Imagine a patient reporting hearing their own eyeball move, feeling dizzy with loud sounds or quick head movements, experiencing aural fullness, autophony, and possibly some hearing loss. These symptoms form a perplexing cluster that can be frustrating for both the affected individual and their healthcare provider.
We take a closer look at the condition known as Superior Canal Dehiscence Syndrome (SCDS), its symptoms, diagnosis, and treatment options.
Superior Canal Dehiscence Syndrome: An Overview
In 1998, Dr. Lloyd Minor of Johns Hopkins identified Superior Canal Dehiscence Syndrome, a condition that can cause hearing difficulties, balance issues, or a combination of both. SCDS occurs when there is an opening in the bone covering one of the inner ear balance canals, resulting from a congenital defect, trauma, or infection.
Symptoms and Audiometric Findings: Patients with SCDS may present with a range of symptoms, including hearing their own eyeball move, dizziness triggered by loud sounds (Tullio phenomenon) or head movements, aural fullness, autophony (hearing echoes or reverberation when speaking, chewing, or swallowing), and potential hearing loss. Audiometric evaluation typically reveals a low to mid-frequency conductive hearing loss (250-1,000 Hz) without middle ear involvement. This conductive loss is characterized by air/bone gaps and bone conduction thresholds that exhibit hypersensitivity, with thresholds as low as -5dB HL at 250-500 Hz and decreasing sensitivity as frequency increases.
The thinning or absence of bone overlying the superior canal creates a “third window” in the inner ear, allowing air-conducted sound energy to be diverted away from the cochlea and reducing pressure between the scala vestibuli and scala tympani. This “third window” does not affect bone conduction thresholds but enhances air conduction thresholds.
Superior Canal Dehiscence Syndrome (SCDS) presents a unique challenge, with patients often experiencing a range of unusual symptoms, including hearing their own eyeball move and dizziness triggered by loud sounds. Audiometric findings reveal a distinctive low to mid-frequency conductive hearing loss, characterized by hypersensitivity. Understanding the ‘third window’ effect in the inner ear is key to managing this condition effectively.
Misdiagnosis and Diagnostic Methods
SCDS is often misdiagnosed as other conditions such as Eustachian tube dysfunction, patulous Eustachian tube, Benign Paroxysmal Positional Vertigo (BPPV), Meniere’s disease, vestibular neuronitis, perilymph fistula, or labyrinthitis.
To confirm the diagnosis, high-resolution CT scans of the temporal bone are performed, with reformatted images in the Poeschel and Stenver planes. These scans reveal the absence of proper bone connectivity over the superior canal, confirming the presence of SCDS.
Treatment for SCDS depends on the impact of the condition on the individual’s quality of life. Options include using a hearing aid for the affected side, avoiding loud sounds, or surgical intervention. Surgical procedures such as middle fossa craniotomy or transmastoid repair can help address the underlying issue. However, it is important to note that surgery carries risks, including a 12% chance of hearing loss and the possibility of SCDS recurrence.
Superior Canal Dehiscence Syndrome presents a unique set of symptoms and challenges for both patients and healthcare providers. Misdiagnosis is common due to similarities with other conditions. Accurate diagnosis through high-resolution CT scans is crucial for appropriate management.
Treatment options range from hearing aids to surgical interventions, but each comes with its own considerations and risks.
**this piece has been updated for clarity. It originally published on February 12, 2012