Primary progressive aphasia (PPA) is a neurological effect specifically associated with certain types of dementia (Alzheimer’s Disease and frontotemporal dementia are the most common underlying forms of dementia in which PPA occurs) that results in linguistic abilities becoming slowly and progressively impaired until they are completely gone.

PPA commonly begins as a subtle disorder of language that progresses to a nearly total inability to speak at all in its end stage.

There are three variants of PPA: non-fluent/agrammatic, semantic, and logopenic (LPA). 

In some people with PPA only one variant affects the brain (the semantic variant is the dominant type and is present in most instances of PPA) while in other people two or all three variants of PPA may affect the brain.

The reasons for the differences in how this neurodegenerative process manifests its variants in exact relationship to dementia are not yet known, but much research is currently being done to understand the pathology.

In the non-fluent/agrammatic variant of PPA, the first visible sign is consistent hesitant and effortful speech. Despite this difficulty in speaking, people with non-fluent/agrammatic PPA maintain their ability to comprehend what others well into the middle stage or so of this neurological decline, but this ability disappears beyond the middle stage.

Another characteristics of non-fluent/agrammatic PPA includes increasing difficulty producing speech because of vocal weakness and a lack of mental coordination – speech is audibly weak and it is imprecise (either general or off-topic altogether) and uncoordinated (words are out of order or they are random).

With the non-fluent/agrammatic variant of PPA, reading and writing abilities tend to be preserved longer than speech abilities, but as the neurological damage increases, the ability to read and write completely disappear.

People with the non-fluent/agrammatic variant of PPA become mute as well in the later stages, and in the end stage, difficulty with swallowing or the inability to swallow at all is common. 

Loss of brain volume in the left frontal lobe and parietal areas of the brain are seen in non-fluent/agrammatic PPA.

The semantic variant of PPA has the hallmark feature of difficulty generating or recognizing familiar words (as well as familiar objects and faces), even though in the early stages, fluent spontaneous speech remains (people with the semantic variant of PPA “talk around” the words they can’t generate to try to convey the meaning of what they are trying to say).

This happens with rarer words first and then common nouns in later stages. Surprisingly, verbs and abstract words are spared. 

In the semantic variant of PPA, neurological damage is seen in the left temporal lobe of the brain (in left-handed people, interestingly, the same kind of neurodegeneration is seen in the right temporal lobe of the brain).

The logopenic variant of PPA is first identified by the deterioration of a person’s ability to retrieve words. Additionally, people with the logopenic variant of PPA have a slow rate of speech with frequent pauses due to significant word-finding problems.

The latest neuroscience research seems to indicate that the fundamental loss in the logopenic variant of PPA is in phonologic short-term memory, which also contributes to difficulty with sentence and phrase repetition, and understanding long or complex sentences.

The logopenic varient of PPA occurs because of atrophy in the left posterior temporal cortex and inferior parietal lobule.

Recently, Terry Jones of the well-known, “you-either-find-them-hysterically-hilarious-or-maddeningly-tedious” (I confess to falling into the latter category), British comedic group, Monty Python, has revealed that he has been diagnosed with dementia and PPA.

While it’s unclear which variant of PPA, Jones, who is 74 years old, has, his managerial team has announced that he is no longer able to give interviews.