Objective diagnosis of olfaction can be performed by registration of cortical olfactory evoked potentials (OEP) and of contingent negative variation (CNV). The CNV is a negative voltage developing at the vertex after discrimination of one of two smells while the patient is expecting a second stimulus. By an adequate procedure, including a long time window for averaging (2.56 seconds) with appropriate filters, the two tests can be performed simultaneously in a single session of less than 10 minutes. Anosmia is determinable by both OEP and CNV, although CNV shows less variability. On the other hand, CNV requires attention and some cooperation of the patient. Parosmia is accessible by CNV only; two odor qualities presented in random order have to be distinguished. Hyposmia can also be detected; just above the discrimination threshold, CNV amplitudes tend to be large--even enhanced--whereas OEP amplitudes may still be undetectable.

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We conducted a long-term study of 85 children with known transient neonatal hyperbilirubinemia to determine if their hearing had been affected. None of the children had neural symptoms such as kernicterus. The children ranged in age from birth to 9 months and were studied by means of brainstem evoked response audiometry (BERA). Thirty-four of the children were studied sequentially between 15 and 80 months after the initial examination. Our results showed that there was no significant correlation between serum bilirubin concentrations and BERA thresholds or latencies. These findings indicate that, unlike manifest cases of kernicterus, neonatal hyperbilirubinemia does not affect neonatal hearing when treated promptly.

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