Progress and Prospects in Parkinson's Research/Symptoms/Aphonia

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Aphonia

Inability to make sounds

The following references are relevant:-

Critchley (1981)  Speech disorders of Parkinsonism: a review 

Russell et al (2010) Targeted exercise therapy for voice and swallow in persons with Parkinson’s disease 

Hallett (2011)  Psychogenic Parkinsonism