LEFT NON-RECURRENT LARYNGEAL NERVE ASSOCIATED WITH IPSILATERAL THYROID LOBE HYPOTROPHY: RARE CASE PRESENTATION adolfo.fuentes2001@gmail.com

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LEFT NON-RECURRENT LARYNGEAL NERVE ASSOCIATED WITH IPSILATERAL THYROID LOBE HYPOTROPHY: RARE CASE PRESENTATION

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Mexico

Oral or Poster

The non-recurrent laryngeal nerve (NRLN) is an extremely rare anatomical variant, usually associated with embryological anomalies. With an incidence <1% on the right and nearly 0% on the left, failure to recognize it during surgery increases risk of complications. Its association with an ipsilateral thyroid lobe hypotrophy is yet to be described.

We present the case of a 55-year-old female evaluated for a thyroid nodule. Preoperative ultrasound revealed a 1.5cm, hypoechoic, irregular nodule with microcalcifications in the right lobe, with the left lobe appearing hypotrophic. Fine-needle aspiration confirmed papillary thyroid carcinoma (Bethesda VI). Thyroid function tests were normal, total thyroidectomy was indicated.

During surgery, a nerve was initially identified appearing to be the superior laryngeal nerve (SLN), however, the recurrent laryngeal nerve could not be observed along its usual path. Upon re-evaluation, the actual SLN was identified caudally entering at the cricopharyngeal muscle. Neuromonitoring confirmed that the nerve initially identified was in fact a left NRLN entering the larynx horizontally. The left thyroid lobe was markedly hypotrophic. The procedure was completed without complication, with a preserved vocal cord function post-operative. A video documenting intraoperative nerve mapping and anatomical findings is available.

This case emphasizes the importance of recognizing anatomical variants of the recurrent laryngeal nerve. The association of a NRLN with an ipsilateral thyroid lobe hypotrophy has not been previously reported. Knowledge of embryology, correct anatomical assessment, and use of intraoperative neuromonitoring are crucial to guarantee patients safety during thyroid surgery, particularly when an anatomical variation is present.