The effect of nasopharyngeal obstruction on the olfactory bulb volume and olfactory sulcus depth in children

Smell ability is associated with nasopharyngeal obstruction. Herein, we evaluated the effect of nasopharyngeal obstruction by adenoid hypertrophy on the olfactory bulb (OB) volume and olfactory sulcus (OS) depth in children.

A total of 135 children who were candidates for brain magnetic resonance imagining scanning were enrolled in the study. The olfactory disorder-negative statements questionnaire was utilized to assess the patient-reported olfactory status. A validated sleep questionnaire was used to assess sleeping status. According to the adenoidal/nasopharyngeal (A/N) ratio, the children were divided into two groups: those with an A/N ratio ≤ 0.5 (n = 70) and those with an A/N ratio > 0.5 (n = 65). OB volume and OS depth measurements were performed on coronal T2-weighted images using planimetric manual contouring. The mean OB volumes and OS depths on the right and left sides were used for the evaluation.

The mean OB volume of the group with an A/N ratio > 0.5 was significantly lower than that of the group with an A/N ratio ≤ 0.5 (P = 0.003), while there was no difference in the mean OS depth between groups (P = 0.061). In those with an A/N ratio > 0.5, the mean OB volume in older children (aged 9–12 years) was significantly lower than that in younger children (aged 5–8 years) (P = 0.012). In terms of laterality, the OS depth on the right side was significantly larger than that on the left side in both groups (P = 0.039 and P = 0.001). In the group with an A/N ratio ≤ 0.5, the OB volume on the right side was also significantly larger than that on the left side (P = 0.040); however, no such difference was observed in the group with an A/N ratio > 0.5 (P = 0.630). No sex-based differences were evident for any variable.

Children with nasopharyngeal obstruction greater than 50% have a significantly smaller OB volume. Our results suggest that morphological alterations in OB may contribute to the pathogenic mechanism of olfactory dysfunction related to nasopharyngeal obstruction.