STUDY TO EXPLORE RISK FACTORS AND INCIDENCE OF RECURRENT LARYNGEAL INJURY DURING THYROID SURGERY IN A SURGICAL UNIT OF A TERTIARY CARE HOSPITAL

Objectives: Paralysis or vocal cord paresis due to iatrogenic recurrent laryngeal nerve injury (RLNI) is one of the serious problems in thyroid surgery.

Recurrent laryngeal nerve (RLN) injuries represent one of the most feared complications after thyroid and parathyroid surgery. Albeit many procedures have been introduced to prevent nerve damage, the incidence of recurrent laryngeal nerve palsy ranges between 1.5–15%. The purpose of this study is to identify the risk factors for permanent and temporary recurrent laryngeal nerve injury during thyroid surgery.

Place and Duration:  All consecutive patients operated on at the Surgical Unit II of Ayub Teaching Hospital, Abbottabad for two years duration from May 2017 to May 2019 for thyroid surgery were reviewed.

Methods:  All consecutive patients who underwent thyroid surgery were admitted to the surgical ward were qualified for retrospective review.

Factors predisposing to recurrent laryngeal nerve injury, such as pathology of changes and type of surgery, and identification of recurrent laryngeal nerve intra-operatively were evaluated. All patients underwent pre-operative and postoperative indirect laryngoscopic examinations. Patients with preoperative RLN injury were excluded.

Vocal cord paresis was defined as a dysfunction of the vocal cord mobility compared to the contralateral one, based on postoperative fiberoptic laryngoscopy. Vocal cord palsy was defined as a total absence of movement of the vocal cord. Diagnosis of vocal cord paresis or palsy was made by the ENT specialist during the fiberoptic laryngoscopy.

Results: During the study period, 680 patients underwent thyroid surgery. Their data was recorded. Transient unilateral problems with the vocal cords occurred in 22 (3.2%) cases and in 2 (0.3%) cases permanent (after Rt hemithyroidectomy). Bilateral problems with the vocal cords occurred in 4 cases (0.58%), but none became permanent. There was a significant increase in recurrent laryngeal nerve damage during secondary surgery (21.7% in secondary vs. 2.8% in primary, p=0.001), total/near total thyroidectomy (7.2% in total vs. 1.9% in subtotal, p=0.024), non-identification of RLN during surgery (7.6% in non- identification vs. 2.6% in identification, p=0.039) and in malignant disease (12.8% in malignant vs. 2.9% in benign, p=0.004). However, there was no significant difference in the frequency of recurrent laryngeal nerve damage in relation to sex (4.1% in men vs 3.8% in women, p = 0.849).

Conclusion: The current study showed that thyroid cancer, recurrent goiter surgery, lack of RLN identification and total thyroidectomy were associated with a significantly increased risk of surgical recurrent laryngeal nerve damage.

Keywords: Recurrent laryngeal nerve injury, Thyroid Surgery, carcinoma of thyroid, Vocal cord paresis, Parathyroid Surgery.