Speech and language therapy versus placebo or no intervention for dysarthria in Parkinson's disease

Deane K, Whurr R, Playford ED, Ben-Shlomo Y, Clarke CE

Summary

Many people with Parkinson's disease suffer from disorders of speech. These are characterised by speech that is quiet, hoarse and breathy. People with the condition also tend to give fewer non-verbal cues, such as facial expressions and hand gestures. These disabilities tend to increase as the disease progresses and can lead to serious problems with communication.

This review will compare the benefits of speech and language therapy versus placebo (sham therapy) or no treatment for speech disorders in Parkinson's disease. Relevant trials were identified by electronic searches of 21 medical literature databases, various registers of clinical trials and an examination of the reference lists of identified studies and other reviews.

Only randomised controlled trials were included in this review. These were studies where two groups of patients were compared, one group of patients had speech and language therapy, the other was untreated. The patients were assigned to each of the groups in a random fashion so as to reduce the potential for bias.

Three trials were found comparing speech and language therapy with an untreated group in 63 patients. The quality of the trials' methods was variable with all studies failing in at least one critical area. All three of the controlled trials reported a positive effect of speech and language therapy for speech disorders in Parkinson's disease. Many of the outcome measures examined appeared to improve by a clinically significant amount after therapy.

Considering the flaws in the studies' methods, the small number of patients examined, and the possibility that studies with a negative result were not published (publication bias), there is insufficient evidence to prove or disprove the benefit of speech and language therapy for the treatment of speech disorders in people with Parkinson's disease. However it should be emphasised that this lack of evidence does not mean lack of effect.

A large well designed placebo-controlled randomised trial is needed to assess the effectiveness of speech and language therapy for speech disorders in Parkinson's disease. Outcome measures with particular relevance to patients should be chosen and the patients followed for at least 6 months to determine the duration of any improvement. As there does not appear to be a consensus as to the 'standard' form of speech and language therapy to use to treat dysarthria in Parkinson's disease, a survey of therapists is needed to determine what methods of speech and language therapy are currently being used by therapists to treat Parkinsonian dysarthria, and whether there is a consensus as to 'best-practice'. This could then be used to inform the design of the randomised controlled trial.