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Speech Characteristics of Parkinson's Disease

Akinesia, or inability to control small muscle movements, is one of the distinctive features of Parkinson's disease. The akinetic mechanism that's involved affects not only the motor activities but also the speech characteristics.

  1. Speech Characteristics

    • A person with Parkinson's disease exhibits monotonous (constant tone) quality, difficulty in changing tempo (speed), decreased amplitude (loudness) and in some cases a sustained voice. The speech disturbance varies for each patient, depending on the progression of the disease.

    Probable Cause

    • One of the probable causes of speech disturbance in patients with Parkinson's disease is akinesia. The akinetic mechanism induces continuous pressure on muscles so that it repetitively performs movements, which are, in fact, simple involuntary actions to a normal person.

    Rationale

    • In Parkinson's disease, the dopamine deficiency resulting in neuron imbalance in the brain causes muscle weakness (rigidity). This state of weakness makes it hard for patients to control or resist the constant force from akinetic mechanisms.

    Cranial Nerve

    • The sustained forceful contraction (akinesia) of weak muscles (rigidity) produces lesions to cranial nerves of the brain. The specific cranial nerve affected is called trigeminal (cranial nerve V - shown in image 1). This is also responsible for the regulation of swallowing, speaking, smooth muscle contractions, reflex actions and kinesthesia (sense of position).

    Speech Muscle

    • The intrinsic muscles of the larynx (stylohyoid) controlled by the trigeminal nerve are subjected to forceful contraction producing abnormal speech characteristics of Parkinson's disease (shown in image 2).
      Note that in reality, many factors (age, nutrition, other diseases) could affect the speech disturbance exhibited in this type of neurological disorder.

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