Communication is a cornerstone of human interaction, enabling the exchange of ideas, the formation of connections, and the capacity to engage with new information. At its core, communication begins with the intent of sharing a thought or idea with another person. This intent is translated into language, a structured system of symbols and rules used to communicate our ideas and process those expressed by others. Language, in turn, is expressed through speech or alternative methods, such as writing or gestures. Speech itself is supported at different levels; the signals are sent to the muscles to orchestrate a plan (motor programming) and ultimately move to produce sounds (neuromuscular execution).

In FTD, any of these processes can become disrupted, significantly impacting individuals’ ability to interact with others. There is a tendency to create one-to-one mappings between communication difficulties and specific FTD diagnoses (e.g., language and primary progressive aphasia, social interactions and behavioral variant FTD). However, communication difficulties across the entire FTD spectrum can include disruptions to speech, language, cognition, and behavior.^1-6 Recognizing and distinguishing amongst these challenges is critical for diagnosing and addressing them, with the goal of enhancing the quality of life for those diagnosed and their care partners. Here, we focus specifically on how to differentiate between speech and language symptoms.

Motor speech disorders in FTD involve disruptions in the planning/programming or execution of speech movements, and clinically manifest as apraxia of speech or dysarthria, respectively.⁷ Because apraxia of speech is caused by a disruption in motor speech planning/programming, the muscles used for speaking are typically intact, without evidence of weakness or spasticity. Disruptions can include a slower speaking rate, longer than expected pauses between or within words, difficulty pronouncing longer, more complex words, and inconsistent errors (for example, pronouncing a word differently each time it is spoken). By contrast, automatic speech that is overpracticed (e.g., counting) is often more fluid and accurate. People with apraxia of speech often describe frustration because they know the word and hear it as they always have in their head, but their mouth is “disconnected” or does not “cooperate.” That disconnect can be heard or seen in repeated attempts to try to pronounce the target word correctly (also called groping).

In contrast, people with dysarthria have neuromuscular changes that impact the muscles themselves (e.g., weakness, slowness, hypokinesia, involuntary movements, incoordination) and the execution of the movements needed to speak. As a general rule, the articulation or prosody difficulties are more consistent than in apraxia of speech, and changes can also be present in respiratory support, vocal quality, and resonance. For example, someone with ALS-FTD might have weak articulators, which causes their speech to sound less precise. Their voice might also sound breathy or strained, and they might have palatal weakness that makes it difficult to stop air from coming through their nose as they speak. People with dysarthria also commonly report difficulties chewing or swallowing, since those functions involve the same muscles. These motor speech disorders can occur in isolation, co-occur with one another, or occur together with other types of communication difficulties.

Before the speech signal can be planned and executed, the right words need to be identified and arranged in the right order, which are skills associated with the language system. Above and beyond speaking, the language system also contributes to writing, listening, and reading. Aphasia refers to difficulties with any number of these language modalities and can occur at any level of the language system. For example, someone with semantic variant primary progressive aphasia may have anomia, or difficulty retrieving words, and might use non-specific language. These difficulties linking words with familiar objects may also interfere with their ability to understand what other people are saying. Their word knowledge may also be disrupted; when reading and writing, they may not remember how to recognize or spell words that cannot be sounded out (e.g., they would pronounce the “k” in “knife,” or spell “yacht” as “yot”). Emerging evidence also suggests that people with behavioral variant FTD (bvFTD) frequently have anomia.^2,3,8

Another key, dissociable part of the language system is the ability to put words together to form grammatical sentences. Agrammatism encompasses leaving out important little words (e.g., “The boy is flying kite”) or rearranging words (e.g., “Is that the pouring of bottle?”). In both examples, the content words were accurately retrieved, but the sentences were not assembled correctly. Requesting input from communication partners about this symptom can be useful; the person with FTD is often unaware that they are forming their sentences incorrectly.

Finally, pragmatics refers to the social norms around language use. Someone with bvFTD might perseverate on a set of limited topics or stories that are unrelated to the conversation rather than responding to what their conversation partner is saying.

Learning to differentiate between motor speech and language symptoms can be challenging at first, but the key is identifying the underlying source of what you are hearing. For example, frequent pauses or hesitations during conversation could reflect either aphasia (e.g., slow word retrieval), a motor speech disorder (e.g., the word is identified, but disruptions in motor planning make it difficult to pronounce), or both. In many cases, asking the person to describe their perception of the obstacle can help you distinguish between these symptoms. Testing other language modalities can also provide clues; if the difficulty also occurs in writing or a similar issue arises during comprehension, this will support the presence of a language difficulty. In contrast, if spoken expression is impacted without evidence of difficulties in other modalities, then a motor speech disorder is more likely. Several resources provide helpful videos of speakers who have apraxia of speech with and without aphasia that illustrate this differential diagnostic process.^1,6,9

Recognizing what aspects of communication are disrupted and the associated impact on day-to-day life is a critical part of assessing and treating someone with FTD. Although this is a shared responsibility among care team members, speech-language pathologists can provide unique expertise in this regard and can be consulted for communication strategies, regardless of whether communication difficulties are the only symptom or one of many.