SAN DIEGO—A 69-year-old man recently came to see Yuri Agrawal, MD, MPH, associate professor of otolaryngology at Johns Hopkins University in Baltimore, with chronic dizziness and a history of superior semicircular canal dehiscence (SSCD) that was repaired in a 2015 procedure.
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April 2020The man’s vertigo resolved four months after the 2015 procedure, but he then developed chronic dizziness, unsteadiness, and gait impairment that caused him to veer to his left. He’d fallen several times, and more falls were his biggest concern. His dizziness wasn’t typical of canal dehiscence, he still had vestibulo-ocular reflex (VOR) gain at 0.81, despite what appeared to be plugging of the superior canal space, and he had a persistent air-bone gap.
The complex case was presented here in January at the Triological Society Combined Sections Meeting in a kind of adventures-in-dizziness session that put clinicians to the test.
Basics First
Dr. Agrawal’s case was an illustration of why it is important to go back to basics when confronted with unusual symptoms. Her team had to revisit “first principles and consider the canal anatomy and physiology,” she said.
The atypical dizziness for an SSCD case, they reasoned, could have been due to the plug migrating to the wider section of the superior and horizontal canals near the utricle, where it could cause a constant deflection of the cupula, triggering an acceleration stimulus perceived by the brain. The result is dizziness, Dr. Agrawal said.
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They also found it odd that the patient’s eye movements mostly remained in sync with his vestibular system, even though it looked like his superior canal was plugged. But a 2017 study (Biophys J. 2017;113:1133-1149) holds a reasonable explanation: While the plug can be enough to prevent endolymph from flowing during slower head movements, faster head movements can cause a distension of the membranous duct.
As for the persistent air-bone gap, Dr. Agrawal said, the migration of the plug could have led to exposure of the initial dehiscence or to a new, persistent dehiscence.
The patient went through multiple courses of vestibular therapy with no improvement. He is now considering replacement surgery, including removal of the existing plug. That calls for careful patient counseling, Dr. Agrawal said.
“When you’re signing up for a revision plugging, you have to indicate to the patient that they may end up with a functional labyrinthectomy at that time, and there is some potential risk to their hearing as well. That may be a more desirable state than the patient is in, if they are having incredibly disabling symptoms,” she said. “I think it’s an interesting case of just thinking about the surgical approach, the anatomy of the dehiscence, what might be some of the consequences for that, and what might be ways to manage that.”