Citation: Isolated Aplasia of Lateral Semicircular Canal. American Research Journal of Otolaryngology; 1(1): 1-6.
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We aim to review the recent literature about inner ear embryology and discuss the audio vestibular findings in a patient with isolated lateral semicircular canal (LSCC) aplasia. Patient presented with dizziness for the past two years along with lightheadedness and spinning sensations. Radiological and vestibular test results are reviewed. Isolated lateral semicircular canal aplasia is a problem of embryological origin, it may manifest itself with audio vestibular complaints in late ages.
Keywords: Semicircular canals; Sensorineural hearing loss; Dizziness; Vestibular labyrinth
INTRODUCTION
Aplasia of lateral semicircular canal (LSCC) is the most
common congenital labyrinthine anomaly. LSCC aplasia is the result of
incomplete partition from vestibular anlage [1].Usually aplasia of semicircular
canal (SCC) cases are seen in association with syndromic or non-syndromic
congenital anomalies of cochlea [2,3,4]. The LSCC is the last of the three SSCs
which develops during the fetal period, and temporal bone histopathologist
suspected that is why it is the most common labyrinthine anomaly[ 5]. Our
report reviews the recent literature about inner ear embryology and discusses
the audio vestibular findings in a patient with isolated LSCC aplasia.
CASE PRESENTATION
A 46-year-old woman presented with dizziness for the past two years with lightheadedness and spinning sensations. Her dizziness was characterized with spontaneous episodes which last seconds. Between episodes she felt normal. She could tell when she was going to have an attack as it starts with a pressure feeling in her head. She has history of severe migraine headaches and her mother had left sided Meniere’s disease. Otoscopic examination was normal. Pure tone air and bone conduction audiometry revealed normal low frequency hearing, falling to a moderately-severe mid-frequency sensorineural hearing loss, improving to mild high frequency sensorineural hearing loss, slightly poorer for her right ear at 1000 and 6000-8000 Hz (Figure 1). There was a very weak spontaneous nystagmus to the right, which was barely noticeable at right gaze under examination with video Frenzel goggles. Vibration to mastoid triggered brisk right beating nystagmus. Caloric test revealed left unilateral labyrinthine weakness (Figure 2). VEMP (vestibular evoked myogenic potentials) showed normal response at the right but there was no response at left (Figure 3). Radiological assessment with Computerized Tomography (CT) and Magnetic Resonance imaging (MRI) showed us left LSCC aplasia (Figure 4A-B, 5A-B, 6A-B). No cochlear malformation was seen in either side. The internal auditory canal and the cerebellopontine angle were strictly normal.
