From the Guidelines
Posterior semicircular canal dehiscence should be diagnosed when vertigo associated with torsional, upbeating nystagmus is provoked by the Dix-Hallpike maneuver, as recommended by the clinical practice guideline: benign paroxysmal positional vertigo (update) 1.
Diagnosis
The diagnosis of posterior semicircular canal dehiscence involves a thorough clinical evaluation, including a detailed medical history and physical examination. The Dix-Hallpike maneuver is a crucial diagnostic tool, as it can provoke vertigo and nystagmus in patients with posterior semicircular canal dehiscence. The maneuver should be performed by bringing the patient from an upright to supine position with the head turned 45° to one side and neck extended 20° with the affected ear down.
- The Dix-Hallpike maneuver should be repeated with the opposite ear down if the initial maneuver is negative, as recommended by the clinical practice guideline: benign paroxysmal positional vertigo (update) 1.
- Clinicians should differentiate posterior semicircular canal dehiscence from other causes of imbalance, dizziness, and vertigo, as stated in the clinical practice guideline: benign paroxysmal positional vertigo (update) 1.
Treatment
The initial management of posterior semicircular canal dehiscence is usually conservative, focusing on symptom management and avoidance of triggers.
- Clinicians should treat patients with posterior canal BPPV with a canalith repositioning procedure, as recommended by the clinical practice guideline: benign paroxysmal positional vertigo (update) 1.
- The canalith repositioning procedure (CRP) is a series of head position changes designed to move the canaliths from the posterior semicircular canal to the vestibule, thereby relieving the stimulus from the semicircular canal that had been producing the vertigo in BPPV.
- Clinicians should not recommend postprocedural postural restrictions after canalith repositioning procedure for posterior canal BPPV, as stated in the clinical practice guideline: benign paroxysmal positional vertigo (update) 1.
Outcome Assessment
Clinicians should reassess patients within 1 month after an initial period of observation or treatment to document resolution or persistence of symptoms, as recommended by the clinical practice guideline: benign paroxysmal positional vertigo (update) 1.
- Clinicians should evaluate patients with persistent symptoms for unresolved BPPV and/or underlying peripheral vestibular or central nervous system disorders, as stated in the clinical practice guideline: benign paroxysmal positional vertigo (update) 1.
From the Research
Posterior Semicircular Canal Dehiscence
- Posterior semicircular canal dehiscence is a rare condition that can cause vertigo, sound-induced vertigo, and pressure-induced nystagmus 2, 3.
- The condition is characterized by a bony dehiscence in the posterior semicircular canal, which can be caused by a variety of factors, including developmental abnormalities, congenital defects, and high-riding jugular bulb 4.
- Symptoms of posterior semicircular canal dehiscence can include disequilibrium, sound-induced vertigo, and reduced ocular vestibular evoked myogenic potential threshold 2.
- Surgical treatment of posterior semicircular canal dehiscence can be effective in relieving symptoms, with techniques including resurfacing of the defect site via a transmastoid approach 2, 5.
- The transmastoid approach has been shown to be a safe and effective alternative to the middle cranial fossa approach for the treatment of semicircular canal dehiscence 6, 5.
Diagnosis and Treatment
- Diagnosis of posterior semicircular canal dehiscence typically involves a combination of clinical evaluation, audiometric testing, vestibular evoked myogenic potential testing, and computed tomography scans 2, 3.
- Treatment options for posterior semicircular canal dehiscence include surgical repair, with the goal of relieving symptoms and improving quality of life 2, 5, 3.
- Surgical techniques for the treatment of posterior semicircular canal dehiscence may include resurfacing of the defect site, plugging of the semicircular canal, or occlusion of the affected canal 2, 6, 5.