Background: The External  branch  of  superior  laryngeal  nerve  is  intimately  associated  with  the  superior  thyroid  artery, and  is  vulnerable  to  injury  during  thyroidectomy.  EBSLN  supplies  the  cricothyroid  muscle  which  is  the  tensor  of  vocal cord.  Injury  to  this  nerve  can  have  catastrophic  consequences  in  people  who  use  their  voice  professionally.  Variations of EBSLN  anatomy  make  its    intra  operative   assessment   challenging.

Aim: To  describe  the  anatomic  variations  of  the  external  branch  of    superior  laryngeal  nerve  observed  during thyroidectomy.

Methods:  Patients  who  underwent  thyroidectomy    from  2010  to  2016   at  a tertiary  care  centre  in North  Malabar  were  included.  Intra operatively  the  EBSLN  was  identified  and  the  topographic  anatomy  in  relation  to  the  superior  thyroid  pedicle  and  upper  pole  of  the  thyroid  gland  were  noted.

 Results: Total 406   thyroidectomy   were  analysed,. The nerve  could be  identified  in 94.7%  cases.  Type  IIa  nerve  was   most  commonly  seen,  and  type IIb  was  the  least.  Fourth type nerve was  not  identified. 

Conclusion:  Preservation of EBSLN is  important  in  every  thyroid  surgery.  During  surgery the  risk of  nerve  injury do  exist,  although  injury  rates  are  not  clearly  established.  Type  IIa  variant  of  EBSLN  is  the  commonest  followed  by  type I.  With  careful medial  dissection  and  lateralisation  in  Jolls  triangle,  EBSLN  is  easly identified.  Identification   and  ligation   of  individual  vessels in  the  superior  pole  in  a  bloodless   back ground  will prevent  damage  to  the  nerve.  Surgeons   should  show  greater  awareness   regarding   the  anatomical  interpretation  of  EBSLN  and  its  branches  to  reduce  the  incidence  of  iatrogenic nerve  injury.

Keywords:  External  branch  of  superior  laryngeal  nerve,  Cricothyroid    muscle,  Joll’s  triangle,  Cernea  classification, Laryngeal  nerves,  Thyroidectomy. Kierner’s  classification.

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