When hearing loss mimics autism: Enlarged vestibular aqueduct syndrome in an 11-year-old child—A case report

Abstract

The relationship between auditory input and cognitive development is fundamental, as early sensory deprivation can impair social communication and mimic neurodevelopmental disorders. Comprehensive audiological assessment is critical for children suspected of autism spectrum disorder to prevent “diagnostic overshadowing,” where behavioral symptoms of hearing loss—such as social withdrawal and speech delay—are mislabeled as neurodevelopmental deficits. Although autism spectrum disorder involves social communication deficits under DSM-5 criteria, congenital progressive sensorineural hearing loss often presents with similar clinical features. Enlarged vestibular aqueduct syndrome is the most common congenital inner ear anomaly associated with progressive hearing loss and must be considered in differential diagnoses. This report describes a patient in his early teens, misdiagnosed with autism spectrum disorder for 8 years, whose diagnosis was corrected to enlarged vestibular aqueduct syndrome based on high-resolution imaging. Early identification is vital for timely interventions such as cochlear implantation.

Introduction

The vestibular aqueduct is a slim, bony passage located in the temporal bone, which serves as a structural bridge connecting the vestibule of the inner ear to the posterior cranial fossa. Based on anterior coronal imaging, the typical measurements of the isthmus are as follows: (a) length: 3.1 ±1.8 mm; (b) width: 1.6 ± 0.8 mm; and (c) axial diameter: approximately 2 mm using computed tomography (CT). Interestingly, the anterior coronal view allows visualization of nearly 100% of normal vestibular aqueducts. Enlarged vestibular aqueduct syndrome (EVAS) is defined by an operculum diameter greater than 2 mm on axial CT or greater than 6.8 × 3.3 mm on coronal CT at the isthmus level. ¹

Beyond its primary structure, the inner layer of the aqueduct contains a network of microcanals and Volkmann’s canals. These tiny channels play a critical role in maintaining the homeostatic environment of the inner ear. ²

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social communication and restricted interests and repetitive behaviors. The Centers for Disease Control and Prevention (CDC) estimates that approximately 1.68% of children aged 8 years (or 1 in 59 children) are diagnosed with ASD in the United States; autism-specific screening is conducted at 18 months and once again at 24 or 30 months. The Modified Checklist for Autism in Toddlers, Revised, with Follow-up (M-CHAT-R/F) is used as a screening tool for ASD; to arrive at a definitive diagnosis, children with ASD should meet the diagnostic criteria for ASD according to DSM-5: a child must have persistent deficits in each of the three areas of social communication and interaction plus at least two of four types of restricted, repetitive behaviors. ³

Case presentation

A male patient in his early teens presented to our clinic in June 2025 with a history of speech delay first noticed by his parents at the age of 2 years. Initial evaluations by pediatricians and neurologists contributed to a misdiagnosis of ASD and nonspecific neurological impairment.

At the age of 3 years, an auditory brainstem response (ABR) test was performed, which revealed severe sensorineural hearing loss (SNHL). The parents were informed that the auditory nerve was “nonfunctional,” and the patient was managed with conventional hearing aids for 8 years. However, the patient’s hearing deteriorated significantly over the past year, prompting a referral for advanced imaging.

Audiometry

Pure tone audiometry revealed asymmetrical SNHL. A low-frequency air-bone gap and progressive high-frequency loss were observed (Figure 1).

Figure 1.

Pure-tone audiogram. High-resolution illustration showing asymmetrical hearing loss. Right ear (red): mixed-type hearing loss with a notable low-frequency air-bone gap (AC-O, BC-[), characteristic of EVAS third-window effects. Left ear (Blue): symmetrical sensorineural hearing loss with milder thresholds (AC-X, BC-]).

ABR confirmed the diagnosis of SNHL.

High-resolution CT (mastoids) revealed a bilateral enlargement of the vestibular aqueducts. The operculum of the right vestibular aqueduct was 2.2 mm in diameter, while that of the left vestibular aqueduct was 2.1 mm (Figure 2).

Figure 2.

