Genotype-Phenotype Correlation Study in a Large Series of Patients Carrying the p.Pro51Ser (p.P51S) Variant in COCH (DFNA9) Part II: A Prospective Cross-Sectional Study of the Vestibular Phenotype in 111 Carriers.
Sebastien P F JanssensdeVarebeke, Julie Moyaert, Erik Fransen and 9 others
PMID 34369417WHAT IT FOUND
In 111 carriers of the DFNA9 p.P51S variant, cervical VEMP thresholds rose first, starting in the third decade.
Caloric responses and posterior semicircular canal gains followed in the fourth and fifth decades. Lateral and superior canal gains deteriorated last, in the sixth decade.
Key findings
01Cervical VEMP thresholds showed the earliest signs of decline, with onset estimated at 31.386 years and maximal signal loss at 45.485 years.
02Caloric responses deteriorated next, with decline starting at 35.397 years for water irrigation and 25.085 years for air irrigation.
03Video head impulse test gains declined last, with the posterior semicircular canal starting at 47.505 years and the lateral and superior canals at 51.785 and 56.649 years respectively.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The study is cross-sectional, not longitudinal, so the sequence of decline is inferred from comparing different age groups rather than following individuals over time. Ocular VEMP testing was only performed in 27% of the participants, limiting the generalizability of those findings. Two different caloric stimulation methods were used (water and air), which produced significantly different results and prevented pooled analysis. The study excluded individuals with other causes of vestibular or hearing loss, so the findings may not apply to patients with comorbidities. The Barany Society criteria for bilateral vestibulopathy are defined for water irrigation, making the interpretation of air-caloric results more complex.
Declared interests
The authors have no conflicts of interest to disclose.
The easy way to misread this
Do not assume that a normal video head impulse test rules out vestibular pathology in these patients. The study shows that caloric responses and cervical VEMP thresholds decline years before head impulse gains become abnormal. A patient can have significant vestibular damage on caloric or VEMP testing while still having normal head impulse gains.