Table 1.

Overview of phenotypic presentation of all AI-family members

	AI-100	AI-101	AI-000	AI-001	AI-010	AI-011
Age (y)	51	41	15	11	9	0.7
Gender	Male	Female	Female	Male	Male	Male
Phenotype p.Arg98*	+/−	+/−	−/−	+/−	+/+	+/+
HL (dB) Right ear	7	10	8	12	63	55
HL (dB) Left ear	2	10	5	10	67	58
HIT test	Normal	Abnormal right side	Normal	Normal	Abnormal right and left side	Normal
Smooth pursuit	Normal	Saccadic	Normal	Normal	Normal	Normal
Velocity stop tests	N/A	N/A	Normal	Normal	Abnormal right & left VOR	Normal
VNG (oculomotor function)	Normal	Saccadic smooth pursuit & hypometric saccades tests	N/A	Normal	Normal	N/A
VNG (caloric function)	Normal	Hyporeflexia (76%) right side	N/A	Normal	Hyporeflexia right & left sides (50%)	N/A
VNG (pendular function)	Normal	Normal	N/A	Normal	Normal (high amplitude)	N/A

VNG videonystagmography, N/A not available, HL hearing loss, VOR vestibulo-ocular reflexes. VNG was not carried out on AI-011, the youngest male proband, who is homozygeous for the c.292C>T(p.Arg98*) variant in COCH, due to age limitations. Heterozygous carriers AI-100 and AI-001 show normal vestibular function, both on clinical as well as on functional investigations (VNG). Only heterozygous carrier AI-101, mother of both probands, shows hyporeflexia on the right vestibular organ and abnormal central oculomotor function