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NEUROSCIENCE

  • Electromyelography (EMG)
  • Nerve Conduction Test (NCV)
  • Electroencephalogram (EEG)
  • Brain CT, Cerebral angiogram with 128 Slice Ultrafast PET-CT Scan, MDCT
  • Brain MRI with 1.5 Tesla MRI
  • Brain MRI with Open Gantry MRI
  • Digital X-Ray Myelogram
  • Neurosonology by Ultrasound
  • Neurologist Consultation
  • Neurosurgeon Consultation

Electromyelography (EMG)

Electromyography (EMG) is a diagnostic procedure to assess the health of muscles and the nerve cells that control them (motor neurons).

Motor neurons transmit electrical signals that cause muscles to contract. An EMG translates these signals into graphs, sounds or numerical values that a specialist interprets.

An EMG uses tiny devices called electrodes to transmit or detect electrical signals.

During a needle EMG, a needle electrode inserted directly into a muscle records the electrical activity in that muscle.

A nerve conduction study, another part of an EMG, uses electrodes taped to the skin (surface electrodes) to measure the speed and strength of signals traveling between two or more points.

EMG results can reveal nerve dysfunction, muscle dysfunction or problems with nerve-to-muscle signal transmission.

Why it’s done

Your doctor may order an EMG if you have signs or symptoms that may indicate a nerve or muscle disorder. Such symptoms may include:

  • Tingling
  • Numbness
  • Muscle weakness
  • Muscle pain or cramping
  • Certain types of limb pain

EMG results are often necessary to help diagnose or rule out a number of conditions such as:

  • Muscle disorders, such as muscular dystrophy or polymyositis.
  • Diseases affecting the connection between the nerve and the muscle, such as myasthenia gravis.
  • Disorders of nerves outside the spinal cord (peripheral nerves), such as carpal tunnel syndrome or peripheral neuropathies
  • Disorders that affect the motor neurons in the brain or spinal cord, such as amyotrophic lateral sclerosis or polio
  • Disorders that affect the nerve root, such as a herniated disk in the spine.

Risks

EMG is a low-risk procedure, and complications are rare. There’s a small risk of bleeding, infection and nerve injury where a needle electrode is inserted.

When muscles along the chest wall are examined with a needle electrode, there’s a very small risk that it could cause air to leak into the area between the lungs and chest wall, causing a lung to collapse (pneumothorax).

How you prepare

The nervous system specialist (neurologist) conducting the EMG will need to know if you have certain medical conditions. Tell the neurologist and other EMG lab personnel if you:

  • Have a pacemaker or any other electrical medical device
  • Take blood-thinning medications
  • Have hemophilia, a blood-clotting disorder that causes prolonged bleeding

Bathing

Take a shower or bath shortly before your exam in order to remove oils from your skin. Don’t apply lotions or creams before the exam.

What you can expect

You’ll likely be asked to change into a hospital gown for the procedure and lie down on an examination table. The following explanations can help you understand what will happen during the exam:

  • Electrodes.The neurologist or a technician places surface electrodes at various locations on your skin depending on where you’re experiencing symptoms. Or the neurologist may insert needle electrodes at different sites depending on your symptoms.
  • Sensations. The electrodes will at times transmit a tiny electrical current that you may feel as a twinge or spasm. The needle electrode may cause discomfort or pain that usually ends shortly after the needle is removed. If you’re concerned about discomfort or pain, you may want to talk to the neurologist about taking a short break during the exam.
  • Instructions. During the needle EMG, the neurologist will assess whether there is any spontaneous electrical activity when the muscle is at rest — activity that isn’t present in healthy muscle tissue — and the degree of activity when you slightly contract the muscle.

He or she will give you instructions on resting and contracting a muscle at appropriate times. Depending on what muscles and nerves the neurologist is examining, he or she may ask you to change positions during the exam.

After your EMG

You may experience some temporary, minor bruising where the needle electrode was inserted into your muscle. This bruising should fade within several days. If it persists, contact your primary care doctor.

Results

The neurologist will interpret the results of your exam and prepare a report. Your primary care doctor, or the doctor who ordered the EMG, will discuss the report with you at a follow-up appointment.

Nerve Conduction Test (NCV)

Nerve conduction velocity (NCV) test–also called a nerve conduction study (NCS)–is a measurement of the speed of conduction of an electrical impulse through a nerve. NCV can determine nerve damage and destruction.

During the test, the nerve is stimulated, usually with surface electrode patches attached to the skin. Two electrodes are placed on the skin over the nerve. One electrode stimulates the nerve with a very mild electrical impulse and the other electrode records it. The resulting electrical activity is recorded by another electrode. This is repeated for each nerve being tested.

The nerve conduction velocity (speed) is then calculated by measuring the distance between electrodes and the time it takes for electrical impulses to travel between electrodes.

A related procedure that may be performed is electromyography (EMG). An EMG measures the electrical activity in muscles and is often performed at the same time as NCV. Both procedures help to detect the presence, location, and extent of diseases that damage the nerves and muscles.

