HSC Section 6 Nov2016 Green Book

Spataro et al

Table 2. Unilateral Vocal Fold Paralysis Laterality. a

P -value b

Etiology

n

Right

Left

Skew

Thyroid surgery

140

64 15 25

76 58 36 49 21 31 16 85 67 41 16 14 13 14 11 6 9 7

–0.04 –0.29 –0.09 –0.34

.31

Lung surgery

73 61 58 48 37 22 18 18 17 73 58 30 24 20 18 18 14 11

<.01

Lateral neck surgery

.16

Cardiac surgery

9

<.01

Cervical spine surgery Esophageal surgery Carotid surgery Skull base surgery Parathyroid surgery Mediastinal surgery

27

0.06

.39

6 6

–0.34 –0.23

<.01

.03 .16

12

0.17

9

0

1.00

10 39

0.09

.47

Idiopathic

124

–0.19 –0.42 –0.21 –0.03 –0.08 –0.15 –0.28 –0.11 –0.07 –0.14

<.01 <.01 <.01

Lung cancer Intubation

6

17 14 10

Trauma

.72 .41 .18 .02 .35 .59 .37

Metastatic cancer Laryngeal cancer Skull base tumor

7 4 7 6 4

CVA

Thyroid cancer—direct invasion

8 7

Esophageal cancer

Abbreviation: CVA, cerebral vascular accident. a Etiologies with less than 10 patients not shown. b P values based on x 2 comparison with 50-50 L-R split with same N. Bold, P \ .05.

the literature reported a rate of idiopathic UVFP of 24% 6 10%. 21 The decrease in idiopathic UVFP is likely due to better imaging capabilities to find small lesions along the nerve, as well as the shift toward surgery-related UVFP, which increases the proportion of cases with a clear etiology. The data in this study by comparison to earlier studies of UVFP etiologies show the trend toward increasing surgical rather than malignant or idiopathic causes. This trend may be due to several factors. Since this study was conducted at a large tertiary referral center, as were the other recent stud- ies by Rosenthal et al 15 and Takano et al, 16 a greater amount of surgery, as well as more complicated surgery, was likely being performed. An increased number of com- plicated surgeries both increase the risk of injury to the recurrent laryngeal nerve, as well as the relative numbers of UVFP due to surgical causes. In addition, as diagnostic ima- ging capabilities continue to improve, UVFP due to malig- nant or idiopathic causes will continue to decrease, as tumors are identified before causing UVFP and the course of the vagus and recurrent nerve can be imaged to deter- mine the etiology of cases formerly diagnosed as idiopathic. In analysis of laterality, 621 (66.2%) patients had left- sided UVFP, consistent with previous studies showing left-sided UVFP ranging from 59% to 81%. 1,2,7,8,11,15,16 Intrathoracic etiologies had the expected left-sided predomi- nance, due to the anatomic course of the left recurrent laryn- geal nerve. The statistically significant left-sidedness of some other etiologies may be a little harder to explain:

reported. In a recent review by Misono and Merati, 24 the risk of vocal fold paralysis in thyroidectomy was between 0.8% and 2.3%; anterior cervical spine injury, less than 1%; cardiac/aortic surgery, 2%; mediastinoscopy, 0.2% to 6%; esophagectomy, 11%; and carotid endarterectomy, 4%. Idiopathic UVFP was the etiology in 124 (13.2%) patients. Some older studies reported idiopathic etiologies to be the most common cause of UVFP, 2,6-10 but a recent review of Figure 1. Left-right skew by etiology. Solid circles, statistically signif- icantly skewed; open circles, not significant. Skew = (# cases on right / total cases for etiology) – 0.5. If left = right, skew = 0 (as seen for 18 parathyroid cases); if all cases occurred on left, skew = –0.5. Grouped are the intrathoracic causes of unilateral vocal fold paraly- sis (lung malignancy, thoracic, cardiac, and esophageal surgery).

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