Service manual

Neurodiagnostic Instruments Service Manual
2 - 4 Revision 2/18/05
Evoked Potentials (EP)
An evoked potential (EP) is an electrical response of the
nervous system to a sensory stimulation. EP’s are used
to check the condition of nerve pathways. A healthy
nervous system uses electrical energy to carry messages
smoothly along nerve cells to the brain. An EP test will
measure the brains’s electrical response to the signals
sent by the nerves.
The types of evoked potential stimulation are:
• Auditory (ABR, AER, AEP)
• Visual (VEP)
• Somatosensory (SEP)
Each type of response has a unique appearance.
Auditory Brainstem Response
This test is used to check the pathway from the ear to the
brain. The ABR is a series of waves that occur within
the first 10 msec following the onset of an auditory
stimulus. These waves originate from the auditory nerve
and auditory nuclei of the brainstem.
Typical system parameters for recording an ABR are:
• Stimulus=Rarefaction Click@75dB nHL
• Rate=11.4 clicks/sec.
• Duration=100usec
• Repetitions=2000
• Low Frequency Filter=30Hz to 150 Hz
• High Frequency Filter=3KHz
Example of an ABR Recording
Somatosensory Evoked Potential
A Somatosensory Evoked Potential (SEP) is used to
evaluate peripheral and central nervous system
functions. This test checks the pathway from the nerves
in the limbs to the brain. Electrodes are placed at various
points along to nerve pathway between the electrical
stimulus and the brain. The recorded waveforms
indicate the condition of the nerves tested.
Typical system parameters for recording a SEP are:
• Stimulus=Current Pulse set for mild twitch
• Rate=5.1/sec.
• Duration=100usec
• Repetitions=500
• Low Frequency Filter=5Hz
• High Frequency Filter=1.5KHz
Example of SEP Waveforms