PMC9124807_01
Hearing test. (A) Preoperative, demonstrating left-sided low-frequency conductive hearing loss with mild high-frequency hearing loss on the contralateral ear (blue/red traces) and (B) postoperative, with the persistence of similar conductive hearing loss on the left (black traces).
fneur-13-844687-g0001.jpg
PMC9124807_01_fneur-13-844687-g0001.jpg
F1
On the hearing test, there was left-sided low-frequency conductive hearing loss (Figure 1), which was either due to the presence of middle ear scar tissue linked to his prior middle ear surgery or conductive hearing loss associated with the SCC dehiscence. The only residual symptoms were the pre-existing tinnitus and conductive hearing loss, which, after the plugging of the anterior canal, neither improved nor worsened (Figure 1).
Video head impulse test (vHIT) results. (A) Preoperatively, showing anterior canal hypofunction and (B) postoperatively (2 months) showing diminished VOR gain values on the left side (operated side) for all 3 canals. This initial left-sided postoperative hypofunction fully recovered over time.
fneur-13-844687-g0002.jpg
PMC9124807_01_fneur-13-844687-g0002.jpg
F2
The preoperative vHIT demonstrated hypofunction of the left anterior canal with a gain of 0.64 and with normal gains bilaterally in all other canals (Figure 2). The video head impulse test (vHIT) showed on the left side (operated side) normal Vestibulo-Ocular reflex (VOR) gain values for the lateral semicircular canal but pathological gains for the posterior and anterior canals (Figure 2). oVEMPs were symmetrical (reduced to 20% asymmetry) in their responses with normal amplitudes.
oVEMPS performed (A) preoperatively and (B) postoperatively. (A) A substantial increase in trace amplitude (based on normative data) is present on the left ear, with normal traces on the right ear confirming the presence of left-sided SCC-Dehiscence. The peak-to-peak asymmetry was 94%. (B) Postoperative findings demonstrate symmetrical results on both ears (amplitudes restored back to normal values).
fneur-13-844687-g0003.jpg
PMC9124807_01_fneur-13-844687-g0003.jpg
F3
On the oVEMPS, amplitudes were elevated on the left hand side (Figure 3) with significant asymmetry (94%) of the peak-to-peak amplitude.
High-resolution temporal bone imaging CT (slice thickness 0.6 mm). The semicircular canal (SCC) dehiscence is indicated by the white arrows in the (A) coronal plane, (B) plane of Stenvers, and (C) plane of Poschl.
fneur-13-844687-g0004.jpg
PMC9124807_01_fneur-13-844687-g0004.jpg
F4
A neuroradiological workup was undertaken in our institution; on the thin cut high-resolution temporal bone CT with a slice thickness of 0.6 mm, there was a bony discontinuity along the roof of the left superior SCC with a dehiscence measuring 5.4 mm (Figure 4).
Case report Timeline.
fneur-13-844687-g0005.jpg
PMC9124807_01_fneur-13-844687-g0005.jpg
F5
The patient was scheduled for left transmastoidal plugging of the superior SCC dehiscence (Figure 5).