The adenoid A/N value, refers to the ratio of the thickness of the adenoids to the anteroposterior diameter of the largest space in the nasopharynx.
A is the vertical distance from the most prominent point of the adenoid in the nasopharyngeal cavity to the osteocutaneous line at the base of the skull, i.e. the maximum thickness of the adenoid, and N is the distance from the osteocutaneous line at the base of the skull to the posterior edge of the soft palate in the plane of A, the width of the nasopharyngeal cavity at the most prominent part of the adenoid.The A/N is the ratio of the two and reflects the maximum extent to which the tip of the adenoid is blocking the anterior and posterior spaces of the nasopharynx.
The A/N value can be used in conjunction with other tests such as fiberoptic nasopharyngoscopy to determine obstruction.
Adenoids, also known as pharyngeal tonsils, are lymphoid tissues in the nasopharynx that develop to their maximum size at the age of 6-7 years under normal physiological conditions, gradually shrink after puberty, and basically disappear in adults. The nasopharyngeal space is also slowly expanding as the body grows. This results in a dynamic change in the A/N ratio during the development of the human body.
When a lateral skull base radiograph is taken, the attending physician can be consulted to fully understand the clinical significance of the results obtained and to choose a standardized treatment based on the symptoms and other investigations.