Science Capsule: Primary Progressive Aphasia
Primary progressive aphasia (PPA) is a type of dementia defined by the gradual loss of language abilities as the principal feature of a degenerative disease of the brain. First identified as a distinct disorder in 1982, PPA differs from other dementias, such as Alzheimer’s disease, because the language deficit is present during early phases of the disease in the absence of memory problems, other cognitive deficits, or traumatic brain injury. PPA is divided into three clinical subtypes: agrammatic (difficulty with word order), semantic (difficulty understanding words, but word production is near normal), or logopenic (difficulty with word finding, resulting in halted speech).
In recent years, significant progress has been made in discriminating between people with PPA and other dementias, and between the subtypes of PPA. In 2009, NIDCD-supported scientists identified a series of word performance tasks that discriminate quantitatively between the three clinical subtypes of PPA.138 In addition, the individuals categorized using this methodology showed specific and different brain regions that had atrophied in correlation with the subtype. These results provide a foundation for researchers and clinicians to be able to predict the likely progression of PPA, such as whether affected people will go on to develop additional dementias or experience other neurodegenerative deficits.
While a drug therapeutic has not yet been proven effective to treat PPA through a clinical trial, case reports have demonstrated rapid improvement in symptoms for specific individuals.139 Behavioral interventions have also been effective in case studies.140 These case reports provide hope for affected people and their families that future research will validate these or other interventions and provide a template for treatment.