Primary Progressive Aphasias and Apraxia of Speech

Abstract

Purpose of review: This article reviews two of the primary progressive aphasias (PPAs), disorders characterized by the early and predominant impairment of language, and primary progressive apraxia of speech, a degenerative motor speech disorder that is closely related to PPA. An outline of the history and controversy surrounding how these disorders are classified is provided before the article focuses on each disorder's clinical and imaging features.

Recent findings: Over the past decade, the classification of degenerative speech and language disorders has been refined. Clinical, imaging, and pathologic evidence suggests that primary progressive apraxia of speech is a distinct degenerative disorder. Furthermore, multiple lines of evidence have highlighted issues with nonfluent/agrammatic variant PPA, which complicates the diagnosis, prognosis, and study of this disorder. Semantic variant PPA, while not without controversy, remains one of the most well-defined disorders, with good clinicopathologic correlation.

Summary: Accurate classification and diagnosis of these degenerative speech and language disorders is crucial in clinical practice and ongoing research efforts. For nonfluent/agrammatic variant PPA, the authors suggest emphasizing agrammatism as the core inclusion criterion and taking care not to include patients with isolated or predominant apraxia of speech. Isolated apraxia of speech can be the manifestation of a degenerative disease and, based on the different prognosis, should be recognized as distinct from PPA. Finally, it is important to recognize that some patients with semantic dementia, despite sharing the same pathologic associations, may not meet criteria for PPA.

FIGURE 5-1

MRI and fludeoxyglucose positron emission tomography (FDG-PET) findings of the patient in case 5-1. A, Coronal T1-weighted MRI shows a relative lack of atrophy. B, The stereotactic surface projection z-score map of the patient’s FDG-PET shows focal hypometabolism of the supplementary motor and dorsolateral premotor areas. (Black/dark blue represent normal uptake; green/yellow/red represent worsening degrees of hypometabolism.)

FIGURE 5-2

Surface projections of typical patterns of hypometabolism in primary progressive apraxia of speech (A) and dominant apraxia of speech with coexisting agrammatic aphasia (B).

FIGURE 5-3

Imaging of the patient in case 5-2. A, Coronal T1-weighted MRI shows medial and lateral prefrontal, insular, and inferior frontal atrophy on the left. B, The stereotactic surface projection z-score map of the patient’s fludeoxyglucose positron emission tomography (FDG-PET) scan shows focal hypometabolism involving the left inferior frontal and medial prefrontal regions. (Black/dark blue represent normal uptake; green/yellow/red represent worsening degrees of hypometabolism.)

FIGURE 5-4

Example of agrammatism in written picture description.

FIGURE 5-5

Surface projections of typical patterns of hypometabolism in nonfluent/agrammatic variant primary progressive aphasia (A) and semantic variant primary progressive aphasia (B).

FIGURE 5-7

Example of surface dysgraphia when writing to dictation.

FIGURE 5-6

Imaging of the patient in case 5-3. A, Coronal T1-weighted MRI shows severe medial, inferior, and anterior temporal atrophy on the left as well as left insular and left frontal atrophy. B, The stereotactic surface projection z-score map of the patient’s fludeoxyglucose positron emission tomography (FDG-PET) scan shows left anterior temporal hypometabolism, most severe in the polar and medial temporal areas, as well as left inferior temporal and orbitofrontal hypometabolism. (Black/dark blue represent normal uptake; green/yellow/red represent worsening degrees of hypometabolism.)

FIGURE 5-8

Approach to the patient with a suspected degenerative speech or language disorder. ¹ Note that some would suggest including these patients in the nonfluent/agrammatic variant primary progressive aphasia group, which may be appropriate provided agrammatism is present. ² For example, apraxia of speech may be embedded in a corticobasal syndrome phenotype. ³ For example, progressive spastic-flaccid dysarthria may suggest motor neuron disease. ⁴ The patient may have an aphasic dementia due to any number of etiologies, for example. ⁵ Note that some would suggest including these patients in the semantic variant primary progressive aphasia group. ⁶ Some patients present with language symptoms but, in fact, have visual or working memory dysfunction. agPPA = nonfluent/agrammatic variant primary progressive aphasia; DAOS = dominant apraxia of speech; lvPPA = logopenic variant primary progressive aphasia; PPA = primary progressive aphasia; PPAOS = primary progressive apraxia of speech; PPA-U = unclassified primary progressive aphasia; rSD = right temporal semantic dementia; svPPA = semantic variant primary progressive aphasia.