Why should multiple dehiscences of the otic capsule be considered before surgically treating patients with superior semicircular canal dehiscence? A radiological monocentric review and a case series

Abstract

This review aims to draw attention to the multiple ipsilateral otic capsule dehiscences (OCDs), which may cause therapeutic failure in operated patients. A series of six severely disabled patients with symptoms and signs consistent with a superior semicircular canal dehiscence (SSCD) diagnosis, confirmed by a high-resolution CT scan, is presented here. Five of the patients underwent surgery, and in four of the cases, the postoperative results were poor and/or disappointing. The ethical principles underlying modern medicine encourage medical staff to learn from past experience even when the results are modest despite the accuracy of the treatment applied to a patient. Consequently, we reviewed the radiological records of symptomatic and asymptomatic patients diagnosed or referred to our center for confirmation over the past 5 years to determine the incidence of multiple OCD in this population. Multiple localizations of suspected OCD in the ipsilateral ear did not appear to be rare and were found in 29 of 157 patients (18.47%) in our retrospective review using high-resolution thin-sliced CT scans. The decision to perform surgery for a documented symptomatic superior SSCD should be made with caution only after ruling out concomitant lesser-known variants of OCD in the ipsilateral ear.

Posterior Semicircular Canal Dehiscence with Vestibulo-Ocular Reflex Reduction for the Affected Canal at the Video-Head Impulse Test: Considerations to Pathomechanisms

“…The lady who underwent canal plugging developed a transient global vestibular hypofunction overlapping the postoperative findings in patients after SSC occlusion in SSCD [48,50,51]. On the other hand, the man who underwent RW reinforcement developed symptoms due to a contralateral HSCD with the FN after surgery, similar to what has been described in patients with multiple third window disorders, highlighting the importance of an extensive preoperative clinical, instrumental and radiological assessment [13].…”

“…Even though aural fullness and autophony can also be found in both patulous Eustachian tube and SCD, patients with a patulous Eustachian tube generally have autophony for their own breath sounds, while patients with SCD usually do not [9]. Besides SCD, other conditions resulting in a TMWM have been described over the years, including an enlarged vestibular aqueduct, X-linked gusher disorder and cochlear dehiscence either involving the internal carotid artery or the facial nerve (FN) [3,5,6,[10][11][12][13][14]. Despite being rare, posterior SCD (PSCD) represents the second most common SCD after SSCD, with a 2% incidence among adult patients and a variable incidence ranging from 1.3 to 43% in the pediatric population [15][16][17][18].…”

“…This huge variability likely depends on several factors, including the type of surveys (histopathological versus radiological), the age of the cohort and the adopted slice thickness for CT scan. Although it is usually associated with a high-riding jugular bulb (HJB), cases with PSCD at the posterior cranial fossa (PCF) have been reported, even in association with other SCD [13,15,[18][19][20][21][22][23]. According to a recent proposal for a unitary classification of all otic capsule dehiscences, PSCD due to a HJB should be classified as vascular extralabyrinthine dehiscence (type II), while PSCD at the PCF should be classified as meningeal dehiscence (type I) [11].…”

“…Nevertheless, HSCD has been anecdotally detected in cases of normal middle ear status [30,31]. Recently, the dehiscence between the HSC and the tympanic tract of the FN has been described as a potential cause of a TMWM [12,13]. In this case, reformatted images along the SSC plane (Pöschl plane) can better visualize the bony defect.…”

Skull Vibration-Induced Nystagmus in Superior Semicircular Canal Dehiscence: A New Insight into Vestibular Exploration—A Review

“…There is otherwise individual patient anatomic variability in SCD, and recent papers [44] showed that 18% had a concomitant additional ipsilateral dehiscence. Some of these dehiscences may have a significant impact on SVIN components.…”