What is the role of brainstem auditory evoked potential (BAEP) testing in the workup of brainstem tumor?

Updated: Oct 25, 2019
  • Author: Andrew B Evans, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Bilateral prolongation of latencies and interpeak latencies may be seen. Gordon et al evaluated the efficacy of ABR as a screening test for small acoustic neuromas by assessing the diagnostic sensitivity of BAEP in these tumors. [33] Patients with surgically proven acoustic neuromas underwent preoperative BAEP tests within 2 months of surgery. A result was considered abnormal if the interaural wave I-V latency difference exceeded 0.2 msec, the absolute wave V latency was abnormally prolonged, or waveform morphology was abnormal or absent.

Of the 105 patients, 92 (87.6%) had an abnormal BAEP result, and 13 (12.4%) had completely normal waveforms and wave latencies. [33] Of the 18 patients who had tumors larger than 2 cm, 12 had tumors 2.5 cm or larger and 6 had tumors between 2.1 and 2.4 cm; all 18 had abnormal BAEPs. Of the 29 patients with tumors between 1.6 and 2 cm, 25 (86%) had abnormal BAEPs. Of the 45 patients with tumors between 1 and 1.5 cm, 40 (89%) had an abnormal response. Of the 13 with tumors 9 mm or smaller, only 9 (69%) had an abnormal ABR finding.

These data show that BAEP sensitivity decreases with decreasing tumor size. [33] Therefore, MRI scanning is the preferred study in this setting because the accuracy for detection of tumors smaller than 1 cm through BAEP testing is 70%. Nevertheless, BAEP studies are useful in patients who have implanted medical devices (eg, pacemakers) that prevent MRI scanning.


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