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CASE REPORT
Year : 2022 | Volume
: 28
| Issue : 4 | Page : 322-324
Superior semicircular canal dehiscence presenting as long-standing vertigo
Noor Elyana Ahmad Fawzi1, Azila Alias2, Nik Adilah Nik Othman3, Mohd Khairi Md Daud3
1 Department of Otorhinolaryngology, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Malaysia
2 Department of Otorhinolaryngology, Head and Neck Surgery, Hospital Kuala Lumpur, Wilayah Persekutuan, Malaysia
3 Department of Otorhinolaryngology, School of Medical Sciences, Universiti Sains Malaysia, Health Campus; Otorhinolaryngology Specialist Clinic, Hospital Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
Correspondence Address:
Dr. Mohd Khairi Md Daud
Department of Otorhinolaryngology, School of Medical Sciences, Universiti Sains Malaysia, Health Campus; Otorhinolaryngology Specialist Clinic, Hospital Universiti Sains Malaysia, Kubang Kerian, Kelantan
Malaysia
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/indianjotol.indianjotol_68_22
Superior semicircular canal dehiscence (SSCD) is a complex syndrome and the symptoms can mimic other otologic diseases. We describe a case of a female who presented with imbalance for 10 years which has been psychologically disturbing. Cervical vestibular-evoked myogenic potentials and high-resolution computed tomography scan of the temporal bone confirmed the diagnosis of SSCD. The patient's symptoms improved after the closure of the defect. SSCD should be considered as a differential diagnosis in a case of long-standing vertigo.
Keywords: Semicircular canals, vertigo, vestibular disease
Superior semicircular canal dehiscence (SSCD) is a disease due to bony dehiscence of the canal. The defect leads to the creation of “mobile third window” of the inner ear.[1] The incidence of SSCD is not known. However, radiological studies of coronal computed tomography scan (CT scan) showed that SSCD occurs in between 3% and 9% of the temporal bones.[2],[3] The symptoms of SSCD include the Tullio phenomenon, oscillopsia, and pressure-induced vertigo. They may also have other symptoms such as hyperacusis, autophony, pulse hearing, or even hearing loss.[4] We report a case of middle age female with a history of chronic vertigo.
Case ReportA 50-year-old female presented with persistent vertigo for 10 years. She describes vertigo as the room spinning which was triggered by sound. It was associated with mild hearing loss and tinnitus. She then developed hyperacusis and autophony with worsening of symptoms during the past 3 years. The conditions disturbed her daily activities and caused psychological disturbances. She has no other underlying comorbid.
On examination, her gait was normal with a negative cerebellar sign. She seems to be disturbed by any sound. The ear examination was normal and the fistula test was negative. However, she refused the tuning fork test due to her sensitivity to sound. Cervical vestibular-evoked myogenic potentials (cVEMP) showed a lower threshold at 70 dB over the right side [Figure 1]. High-resolution CT scan revealed a defect at the arcuate eminence of the right superior semicircular canal (SCC) [Figure 2]. The rest of the labyrinth bone was normal. The patient's symptoms were well controlled after the canal dehiscence was repaired through the medial cranial fossa approach. In her case, the surgery was done with the help of a neurosurgical team. An inverted “U” incision was made. The fascia and the temporal muscle were incised and retracted to expose the temporalis squama and the root of the zygomatic arch. Craniotomy was then performed using a diamond burr. The dura was elevated and with the aid of an operating microscope, the middle meningeal artery was identified, cauterized, and sectioned. The area of the dehiscence was then visualized and plugged with fat followed by resurfaced using a temporalis fascia graft.
Figure 1: Lower cVEMP threshold on the right ear suggesting SSCD. cVEMP: Cervical vestibular-evoked myogenic potentials, SSCD: Superior semicircular canal dehiscence
Figure 2: Coronal view of HRCT temporal shows dehiscence at the right superior semicircular canal (arrow). HRCT: High-resolution computed tomography Discussion SSCD is a rare disease but the patient who suffers from the condition may have a reduced quality of life. Canal dehiscence may occur at any SCC but most commonly in the superior canal. The etiology is unknown. Nystagmus evoked by sound or pressure is a classic feature. The diagnosis can be challenging and therefore investigations such as cVEMP and CT scan should be considered. Even though CT scan is highly sensitive in detecting dehiscence but it may give rise to false positives. The cVEMP assesses vestibulocollic pathway in the presence of a third window. A low threshold on cVEMP testing[5] with canal dehiscence shown by a high-resolution CT scan confirms the diagnosis.[6]
The disorders that can mimic SSCD include patulous Eustachian tube, otosclerosis, Meniere's disease, and perilymph fistula.[7] Autophony is a symptom of a patulous Eustachian tube. The hearing loss component that appears in adulthood is similar to otosclerosis. Episodic vertigo may indicate a perilymphatic fistula. The triad of episodic vertigo, hearing loss, and tinnitus is a characteristic of Meniere's disease. Quite a number of patients with migraines have vertigo as the main symptom rather than headache.
The treatment for SCCD can either be conservative or surgical. As our patient condition was worsening, thus, she opted for surgery. There are a few approaches for the repair. The middle cranial fossa approach is more invasive but can give good exposure to the SCC. At least a 4 cm × 4 cm craniotomy flap is created and removed. The temporal lobe dura is elevated off the floor of the middle cranial fossa to expose the superior canal at the area of arcuate eminence. The dehiscence may be visualized at this point. Endoscopic-assisted middle cranial fossa repair has been described as well.[8] The technique has the advantage of a smaller craniotomy to be performed. The transmastoid approach is less invasive and gaining popularity.[9] However, it may not give direct visualization of the dehiscence. The technique begins with a postauricular incision followed by mastoidectomy. The presigmoid area, the middle fossa dura, and the three SCC are skeletonized. The tegmen lateral to the superior SCC is removed with a diamond burr. The middle fossa dura is elevated from superior SCC. The dehiscence is then identified.
The surgical treatment can be done either by resurfacing or plugging the SCC using bone dust or fascia. Palma Diaz et al. in their review have found that plugging and capping techniques were associated with higher success rates than resurfacing.[8] In our patient, she was relieved from the symptoms after the dehiscence part was plugged with fat as well as resurfaced using temporalis fascia graft through the middle fossa approach.
ConclusionSSCD should be considered as a differential diagnosis in a case of chronic vertigo. The outcome of canal repair is generally good.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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