Hyperlalia: a right cerebral hemisphere syndrome

Area of Science:

• Neuroscience
• Behavioral Neurology
• Clinical Psychology

Background:

• The left hemisphere is traditionally dominant for speech production.
• Right hemisphere lesions can cause subtle behavioral changes, but a distinct syndrome related to speech disinhibition was not well-defined.

Purpose of the Study:

• To describe a novel behavioral syndrome associated with right hemispheric lesions.
• To investigate the neuroanatomical basis of this syndrome.
• To differentiate it from other known disorders of talkativeness.

Main Methods:

• Clinical case description of patients presenting with specific behavioral and speech characteristics.
• Neuroimaging using computed tomography (CT) to identify lesion locations.
• Comparison with existing literature on speech disorders and hemispheric lateralization.

Main Results:

• A new syndrome, termed "hyperlalia," is described, characterized by unconcerned, expressionless patients exhibiting remarkable volubility.
• Speech content is often loose and incoherent, with a low, monotonous voice.
• All confirmed brain lesions overlapped in the right perisylvian area, supplied by the right middle cerebral artery.

Conclusions:

• Damage to the right perisylvian area can disrupt the balance with the left hemispheric speech centers, leading to disinhibition of speech.
• Hyperlalia represents a distinct behavioral syndrome resulting from acute right hemispheric damage.
• Further research is needed to fully understand the neurobiological underpinnings and clinical implications of hyperlalia.