Somatosensory Evoked Potentials (SSEP)
Somatosensory Evoked Potentials are used to evaluate the integrity of the afferent sensory pathway and spinal cord. SSEPs are obtained by stimulating electrodes on groups of extremities, which sends a response up the spinal cord to corresponding recording electrodes placed on the scalp. SSEPs can also help monitor for peripheral nerve injury due to positioning in an intraoperative environment.
Transcranial Motor Evoked Potentials (TcMEP/'Motors')
Transcranial Motor Evoked Potentials are used to evaluate the integrity of efferent signals which run along the anterior portion of the spinal cord. TcMEPs are obtained by stimulating certain parts of the homunculus, sending a signal down the spinal cord to corresponding recording electrodes on the extremities.
Brainstem Auditory Evoked Response (BAER/ABR)
Brainstem Auditory Evoked Responses are used to evaluate the integrity of the signal pathway between the cochlea and the brainstem. It is obtained by using a audible clicking stimulus near the cochlea, and recorded with corresponding referential electrodes.
Visual Evoked Potentials
Visual Evoked Potentials are used to evaluate the signal integrity of the visual neuralpathway. VEPs are obtained using specific patterns of either flashing light (in an intraoperative setting) or geometric patterns on a screen (in a clinical setting).
Electromyography records muscle activity and response. It is used to evaluate the integrity of Spinal Nerve Roots, Peripheral Nerves, and some Cranial Nerves. In spinal surgeries, EMG is used to monitor for both spontaneous and chronic nerve irritation which can be caused by surgical manipulation. In clinical EMG tests, neurologists are able to see the extent of any neuropathy/nerve damage.
Nerve Conduction (NCV)
Nerve Conduction tests are used to measure the velocities of both afferent and efferent signals along the peripheral nerves. These velocities will show any 'speed bumps' along the nerves, and can indicate any present neuropathy. Nerve Conduction Velocity is obtained by sending afferent signals along a specific nerve pathway. Efferent signals are also measured for Motor components. NCV records one extremity at a time, but typically will be recorded in pairs for comparison.
Triggered EMG (tEMG)
Triggered EMG is used to test the signal threshold of both nerve roots and spinal screws. Surgeons are given a stimulator and reference electrode, which will both identify which nerve is present and test signal thresholds.
EEG is a running visualization of activity within the brain, which can help diagnose existing conditions, or monitor for changes during a surgery. EEG is obtained by placing multiple electrodes on the scalp, which record activity between specific landmarks on the head. EEG is used in both IOM and clinical conditions. Clinical EEG is performed in both inpatient and outpatient settings, most commonly running 20-45 minutes. Long term and Ambulatory EEG is also available, running from 24-72 hours or longer at a time.
Brain mapping is used in the intraoperative environment to locate the Sensory/Motor Cortex. This is done by (the surgeon) placing a strip of intra-cranial EEG leads directly on the exposed cerebrum.
These are the day-to-day systems we use, but we are not afraid to 'Think outside the Box' if you have special needs!
Modalities (See below for full descriptions)