Progressive apraxia of speech presenting as isolated disorder of speech articulation and prosody: a case report

Primary Progressive Apraxia of Speech: From Recognition to Diagnosis and Care

BACKGROUND

Apraxia of speech (AOS) can be caused by neurodegenerative disease and sometimes is its presenting sign (i.e., primary progressive apraxia of speech, PPAOS). During the last several decades our understanding of PPAOS has evolved from clinical recognition to a fuller understanding of its core and associated clinical features, its distinction from but relationship with primary progressive aphasia, its temporal course and eventual progression to include other neurological deficits, and its neuroimaging correlates and underlying pathology.

AIMS

This paper provides a comprehensive summary of the literature that has built the current knowledge base about PPAOS and progressive AOS as it co-occurs with progressive aphasia. It reviews the history of its emergence as a recognized syndrome; its relationship with the agrammatic/nonfluent variant of primary progressive aphasia; its salient perceptual features and subtypes; the acoustic and structural/physiological imaging measures that index its presence, severity, and distinction from aphasia; and principles and available data regarding its management and care.

MAIN CONTRIBUTION

A broad summary of what is known about AOS as a manifestation of neurodegenerative disease.

CONCLUSIONS

Primary progressive apraxia of speech is a recognizable syndrome that can be distinguished from other neurodegenerative conditions that affect speech and language.

Primary progressive apraxia of speech: clinical features and acoustic and neurologic correlates

PURPOSE

This study summarizes 2 illustrative cases of a neurodegenerative speech disorder, primary progressive apraxia of speech (AOS), as a vehicle for providing an overview of the disorder and an approach to describing and quantifying its perceptual features and some of its temporal acoustic attributes.

METHOD

Two individuals with primary progressive AOS underwent speech-language and neurologic evaluations on 2 occasions, ranging from 2.0 to 7.5 years postonset. Performance on several tests, tasks, and rating scales, as well as several acoustic measures, were compared over time within and between cases. Acoustic measures were compared with performance of control speakers.

RESULTS

Both patients initially presented with AOS as the only or predominant sign of disease and without aphasia or dysarthria. The presenting features and temporal progression were captured in an AOS Rating Scale, an Articulation Error Score, and temporal acoustic measures of utterance duration, syllable rates per second, rates of speechlike alternating motion and sequential motion, and a pairwise variability index measure.

CONCLUSIONS

AOS can be the predominant manifestation of neurodegenerative disease. Clinical ratings of its attributes and acoustic measures of some of its temporal characteristics can support its diagnosis and help quantify its salient characteristics and progression over time.

The evolution of primary progressive apraxia of speech

Primary progressive apraxia of speech is a recently described neurodegenerative disorder in which patients present with an isolated apraxia of speech and show focal degeneration of superior premotor cortex. Little is known about how these individuals progress over time, making it difficult to provide prognostic estimates. Thirteen subjects with primary progressive apraxia of speech underwent two serial comprehensive clinical and neuroimaging evaluations 2.4 years apart [median age of onset = 67 years (range: 49-76), seven females]. All underwent detailed speech and language, neurological and neuropsychological assessments, and magnetic resonance imaging, diffusion tensor imaging and (18)F-fluorodeoxyglucose positron emission tomography at both baseline and follow-up. Rates of change of whole brain, ventricle, and midbrain volumes were calculated using the boundary-shift integral and atlas-based parcellation, and rates of regional grey matter atrophy were assessed using tensor-based morphometry. White matter tract degeneration was assessed on diffusion-tensor imaging at each time-point. Patterns of hypometabolism were assessed at the single subject-level. Neuroimaging findings were compared with a cohort of 20 age, gender, and scan-interval matched healthy controls. All subjects developed extrapyramidal signs. In eight subjects the apraxia of speech remained the predominant feature. In the other five there was a striking progression of symptoms that had evolved into a progressive supranuclear palsy-like syndrome; they showed a combination of severe parkinsonism, near mutism, dysphagia with choking, vertical supranuclear gaze palsy or slowing, balance difficulties with falls and urinary incontinence, and one was wheelchair bound. Rates of whole brain atrophy (1.5% per year; controls = 0.4% per year), ventricular expansion (8.0% per year; controls = 3.3% per year) and midbrain atrophy (1.5% per year; controls = 0.1% per year) were elevated (P ≤ 0.001) in all 13, compared to controls. Increased rates of brain atrophy over time were observed throughout the premotor cortex, as well as prefrontal cortex, motor cortex, basal ganglia and midbrain, while white matter tract degeneration spread into the splenium of the corpus callosum and motor cortex white matter. Hypometabolism progressed over time in almost all subjects. These findings demonstrate that some subjects with primary progressive apraxia of speech will rapidly evolve and develop a devastating progressive supranuclear palsy-like syndrome ∼ 5 years after onset, perhaps related to progressive involvement of neocortex, basal ganglia and midbrain. These findings help improve our understanding of primary progressive apraxia of speech and provide some important prognostic guidelines.

