Common Neurological Tests
When you come to NYU Langone for treatment of a neurological condition that might require surgery, you may have had one or more of the following diagnostic tests so that doctors can pinpoint the cause of your condition and develop effective treatment strategies.
As a new patient, please bring copies of any previous test results for your surgeon to review.
Some diseases, such aneurysms, arteriovenous malformations, and vasculitis, affect the blood vessels of the brain. A cerebral angiogram is the gold standard for assessing these conditions. This test involves injecting dye into the blood vessels of the brain and then taking X-rays of these vessels.
The patient lies flat on a table and a catheter is inserted into an artery in the groin. The catheter is then passed through the arterial system to the head, where the dye can be injected. This is typically a painless procedure.
Some patients with implanted metal devices cannot undergo MRI scanning. In order to assess the spinal cord in these patients, a special type of CT called a CT myelogram can be done.
In this test, contrast dye is not injected into the blood, but rather into the cerebrospinal fluid that coats our brain and spinal cord. This injection is done by means of a spinal tap or lumbar tap. Local anesthetic is given prior to the needle being placed in the lower back.
CT scans allow surgeons to pinpoint the location of lesions in the brain or spinal cord. It is particularly useful in determining if there is bleeding in the brain, or bony destruction in the spinal column. For this test, you are asked to lie on a comfortable, open-air table while a series of special X-rays are taken. A simple head CT can take less than 30 seconds.
Scans of other body parts may take up to 30 minutes. Some tests require that intravenous contrast dye be administered. People with kidney problems, allergies to shellfish, or previous reactions to contrast dye should make certain that their physician is aware of these conditions prior to receiving contrast dye.
Nerve Conduction Studies
If a person has weakness or twitching in a muscle, an electromyogram, or nerve conduction study, can help to distinguish between problems in muscles, in the nerves that support the muscles, or in the spinal cord itself.
A sterile needle is placed into the muscle. From the needle, small electrical signals are recorded when the muscle is contracted and when it is relaxed. This process is repeated for each muscle to be tested. This is similar to acupuncture.
Nerve Conduction Velocity
Nerve conduction velocity tests assess peripheral nerves. Peripheral nerves connect the spinal cord with the muscles. Electrodes are placed over the nerve to be assessed as well as the muscles it stimulates. Small electric shocks are applied at one electrode.
Physicians use the time it takes for these electrical pulses to reach the other electrode to determine if a disease of the peripheral nerves is the cause of pain, weakness, or numbness in the muscle.
Cerebrospinal fluid bathes and protects our brain and spinal cord. Examining this fluid can be important in determining if an infection or tumor has spread to this part of the body. The fluid is obtained by a lumbar puncture or spinal tap.
The patient is placed on his or her side with the knees tucked to the chest in a fetal position. An area in the middle of the low back is numbed with local anesthetic. A needle is then inserted and fluid removed. The procedure generally takes less than a minute or two. In experienced hands, this procedure is minimally painful.
While a CT scan is particularly useful for assessing bony anatomy, MRI is best for imaging soft tissues, such as the brain and spinal cord. The MRI works by assessing the alignment of hydrogen atom nuclei in a very powerful magnetic field. The use of a magnet rather than ionizing radiation is another advantage of MRI over CT.
However, because of this magnet, people with heart pacemakers and some other implantable devices cannot undergo MRI testing. Additionally, some patients will find that the longer testing period of MRI, sometimes up to one hour, in a small confined space can induce feelings of claustrophobia and anxiety. Patients who are at risk for such feelings can be given appropriate sedating medication prior to the procedure.
The neurological examination is divided into five parts: mental status, cranial nerves, motor function, sensory function, and reflexes.
In the mental status exam, you are asked questions designed to assess your level of alertness, orientation, mood, and cognition. The simplest form of this test requires that you state your name, where you are, and the month, year, and date. You may also be asked to follow commands, such as “Touch your right ear with your left index finger,” solve simple arithmetic problems, repeat a phrase, name an object and what it is used for, or write your name.
Cranial nerves are responsible for strength and sensation in the head. Special senses, including vision, hearing, smell, and taste, are part of these tests. A light is shone in your eyes to assess pupil reactivity. Your peripheral vision or visual fields as well as visual acuity are assessed. Eye movements are assessed by having you follow the examiner's moving finger without turning your head. Facial muscles are tested by having you close your eyes tightly, raise your eyebrows, and smile widely. You are also asked to stick out your tongue, shrug your shoulders, and turn your head from side to side as part of the cranial nerve test.
The motor function examination tests muscle strength. Individual muscles in both the upper and lower extremities on both sides are tested. Motor assessment will often start with the drift test. You will be asked to place your arms outstretched in front of you with your palms facing upward. You will then be told to close your eyes and count to 10 out loud without moving your outstretched arms. This test can often detect subtle weakness on one side of the body.
The remainder of motor function testing is completed by having you bend or straighten a joint, such as the elbow, against resistance provided by the examiner. For example, in order to test the triceps muscle in the back of the arm, you will be told to keep your arm straight at the elbow while the examiner attempts to bend it.
The sensory function examination tests your sense of touch. You are told to keep your eyes closed while the examiner lightly touches your skin with a safety pin. You are asked whether the sharp or dull end of the pin touched your skin. This can detect lesions in the spinal cord.
Another important part of the sensory exam is assessment of proprioception, a measure of how well you can sense your body’s position and movements. Again with your eyes closed, your toe or your finger will be moved either up or down. You will then state which direction your finger was moved in. This ability to determine the relative position of body parts—without looking—can be compromised by certain neurological conditions.
To test reflexes, a small rubber hammer is used to check response at the knee, elbow, wrist, and ankle. These reflexes may be exaggerated or absent in certain pathological conditions. Additionally, the bottom of the foot or the fingernail of the middle finger may be stroked to elicit certain abnormal reflexes.
Depending on the suspected neurological condition, the examiner may do other tests as well. For example, the examiner may wish to observe you walking or have you slide the heel of one foot up and down the shin of the opposite leg.
Shunt Series and Shuntogram
A common neurosurgical operation involves the diversion of excess cerebrospinal fluid (CSF) from the brain. Most commonly, a tube called a shunt is tunneled under the skin from the brain to the abdomen. This implantable device generally stays in place for life. Problems with the shunt, including infection, obstruction, or disruption of the tubing, are occasionally encountered.
Workup for a shunt problem includes several tests. A CT scan tells doctors how much CSF is in the brain. Excessive CSF can mean that the shunt is not working properly. A shunt series is a simple set of X-rays of the skull, chest, and abdomen that can reveal a break in the tubing.
A shuntogram is a more sophisticated study that involves placing a radioactive isotope in the shunt reservoir in the head and measuring the speed with which it moves to the abdomen. Delayed movement of CSF to the abdomen may imply a problem with the shunt. Lastly, a shunt infection may be assessed by sterilely removing some spinal fluid from the shunt reservoir and sending it to the microbiology lab for culture.
Certain neurological conditions can impair a person’s ability to swallow. If there is some question as to whether you can safely be allowed to eat, a swallow study can be done.
This involves taking X-rays while you eat food and liquids mixed with barium. This test is done under the supervision of a speech pathologist who determines how well you are able to swallow foods of various consistencies.
Simple X-rays are often useful in assessing the bones of the skull and spine. X-rays of the spine can be used to evaluate fractures or misalignment. X-rays are also particularly useful in determining the stability of the spine. This is achieved by taking X-rays of the cervical or lumbar spine both in flexion, bent forward at the neck or hips, and extension, straightened at the neck or hips. The surgeon or radiologist looks for abnormal movement of the bones of the spine on these dynamic images.