Neurodiagnostic Technology is a specialized field of Allied Health Care, in which nervous system function is analyzed and monitored by the recording of electrical activity arising from the brain, spinal cord and peripheral nerves using a variety of techniques and instrumentation.

Relying on the EEG

The most common neurodiagnostic procedure is the electroencephalogram (EEG), which is used primarily in the diagnosis of epilepsy and evaluation of seizure disorders.

Traumatic Brain Injury (TBI) can result in a pathophysiologic response of the brain that induces seizure activity. In fact, more than 20 percent of TBI patients experience early — within seven days of injury — post-traumatic seizures (PTS). Half of these are nonconvulsive, with no overt clinical symptoms.

The recurrence rate of a seizure after a single late — more than seven days after injury — PTS is greater than 75 percent. Seizures can produce secondary brain injury and lead to poor neurofunction by increasing brain tissue oxygen demand, depleting glucose supply and elevating intracranial pressure and cerebral metabolic distress. Since subclinical seizures are common in patients with severe TBI, continuous EEG monitoring is a critical tool for proper patient management and may divulge remedial opportunities to prevent seizure-related secondary brain injury.

EP studies

Another common neurodiagnostic test of neurologic function in TBI patients is Evoked Potential (EP) studies. EP studies detect electrical signals in the brain induced by the visual, auditory or sensory system of the body and provide a non-invasive assessment of cortical reactivity by measuring the brain’s responsiveness to external stimulation.

“For unstable, critically ill or injured patients, neurodiagnostic testing can be readily performed at the bedside”

Somatosensory-evoked potential (SSEP) studies have been commonly used to predict outcome in patients with severe TBI and are being used more frequently in intensive care units as a prognostic tool for coma and critically ill patients. Although SSEP has been used for many years in predicting patient outcome, EP studies are not only used for patients with severe TBI.

Neurodiagnostic testing

Because the human brain contains many distinct cortical areas that receive or process visual information, patients with mild TBI often exhibit dysfunction of the visual system. Visual EP is a neurodiagnostic test that provides a rapid, objective assessment of visual system deficits, as well as recovery following therapeutic intervention.

The benefits of neurodiagnostic testing in mild and severe TBI patients are many. Neurodiagnostic testing allows for a real-time assessment of neurofunction and integrity, signal transmission, and secondary processing of sensory information. TBI often causes a delay in the decline of neurofunction, secondary to cerebral edema, compression or bruising, and elevated intracranial pressure.

As such, changes in neurodiagnostic signals can be evaluated over time, with serial testing or continuously, to determine neurofunctional response to therapeutic interventions, recovery of brain function, or the progression of brain injury. For unstable, critically ill or injured patients, neurodiagnostic testing can be readily performed at the bedside, without the need for patient transport as with CT scan or MRI.