Anatomy of the nervous system

Illustration of a nerve conduction velocity test

The nervous system is a complex, sophisticated system that regulates and coordinates body activities. It is made up of two major divisions, including the following:

  • Central nervous system. This consists of the brain and spinal cord.
  • Peripheral nervous system. This consists of all other neural elements.

Interpretation of the test results

The speed of nerve conduction is related to the diameter of the nerve and the degree of myelination (a myelin sheath is a type of “insulation” around the nerve). A normally functioning nerve will transmit a stronger and faster signal than a damaged nerve. This is kind of like an electric wire with rubber or plastic insulation around it. The larger the wire or electric cable and the better the insulation, the more consistent and stronger the signal.

In general, the range of normal conduction velocity will be approximately 50 to 60 meters per second. However, the normal conduction velocity may vary from one individual to another and from one nerve to another.

Abnormal results may be caused by some sort of neuropathy (damage to the nerve) that can result from a contusion or traumatic injury to a nerve. Various diseases can also cause the impulses to slow down.

Reasons for the procedure

Nerve conduction velocity is often used along with an EMG to differentiate a nerve disorder from a muscle disorder. NCV detects a problem with the nerve whereas an EMG detects whether the muscle is functioning properly in response to the nerve’s stimulus.

Diseases or conditions that may be evaluated with NCV include, but are not limited to, the following:

  • Guillain-Barré syndrome. A condition in which the body’s immune system attacks part of the peripheral nervous system. The first symptoms may include weakness or tingling sensations in the legs.
  • Carpal tunnel syndrome. A condition, in which the median nerve, which runs from the forearm into the hand, becomes pressed or squeezed at the wrist by enlarged tendons or ligaments. This results in pain and numbness in the fingers.
  • Charcot-Marie-Tooth disease. A hereditary neurological condition that affects both the motor and sensory nerves. One characteristic is weakness of the foot and lower leg muscles.
  • Herniated disk disease
  • Chronic inflammatory polyneuropathy and neuropathy.
    These are conditions resulting from diabetes or alcoholism.
  • Sciatic nerve problems
  • Pinched nerves
  • Peripheral nerve injury

Nerve conduction studies may also be performed to identify the cause of symptoms such as numbness, tingling, and continuous pain.

There may be other reasons for your doctor to recommend NCV.

Risks of the procedure

The voltage of the electrical pulses used during NCV is considered very low.

There may be risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.

Certain factors or conditions may interfere with the results of NVC test, such as damage to the spinal cord, severe pain before the test, and body temperature.

Tell your doctor if you have a cardiac defibrillator or pacemaker, as precautions may need to be taken.

Before the procedure

  • Your doctor will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.
  • You will be asked to sign a consent form that gives your permission to do the procedure. Read the form carefully and ask questions if something is not clear.
  • Generally, no fasting or sedation is required prior to the procedure.
  • Normal body temperature must be maintained before and during the procedure, as low body temperature slows nerve conduction.
  • Notify your doctor of all medications (prescribed and over-the-counter) and herbal supplements that you are taking.
  • Dress in clothes that permit access to the area to be tested or that are easily removed.
  • Stop using lotions or oils on your skin for a few days before your procedure.
  • Based on your medical condition, your doctor may request other specific preparation.

During the procedure

An illustration of a nerve conduction velocity test

A nerve conduction velocity procedure may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor’s practices.

The NCV is performed by a neurologist (a doctor who specializes in brain and nerve disorders), although a technologist may also perform some portions of the test.

Generally, a NCV procedure follows this process:

  1. You will be asked to remove any clothing, jewelry, hairpins, eyeglasses, hearing aids, or other metal objects that may interfere with the procedure.
  2. If you are asked to remove clothing, you will be given a gown to wear.
  3. You will be asked to sit or lie down for the test.
  4. A neurologist will locate the nerve(s) to be studied.
  5. A recording electrode will be attached to the skin over the nerve with a special paste and a stimulating electrode will be placed at a known distance away from the recording electrode.
  6. The nerve will be stimulated by a mild and brief electrical shock given through the stimulating electrode.
  7. You may experience minor discomfort for a few seconds.
  8. The stimulation of the nerve and the detected response will be displayed on an oscilloscope (a monitor that displays electrical activity in the form of waves).

After the procedure

The paste used to attach the electrodes will be removed from your skin.

After the test, you may return to your previous activities, unless your doctor advises you differently. Your doctor may instruct you to avoid strenuous activities for the rest of the day.

Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.

Electroencephalogram (EEG)

An electroencephalogram (EEG) is a test used to evaluate the electrical activity in the brain. Brain cells communicate with each other through electrical impulses, and an EEG can be used to help detect problems associated with this activity.

An electroencephalogram (EEG) is a test used to evaluate the electrical activity in the brain. Brain cells communicate with each other through electrical impulses, and an EEG can be used to help detect problems associated with this activity.

Why Is an EEG Performed?

