Primary Progressive Aphasia (PPA) is categorized as a neurological disorder that progressively inhibits language capabilities . Distinct from other forms of aphasia, PPA results from deteriorating brain tissue caused by neurodegenerative diseases. Recent research has categorized PPA into 3 forms: Nonfluent/Agrammatic Aphasia (nfvPPA), Semantic Variant (svPPA), and Logopenic Progressive Aphasia (lvPPA). These variants have clinical syndromes that relate to specific pathology. Treatment for PPA remains limited, although speech therapy can be effective for some.
Primary Progressive Aphasia is a neurological syndrome in which underlying neurodegenerative diseases, like Alzheimer's or frontotemporal lobar degeneration, cause damage to regions in the brain responsible for speech and language. Unlike acquired aphasia caused by trauma, PPA’s progressive nature makes recovery unlikely. It is relatively rare and has an age of onset ranging from 40-60; ergo it is categorized as “young-onset dementia”.  Although symptoms differ for each affected individual, it is common for patients to initially find trouble in naming of objects, word association, pronunciation, spelling, comprehension, and other language-related functions. Basic intellect is often spared during the initial stages; however, as the severity of symptoms escalates, individuals may experience a blanket inability to speak and communicate .
The pattern of PPA impairment varies with the individual, resulting in classification of three subtypes: Nonfluent/Agrammatic Variant (nfvPPA), Semantic Dementia Variant (svPPA), and Logopenic Variant (lvPPA). Each variant differs in regards to core and supporting features, pathology, and affected regions .
Clinical diagnosis of nfvPPA requires that an individual express one of two primary symptoms: apraxia of speech and agrammatic production of sentences. Secondary symptoms include a decreased ability to comprehend syntactically complex sentences. Nevertheless, it is just as important that single word and object knowledge are spared. In imaging-supported nfvPPA diagnosis, the aforementioned features in clinical diagnosis must be supplemented by atrophy in the left posterior frontal lobe on MRI, SPECT, or PET. The pathology of nfvPPA often involves tau from frontotemporal lobar degeneration (FTLD-t) or, occasionally, Alzheimer’s Disease .
Diagnosis of Semantic PPA requires the presence of 2 primary symptoms: impaired object naming and impaired single word comprehension. Secondary symptoms of svPPA include impaired object knowledge for unfamiliar items with a spared repetition and spared grammatical speech production. Although speech patterns of Wernicke’s Aphasia and svPPA resemble each other in regards to their shared nonsensical patterns, svPPA can affect both temporal lobes, which leads to impaired understanding of object meaning. As a result, individuals with svPPA may misuse certain objects due to its misunderstood purpose. Semantic PPA generally affects anterior and inferior regions of the left temporal lobes. Similar to nfvPPA, frontotemporal lobar degeneration is the most common pathology, although it more frequently involves Tau DNA Binding Protein.
Logopenic PPA is the most recently categorized PPA variant whose core symptoms relate to word retrieval in conversation, confrontational naming, and repetition difficulty.  It is important to understand that speech hesitation and difficulty with lexical retrieval don’t automatically equate to agrammatism. Logopenic affected individuals are often unable to recall specific objects (anomic), but retain the ability to produce fragments of a grammatical sentence. The sentence often breaks down when they begin to struggle with recalling an object.
In comparison to the other variants, symptoms of lvPPA can include halted mannerisms that additionally produce dysprosodic language. The supporting features such as naming inhibitions are slightly less severe than the semantic variant, as it is usually limited to phonological error. Furthermore, the supporting features for a diagnosis often require a preservation of motor speech, single-word comprehension, and blatant agrammatism—functions more significantly impaired in the other variants.  They are lvPPA’s exclusionary factors.
The pathology of lvPPA includes amyloid plaques and neurofibrillary tangles of Alzheimer’s disease with a slight variation on the distribution that results in a temporarily spared mesial temporal structure. As a result, the areas of the brain that are affected are usually the posterior inferior parietal and posterior superior temporal lobe (although some pictures show the entire external temporal lobe, only atrophy in the aforementioned areas are required for diagnosis).
Depending on the individual, symptoms of the PPA variants can occur simultaneously , creating challenges in diagnosis. This complication often correlates with the stage of progression. Early singular symptoms such as difficulty with naming or spelling are too broad and present amongst all variants, therefore insufficient to provide a basis for diagnosing a specific aphasia. Similarly, late stage patients are often affected in numerous distinct areas that make it difficult to assess the original variant.
The current means of clinical diagnosis and classification involve a two-step process derived from Marsel Mesulam’s criteria. As a part of this classification process, there are inclusionary factors and exclusionary factors. The inclusionary requirements are the standards that must be observed in the individual. An example would include aphasia; the loss or inhibited ability to use and comprehend has to be present and it has to be the most prominent clinical feature. 
On the other hand, exclusionary factors are conditions that cannot be present in order for a PPA diagnosis. Exclusionary factors that differentiate PPA from other diseases include nonverbal memory loss, visuospatial impairment, physical trauma, and impairments resulted from behavioral shifts. As previously mentioned, the primary inclusive factor is linguistic complication. Therefore, behaviors like palilalia(an involuntary repetition of words/phrases), whose symptoms are based primarily in non-linguistic speech repetition, cannot be included within PPA syndrome categories .
A critical component of accurate diagnosis is examining the patient to isolate the cause of the aforementioned symptoms. Neuropsychological examinations reveal any variation in thinking and behavior and document the severity. Psychosocial evaluations deal with the social interactions that take place at home or with other involved individuals in order to understand the patient’s inhibition in expressing basic needs. Depending on the results of the evaluation, different treatment strategies can be used. As PPA progresses, it is also suggested that psychiatric evaluations are performed in order to note behavioral changes and identify potential causes. The rarity of PPA and its young onset age make it beneficial to receive various input from different doctors for a final diagnosis. .
Treatment for PPA remains limited; there aren’t any procedures or medicine that cure PPA. However, despite the inconclusive pharmacological treatments, even a temporary form of treatment, like language therapy, can vastly improve an affected individual’s quality of life. 
Speech-Language Pathologists are involved in both developing strategies to manage the recurring symptoms as well as providing necessary resources. In moderate stages of PPA, self-cueing strategies are practiced to improve lexical retrieval.  This often involves training of family members in order for the individual to begin recognizing and responding to conversational cues by themselves during normal interactions. Some forms of self-cueing include internal use of synonyms, rhymes, and spelling. For motivated individuals there are script trainings, which repetitively cover certain tasks in the form of a dialogue (or monologue). The purpose is to simulate a conversational environment in order to elicit an automatic response without the script . The most effective treatment for PPA doesn’t involve management of the pathology; it focuses on learning to cope and adapt to a new way of life. A loss of certain linguistic abilities is not a permanent barrier to fulfilling a meaningful life. With professional consultation, familial support, and personal effort, affected individuals can prolong their ability to communicate.
Marsel Mesulam - A neurologist who identified PPA and established a basic criteria for diagnosis/characterization in 1982
Apraxia of speech - Reduced motor speech functions
Atrophy - Organ or tissue mass decrease
Pathology- The structure and function of disease
Tau - Protein that functions in association with cytoskeletal stabilization and polymerization; located in cerebral neurons in neurodegenerative diseases
Dysprosodic- Impaired oral speech articulation
Lexical retrieval - Word (often object) recollection
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