What is a Electroencephalogram (EEG)?
An electroencephalogram (also called EEG) is a diagnostic tool used to record, measure and monitor the brain’s electrical activity with the use of special sensors (or electrodes) that are superficially attached from the scalp. These electrodes are attached to a specialized computer so that the behavior of electric waves can be studied by the physician in order to arrive with a specific diagnosis.
The human brain is composed of a complex network of nerves which uses electrical impulses that are passed from one nerve to another in order to send thoughts, emotions, and commands. The constant traffic of incoming and outgoing electrical signals may come from within various parts of the body and external environment. The patterns of electrical waves that occur in the brain in response to touch, sound, light and stress (such as lack of sleep) are recorded by an EEG in order to aid in identifying the underlying cause of a disease or condition. A deviation from the normal trend of electrical impulses within the brain may be a sign of a medical abnormality. In this case, an EEG may be ordered by a physician.
Why are EEGs performed?
EEGs are performed to rule out, provide information or confirm the diagnosis of a condition or disease. Some of which are, but not limited to, the following:
- Sleep disorders like
- Brain infections or the collection of fluid in the brain
- e.g. Meningitis
- Brain hemorrhage
- Degenerative brain disorders like
- Metabolic conditions that affect brain tissue
- Hormonal conditions that affect brain tissue
- Stroke or cerebrovascular accident (death of brain tissues because of a blockage in blood flow)
- Malignancies and tumors of the brain
- Establish the brain function of coma patients
- Head injuries and trauma
The results of EEG are typically deciding factors in the course of treatments prescribed.
How does an Electroencephalogram work?
Small electrodes (wires) attached to the scalp with paste are used to amplify electrical signals from the brain. These electrodes are connected to a polygraph machine or computer to record and graphically present brain signals in a wave-like pattern. For example, a spike seen on the EEG graph may indicate an abnormal burst of electricity indicative of typical epileptic activity.
There are several types of EEGs. Depending on the disease condition that is being ruled out, your physician will determine which among the following types of EEGs will be used in order to get a useful reading of your brain’s electrical signals.
- Sleep EEG: Sleep EEGs are done while the patient is asleep or when tired. This is usually done within the hospital premises.
- Sleep Deprived EEG: This type of EEG is done while the patient is asleep, only that the patient is intentionally kept awake and deprived of sleep. This is to assess the effect of sleep deprivation in the brain waves.
- Ambulatory EEG: Ambulatory EEG is carried out if a normal EEG gives an ambiguous result. The patient is given a portable EEG device which records the brain waves while the patient performs normal daily activities.
- Video-Telemetry: Video telemetry is ambulatory EEG combined with a camera that records the patient’s brain waves correlated with a video image of the patient’s activities. Video-telemetry is prescribed if the diagnosis for seizure is unclear.
When is an Electroencephalogram ordered?
EEG is ordered to rule out and identify the presence of a neurologic disorder, such as seizures and sleep disorder. EEGs are also useful to assess the extent of damage caused by nerve lesions (such as nerve damage found in brain stroke, physical trauma), and other psychiatric conditions like dementia and Alzheimer’s disease. In children, an EEG may be useful in diagnosing obstructive sleep apnea (complete or partial blockage of upper airway passage while sleeping, characteristically manifested by snoring).
How is Electroencephalogram done?
Around 20 electrodes with wires are placed on a patient’s scalp. Before the test, the patient should ensure that their hair is clean and free from any wax, gel or styling products. No hair accessories can be worn. Patients may eat before the test but should refrain from drinking caffeinated beverages at least 4 hours before the procedure. During the procedure, the technician may ask you to do a certain task such as standing, sitting and may even display flashing light to your eyes. Most of the time, you will be lying on a reclining chair with eyes closed.
What to expect after the procedure?
The paste applied on your scalp will be cleaned off and the electrodes will be removed quickly. EEGs are generally painless and safe, and the patient may go home right after the procedure. The results will be evaluated by a physician to study the trend of brainwaves in order to correlate results to diagnosis.
