Till now, there is no universal clinical classification about variations of the external branch of the superior laryngeal nerve despite the multiple classifications that was proposed. The aim of this research is identification and systematization of topographic types of the external branch of the superior laryngeal nerve. The study is based on the autopsy material (21 complexes organs of the neck) and on identification of variations of 40 external branches of the superior laryngeal nerve. We identify two permanent landmark that are located at the minimum distance from nerve and on which we made metrical calculations: oblique line of thyroid cartilage, tendinous arch of the inferior pharyngeal constrictor muscle. The “entry” point of the nerve is always located on the inferior pharyngeal constrictor muscle,and not protruding beyond the oblique line of thyroid cartilage superiorly and tendinous arch of the inferior pharyngeal constrictor muscle anteriorly. The proposed topographic classification of the location of the external branch of the superior laryngeal nerve is based on localization of point of pierced of the nerve relating to the length of the oblique line of thyroid cartilage. In 64.2% of cases, the external branch of the superior laryngeal nerve was in close proximity to the upper pole of the thyroid gland, which could lead to its damage during surgery (type I and II). In type III and IV (35.8%) - the point of "entry" in the muscle was located as far as possible from the upper pole of the thyroid gland, and most of the nerve was covered by the fibers of the inferior pharyngeal constrictor muscle.

Hypoparathyroidism is the most common complication after surgery on the thyroid gland. All authors confirm the fact that the main cause of hypoparathyroidism is a violation of the blood supply of parathyroid glands, as well as their damage or even accidental removal during surgery. Having analyzed the real cases, and based on our own experience, we came to the conclusion that in order to prevent complications, we will need to study the types of blood supply of the parathyroid glands in details. To this end, we have performed 46 unilateral microdissections and X-ray angiography studies of the arterial supply at 23 organocomplexes of the neck. 42 upper and 43 lower parathyroid glands were detected. It has been established that the main feeding vessel of parathyroid glands is the inferior thyroid artery (type I). The association of glands with the inferior thyroid artery was revealed in 71.8% of cases. A mixed variant of blood supply (simultaneously from the superior and inferior thyroid arteries) was revealed in 14.1% cases (type II). Only 10.6% of the gland were fed isolated from the superior thyroid artery (type III). In addition, in 8.7% cases in the preparations there was no inferior thyroid artery. In 3.5% cases, the connections of the lower parathyroid glands with the thyroid arteries were not reliably detected. Most probably, their feeding was provided at the expense of small collaterals from surrounding organs (type VI).

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