Evoked Potential

Principles of Analysis and Interpretation


  • Generally, most analysis and interpretation techniques take place following the completed, averaged recording
  • Auditory steady-state response (ASSR) is analyzed spectrally through a time to frequency conversion process
  • Important questions
    • Is a response present, or is it just artifact or noise?
    • Is the response reliable and repeatable?
    • If the response is present, how does it compare with others obtained from individuals with normal hearing and auditory processes?
    • How confident am I that the recorded response will help me with differential diagnosis or threshold estimation?
    • Are there internal or external factors that explain the outcome of the recording?
  • ​Still depends on a final, subjective judgment from the clinician
    • ​Example: the ABR is commonly recorded with 256 points in a 10-msec time window, each individual point is 0.039msec in duration
      • ​10 msec / 256 points = 0.039 msec OR 0.010s / 256 * 1000 = 0.039msec
  • ​​Appreciate that any part of a recorded waveform may be selected and compared with normative data collected from a larger group of individuals
    • ​normative data typically yield the central tendency of the group (mean) as well as the variability of the group (standard deviation)
    • if a patient has a measurement that exceeds 2SD above or below the mean, there is a greater likelihood that there is an abnormality

Analyses in the Time Domain
  • analyses and interpretation techniques that follow the collection of the averaged response​
    • ABR
      • Marking of primary waves I, III, V although other waves may be marked such as II and IV
      • Marking wave V only and tracking its presence to decreasing intensity levels
      • Looking for signs of ringing cochlear microphonic in an absent or grossly malformed ABR waveform
        • as is in the case of auditory neuropathy spectrum disorder (ANSD)
      • ​LATENCIES
        • ​Absolute and relative latencies for waves I, III, V, I-III, III-V and I-V are deemed most important; interaural latency difference for wave V between ears
        • Wave V usually appears around 5.6msec following a high intensity click
      • ​AMPLITUDE
        • ​Absolute amplitudes are too variable to be used clinically; however, wave V/I ratio and wave V can be used for threshold estimation and stacked ABR

Marking or Labeling Waves
  • Each individual sample's latency and amplitude value will be influenced by the overall signal to noise ration achieved during the averaging process
  • Because of signal to noise issues that effect every recording, no two recordings will ever appear exactly alike
    • ​thus the repetition of every recording is a practice that is strongly encouraged to increase confidence that a response is present or absent
    • having two or more recordings can help with marking the waveform

Latency-Intensity functions
  • graph to observe shifts in peak latency with decreases in stimulus intensity
Evoked Potential
1640 Stockton Street ​#330071
San Francisco, California 94133
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