Speech Problems in Patients May Indicate Freezing of Gait Risk

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by Steve Bryson, PhD |

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Speech impairments appear to associate with freezing of gait symptoms — a sudden inability to walk — in people with Parkinson’s disease, a study reported.

Speech assessments, especially during the “on-state” of medication use — immediately after taking dopamine-based medicines — may identify Parkinson’s patients vulnerable to freezing of gait, its scientists noted.

The study, “Parkinson’s disease patients with freezing of gait have more severe voice impairment than non-freezers during ‘ON state’,” was published in the Journal of Neural Transmission.

Freezing of gait (FOG) is characterized by a sudden and brief inability to walk when starting to walk, turn, or when facing an obstacle. FOG increases the risk of falls which can affect quality of life.

FOG can ease with medications such as levodopa and its derivatives that replace dopamine, the nerve cell signaling molecule lacking in people with Parkinson’s. FOG commonly occurs during a so-called “off-state,” when dopamine-based medications wear off or become less effective.

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Speech disorders are also common in Parkinson’s, affecting up to 90% of patients. Collectively known as hypokinetic dysarthria, these deficits include low speech volume, hoarseness, pronunciation difficulties, monotone pitch, and variable speech speed.

Studies suggest speech problems and FOG may share underlying disease-related mechanisms, and that voice impairment during an “on-state” may indicate a vulnerability to FOG.

Researchers with Chongqing Medical University in China compared the voice characteristics of Parkinson’s patients experiencing FOG (PD-FOG) to those without FOG (PD-nFOG) during an “on-state” to determine whether speech impairment can identify those susceptible to FOG.

“We hypothesized that PD-FOG would manifest greater voice impairment severity than PD-nFOG ‘ON state’ voice features,” and may help to distinguish between these patient groups, the team wrote.

The study enrolled 40 adults with Parkinson’s, ages 50 to 75, diagnosed with FOG based on a questionnaire and a motor test. All were considered dopamine-responsive because their FOG occurred mainly during an “off state.”

A group of 40 age-, sex-, and disease duration-matched Parkinson’s patients without FOG were also recruited, as well as 40 age- and sex-matched healthy controls without speech impairments. Researchers conducted clinical and speech assessments one to two hours after patients received their dopamine-based medications.

Relative to patients without FOG, those with FOG had more severe disability, as assessed by Hoehn and Yahr (H&Y) stage and UPDRS III scores (which rates the severity of Parkinson’s motor symptoms), and a higher levodopa equivalent daily dose (LEDD), the combined total of Parkinson’s medications.

FOG was also associated with body rigidity and slowness of movement (bradykinesia), posture impairment and gait disorder (PIGD), and a worse voice handicap index — a patient-reported questionnaire on perceived speech impairment. There were no differences in tremor scores between these two groups.

To assess speech, all participants were also asked to pronounce the vowels “a,” “u,” and “e” as long as possible in one breath. Voices were recorded and 27 speech features, including variations in frequency (tone) and amplitude (loudness), were analyzed. Adjustments were made for H&Y stage, LEDD, and UPDRS III scores.

Relative to participants without FOG, those with FOG had measured voice features that were significantly different, including variations in frequency, called jitter, and in fundamental voice frequency (lowest tone).

Pulse periods between words were different, as well as the maximum phonation time (to sustain the “ah” sound) and the noise-to-harmonics ratio, used to analyze vocal acoustics by measuring the ratio between periodic and non-periodic components of speech.

During the “a” sound, FOG patients had significantly more voice jitter, both by percentage and absolute amount, a different pulse period and noise-to-harmonics ratio, and a shorter maximum phonation time compared with non-FOG patients. With the “e” sound, FOG patients were associated with a different noise-to-harmonics ratio, and voicing the “u” sound linked with a lower fundamental frequency.

Because the vowel “a” showed the most significant difference between the two groups, researchers compared these voice data with motor symptom scores.

Greater posture impairment and gait disorder (PIGD) scores correlated with a higher percentage of voice jitter, different noise-to-harmonics ratio and pulse periods, and a shorter maximum phonation time. Rigidity scores were associated with jitter, noise-to-harmonics ratio, and maximum phonation time. No voice parameter was related to tremor and bradykinesia.

Voice impairments more strongly correlated with body rigidity in male patients and with the FOG questionnaire and PIGD in female patients.

The ability of the speech impairment test to accurately predict FOG based on the three vowel sounds was 75.6%. The test’s specificity to correctly identify people with FOG was 75.7%, and its sensitivity in identifying patients without FOG was 71.4%.

“Our results suggest that [Parkinson’s disease] with dopamine-responsive FOG have more severe voice impairment than PD-nFOG during ‘ON state’, and voice features of sustained vowel phonation may reflect FOG to some extent,” the scientists concluded.

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