An EEG is used to detect problems in the electrical activity of the brain that may be associated with certain brain disorders. The measurements given by an EEG are used to confirm, rule out, or provide information about disorders such as:

  • seizure disorders, including epilepsy
  • head injury
  • encephalitis, or inflammation of the brain
  • brain tumor
  • encephalopathy, or brain dysfunction resulting from various causes
  • memory problems
  • stroke
  • sleep disorders

An EEG can be used to monitor activity during brain surgery. It is also performed to determine the level of brain activity in someone who is in a coma.

An EEG cannot provide a measurement of intelligence and is not used to diagnose mental illness.

An EEG is used to detect problems in the electrical activity of the brain that may be associated with certain brain disorders. The measurements given by an EEG are used to confirm, rule out, or provide information about disorders such as:

  • seizure disorders, including epilepsy
  • head injury
  • encephalitis, or inflammation of the brain
  • brain tumor
  • encephalopathy, or brain dysfunction resulting from various causes
  • memory problems
  • stroke
  • sleep disorders
How Is an EEG Done?

Electrical impulses in the brain are evaluated using an EEG. The test measures this electrical activity through several electrodes placed on your scalp. An electrode is a conductor through which an electric current can pass safely. The electrodes transfer information from your brain through wires to an amplifier and a machine that measures and records the data.

The test is administered at a hospital, at your healthcare provider’s office, or at a laboratory by a specialized technician. The test usually involves the following steps:

  • You will be asked to lie down on your back in a reclining chair or on a bed.
  • The technician will measure your head and use a pencil to mark where electrodes will be attached to your scalp. These spots are then scrubbed with a special cream that helps the electrodes get a high-quality reading.
  • The technician will put a sticky gel adhesive on 16 to 25 electrodes and will place these electrodes at various spots on your scalp. The electrodes look like flat metal disks.
  • Once the test begins, the electrodes send electrical impulse data from your brain to the recording machine. This machine converts the electrical impulses into visual patterns that can be seen on a screen and are saved to a computer. On the screen, the electrical impulses look like wavy lines with peaks and valleys.
  • You may be directed by the technician to do certain things while the test is in progress, such as lie still, close your eyes, breathe deeply or quickly, or look at stimuli like a flashing light or a picture.
  • The EEG usually takes 30 to 60 minutes.
  • After the test is complete, the technician will remove the electrodes.

During the test, very little electricity is passed between the electrodes and your skin. The electrodes do not send any sensations, and you will feel little to no discomfort.

Are There Risks Associated With an EEG?

There are no risks associated with an EEG. The test is painless and safe.

In the case of testing people with epilepsy and other seizure disorders, the stimuli presented during the test, such as a flashing light or fast breathing, may cause a seizure. The technician performing the EEG is trained to safely manage patients, if this is to occur.

How to Prepare For an EEG

The following should be done prior to having an EEG:

  • Wash your hair the night before the EEG and do not put any products, such as conditioners, sprays, or gels in your hair before the test.
  • Check with your doctor to see if you should stop taking any medications before the test and bring a list of your medications to give to the technician performing the EEG.
  • Avoid any food or drinks with caffeine for eight hours prior to the test.
  • If you are required to sleep during the EEG, your doctor may ask you to sleep as little as possible before the test. Also, you may be given a sedative to help you to relax and sleep before the test begins.

What Can I Expect After the EEG?

After the EEG is finished and the technician removes the electrodes from your scalp, you should not feel any side effects from the test, and you can continue with your regular routine for the day.

However, if you were given a sedative, the medication will be in your system for a short while. You will need someone to take you home after the test, and you will be instructed by the technician to rest and not drive for the rest of the day.

How Do I Find Out Results from the EEG?

A specialized doctor interprets the recordings taken from the EEG and then sends the results to the doctor that ordered the test for you. Your doctor may schedule an appointment to go over the test results. It may be helpful to write down any questions you might want to ask your doctor about the results. Be sure to speak up if there is anything about the results that you do not understand.

Normal Results

Electrical activity in the brain is seen in an EEG as a pattern of waves. Different levels of consciousness, such as sleeping and waking, have a specific range of frequencies of waves per second that are considered to be normal. For example, the wave patterns move faster when you are awake than when you are asleep. The EEG will show if the frequency of waves or patterns are normal.

Abnormal Results

Abnormal EEG results may be due to:

  • epilepsy or other seizure disorder
  • abnormal bleeding or hemorrhage
  • sleep disorder
  • swelling of the brain or encephalitis
  • tumor
  • problems with attention
  • death of tissue because of a blockage of blood flow or cerebral infarction
  • migraines
  • alcohol or drug abuse
  • head injury

We have also the facilities of:

  • Brain CT, Cerebral angiogram with 128 Slice Ultrafast PET-CT Scan, MDCT
  • Brain MRI with 1.5 Tesla MRI
  • Brain MRI with Open Gantry MRI
  • Digital X-Ray Myelogram
  • Neurosonology by Ultrasound
  • Neurologist Consultation
  • Neurosurgeon Consultation