Transcript Middle and long-latency evoked potentials

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.