4 DISCUSSION
4.1 Synopsis of key findings
In this study, we detailed the clinical manifestations, genetic results
and audiological features of four patients with BOR syndrome who
accepted CI. Auditory and speech performance after CI may vary
postoperatively. In addition, the surgery of case 2 was most challenging
as with aural atresia.
4.2 Comparisons with other studies
CI outcomes in patients with ROR syndrome were scarcely documented in
the literature, because it accounts for only about 2% profound hearing
loss(1). Most surgical process reported in the
literature seemed normal, no further details were provided(2-5). A perilymphatic gusher was reported in one
adolescent case with bilateral dilated vestibule, enlarged vestibular
aqueduct, ossicular anomalies, and bilaterally deviated facial nerves.
However, this was easily controlled by conventional
methods(3).
But there were challenging case report due to ear deformity. Absent
temporal bone structures including the lateral semicircular canal, incus
and stapes, and oval windows were mentioned in previous case reports,
then it took more time to expose the cochlea(6).
Patient with aural atresia is most challenging, because few anatomical
landmarks were present and the dura might get exposed during
mastoidectomy as intraoperative complications. Previous imaging study
had showed that non-pneumatized mastoid, antrum and low lying tegmen
were very common in BOR. Thus, restricted transmastoid access should be
anticipated (7).
Furthermore, aberrant courses of facial nerve definitely makes the
operation more difficult(6). Residual soft tissue
resembling the nerve definitely increased operating time, such as in
case 2. Thus facial nerve monitoring were essential. It is important to
not cut any soft tissue too hastily. Finally, malformed cochlea also
made precise location of the scala tympany and insertion difficult. Full
insertion was unattainable. Cochleostomy was sited more anterosuperior
to the round window niche than usual as a result of rotated cochlea,
such as in case 3(6). Intraoperative navigation CT may
be helpful with cochlear location in such patients.
Most previous studies reported promising outcomes no matter in
pediatric(4, 8), adolescent(3) or
adult patients(5). Morisada reported 4 in 11 patients
who didn’t show good effect without details(8). In this study, we
observe unfavorable CI outcomes in three patients. Dysplasia of cochlear
nerve is the main reason (9), which was rarely
mentioned before. Cochlear implant in children with CND, especially
those with CN aplasia, has been controversial. Oblique sagittal
high-resolution MRI is routinely performed to screen CND in most CI
centers, although it’s not the golden standard test due to limited
resolution. Audiological effective cases indicate that certain children
do benefit from CI despite of radiographic CND. Thus preoperative
communication with CI candidates and their families are essential to
help them establish reasonable expectations.
4.3 Strengths and limitations of the study
This study is the first to describe the correlation between CND and CI
outcomes in patients with BOR syndrome. However, because of the limited
number of cases (only four patients) in this study, our speculation is
not conclusive. As BOR syndrome is a disease with extremely low
prevalence, large-scale meta-analyses are essential to clearly delineate
the correlation between CND, audiological features and CI outcomes.
5 . CONCLUSION
BOR syndrome patients with profound hearing loss could benefit from
cochlear implantation. the surgery is challenging in the presentence of
complex ear malformations. CI outcomes may be affected by dysplasia of
cochlear nerve.