Levodopa Use by Early-stage Patients Not Seen to Ease Speech Problems
Short-term treatment with levodopa does not significantly ease speech difficulties in people with early Parkinson’s disease, a new study indicates.
Results suggest that monitoring changes in speech could be useful for tracking the progression of Parkinson’s in patients on treatment.
The study, “Short-term effect of dopaminergic medication on speech in early-stage Parkinson’s disease,” was published in npj Parkinson’s Disease.
Parkinson’s is caused by the death and dysfunction of brain cells that make dopamine, a signaling molecule (neurotransmitter) that nerve cells use to communicate with each other.
Among the disease’s symptoms, as many as 90% of patients experience speech difficulties, a condition known as hypokinetic dysarthria. People with Parkinson’s and hypokinetic dysarthria often have a voice that is unusually quiet, with less inflection in tone, and imprecise articulation that sounds like slurring.
Levodopa and its derivatives are a standard part of Parkinson’s therapy; these medications basically work by giving the brain more raw materials with which to make dopamine, ultimately boosting its levels. It is well-established that levodopa’s use can ease Parkinson’s motor symptoms. However, its effect on speech is unclear, as prior studies have yielded inconsistent results.
Scientists in the Czech Republic conducted computer-based speech analyses of 60 Parkinson’s patients. For each patient, two analyses were taken: one before levodopa treatment, and one about an hour after taking levodopa (when the medication is in full effect). For comparison, the analysis also included 30 people without Parkinson’s but of similar age as controls.
Patients were divided into two groups based on the extent that levodopa eased their motor symptoms: responders (30 patients) and non-responders (30 patients).
Results showed that, compared with controls, Parkinson’s patients scored significantly poorer in measures of consonant articulation and pitch variation.
Statistical analyses generally revealed no significant differences in voice qualities among either Parkinson’s group before and after treatment.
“No effect of levodopa was found on voice and speech performances in any PD [Parkinson’s disease] subgroup, despite the PD responders subgroup manifested obvious improvement in motor function after levodopa intake,” the researchers wrote.
These results suggest “that speech could be considered as a PD symptom resistant to short-term levodopa treatment,” they wrote.
Based on these findings, the researchers proposed that monitoring changes in speech could be a useful way to assess Parkinson’s progression, even in people who are on treatments that control their motor symptoms.
“Our results indicate that evaluation of speech impairment is more stable and not easily influenced by short-term variations in dopaminergic [dopamine-replacing] medication dose,” they wrote. “Therefore, speech could be used as a complementary motor marker of disease severity that may be less affected by fluctuating [blood] levels of dopaminergic drugs.”