Abnormal laughter-like vocalisations replacing speech in primary progressive aphasia.

Area of Science:

• Neurology
• Linguistics
• Speech-Language Pathology

Background:

• Primary progressive aphasia (PPA) is a neurodegenerative disorder affecting language.
• Patients with PPA typically experience progressive impairment in speech output.
• Abnormal vocalizations are not a commonly recognized feature of PPA.

Purpose of the Study:

• To describe a series of patients with PPA who developed abnormal laughter-like vocalizations.
• To investigate the characteristics and potential underlying mechanisms of these vocalizations.
• To determine if this vocal behavior represents a distinct PPA subgroup.

Main Methods:

• Case series description of ten patients with PPA and abnormal vocalizations.
• Clinical diagnosis and pathological confirmation in a subset of patients.
• Acoustic analysis of vocalizations in two patients to assess motor features.

Main Results:

• Ten patients with PPA exhibited progressive speech impairment leading to mutism, accompanied by increasing abnormal laughter-like vocalizations.
• These vocalizations became the patients' primary form of extended utterance, lacking contextual sensitivity.
• Acoustic analysis revealed motor abnormalities in the vocalizations, including variable timing and loss of normal acoustic features.

Conclusions:

• Abnormal, automatic laughter-like vocalizations may be a characteristic feature of a specific PPA subgroup.
• This vocal behavior likely results from disrupted fronto-temporal networks controlling vocalization.
• Impaired control and production of nonverbal vocal behavior may be a hallmark of this PPA subtype.