High-resolution axial computed tomography of the temporal bones revealing bilateral enlargement of the vestibular aqueducts. The right vestibular aqueduct operculum measures 2.2 mm in diameter (a), whereas the left vestibular aqueduct operculum measures 2.1 mm in diameter (b).

Magnetic resonance imaging (MRI) (internal auditory canal/inner ear) confirmed the presence of a fluid-filled, dilated vestibular aqueduct and an enlarged endolymphatic sac (Figure 3).

Figure 3.

Axial T2-weighted magnetic resonance imaging (MRI): corresponding T2-weighted MRI demonstrating prominent, hyperintense signals (white arrows) located along the posterior surface of the petrous pyramids. These findings are consistent with enlarged endolymphatic sacs.

A final diagnosis of EVAS was established, resulting in progressive bilateral SNHL and secondary speech delay.

Management and progress

Although the patient had used hearing aids since early childhood, he derived insufficient benefit owing to the progressive nature of the syndrome and the recent drop in auditory thresholds.

Cochlear implantation (CI) is recommended for the definitive treatment. This would provide the necessary auditory stimulation to potentially develop functional communication, even at this late stage. However, the family currently faces significant financial constraints, preventing surgical intervention.

The reporting of this study conforms to the Case Report (CARE) guidelines. ⁴

Discussion

EVAS—a congenital abnormality that often occurs bilaterally—was first described in 1978 by Valvassori. ⁵ EVAS is the most common congenital inner ear anomaly associated with SNHL. ⁵

EVAS symptoms most commonly include SNHL (inconsistent response to sound, social withdrawal, and isolation) and vestibular symptoms such as episodic vertigo, dizziness, and imbalance. Hearing loss is typically bilateral, is progressive, and may be triggered or worsened by minor head trauma or changes in intracranial or barometric pressure.^6,7

Patients with ASD commonly present with difficulty in processing language and focusing on multiple sounds or stimuli and hyposensitivity or hypersensitivity based on the stimulus. Several studies have also suggested difficulties in processing complex sounds and speech. ⁸

Characteristic ABR findings in patients with ASD include smaller amplitudes in waves I, II, III, IV, and V and longer latencies between waves I–III and waves I–V. ⁸ As ASD is a neurodevelopmental disorder, comorbid sensory deficits can complicate the clinical picture; thus, the incidence of SNHL in patients with ASD is higher than that of the general population. ⁹

Conversely, ABR findings in patients with EVAS show three distinct patterns: SNHL-like pattern (most common at 57%), large wave I pattern (28.6%), and auditory neuropathy spectrum disorder pattern (14.3%). ¹⁰

Genetic testing is not necessary for diagnosing EVAS. The definitive diagnosis of EVAS is primarily established through radiological imaging, specifically high-resolution CT or MRI of the temporal bones, based on the established size criteria. Currently, an operculum diameter >2 mm on axial CT is considered the standard diagnostic threshold. Although genetic screening for mutations such as SLC26A4 can provide additional context regarding associated conditions such as Pendred syndrome, the structural identification of the enlarged aqueduct via imaging remains the diagnostic cornerstone. ¹¹ In the present case, the diagnosis was confirmed by high-resolution CT findings of bilateral widened vestibular aqueducts measuring 2.2 mm and 2.1 mm, respectively.

The clinical presentation of profound hearing loss frequently mimics ASD in toddlers. Behavioral symptoms—such as diminished response to name, social withdrawal, and severe speech delay—are shared by both conditions. This “diagnostic overshadowing” often leads clinicians to mislabel sensory deprivation as a neurodevelopmental deficit. High-quality audiological evaluation and imaging are critical for differentiating these pathologies, ensuring that treatable structural anomalies such as EVAS are not overlooked.

Conclusion

EVAS can frequently mimic the clinical presentation of ASD due to shared behavioral markers such as social isolation and speech delay. This case highlights an important clinical point: early intervention is essential. Accurate diagnosis of EVAS is needed to ensure timely access to appropriate treatments, such as CI, which remains the most effective treatment for advanced progressive hearing loss associated with EVAS.