the tumor center and cochlea modiolus less than 20 mm.</p> <p><b>Conclusions:</b> A significant hearing deterioration was shown in 2 years after GKRS. Tumor location, number of radiation shots, and distance between the tumor and cochlea affected hearing level after GKRS.</p

Representative endoscopic and CT images of the stented ET over time.

(A) Endoscopic images taken immediately after stent placement, showing the proximal end of the Mg stent (arrows) in the porcine ET. The proximal end of the stent with mild secretion (arrows) is observed around the Mg stent at two weeks, while the Mg stent is not observed at four weeks (arrowheads). (B) 3D-reconstructed CT images of the degraded Mg stent showing a residual Mg stent with a collapsed distal end at two weeks and only a small piece of the Mg stent at four weeks. Note. CT, computed tomography; Mg, magnesium; ET, Eustachian tube.</p

Schematic image of an absorbable magnesium stent to manage ETD showing prevention of stent-induced tissue hyperplasia and maintaining the ET patency.

Schematic image of an absorbable magnesium stent to manage ETD showing prevention of stent-induced tissue hyperplasia and maintaining the ET patency.</p

Representative histological images of the porcine ET and histological findings.

(A) Histological images showing the submucosal tissue hyperplasia increased at two weeks and then significantly decreased at four weeks. (B) Histological results of the thickness of submucosal tissue hyperplasia and the degree of inflammatory cell infiltration in the proximal and distal portions of the stented ET over time after the Mg stent placement. Note. Mg, magnesium; ET, Eustachian tube.</p

The Mg stent and the technical steps of ET stent placement under endoscopic guidance.

Photographs showing (A) the Mg stent loaded onto a balloon catheter and (B) when fully expanded. (C) Endoscopic image showing the nasopharyngeal ostium (arrowheads). (D) The steerable guiding sheath (arrows) was inserted into the nasopharyngeal ostium. (E) The balloon catheter crimped with the Mg stent (arrowheads) is advanced into the ET. (F) The balloon catheter was fully inflated with saline. (G) After verifying the fully expanded stent (arrows), the sheath with the balloon catheter was removed. (H) An endoscopic image of the Mg stent (arrowheads) in the porcine ET. Note. Mg, magnesium; ET, Eustachian tube.</p

Surface morphologies of the Mg stent and mass loss rates.

(A) SEM images showing the size and number of the cracks increasing over time (arrows) on the surface of Mg stent samples obtained at one, two, and four weeks, respectively. (B) The bridges (arrows) between the struts are disconnected, and the strut was sequentially separated. (C) A graph depicting the mass loss rates of the Mg stent over a four-week period. Note. Mg, magnesium; SEM, scanning electron microscopy.</p

Table_1_Prospective analysis of video head impulse tests in patients with acute posterior circulation stroke.DOCX

BackgroundVideo head impulse tests (vHITs), assessing the vestibulo-ocular reflex (VOR), may be helpful in the differential diagnosis of acute dizziness. We aimed to investigate vHITs in patients with acute posterior circulation stroke (PCS) to examine whether these findings could exhibit significant abnormalities based on lesion locations, and to evaluate diagnostic value of vHIT in differentiating dizziness between PCS and vestibular neuritis (VN).MethodsWe prospectively recruited consecutive 80 patients with acute PCS and analyzed vHIT findings according to the presence of dorsal brainstem stroke (DBS). We also compared vHIT findings between PCS patients with dizziness and a previously studied VN group (n = 29). Receiver operating characteristic (ROC) analysis was performed to assess the performance of VOR gain and its asymmetry in distinguishing dizziness between PCS and VN.ResultsPatients with PCS underwent vHIT within a median of 2 days from stroke onset. Mean horizontal VOR gain was 0.97, and there was no significant difference between PCS patients with DBS (n = 15) and without (n = 65). None exhibited pathologic overt corrective saccades. When comparing the PCS group with dizziness (n = 40) to the VN group (n = 29), patients with VN demonstrated significantly lower mean VOR gains in the ipsilesional horizontal canals (1.00 vs. 0.57, p ConclusionSignificantly abnormal vHIT results were rare in patients with acute PCS, even in the presence of DBS. Moreover, vHIT effectively differentiated dizziness between PCS and VN, highlighting its potential for aiding differential diagnosis of acute dizziness.</p