Primary progressive aphasia: a tale of two syndromes and the rest

OBJECTIVE

Primary progressive aphasia (PPA) has been proposed to comprise 3 discrete clinical subtypes: semantic, agrammatic/nonfluent, and logopenic. Recent consensus recommendations suggest a diagnostic framework based primarily on clinical and neuropsychological findings to classify these variants. Our objective was to evaluate the extent to which patients with PPA would conform to the proposed tripartite system and whether the clustering pattern of elements of the linguistic profile suggests discrete clinical syndromes.

METHODS

A total of 46 patients with PPA were prospectively recruited to the Cambridge Longitudinal Study of PPA. Sufficient data were collected to assess all consensus-proposed diagnostic domains. By comparing patients' performances against those of 30 age- and education-matched healthy volunteers, z scores were calculated, and values of 1.5 SDs outside control participants' means were considered abnormal. Raw test scores were used to undertake a principal factor analysis to identify the clustering pattern of individual measures.

RESULTS

Of the patients, 28.3%, 26.1%, and 4.3% fitted semantic, nonfluent/agrammatic, and logopenic categories respectively, and 41.3% did not fulfill the diagnostic recommendations for any of the 3 proposed variants. There was no significant between-group difference in age, education, or disease duration. Furthermore, the outcome of the factor analysis was in keeping with discrete semantic and nonfluent/agrammatic syndromes but did not support a logopenic variant.

CONCLUSION

Taken together, the results of this prospective data-driven study suggest that although a substantial proportion of patients with PPA have neither the semantic nor the nonfluent variants, they do not necessarily conform to a discrete logopenic variant.

Characterizing a neurodegenerative syndrome: primary progressive apraxia of speech

Apraxia of speech is a disorder of speech motor planning and/or programming that is distinguishable from aphasia and dysarthria. It most commonly results from vascular insults but can occur in degenerative diseases where it has typically been subsumed under aphasia, or it occurs in the context of more widespread neurodegeneration. The aim of this study was to determine whether apraxia of speech can present as an isolated sign of neurodegenerative disease. Between July 2010 and July 2011, 37 subjects with a neurodegenerative speech and language disorder were prospectively recruited and underwent detailed speech and language, neurological, neuropsychological and neuroimaging testing. The neuroimaging battery included 3.0 tesla volumetric head magnetic resonance imaging, [¹⁸F]-fluorodeoxyglucose and [¹¹C] Pittsburg compound B positron emission tomography scanning. Twelve subjects were identified as having apraxia of speech without any signs of aphasia based on a comprehensive battery of language tests; hence, none met criteria for primary progressive aphasia. These subjects with primary progressive apraxia of speech included eight females and four males, with a mean age of onset of 73 years (range: 49–82). There were no specific additional shared patterns of neurological or neuropsychological impairment in the subjects with primary progressive apraxia of speech, but there was individual variability. Some subjects, for example, had mild features of behavioural change, executive dysfunction, limb apraxia or Parkinsonism. Voxel-based morphometry of grey matter revealed focal atrophy of superior lateral premotor cortex and supplementary motor area. Voxel-based morphometry of white matter showed volume loss in these same regions but with extension of loss involving the inferior premotor cortex and body of the corpus callosum. These same areas of white matter loss were observed with diffusion tensor imaging analysis, which also demonstrated reduced fractional anisotropy and increased mean diffusivity of the superior longitudinal fasciculus, particularly the premotor components. Statistical parametric mapping of the [¹⁸F]-fluorodeoxyglucose positron emission tomography scans revealed focal hypometabolism of superior lateral premotor cortex and supplementary motor area, although there was some variability across subjects noted with CortexID analysis. [¹¹C]-Pittsburg compound B positron emission tomography binding was increased in only one of the 12 subjects, although it was unclear whether the increase was actually related to the primary progressive apraxia of speech. A syndrome characterized by progressive pure apraxia of speech clearly exists, with a neuroanatomic correlate of superior lateral premotor and supplementary motor atrophy, making this syndrome distinct from primary progressive aphasia.

