Anatomical variations of the external branch of the superior laryngeal nerve in relation to the inferior constrictor muscle: cadaveric dissection study.
OBJECTIVE
To determine anatomical variations in the external branch of the superior laryngeal nerve in relation to the inferior constrictor muscle, and to propose a rational approach for the preservation of the nerve in thyroid surgery based on anatomical principles.


METHODS
A cadaveric dissection study of the anatomy of the external branch of the superior laryngeal nerve in relation to the inferior constrictor muscle was conducted. Twenty-nine formalin-fixed cadavers of both sexes (age 50-70 years), with normal necks, were examined.


RESULTS
In relation to the Friedman classification, three anatomical variations of the external branch of the superior laryngeal nerve were found. Type 1 variation was found in 57.1 per cent of cases, type 2 in 26.8 per cent and type 3 in 16 per cent.


CONCLUSIONS
The prevalence of type 3 variation of the external branch of the superior laryngeal nerve suggests that the nerve will not be encountered in a certain percentage of individuals as it lies under the cover of the inferior constrictor. Therefore, there is no justification for attempting to identify the nerve in all cases.
Department of ENT, Base Hospital and Army College of Medical Sciences, New Delhi, India. umi75pat@gmail.com
U
U
Patnaik
A
A
Nilakantan
T
T
Shrivastava
D000368:Aged; D002102:Cadaver; D005260:Female; D006801:Humans; D007821:Laryngeal Muscles / Q000294:innervation; D061224:Laryngeal Nerve Injuries / Q000517:prevention & control; D007823:Laryngeal Nerves / Q000033:anatomy & histology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D010609:Pharyngeal Muscles / Q000033:anatomy & histology*; D013965:Thyroidectomy / Q000379:methods*