Mrowinski D, Eichholz S, Scholz G
Hals-Nasen-Ohrenklinik, Charité Campus Virchow-Klinikum, Humboldt-Universität Berlin, Germany.
Laryngorhinootologie. 2002 Sep;81(9):624-8. doi: 10.1055/s-2002-34447.
An objective smelling test is indicated for a reliable assessment of olfactory disorders. Usually olfactory evoked potentials (OEP) are registered. But the technique of this measurement is complicated and the generation of the OEP depends on the respiration of the subject. Alternatively, the contingent negative variation (CNV) can be used in the diagnosis of anosmia and parosmia, requiring only a simple olfactory stimulator.
OEP and CNV were derived from 25 adults with normal smelling and from 16 patients with anosmia after head injury. First, the "direct" CNV was registered when the subjects expected a tone following a smell stimulus after 1.5 s. Using two different odors in a random order, the tone only followed one of them, so the "selective" CNV was scored.
In both tests a distinct CNV was found in 21 and 23 normal smelling subjects, respectively. OEPs were absent in 4.3 % of this control group. No patient with anosmia showed an OEP or a CNV. The amplitudes of the "selective" CNV are significantly higher than those of the "direct" CNV. No gender dependency was found.
The results show that an objective olfactometry can be realized by registration of CNV. Contrary to the measurement of OEP which depend on the physical parameters of olfactory stimuli, CNV correlates well with the cognitive identification of odor.
客观嗅觉测试对于可靠评估嗅觉障碍至关重要。通常会记录嗅觉诱发电位（OEP）。但这种测量技术复杂，且OEP的产生依赖于受试者的呼吸。另外，关联负变（CNV）可用于嗅觉丧失和嗅觉异常的诊断，仅需一个简单的嗅觉刺激器。
对25名嗅觉正常的成年人和16名头部受伤后嗅觉丧失的患者进行OEP和CNV检测。首先，当受试者预期在嗅觉刺激1.5秒后会出现一个音调时，记录“直接”CNV。以随机顺序使用两种不同气味，音调仅跟随其中一种，从而对“选择性”CNV进行评分。
在两项测试中，分别在21名和23名嗅觉正常的受试者中发现了明显的CNV。该对照组中有4.3%的人未检测到OEP。没有嗅觉丧失的患者出现OEP或CNV。“选择性”CNV的振幅明显高于“直接”CNV。未发现性别差异。
结果表明，通过记录CNV可实现客观嗅觉测量。与依赖嗅觉刺激物理参数的OEP测量不同，CNV与气味的认知识别密切相关。
