Transcranial sonography and RLS.(SLEEP MEDICINE)(Restless legs syndrome)(Report)

A person with restless leg syndrome has uncomfortable, irritating or painful sensations in the legs that usually manifest as the person is settling down before going to sleep. The sensations may feel like burning, tugging, or insects creeping or crawling inside. To relieve the sensations, the person feels an irresistible urge to move his legs by walking, rubbing them, stretching, etc.

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These actions only bring short relief. Inevitably, the RLS sufferer must continue to move his or her legs to bring about relief once again. This process can last up to several hours and prevent the person from going to sleep at a desired time. The sensations usually subside with the onset of sleep. But if the person awakens, the sensations may resume and once again interfere with sleep. This can subsequently result in daytime sleepiness.

Scientists are not sure why RLS occurs. One possibility may be that it results from a dysfunctional neurological process in the brain. Brain imaging technology has revealed some differences in the brains of people with and without RLS. Most recently, transcranial sonography has found that the substantia nigra (SN) in people with RLS has a decreased echogenicity--in other words, a decreased ability to return a signal in response to an ultrasound signal. This feature may some day be useful in diagnosing people with RLS.

Sonography, also called ultrasonography, uses ultrasound waves to visualize structures within the body. When ultrasonic signals are transmitted through a body tissue, a portion of the waves passes through the tissue while a portion of the waves bounces back toward the source of the ultrasound signal.

Continuous wave Doppler sonography and pulsed wave Doppler sonography are commonly used. In continuous wave Doppler sonography, a transducer contains two piezoelectric crystals, which convert electrical impulses into sound waves and vice versa. One crystal in the transducer continually transmits ultrasound waves through a tissue while the second crystal continually records the reflected signals. The strength of the reflected signals is plotted as a waveform called an A-scan (A stands for "amplitude"). The vertical axis of the wave represents the strength of the returned signal, and the horizontal axis represents the time it takes for the signal to return to the transducer.

In pulsed wave Doppler sonography, the transducer contains one crystal which sends a pulse of ultrasound waves through a tissue, waits for the signal to return, and then records the strength of the reflected signals before sending out another pulse of waves. The greater the distance a wave travels, the longer it takes for the signal to return when it is reflected.