NeurodiagnosticThe Neurodiagnostic Department provides testing during regular working hours Monday-Friday. Regular working hours for the lab are 8:30 AM to 5:00 PM, excluding CHI St. Alexius Health's holidays.

What is an electroencephalogram?
An electroencephalogram (EEG) is a procedure that records the electrical activity or brain waves on the brain's surface. Sensors (electrodes) are applied to the scalp and connected by wires to a computer. The computer records your brain's electrical activity on the screen as wavy lines. Certain brain abnormalities can be detected by observing changes in the normal pattern of the brain's electrical activity.

Reasons for the procedure:
Electroencephalography (EEG) may be done to:

  • Help establish a diagnosis of epilepsy and determine what type of seizure a person with epilepsy is having. EEG is the most useful and important test in confirming a diagnosis of epilepsy.
  • Identify the location of a suspected brain tumor and the potential damage caused by it, inflammation, infection (such as encephalitis), or disease in the brain.
  • Evaluate periods of unconsciousness or dementia.
  • Confirm or rule out brain death (ECS - electrical cerebral silence) in a person who is in a coma.

What is an Evoked Potential?
The Evoked Potential (EP) is a recording of electrical activity from the brain, spinal nerves or sensory receptors in response to specific external stimulation. Electrodes are applied to the scalp and other areas of the body, a series of stimuli is introduced, and a computer records the neurological response. Hundreds of responses are received, amplified and averaged by a computer. The final response is plotted on a graph and interpreted by a neurologist who looks for particular waveforms and the time it takes them to occur.

Evoked potentials are helpful in evaluating a number of different neurological problems, including spinal cord injuries, acoustic neuroma and optic neuritis. Each type of EP looks at a different neurological pathway. Evoked potential studies may be used to assess hearing or sight, especially in infants and children, to diagnosis disorders of the optic nerve, and to detect tumors or other problems affecting the brain and spinal cord.

A disadvantage of these tests is that they detect abnormalities in sensory function, but usually do not produce a specific diagnosis about what is causing the abnormality. However, the evoked potential test can confirm a diagnosis of multiple sclerosis.

Evoked potential studies involve three major tests that measure response to visual, auditory, and electrical stimuli.

  • Visual evoked response (VER and/or VEP) - Evaluates the visual nervous system from the eyes to the occipital (visual) cortex of the brain. VEPs can diagnosis problems with the optic nerves that affect sight. The patient is usually asked to stare at the center of a checkerboard pattern on a video screen while remaining fully alert. Each eye is tested separately.
  • Auditory brainstem Response (ABR, BAER and/or BAEP) - Assist in evaluating the auditory nerve pathway from the ears through the brainstem. ABRs can diagnose hearing ability and can indicate the presence of brainstem tumors. Earphones deliver a series of clicks to each ear separately.
  • Somatosensory Evoked response (SSEP and or SSER) - Assess pathways from nerves in the arms (median) or legs(tibial), through the spinal cord, to the brainstem or cerebral cortex. SSEPs can detect problems with the spinal cord as well as numbness and weakness of the extremities. A small electrical current is applied to the skin overlying nerves on the arms or legs. The current creates a tingling sensation, but is not painful. Each leg or arm is tested separately.