Intraoperative Erb's Point-Vertex recording increases brainstem auditory evoked potential wave V amplitude. Issue 2 (February 2020) - Greve, Tobias
Highlights: Referencing vertex to a noncephalic electrode at Erb's point increases brainstem auditory evoked potential (BAEP) wave amplitude V by 55%. Higher BAEP amplitudes overcome difficult signal interpretation when wave V is pathologically low. Erb's point-vertex recording is a valuable addition to standard mastoid recording derivations. Abstract: Objective: Recording derivations for intraoperative brainstem auditory evoked potential (BAEP) monitoring consist of a preauricular electrode referenced to Cz′. These derivations are prone to unfavorable signal amplitude. This study analyses whether an alternative noncephalic electrode positioned over ipsilateral Erb's point, thereby generating a new Erb's point-vertex recording derivation, improves BAEP recordings. Methods: Electrodes were placed preauricularly (A1/A2) and at left and right Erb's point (EP1/EP2). They were referenced to Cz′. Click sound stimulation (80–95 dB above hearing level) was applied. At intraoperative baseline conditions, latencies and amplitudes of waves I–V of all derivations were analyzed. Results: Data of 30 patients (54 ± 15 years/17 females) with normal hearing or mild symmetrical presbycusis undergoing infratentorial surgeries (15 microvascular decompressions) were analyzed. Using EP1-Cz′/EP2-Cz′ derivations compared to A1-Cz′/A2-Cz′, amplitudes for wave IV (left +65%, p < 0.001; right +43%, p = 0.002) and wave V (left +54%, p < 0.001; right +48%, p < 0.001) were significantly increased. Only in the left (EP1) derivation, there was a tendency towards less reproducibility of wave I, resulting in a decrease of amplitude (−35%, p = 0.005). Conclusions: Adding an Erb's point electrode derivation resulted in larger amplitudes of waves IV to V. whereas conventional preauricular or mastoid derivation is preferential for wave I assessment. Significance: Increased wave amplitudes facilitate detection of pathologically reduced wave forms (wave V in particular) which represents a significant advancement.