Before surgery, 6 of the 12 children showed normal VEMPs, 1 showed a decrease in the amplitude of VEMPs and five showed no VEMP response. After surgery, with the cochlear implant device off, 1 child showed a decreased VEMP and 11 showed no VEMPs. With the cochlear implant device on, four children showed VEMPs and eight did not.

Among these 20 severely hearing impaired children, only 3 (15%) showed normal responses in the caloric test, rotational chair test and VEMP recording bilaterally. Seven (35%) showed responses asymmetrically in the caloric test despite normal responses in the rotational chair test and VEMP recording bilaterally. Five (25%) showed hyporeflexia or areflexia in the caloric test bilaterally, but showed normal responses in the rotational chair test and normal reproducible or decreased VEMPs. Five (25%) showed no responses at all in the caloric test, rotational chair test and VEMP recording.

Auditory neuropathy is a hearing disorder characterized by normal outer hair cell function and abnormal neural conduction of the auditory pathway. Aetiology and clinical presentation of congenital or early-onset auditory neuropathy are heterogeneous, and their correlations are not well understood. Genetic backgrounds and associated phenotypes of congenital or early-onset auditory neuropathy were investigated by systematically screening a cohort of 23 patients from unrelated Japanese families. Of the 23 patients, 13 (56.5%) had biallelic mutations in OTOF, whereas little or no association was detected with GJB2 or PJVK, respectively. Nine different mutations of OTOF were detected, and seven of them were novel. p.R1939Q, which was previously reported in one family in the United States, was found in 13 of the 23 patients (56.5%), and a founder effect was determined for this mutation. p.R1939Q homozygotes and compound heterozygotes of p.R1939Q and truncating mutations or a putative splice site mutation presented with stable, and severe-to-profound hearing loss with a flat or gently sloping audiogram, whereas patients who had non-truncating mutations except for p.R1939Q presented with moderate hearing loss with a steeply sloping, gently sloping or flat audiogram, or temperature-sensitive auditory neuropathy. These results support the clinical significance of comprehensive mutation screening for auditory neuropathy.

Congenitally deaf infants and children commonly suffer vestibular failure in both ears, and impairment of postural control, locomotion, and gait. The development of gross motor functions, such as head control, sitting, and walking is likely to be delayed, but fine motor function is usually preserved unless disorders of the central nervous system are present. These children can eventually catch up with their normal peers in terms of development and growth as a result of central vestibular compensation. The visual and somatosensory systems, pyramidal and extrapyramidal motor system (cerebellum, basal ganglia, cerebrum) and intellectual development, compensate for vestibular failure in infants and children with congenitally hypoactive or absent function of the semicircular canals and otolith organs.