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Discussion
The main reasons for UVP are iatrogenic/traumatic paraly-
sis (about 4/5, especially in thyroid surgery) followed by
malignancy-associated and idiopathic paralysis, as shown
recently in a cohort of 400 patients
1
and confirmed in our
study. Iatrogenic paralysis after (thyroid) surgery represents
the majority of patients because we are associated with a
large supra-regional center of thyroid surgery where diffi-
cult cases including revision operations are performed. All
patients with voice problems after surgery were sent to our
department and could be included in this study.
Unilateral vocal fold paralysis often causes severe
impairment of the voice with dysphonia and reduced inten-
sity because of insufficient glottic closure during phonation.
However, UVPs have a potential of resolution that usually
occurs within 12 months and in most cases within the first 6
months
2-4
(also confirmed in our study).
The overall rate of recovery was 75 of 100 (75%) in all
patients and 67 of 82 (82%) in the iatrogenic/traumatic group,
respectively. Studies have shown that permanent paralysis
remains in 15% after thyroid surgery and in up to 20% in 717
patients with an idiopathic paralysis—similar to our study.
2,4
In order to plan therapy and keep the patient informed, it is
advantageous to know if any resolution of paralysis is likely.
Laryngeal electromyography (LEMG) is an established
method of assessing the neuromuscular status of the paralyzed
vocal fold. Early evidence of reinnervation or innervation in
paresis can be shown by this method. Laryngeal electromyog-
raphy criteria for poor prognosis were the presence of sponta-
neous activity and absence or reduced recruitment of motor
unit potentials.
16
In a meta-analysis by Rickert et al
16
and an
analysis by Sittel et al,
17
LEMG predicted defective recovery
defined as absence of completely free vocal fold mobility in
up to 94%. However, in a study with a small cohort, it was
shown that LEMG findings predict only 44.4%of the resolved
cases,
18,19
which is less satisfactory. Adrawback of the LEMG
is the fact that it takes time and is an invasive procedure not
well tolerated by patients. Furthermore, it requires expensive
equipment and an experienced investigator.
9
By analyzing the vibrations of the vocal folds, the state
of the mucosa (cover), and the underlying laryngeal, muscle
tone (body) can be assessed.
9,11
In microlarygostroboscopy,
the mucosal wave represents the clinical correlate for mus-
cular tonicity of the vocal cord. When present, recurrent
nerve function is at least in a sense present, that the epithe-
lium of the vocal cord can exactly follow the musculus
vocalis movements in pitch as well as in intensity. However,
mucosal waves can only be judged when there is no phona-
tion gap
≤
3 mm in UVP, enabling the mucosa to get in con-
tact with each other. Furthermore, MWs are reduced or
absent if mucosa (cover) adheres/sticks to the musculus
vocalis and/or ligamentum vocale (body). This phenome-
non is observed in patients with chronic laryngitis/leucopla-
kia, carcinoma, and scar formation of the vocal folds. The
warning factors for progression of dysplasia to invasive car-
cinomas is a nonvibrating segment/absence or reduction of
the MW in videostroboscopy.
20,21
A scarred vocal fold has
an absent or limited MW
22
as well, and for this reason, such
patients were excluded from our study.
To our knowledge, this is the first clinical study to report
the prognostic relevance of MW in laryngostroboscopy for
Figure 1.
A patient with a unilateral vocal fold paralysis (UVP)
on the right side. Positive mucosal waves (MWs) are seen in
microstroboscopy on the paralyzed right (
→
) and the non-
paralyzed vocal left fold.
Figure 2.
A patient with a unilateral vocal fold paralysis (UVP)
on the left side. Positive mucosal waves (MWs) are seen in
microstroboscopy on the non-paralyzed right side but are
absent in the paralyzed left vocal fold (
→
).
Table 1.
Recovery of Unilateral Vocal Fold Paralysis (UVP)
Dependent on Mucosal Wave (MW) in All Patients.
UVP
Positive MW Negative MW Total
Recovery
73
2
75
No recovery
7
18
25
Total
80
20
100
41