Neurophysiological Monitoring Modalities and Equipment

At Biotronic, our neural monitoring technologists have experience using several types of neurophysiological monitoring equipment and can choose the right combination of monitoring modalities to effectively monitor patients during brain and spinal cord surgeries. With remote neural monitoring, certified professionals are able to supervise each and every procedure through a secure internet connection and can handle complications that may arise.

Monitoring Modalities

Somatosensory Evoked Potentials (SSEP):

Somatosensory evoked responses are obtained by stimulating a peripheral nerve at the wrist or the ankles. The propagation of the sensory action potentials is evaluated along their pathways to the cortex. This modality gives information about the integrity of the sensory pathways. It is also highly correlated with preservation of spinal cord motor pathways.

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Spinal Cord Evoked Potentials:

Mixed motor and sensory evoked potentials can be obtained by electrical depolarization of the spinal cord in the operative field. These are commonly known as NMEP potentials. They are mediated pre-dominantly by the sensory pathways.

Transcranial Motor Evoked Potentials (TcMEP):

Motor evoked potentials can be obtained by transcranial stimulation of the cortical motor areas using electrical current or induced magnetic fields. Monitoring evoked EMG activity or the motor neuron action potentials in the limbs can assess integrity of the motor pathway.

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Cortical Mapping:

Language, motor, and sensory areas of the exposed cortex can be identified by direct brain recording or stimulation. The somatosensory response is recorded from the surface of the brain. Language areas are determined by verbal responses during brain stimulation in the awake patient. Motor areas of the cortex and internal capsule are determined from EMG evoked by electric brain stimulation.

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Deep-Brain Single Unit Recordings:

Globus pallidus, thalamus, and subthalamus structures can be identified by the unique single unit activity recorded from microelectrodes inserted into these structures. The nearby optic tracts can also be located.

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Auditory Evoked Potentials:

Brainstem evoked potentials are obtained by stimulating the auditory system with click stimuli. The neural action potentials between the cochlea and the median geniculate body are evaluated based on the brainstem evoked response. Brainstem evoked responses are sensitive to disturbances of the auditory nerve and to retractor disturbances of the brainstem.

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Visual Evoked Potentials:

Visual evoked potentials are obtained from flash stimulation of each eye. The visual evoked potentials are measured from the occipital region. These responses are fairly labile due to anesthetic effects. Additionally, they do not give good functional information about the retrochiasmal pathways.

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EEG and Computer Enhanced EEG:

The ongoing EEG activity from the scalp is recorded from a multi-electrode array. Or, computer enhanced EEG is obtained by subjecting the EEG waves to FFT analysis. The resulting spectrum is then sampled and monitored at 10-second intervals. Changes in the amplitude or power of the EEG components are correlated with the metabolic state of the cortical structures.

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Electromyography:

Used to monitor the cranial nerves, peripheral nerves, and spinal nerve roots.

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Transcranial Doppler:

Blood flow velocity is measured from intracranial arteries using ultrasonic Doppler.

Cerebral Venous Oxygen Saturation:

Using nearfield and farfield infrared absorption measurements.

Evoked Sensory and Motor Action Potentials:

Peripheral nerves can be evaluated by eliciting a whole-nerve action potential and recording the action potential propagated from that nerve.