The influence of psycholinguistic variables on articulatory errors in naming in progressive motor speech degeneration

We describe an analysis of speech errors on a confrontation naming task in a man with progressive speech degeneration of 10-year duration from Pick's disease. C.S. had a progressive non-fluent aphasia together with a motor speech impairment and early assessment indicated some naming impairments. There was also an absence of significant phonological or semantic impairment. In order to examine naming difficulties and the factors that influence his speech production errors, we selected 210 words varying in frequency, age of acquisition (AoA), imageability, phonemic length and syllable length and conducted a logistic regression analysis on a range of speech production error types (phone omissions, additions, substitutions, response delays, overall errors). No significant naming errors due to lexical access were found. The only significant predictor of speech articulation errors was phonemic length, with none of the other lexical variables influencing speech production error. The only error type predicted was phone omissions. Results suggest that C.S.'s speech and naming errors indicate compromised speech programming/planning rather than lexical selection and we conclude that this pattern of findings is indicative of problems with motor speech production.

Slowly progressive aphemia: a neuropsychological, conventional, and functional MRI study

Slowly progressive aphemia (SPA) is a rare focal degenerative disorder characterized by severe dysarthria, frequent orofacial apraxia, dysprosody, phonetic and phonemic errors without global cognitive deterioration for many years. This condition is caused by a degeneration of anterior frontal lobe regions, mainly of the left frontal operculum. We report a case of SPA with a course of 8 years, evaluated by repeated neuropsychological, conventional, and functional MRI examinations. In our case, neuropsychological examinations showed a progressive impairment of speech articulation including dysprosody, phonetic and phonemic errors, and slight writing errors. No global cognitive deterioration was detected and the patient is still completely autonomous. Morphological and functional investigations showed, respectively, a progressive atrophy and progressive impairment of the left frontal region, confirming the role of the opercular region in determining this rare syndrome. During verbal task generation as the cortical activation of this region gradually decreased, the language articulation worsened.

Progressive apraxia of speech as a window into the study of speech planning processes

We present a 3-year follow-up study of a patient with progressive apraxia of speech (PAoS), aimed at investigating whether the theoretical organization of phonetic encoding is reflected in the progressive disruption of speech. As decreased speech rate was the most striking pattern of disruption during the first 2 years, durational analyses were carried out longitudinally on syllables excised from spontaneous, repetition and reading speech samples. The crucial result of the present study is the demonstration of an effect of syllable frequency on duration: the progressive disruption of articulation rate did not affect all syllables in the same way, but followed a gradient that was function of the frequency of use of syllable-sized motor programs. The combination of data from this case of PAoS with previous psycholinguistic and neurolinguistic data, points to a frequency organization of syllable-sized speech-motor plans. In this study we also illustrate how studying PAoS can be exploited in theoretical and clinical investigations of phonetic encoding as it represents a unique opportunity to investigate speech while it progressively disrupts.