Clin Exp Otorhinolaryngol.  2021 Aug;14(3):268-277. 10.21053/ceo.2020.01942.

Significance of Pseudo-Conductive Hearing Loss and Positional Nystagmus for Perilymphatic Fistula: Are They Related to Third-Window Effects?

• Kim JS
• Son SE
• Kim MB
• Cho YS
• Chung WH

• KMID: 2519181
• DOI: http://doi.org/10.21053/ceo.2020.01942

Abstract

Objectives
. Patients’ clinical presentation is critical for identifying suspected perilymphatic fistula (PLF). The involvement of third-window lesions in the pathomechanism of PLF has been hypothesized. This study investigated the clinical features of PLF and the relationship of the third-window effect with PLF.
Methods
. Sixty patients underwent surgical exploration for suspected PLF and the oval and round windows were reinforced. Clinical features including demographics, pure-tone audiometry (PTA), and videonystagmography were evaluated preoperatively and 1 month postoperatively. Surgical outcomes were analyzed according to the improvement of hearing and vestibular symptoms and signs. The conductive components of PTA (air-bone gap [ABG]) were measured, and the relationship between ABG closure after surgery and hearing improvement was analyzed. In addition, postoperative subjective dizziness was assessed by clinical interviews. Changes in positional nystagmus were analyzed according to ABG closure and hearing improvement.
Results
. ABG at lower frequencies (LFABG; 250 Hz, 500 Hz, 1,000 Hz) was present in 27 patients (45%). Postoperatively, PTA significantly improved after surgical repair. Among the patients with preoperative LFABG (n=27), 15 (55.5%) showed postoperative ABG closure and significant improvement in PTA at all frequencies compared with the patients without ABG closure (P=0.012). Subjective dizziness improved in 57 patients (93.3%). Positional nystagmus was found in 45 of 49 patients. Multiple canal involvement was more common than single canal involvement (67% vs. 33%). The horizontal semicircular canal was most commonly involved, followed by the posterior and anterior canals. Postoperatively, positional nystagmus disappeared, or the number of involved canals decreased in 22 of 34 patients (64.7%).
Conclusion
. Pseudo-conductive hearing loss at lower frequencies and positional nystagmus originating from multiple semicircular canals were common findings in PLF. Surgical reinforcement of the oval and round windows improved the hearing threshold accompanied by closure of ABG. A third-window lesion might explain these clinical features of PLF.

Keyword

Perilymph; Nystagmus; Hearing Loss

Figure

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  Fig. 1. Postoperative hearing outcomes at 1 month after surgical repair in definite and probable perilymphatic fistula (PLF). In both groups, the pure-tone audiometry (PTA) significantly improved. However, there was no significant between-group difference.

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  Fig. 2. Postoperative hearing outcomes at 1 month after surgical repair in the air-bone gap at lower frequencies (LFABG) closure and non-closure groups. (A) In the LFABG closure group, hearing significantly improved at each frequency after surgery. (B) In the LFABG non-closure group, hearing did not improve at each frequency. PTA, pure-tone audiometry.

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  Fig. 3. Examples of preoperative pseudo-conductive hearing loss at lower frequencies and postoperative hearing results in patient 1 (A) and patient 2 (B). The air-bone gap at lower frequencies (LFABG) was closed with hearing improvement after surgical repair. AC, air conduction; BC, bone conduction.

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  Fig. 4. Changes in subjective dizziness after surgical repair of perilymphatic fistula (PLF). Subjective dizziness improved in most patients. There was no significant difference between definite and probable PLF.

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  Fig. 5. Changes in positional nystagmus and the incidence of multiple canal involvement after surgical repair of perilymphatic fistula. Positional nystagmus was found in 97.0% of patients preoperatively, and the number of patients significantly decreased after surgery. In addition, the incidence of multiple-canal involvement significantly decreased after surgery.

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