Surgical approach to the thyroarytenoid branch of the inferior laryngeal nerve through the thyroid cartilage

ABSTRACT PURPOSE: To describe the anatomical course of the intralaryngeal portion of the inferior laryngeal nerve (ILN) and to standardize the surgical access to its thyroarytenoid branch (TAb) through the thyroid cartilage. METHODS: Under surgical microscopy, 33 adult human excised larynges were dissected, to expose the intralaryngeal portion of ILN. The point of entry of TAb, ILN's terminal branch, in the thyroarytenoid (TA) muscle was determined and correlated with thyroid cartilage dimensions. RESULTS: After entering the larynx, the ILN consistently traveled between the thyroid cartilage and the lateral cricoarytenoid muscle in an anterior and slightly cranial course. The distance from the point of entry of the TAb in the TA muscle to the midline (TAb-H) and to the inferior border (TAb-V) of the thyroid cartilage differed according to gender. In females, mean distances of TAb-H and TAb-V were 20.5mm and 5.2mm and in males, 22.3mm and 5.9mm, respectively. CONCLUSION: The intralaryngeal course of the inferior laryngeal nerve presents low variability and measures from landmarks in the thyroid cartilage help to estimate the point of entry of thyroarytenoid branch in thyroarytenoid muscle.

Anatomic relation between the external branch of the superior laryngeal nerve and the thyroid gland / Relação anatômica entre o ramo externo do nervo laríngeo superior e a glândula tireoide

AIM: This prospective study investigated the anatomic relations between the external branch of the superior laryngeal nerve (EBSLN), the superior thyroid artery (STA) and the thyroid gland in human cadavers. MATERIAL AND METHODS: Twenty-two human cadavers aged over 18 years old, less than 24 hours after death. RESULTS: The mean distance between the EBSLN and the superior pole of the thyroid gland was 7.68 ±3.07 mm. A tangent to the inferior edge of the thyroid cartilage between the EBSLN and the STA measured 4.24 ±2.67 mm. A line from the intersection of the EBSLN - related to the STA - to the superior pole of the thyroid gland measured 9.53 ±4.65 mm. A line from the EBSLN to the midline of the most caudal point of the thyroid cartilage measured 19.70 ±2.82 mm. A line from the RENLS to the midline on the most cranial point of the cricoid cartilage was 18.35 ±3.66 mm. CONCLUSION: There is a variable proximity relation between the EBSLN and the superior pole of the thyroid gland; this distance ranges from 3.25 to 15.75 mm. There was no evidence of significant variation between the measures in the ethnic groups comprising the sample.

OBJETIVO: Descrever, prospectivamente, a relação anatômica entre o ramo externo do nervo laríngeo superior (RENLS), a artéria tireoidea superior (ATS) e a glândula tireoide em cadáveres humanos. MATERIAL E MÉTODO: Foram dissecados 22 cadáveres humanos com idade superior a 18 anos, com menos de 24 horas de pós-morte. RESULTADOS: A medida entre o RENLS e o polo superior da glândula tireoide foi 7,68 +/- 3,07mm; entre o RENLS e a ATS foi de 4,24 +/- 2,67mm numa linha tangente ao bordo inferior da cartilagem tireoide; entre o cruzamento da ATS com o RENLS e o polo superior tireoidiano foi 9,53 +/- 4,65mm; entre o RENLS e a linha mediana do pescoço no ponto mais caudal da cartilagem tireoide foi 19,70 +/- 2,82mm; e entre o RENLS e a linha mediana do pescoço no ponto mais cranial da cartilagem cricoide foi 18,35 +/- 3,66mm. CONCLUSÕES: Há uma relação de proximidade variável entre o RENLS e o polo superior da glândula tireoide, variando de 3,25 a 15,75mm. Não constatou-se variações significativas entre as medidas para as diferentes etnias que compõem a amostra.