Sleep studies are performed to evaluate patients for various sleep disorders. These disorders include:
- Obstructive and central sleep apnea.
- Disorders resulting in excessive daytime sleepiness. The most well known disorder in this category is narcolepsy.
- Problems with nighttime behaviors, such as sleepwalking, night terrors, or REM behavior disorder.
- Periodic limb movement disorder.
After the sleep study is performed each 30-second page is hand scored for sleep, as well as abnormalities of breathing, movement and heart-rhythm. A sleep expert interprets the study and a report is written.
The most common sleep studies are:
- Polysomnogram. This is the typical nighttime sleep study. It includes measurement of brain activity, eye movements, chin muscle activity, oxygen levels, heart rate and rhythm, breathing rate, airflow, snoring, limb movements, and chest and abdominal movements. Special procedures may also be added, as needed.
- Multiple sleep latency test (MSLT). This test consists of a series of naps performed throughout the day, and provides an objective assessment of daytime sleepiness. It is typically done the day after a polysomnogram.
- Multiple wake test (MWT). Like the MSLT, this is a daytime study. However, unlike the MSLT, the MWT measures a patients’ ability to stay awake.
Neurovascular Ultrasound Laboratory - Carotid Doppler and Transcranial Doppler
The Neurovascular Ultrasound Laboratory uses state-of-the art equipment to provide comprehensive assessments of blood flow to the brain by ultrasound.
Carotid Doppler ultrasound studies (also known as Extracranial Doppler), primarily examine the carotid arteries, which are the main arteries in the front of neck that supply blood to the brain. The studies look for blockages that can cause strokes and transient ischemic attacks (TIA).
In transcranial Doppler (TCD) ultrasound studies, arteries inside the skull are examined again to look for blockages and also to assess the amount of blood flowing towards the brain.
In both types of study, a small probe (about ½ inch in diameter) is placed on the skin over the arteries and non-invasively detects blood flow by ultrasound. A small amount of gel is placed between the probe and the skin to create a smooth contact so that the probe can detect blood flow.
In addition, TCD is also used to detect certain types of heart and lung problems that cause strokes. TCD can identify conditions in which clots that form in the legs or elsewhere in the body can bypass the lungs, which normally filter them out, and pass instead directly through the heart to arteries in the brain and cause strokes. TCD can also be used to monitor for tiny clots that travel from the heart or from arteries in the chest or neck and can cause strokes by lodging in arteries that supply blood to the brain.
Video-EEG Monitoring Procedure
Video-EEG monitoring has emerged as the "gold standard" for the diagnosis of nonepileptic seizures (NESs) and for characterization of complex seizure disorders. The procedure requires hospital admission for 4-5 days. During video-EEG monitoring, the patient wears an EEG transmitter connected to a wall outlet by coaxial cable. Ceiling mounted video cameras provide continuous behavioral observation. Both EEG and video signals are synchronized and are displayed simultaneously for on-line observation by the physician. The EEG recorded is also stored on optical disc and is available for later review.Although more costly than routine outpatient EEG studies, inpatient video-EEG monitoring is very useful for characterization of complex seizure disorders. Inpatient monitoring also allows recording of a full night's sleep, increasing the possibility of recording sleep-provoked epileptiform activity as well as nocturnal clinical events. All this improves diagnostic certainty and is very helpful in making treatment decisions and choosing the right seizure medication. During the study, the patient can move about and carry out normal activities, such as talking, reading and watching television.