Cochlear potentials recorded from patients with mutations in the OTOF or OPA1 gene. The upper panels show recordings from two subjects carrying, respectively, the R445 H mutation in OPA1 and biallelic mutations in OTOF. The recordings (black line) are superimposed on the mean summation potential-compound action potential (SP-CAP) response (gray line) from 16 controls with normal hearing at 120 dB sound pressure level intensity. The shaded area indicates the 95% confidence limit. The CAP response observed in controls is replaced in AN patients by a low-amplitude prolonged negative deflection following the SP. A small CAP (arrowed) is superimposed on the sustained response only in the child carrying biallelic OTOF mutation. The lower panels show the electrically evoked neural potentials (e-CAP) recorded through cochlear implant. A neural response was obtained only from patients with OTOF mutations.