Abstract
Our experience with 102 patients having superior semicircular canal dehiscence confirm that the clinical manifestations of the disease are very diverse; we also identified 3 patients who showed Meniere-like symptoms. Clinical examination during an acute vertigo attack of a patient with Meniere disease for several years and whom we subsequently diagnosed as having large superior semicircular canal dehiscence on the affected side allowed us to hypothesize that a natural plugging of the superior semicircular canal by the overhanging dura mater could be responsible for the recurrence of symptoms. Clinical and instrumental data were very similar to those recorded in 7 of 9 patients immediately after surgical plugging. The aim of the study was to understand which semiological and instrumental elements could be clinically useful, first in distinguishing Meniere disease from superior semicircular canal dehiscence and, secondly, in understanding if signs of natural plugging are present.
1
Introduction
Dehiscence of the bone overlying the superior semicircular canal (SSCD) is considered a possible structural cause of sound-induced vertigo (Tullio phenomenon) and pressure-induced vertigo and/or hyperacusis to bone-conducted sound .
Electrophysiologic data by vestibular evoked myogenic potentials (VEMPs) and temporal bone high-resolution computed tomography (CT) (HRCT), carried out using 0.5-mm contiguous reconstructions of the oblique plane of the superior semicircular canal (SSC), should be used to confirm the presence of a “mobile third window,” such as SSCD .
Clinical manifestations of SSCD are so diverse and patient specific that its typical features can be totally absent. Patients with a debilitating symptoms may benefit from surgical plugging of the SSCD through the middle fossa or using the transmastoid approach (TM) .
Ever since SSCD was first characterized, only a few authors have described the fact that cochleovestibular symptoms can mimic that of the Meniere disease ; a few cases of SSCD associated with Meniere disease have been reported by Pyykkö and Poe . It is interesting that, in his study, magnetic resonance imaging was used to demonstrate endolymphatic hydrops both before and after surgery .
Clinical observation during an acute vertigo attack of a patient with Meniere disease for several years and who we subsequently diagnosed as having large SSCD on the affected side allowed us to hypothesize, based on several clinical and semiological elements, that recurrent Meniere-like symptoms could be justified by natural plugging of the SSC endolymphatic compartment by the overhanging dura mater. Our hypothesis was borne out by the strict similarity between the symptoms of our case report and that of a small group of patients observed immediately after SSC surgical plugging.
2
Patients and methods
One hundred two patients were identified as having SSCD at the ENT Unit of the Specialistic Surgical and Anaesthesiological Sciences Department of the University of Bologna from January 2003 to December 2010.
Nine patients with incapacitating SSCD symptoms underwent surgical plugging by the senior author (GCM) during the period from October 2005 to December 2010 ( Table 1 ).
| Case | Age, y | Sex | SSCD side | Plug approach | Video nystagmoscopy | Timing nystagmus inversion, d | FU (mo) video nystagmoscopy | C AC-VEMPs threshold Pre→post surgery, dB SPL |
|---|---|---|---|---|---|---|---|---|
| 1 | 43 | M | Bilateral | Left MF | Left SN | 2 | 63, absent SN | 95→120 |
| 2 | 42 | F | R | ZRA | – | – | 20, slight right SN | 95→115 |
| 3 | 45 | M | R | TM | RH BPPV | – | 13, absent SN | 110→130 |
| 4 | 50 | M | L | TM | Left SN | 3 | 10, absent SN | 105→110 |
| 5 | 59 | M | L | TM | Left SN | 2 | 7, absent SN | 110→absent |
| 6 | 19 | M | R | TM | Right SN | 1 | 6, absent SN | 115→132 |
| 7 | 49 | F | L | TM | Left SN | 6 | 4, absent SN | 100→110 |
| 8 | 60 | M | L | TM | Left SN ⁎ | 3 | 4, absent SN | 100→120 |
| 9 | 67 | F | R | TM | Right SN | 1 | 3, absent SN | 115→132 |
⁎ Ipsilesional spontaneous nystagmus appeared 1 day after plugging.
Of 102 SSCD patients, many of them reported an acute vertigo attack (33%, benign paroxysmal positional vertigo excluded), but only 3 of them described Meniere-like symptoms. We will now describe shortly the only 1 case that we had the opportunity of examining in the course of an acute vertigo attack.
2
Patients and methods
One hundred two patients were identified as having SSCD at the ENT Unit of the Specialistic Surgical and Anaesthesiological Sciences Department of the University of Bologna from January 2003 to December 2010.
Nine patients with incapacitating SSCD symptoms underwent surgical plugging by the senior author (GCM) during the period from October 2005 to December 2010 ( Table 1 ).