What is Electromyography (EMG)?
Muscles need electric signals in order to contract and produce movement. Electromyography (also called EMG) is a diagnostic procedure done to evaluate the health of muscles which are under voluntary control (skeletal muscles) and record its electrical activity based on how nerves control them.
Electromyography uses an electromyograph, a machine that allows the physician to see a graphical form of electrical signals to observe and interpret trends of electricity generated by the muscles in response to stimulation and movement.
Why is EMG Performed?
An EMG is prescribed usually when patients experience muscle weakness, muscle pain, cramps, tingling sensation, numbness and all other symptoms related to muscular discomfort. EMG will help physicians get a definite diagnosis and rule out other disease conditions.
The following conditions are common indications for EMG:
- To establish presence of muscle disorders (e.g muscular dystrophy or polymyositis)
- To identify diseases which affects the connection between the nerve and the muscle (e.g. myasthenia gravis)
- To establish presence of nerve disorders outside the spinal cord (peripheral nerves), such as carpal tunnel syndrome or peripheral neuropathies
- To establish and diagnose disorders affecting neurons inside the brain and spinal cord that are mainly responsible for bodily movement (e.g. amyotrophic lateral sclerosis or poliomyelitis)
- To identify nerve root disorders (e.g. herniated disk of the spine)
Types of EMG Tests
There are several types of EMGs which may vary, depending on the purpose of the procedure.
- Needle EMG (Intramuscular EMG): Needle EMG is performed by inserting a small, thin disposable needle through a group of muscles that are suspected to cause discomfort. As the needle is inserted, the patient might feel a small amount of pain. The needle will pick up electric signals generated by the muscles, and then send it to the EMG machine so that the doctor could observe its trend.
- Nerve Conduction Studies: Nerve conduction studies help to understand how effective the flow of electricity through nerves. The physician applies a small amount of mild, tingling electrical shock to the nerve. Nerve conduction tests could be helpful in diagnosing carpal tunnel syndrome, Guillain-Barre syndrome and spinal disc herniation.
- Evoked potentials: Also known as ‘evoked response’, Evoked potentials is a method of EMG testing which checks the nerve pathways and evaluates the amount of time it takes for nerves to respond to stimulation. This test works by stimulating senses such as vision (Visual-evoked response), hearing (auditory brainstem evoked response), or by stimulating the arms and the legs through electrical pulse (somatosensory evoked response).
What are the Diseases/Conditions EMG is typically indicated for?
EMGs are commonly performed to aid in the diagnosis of these diseases:
- Carpal tunnel syndrome
- Cubital Tunnel Syndrome
- Guillain-Barre syndrome
- Guyon’s canal syndrome
- Peripheral neuropathy
- Peroneal neuropathy
- Spinal disc herniation
- Tarsal Tunnel Syndrome
- Ulnar neuropathy
- Neuromuscular Junction Disorders
- Multiple Sclerosis
- Myasthenia Gravis
How is EMG performed?
Before the procedure, you will be asked to wear loose clothing to allow easy access to the site where electrodes/needles will be placed. You should also refrain from applying lotions and oils to the skin. People with a pacemaker, a medical implant which keeps the heartbeat in the proper rhythm, should inform the operator before EMG is done.
During the procedure, you will be asked to remove all jewelry, hair accessories and all other metal objects. The patient may be asked to lie down or to sit during the test. An antiseptic solution will be used to clean the skin before the sterile disposable needle is inserted into the muscle. There will be slight pain as the needle is inserted but in In general, EMGs are a painless procedure.
For nerve conduction tests, a special lubricant may be applied to the skin before patches of electrodes are attached. You may feel a brief period of shock as a small amount of electricity flows through the electrode.
What to expect after the procedure? Are there any risks?
Muscle soreness may be felt in the site of injection after the procedure. If you notice bleeding, or pain that is increasing, accompanied by swelling and pus in the injection site, notify your physician.