Trichosonography: ultrasound of alopecias and hair disorders.

Trichology is the area of dermatology that focuses on the study, diagnosis and management of the different types of alopecia and hair and scalp disorders. In recent years, there have been great advances in the non-invasive diagnosis of these conditions, especially with trichoscopy and more recently with sonography. High frequency ultrasound study of the scalp, for which we propose the name of "trichosonography", may represent a valuable technique in the evaluation of both clinical and subclinical abnormalities of the hair follicle and the innermost layers of the skin, which are otherwise inaccessible to trichoscopy. The purpose of this pictorial essay is to offer a descriptive approach to the clinical and ultrasound findings of the main hair and scalp disorders.