Middle and long-latency evoked potentials

MLEP and LLEP Responses that reflect the synchronous activity of large groups of neurons located at the level of the auditory mid-brain and cortex

Advantages Elicit more frequency-specific responses and are not as dependent on neural synchrony as are the ABR and ECoG. May be used in evaluating hearing in patients suspected to have auditory dyssynchrony/neuropathy LLEP has the added advantage that speech can be used instead of tonal stimuli.

Disadvantages Adversely affected by sedation and anesthesia Can vary considerably depending on subject state Are not fully developed until about 10 years of age Require the patient to be awake and attentive, even if not actively involved in the task.

Indications MLEP and LLEP are often used in cases where the functioning of the higher-order auditory pathways is questioned. They have been shown to be abnormal in individuals with multiple developmental delays, central auditory processing disorders, schizophrenia, and/or learning disabilities; however, the sensitivity and the specificity of these techniques is largely unknown. Finally, it was shown that it is possible to record MLRs and LLRs in subjects diagnosed with no ABR secondary to a diagnosis of auditory neuropathy.