Utility Of Electroglottography (EGG) With Unloading In The Diagnosis Of Vocal Fold Paresis

Using transnasal flexible laryngoscopy (TFL) with high-definition laryngeal imaging and electromyography (EMG), we have begun to recognize that vocal fold paresis (VFP) is more common in voice disorder patients than previously recognized. Electroglottography (EGG) provides an impedance measurement of the glottal cycle, and it is an excellent non-invasive way to screening patients for glottal closure problems such as VFP. In our practices, EGG has proven to be a sensitive diagnostic test for VFP; however, its utilization is dependent upon the voice clinician’s ability to elicit a variety of vocal behaviors during the diagnostic evaluation. The single most important diagnostic concept is that of unloading, which refers to the temporary removal of compensatory laryngeal behaviors in order to elicit and evaluate the underlying glottal condition.

Patients with glottal closure problems (e.g., VFP) frequently present with hyperkinetic voice disorders. On TFL, such patients usually demonstrate supraglottic contraction and an element of pharyngeal squeeze, especially when they try to shout. Extra-laryngeal (especially suprahyoid) muscles are recruited to achieve glottal compression.

The biomechanical patterns observed in VCP are distinctly different than those of patients with primary behavioral (functional, non-organic, psychogenic) voice disorders. The latter demonstrate hyperkinetic laryngeal behaviors and high or normal glottal closure percentages on EGG. What distinguishes behavioral voice disorders from glottal closure problems is that following unloading; the EGG contact percentages in behavioral voice disorders remain in the normal range (45% +/- 2%). On the other hand, with glottal closure problems such as VFP, removal of compensatory laryngeal behaviors (unloading) is associated with falling (worsening) glottal contact percentages. We refer to this as “dropping EGGs.” The purpose of the study reported herein was to investigate the value of EGG with unloading in the diagnosis of VFP.

MATERIALS AND METHODS

A series of twenty patients with clinical and EMG-confirmed VFP were compared to a group of normal controls. The study subjects were a consecutive series of unselected VFP patients undergoing comprehensive evaluation, including videostroboscopy, acoustical analysis (with EGGs), and LEMG.  Twenty unselected patients undergoing a similar workup but without clinical or LEMG evidence of VFP were the controls.

The technique of EGG is beyond the scope of this article, however, A Kay Elemetrics Laryngograph was utilized. Waveforms were captured, one while the subject sustained the vowel /a/ with habitual level of respiratory and laryngeal effort, the other while the subject sustained the vowel /a/ in an unloaded manner.

RESULTS

Of patients with VFP, 50% were female and the mean age was 43 years. The controls were age- and gender-matched. The mean compensated (“loaded”) contact percentage on EGG of patients with VFP was 44.79 (+/- 5.4). This decreased to 36.82 (+/- 4.3) after unloading (mean difference = 8.0, p < 0.001). The mean compensated contact percentage of the controls was 49.35 (+/- 4.2), and it decreased to 47.62 (+/- 3.7) when unloaded (mean difference = 1.7, p > 0.05). Patients with paresis were 4.3 times more likely to exhibit a five-point decrease in glottal contact percentage when unloaded (95% CI = 1.2, 15.7; p < 0.001).

Case Example: Electroglottography of a Patient with Bilateral Vocal Fold Paresis Before and After Unloading … So-Called “Dropping EGGs”

By Jamie Koufman and P. David Blalock

Comments are closed.