New test to improve diagnosis of violent sleep disorder

By / 4th of September, 2014
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NEW software designed by researchers at the Adelaide Institute for Sleep Health (AISH) has the potential to significantly improve the diagnosis of Rapid Eye Movement (REM) sleep behaviour disorder (RBD) – a condition characterised by men acting out violent dreams, often on their partner.

RBD is a little known sleep disorder which occurs during the REM, or dreaming, stage of sleep.

During normal REM sleep a person’s muscles should relax totally, however in RBD cases it is believed abnormal brain signals maintain higher levels of muscle tension, allowing dream-related body movement.

Common features of RBD include abnormal and often violent behaviours, such as shouting, punching, kicking and choking, which occur in response to dreams that are threatening, distressing and often vividly recalled.

While an effective medication is available for patients with RBD, it is likely that many cases go untreated due to a lack of awareness of the condition, the often lengthy period of time between symptom onset and diagnosis, as well as limitations around current diagnostic practice.

Today, diagnosis of RBD relies heavily on the clinical history of both the patient and their partner – who may have been injured during an episode – as well as a polysomnogram (the measurement of muscle activity during a laboratory-based sleep test).

However what constitutes ‘abnormal’ activity is subjective and needs to be clinically determined.

AISH Psychiatrist Dr Richard Weeks and Chief Scientist Associate Professor Peter Catcheside are leading a study to develop a computer-based automated scoring system which can be applied to the polysomnogram (PSG).

The new software will help to define normal reference ranges for muscle activity during REM sleep.

“The development of better diagnostic methods for RBD is crucial to standardise the measurement of muscle tone, or tension, in patients suspected of having RBD, as many other factors can potentially interfere with the interpretation of the results correctly,” Dr Weeks said.

“These include other sleep conditions such as Obstructive Sleep Apnoea, various medical and psychiatric conditions, such as Post Traumatic Stress Disorder, as well as medications including anti-depressants.”

Dr Weeks said providing more accurate diagnosis of RBD was critical due to the significant risk of injury faced by RBD patients and their partners, along with the rising number of cases being identified by AISH – a trend he predicts will continue.

“This increase is cause for concern as it can be difficult to diagnose RBD with our current assessment methods and it is very likely that a significant number of cases remain unidentified and untreated, resulting in ongoing and potentially significant sleep-related injury,” he said.

While both sexes and any age group can be affected by RBD, males aged 50 years and over account for 90 per cent of cases, and as many as 40 to 80 per cent of patients will develop a neurological condition such as Parkinson’s disease within five to 15 years of diagnosis.

“From a clinical perspective, a validated scoring system will improve the sensitivity and specificity of the diagnosis of RBD, allowing for early appropriate treatment,” he said. “In addition, patients would also benefit from the early diagnosis and treatment of associated neurological diseases.”

The development of reference ranges will be based on 28 patients identified as having RBD using the current diagnostic criteria. Laboratory based testing previously performed on these patients will be subjected to repeat analysis using the new software.

The researchers hope to secure funding to pursue a larger trial of the new software in RBD patients.