Evoked Potentials (EP)

Normally, when the brain is stimulated by light, sight, sound, or touch etc, the electrical signals travel along the nerves and spinal cord and reach the brain. Evoked potentials are tests that record electrical activity from the brain after electrical signals are transmitted through peripheral nerves and the spinal cord. The electrical signals are received in the brain in response to stimulation of eyes by visual stimuli, stimulation of ears by stimuli of sound, and electrical stimulation of peripheral sensory nerves in the upper and lower limbs.

A trained healthcare professional places surface electrodes over the scalp to record the electrical signals transmitted to the brain. Neurophysiology consultant physician interprets the data and formulates a report.

The tests are mainly used to assess the integrity of sensory and motor pathways that conduct signals from peripheral receptors to the brain and from the brain to the muscles, through peripheral nerves and spinal cord. These are useful in the diagnosis of various neurologic conditions including multiple sclerosis. The main types of evoked potential tests include visual evoked potentials, somatosensory evoked potentials, brainstem auditory evoked potential tests, motor evoked potential tests.

Visual Evoked Potentials (VEP)

These are the most commonly used evoked potential test in clinical practice. The test involves recording electrical activity transmitted via the visual pathways and received in the brain in response to stimulation of the eyes by visual stimuli. A trained healthcare professional attaches recording electrodes over the scalp. Eyes and the optic nerves are stimulated by asking the patient to watch a checkerboard pattern on a screen for several minutes while electrical signals transmitted to the brain are recorded from the electrodes placed over the scalp. The test is generally safe, painless, and well-tolerated.

The test is used to assess the function of optic nerves and visual pathways which transmit visual signals from the eyes to the brain and help in the diagnosis of various disorders and conditions which can affect visual pathways including multiple sclerosis.

Somatosensory Evoked Potentials (SSEP)

Somatosensory evoked potentials tests record electrical activity transmitted through peripheral nerves and spinal cord and received in the brain in response to electrical stimulation of peripheral sensory nerves in the limbs. For this test, a trained healthcare professional attaches stimulating electrodes to your wrist, ankles or the back of your knee, or other locations, and apply a mild electrical stimulus through the electrodes. A trained healthcare professional places electrodes over the scalp to record the electrical signals transmitted to the brain. Neurophysiology consultant physician then interprets the data, determines various parameters including the time it takes for the signals to travel along the nerves and spinal cord to the brain, and formulates a report.

The test are usually carried out to assess the function of peripheral nerves, spinal cord and brain. The test can detect and help diagnosis of problems in the sensory pathways and conditions like multiple sclerosis that can cause numbness in the arms and legs. These tests are also used by trained neurophysiology technologists and physicians in the monitoring of sensory pathways during complex brain and spinal cord surgeries.

Brainstem Auditory Evoked Potentials (BAEP)

Brainstem Auditory Evoked Potential tests record electrical activity transmitted through peripheral nerves of hearing and the brainstem and received in the brain in response to auditory stimulation of ears.
For this test, a trained healthcare professional attaches head phones which delivers auditory stimuli such as clicking noises and tones, to one ear at a time. A trained healthcare professional places electrodes over the scalp to record the electrical signals transmitted to the brain. Neurophysiology consultant physician interprets the data, determines various parameters including the time it takes for the signals to travel along the nerves to the brain, and formulates a report.

This test helps in the assessment of hearing pathways from the ears to the brain and helps in the diagnosis of various neurologic conditions that can affect hearing and hearing pathways. These tests are also used by trained neurophysiology technologists and physicians in the monitoring of hearing pathways during complex brain and brainstem surgeries.

Motor Evoked Potentials (MEP)

For this test, a trained healthcare professional delivers electrical or magnetic stimuli to the brain. A trained healthcare professional attaches electrodes over the muscles and records electrical signals transmitted to muscles from the brain. Neurophysiology consultant physician interprets the data and formulates a report.

The tests are mainly used to assess the integrity of motor pathways that conduct signals from the brain to the muscles, through peripheral nerves and spinal cord and helps in the diagnosis of various neurologic conditions that can affect motor pathways. These tests are also used by trained neurophysiology technologists and physicians in the monitoring of motor pathways during complex brain and spinal surgeries.

Intra-operative Neurophysiologic Monitoring (IONM)

These tests are used during complex brain, brainstem and spinal surgeries, carried out by trained neurophysiology technologists and physicians. The tests provide useful information to the brain and spinal surgeons, about mapping of various brain and spinal cord regions and monitoring of various brain, brainstem and spinal cord pathways. The tests comprise various neurophysiologic modalities including motor evoked potential, somatosensory evoked potentials, brainstem auditory evoked potential, visual evoked potentials, electrocorticography and electromyography.