Large Vestibular Aqueduct Syndrome (LVAS) — Pediatric Sensorineural Hearing Loss

Large vestibular aqueduct syndrome (LVAS), or enlarged vestibular aqueduct (EVA), is the most common radiographically identifiable inner ear malformation associated with childhood sensorineural hearing loss, accounting for 5–15 percent of pediatric SNHL cases. The vestibular aqueduct is a bony channel within the petrous temporal bone running from the medial wall of vestibule of inner ear to the posterior cranial fossa, encasing the endolymphatic duct that connects the endolymphatic sac (located within dura mater) to the membranous labyrinth.

Cincinnati criteria define LVAS as midpoint diameter >1.5 mm or operculum diameter >2 mm on axial high-resolution temporal bone CT. Alternative criteria propose midpoint >0.9 mm or any vestibular aqueduct larger than adjacent posterior semicircular canal as enlarged. Bilateral involvement in 50–94 percent (asymmetric in many). Frequently associated with cochlear malformations, particularly incomplete partition type II (Mondini malformation — 1.5 turns of cochlea instead of 2.5).

Genetics: strong association with SLC26A4 gene (chromosome 7q22.3) encoding pendrin, a chloride-iodide-bicarbonate anion exchanger. Biallelic SLC26A4 mutations cause Pendred syndrome (autosomal recessive), characterized by sensorineural hearing loss, thyroid goiter (often appearing in adolescence), and abnormal organification of iodide demonstrable by positive perchlorate discharge test. Monoallelic SLC26A4 mutations or biallelic with EPHA2 modifier cause non-syndromic EVA (DFNB4 locus). Other associations: branchio-oto-renal (BOR) syndrome (EYA1, SIX5 mutations), CHARGE syndrome, distal renal tubular acidosis, X-linked deafness with stapes gusher (POU3F4).

Hearing loss characteristics: bilateral in most, often asymmetric, sensorineural (rarely conductive component due to third window effect), ranges from mild to profound, may be present at birth (congenital — fail newborn hearing screening), or develop later (delayed onset). Course: progressive in 50 percent (gradual decline over months to years), fluctuating in 10–35 percent (recovers partially or fully), or sudden drops triggered by: minor head trauma (most common — fall, sports injury, even hitting head on cabinet), barotrauma (scuba diving, airplane descent), Valsalva (heavy lifting, straining), vigorous exercise, or upper respiratory infection. Vestibular symptoms (vertigo, imbalance, motion intolerance) in 30 percent.