Laryngeal recurrent nerve injury in surgery for benign thyroid diseases: effect of nerve dissection and impact of individual surgeon in more than 27,000 nerves at risk

Abstract

Objective: To evaluate the effect of recurrent nerve dissection on the incidence of recurrent laryngeal nerve injury (RLNI) and to analyze the performance of individual surgeons.

Summary background data: Dissection of the recurrent nerve is mandatory in total thyroidectomy, but its relative merit in less extensive resections is not clear. The reported rates of RLNI differ widely; this may reflect a variation in the performance of individual surgeons.

Methods: The authors studied the incidence of RLNI in primary surgery for benign thyroid disease during three periods in a single center. In period 1 (1979-1990; 9,385 consecutive patients, 15,865 nerves at risk), the recurrent nerve was not exposed. In period 2 (1991-1998; 6,128 patients, 10,548 nerves at risk), dissection of the recurrent nerve was the standard procedure. Global outcome and individual performance in these two periods were compared and presented to the surgeons. The effect of this quality control procedure was tested in 1999 (period 3; 930 patients, 1,561 nerves at risk).

Results: Exposure of the recurrent nerve significantly reduced the global rate of postoperative and permanent RLNI. Some but not all surgeons improved their results by recurrent nerve dissection (e.g., permanent RLNI rates ranged from 0% to 1.1%). The documented significant differences in individual performances did not affect the outcome in period 3. The extent of nerve dissection was a source of variability; the rate of permanent RLNI averaged 0.9%, 0.3%, and 0.1% for surgeons who only localized, partially exposed, and completely dissected the recurrent nerve, respectively.

Conclusions: Recurrent nerve dissection significantly reduces the risk of RLNI. Extensive dissection facilitates visual control of nerve integrity during resection and is therefore superior to a more limited exposure of the nerve. Quality control can improve the global outcome and identify the variability in individual performance. This cannot be eliminated by merely confronting surgeons with comparative data; hence, it is important to search for the underlying causes.

Figure 1. Distribution of patients in the three study periods according to the extent of resection. Subtotal lobectomy and near-total lobectomy refer to remnant sizes of 2 to 4 g and 1 g or less, respectively. In total lobectomy, no residual tissue is left; enucleation is the localized removal of a circumscribed pathologic lesion. The proportion of extensive resections increased in periods 2 and 3.

Figure 2. Incidence of postoperative recurrent nerve injury without nerve exposure (period 1, 1979–1990) and with nerve exposure (period 2, 1991–1998, and period 3, 1999). (A) Extensive resections were associated with a higher risk of recurrent nerve injury, in particular in period 1, when the recurrent nerve was not exposed. For subtotal resections there were 14,619, 6,263, and 651 nerves at risk in periods 1, 2, and 3; for near-total lobectomies, the corresponding numbers were 524, 2,412, and 529 nerves at risk. For total lobectomies there were 260, 1,343, and 291 nerves at risk. In all three types of resections, the incidence of recurrent nerve injury declined significantly (P < .01) if period 1 (no nerve exposure) was compared with period 2 (surgery with nerve exposure). (B) The data for subtotal resections have been redrawn with an expanded y-axis to illustrate the significant effect of nerve exposure (P < .001, period 1 vs. 2).

Figure 3. Incidence of postoperative bilateral recurrent nerve injury without nerve exposure (period 1, 1979–1990) and with nerve exposure (period 2, 1991–1998, and period 3, 1999). Nerve exposure resulted in a decline in the incidence of bilateral vocal cord paralysis. Statistical significance was reached only if the data for the two periods with nerve exposure (periods 2 and 3) were combined and compared with period 1. The comparison between period 1 and period 2 gave P = .058.

Figure 4. Comparison among seven surgeons of the incidence of postoperative and permanent recurrent nerve palsy without nerve exposure (period 1, 1979–1990) and with nerve exposure (period 2, 1991–1998, and period 3, 1999). There was a significant improvement between periods 1 and 2 (*P < .05) for surgeons 4, 5, and 6; in surgeon 7, the level of significance was reached only if the combination of periods 2 and 3 was compared (+P < .05); for the comparison of periods 1 and 2, P = .056 was calculated. (G) Global average as shown in Tables 1 to 3.