Electromyography (EMG) – is a test that is used to record the electrical activity of muscles. When muscles are active, they produce an electrical current. This current is usually proportional to the level of the muscle activity. An EMG is also referred to as a myogram.EMGs can be used to detect abnormal electrical activity of muscle that can occur in many diseases and conditions, including muscular dystrophy, inflammation of muscles, pinched nerves, peripheral nerve damage (damage to nerves in the arms and legs), amyotrophic lateral sclerosis (ALS), myasthenia gravis, disc herniation, and others.
Autonomic Nervous System tests – measure how the systems in the body that are controlled by the autonomic nerves respond to stimulation. The data collected during testing will indicate if the autonomic nervous system is functioning as it should, or if nerve damage has occurred.
Nerve Conduction Studies (NCS) – A nerve conduction velocity test (NCV) is an electrical test that is used to determine the adequacy of the conduction of the nerve impulse as it courses down a nerve. This test is used to detect signs of nerve injury. In this test, the nerve is electrically stimulated, and the electrical impulse ‘down stream’ from the stimulus is measured. This is usually done with surface patch electrodes (they are similar to those used for an electrocardiogram) that are placed on the skin over the nerve at various locations. One electrode stimulates the nerve with a very mild electrical impulse. The resulting electrical activity is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to calculate the speed of impulse transmission (nerve conduction velocity). A decreased speed of transmission indicates nerve disease. A nerve conduction velocity test is often done at the same time as an electromyogram (EMG) in order to exclude or detect muscle conditions.
Electroenecephalography/Routine EEG – is the most common test for epilepsy. The EEG technologist first measures the patient’s head so that the electrodes, which are small, metal, cup-shaped disks attached to wires, can be placed in the correct position. A wax crayon, which can be easily washed off later, is used to mark the points on the scalp. Next, the technologist applies the electrodes, usually using a paste that holds them in place for up to several hours. The technologist often scrubs each position on the scalp with a mildly abrasive cream before applying the electrodes. This will help improve the quality of the recording.
The electrodes only record the brain waves. They do not stimulate the head with electricity, and pose no danger to the patient. The EEG machine then records the brain waves as a series of waveforms called traces. Recordings on paper are now mostly replaced by computerized, paperless EEG.
Prolonged Video-EEG monitoring – As with ambulatory EEG, the electrodes used for video-EEG recording are also glued to the scalp with collodion, although in special situations, paste may be used. Inpatient monitoring with close supervision allows the doctor to reduce and, in some cases, discontinue antiepileptic drugs safely. The medication reduction and possibly sleep deprivation, hyperventilation, exercise, or occasionally alcohol intake may be used to induce seizures. Video-EEG can be vital in the diagnosis of epilepsy and epileptic seizures. It allows the doctor to determine:
- Whether events with unusual features are epileptic seizures
- The type of epileptic seizure, and
- The region of the brain from which the seizures arise
Ambulatory EEG Event monitoring -The brain’s electrical activity fluctuates from second to second. The routine EEG provides a 20- to 40-minute sample of brain electrical activity, which is often sufficient. In some patients with epilepsy, however, this recording is normal or shows only minor, nonspecific findings. In such cases, an extended recording that includes long periods of wakefulness and sleep is desired. For example, in some people, epilepsy waves occur only once every 3 or 4 hours or only after an hour of sleep, and a routine EEG will almost always be normal. An ambulatory EEG, on the other hand, can record up to 72 hours of EEG activity with a special recorder that is slightly larger than a portable cassette player. This recorder allows you to go about your normal routine while the EEG is being recorded. Our understanding of epilepsy has been greatly advanced by video-EEG monitoring, which allows prolonged simultaneous recording of the patient’s behavior and the EEG. Seeing EEG and video data at the same time permits precise correlation between seizure activity in the brain and the patient’s behavior during seizures.
Polysomnography/Baseline Sleep Study – Continuous recording of specific physiologic variables during sleep. Polysomnography typically records brain wave changes (electroencephalogram), eye movements (electrooculogram), muscle tone (electromyogram), respiration, electrocardiogram (EKG), and leg movements.
Continuous positive airway pressure (CPAP)/Treatment – is probably the best, non-surgical treatment for any level of obstructive sleep apnea. In finding a treatment for obstructive sleep apnea, the primary goal is to hold the airway open so it does not collapse during sleep. The dental appliances and surgeries (described later) focus on moving the tissues of the airway. CPAP uses air pressure to hold the tissues open during sleep.
CPAP was first used in Australia by Dr. Colin Sullivan in 1981 for obstructive sleep apnea. It delivers the air through a nasal or face-mask under pressure. As a person breathes, the gentle pressure holds the nose, palate, and throat tissues open. It feels similar to holding your head outside the window of a moving car. You can feel the pressure, but you can also breathe easily.
The CPAP machine blows heated, humidified air through a short tube to a mask. The mask must be worn snugly to prevent the leakage of air. There are many different masks, including nasal pillows, nasal masks, and full-face masks. The CPAP machine is a little larger than a toaster. It is portable and can be taken on trips.
Determining CPAP pressure: With CPAP it is important to use the lowest possible pressure that will keep the airway open during sleep. This pressure is determined by “titration.” Titration frequently is performed with the help of polysomnography. It can be performed during the same night as the initial polysomnography or on a separate night. In the sleep laboratory an adjustable CPAP machine is used. A mask is fit to the person and he or she is allowed to fall back asleep.
During baseline sleep the apneas and hypopneas occur, and the the technician then slowly increases the CPAP pressure until the apneas and hypopneas stop or decrease to a normal level. A different pressure may be needed for different positions or levels of sleep. Typically, laying on the back and REM sleep promote the worst obstructive sleep apnea. The lowest pressure that controls obstructive sleep apnea in all positions and sleep levels is prescribed.
Effectiveness of CPAP: CPAP has been shown to be effective in improving subjective and objective measures of obstructive sleep apnea.
- It decreases apneas and hypopneas.
- It decreases sleepiness as measured by surveys and objective tests.
- It improves cognitive functioning on tests.
- It improves driving on driving simulation tests and decreases the number of accidents in the real world.
When adjusted properly and tolerated, it is nearly 100% effective in eliminating or reducing obstructive sleep apnea.
An important clinical outcome of CPAP use is in the area of prevention of the potential complications of obstructive sleep apnea. Studies have shown that the proper use of CPAP reduces hospitalization for cardiac and pulmonary causes in people with obstructive sleep apnea. More generally, treating obstructive sleep apnea with CPAP can reduce the risks of conditions related to obstructive sleep apnea, such as, ischemic heart disease, abnormal heart rhythms, stroke, hypertension, and insulin dependence.
The Multiple Sleep Latency Test (MSLT) – is a daytime sleep study that measures how sleepy you are. It’s typically done the day after a polysomnogram (PSG). The MSLT is primarily used to diagnose excessive daytime sleepiness and narcolepsy.