Neurological Tests

The following tests, some of which can be performed in the office, may be ordered as part of the evaluation your doctor employs in diagnosis of your neurological condition:

This test is most commonly used to help diagnose epilepsy (seizure disorders). An EEG involves the recording of electrical activity along the scalp produced by the firing of neurons within the brain. The recording is obtained by placing electrodes (sensors) on the scalp with a conductive gel or paste. Brain wave activity is recorded on a computer for about 20-30 minutes while you lie relaxed on a bed. The technologist performing the study may use a flashing strobe light and may ask you to hyperventilate for a short while as a means of seeing if these induce any abnormalities in your brain waves. The study will tell your doctor if there seems to be any propensity toward seizures/epilepsy, even if you do not have a spell during the recording.

NCS is a test commonly used to evaluate the function of the motor and sensory nerves of the human body. These studies are used mainly for evaluation of paresthesias (numbness, tingling, burning) and/or weakness of the arms and legs. Some common disorders which can be diagnosed by an NCS are peripheral neuropathy, carpal tunnel syndrome, ulnar neuropathy, Guillain-Barre syndrome, myasthenia gravis, and spinal disc herniation.

The test involves placing an electrode (sensor) on the surface of the skin in one location, then delivering an electrical stimulus down a nerve several times with another electrode. The responses of the nerve are recorded on a computer and will tell the neurologist whether the nerve is functioning properly. Depending on the nature of the symptoms, between 4-8 nerves may be tested in this way.

Used as a complement to an NCS, and usually carried out on the same day, this test is a technique for evaluating and recording the electrical activity produced by skeletal muscles.

To perform the test, a needle containing a recording electrode wire is placed through the skin into a muscle, and then the neurologist evaluates the electrical activity as the needle is inserted into a relaxed muscle, and again as the muscle is contracted by the patient. The number of muscles tested depends upon the patient’s symptoms and the findings in each muscle.

The disorders which can be diagnosed with this test are the same as those diagnosed with NCS, with the addition of muscle disorders such as myopathy and myositis.

MRI is a medical imaging technique which allows your physician to visualize detailed internal structures using a large magnet and radiofrequency pulses (no radiation is used). The good contrast it provides between the different soft tissues of the body make it especially useful in brain imaging.

An MRA is very similar, but specifically visualizes the arteries. Because the machine uses a large magnet, it is unsafe for those with pacemakers, stimulator devices, ear implants, and other internal metal to undergo MRI testing.

During the test, the patient is positioned on a moveable exam table and is moved into a small tunnel (which contains the magnet) until the part of the body being imaged is in the center of the tunnel. As the radiofrequency pulses are emitted, a loud mechanical noise is heard. If ordered by the physician, IV contrast may be injected into an IV placed ahead of time while you lie in the scanner.

The test takes about 30-40 minutes to complete in most cases. See the following link for more information: http://www.radiologyinfo.org/en/info.cfm?pg=headmr

CT is a non-invasive medical imaging technique which allows physicians to visualize internal structures of the body through use of special x-ray equipment in combination with sophisticated computers to produce multiple images or pictures of the inside of the body. This test is optimal for imaging bleeding/hemorrhages and bone structures.

During the test, the patient is positioned on a moveable exam table and moved through a large opening in the machine while the x-ray beams are emitted and recorded by computers. The test is very brief, taking only 1-2 minutes to perform. See the following link for additional information: http://www.radiologyinfo.org/en/info.cfm?pg=headct

Evoked potentials are electrical potentials recorded from the nervous system following presentation of a stimulus. There are several types of evoked potential studies:

Visual Evoked Potential

With a visual evoked potential test, sensors are attached to the scalp to record brain waves, and then a series of visual stimuli are presented to the patient while seated. The patient is asked to visually focus on the pattern while brain waves are recorded. This test is used to check the function of the optic nerves and their connections to the brain, allowing for diagnosis of problems with vision loss, in some cases.

Somatosensory Evoked Potential

With this test, sensors are attached to the scalp and/or spine, then a surface electrical stimulus is given to a site on the arm or leg and the brain’s response to this stimulus is recorded. This test studies the relay of body sensations to your brain and how well the spinal cord and brain receive those sensations. It is useful in determining the site of the problem in patients who are experiencing numbness or weakness of the limbs.

Brainstem Auditory Evoked Potential

For this study, sensors are placed on the scalp and on each earlobe. While the patient is lying in a chair or bed, earphones are worn which give off a brief click or tone. The electrodes pick up the brain’s responses to these sounds and record them. This test can help to diagnose problems with hearing loss or other nervous system dysfunction

This study is a diagnostic test during which a number of variables are measured and recorded during sleep. The purpose of the study is to diagnose obstructive sleep apnea, periodic limb movements of sleep, or other sleep related disorders.

During the study, patients are asked to spend the night in a “sleep lab” located in an outpatient facility and to bring personal items to the test center including whatever sleep clothing and toiletries they would normally bring to a hotel for an overnight stay. Physiologic sensorors are placed in order to record the following parameters: brain electrical activity, eye and jaw muscle movement, leg muscle movement, airflow, respiratory effort (chest and abdominal excursion), EKG, and oxygen saturation. Information is gathered from all leads and fed into a computer, generating numbers and waveforms that help the technician and doctor to diagnose any sleep related problems. A camera with microphone is also used to record behaviors during sleep and detect evidence of any snoring. If a patient has trouble sleeping in unfamiliar surroundings, he/she may be prescribed a sleep aid for the night of the test.