Speech and Language Disorders Associated with Corticobasal Degeneration

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Corticobasal degeneration (CBD) is a neurodegenerative disease characterized by asymmetric cortical and extrapyramidal signs including progressive asymmetric limb rigidity and apraxia. Other commonly occurring signs include alien limb phenomena, frontal release signs, postural instability, cognitive and/or memory deficits, aphasia, apraxia of speech, and dysarthria. An extensive literature review revealed that although speech and language deficits are common, they rarely are described in detail. The current study examined the speech and language characteristics of 13 cases of autopsy-confirmed CBD. Findings indicate that speech and language disorders were common signs of the disorder and often were among the first signs of CBD. Aphasia was present in over half of the patients and was most often characterized as nonfluent, or anomic. Dysarthria and apraxia of speech were present in approximately 30% and 40% of patients, respectively. Dysarthria type was typically mixed, with either spastic or hypokinetic features present in all affected cases. Although the presentation of speech and language disorders was heterogeneous across patients, the findings highlight the importance of these disorders in the detection and diagnosis of CBD.

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Degenerative neurological disorders frequently result in speech and language deficits, including dysarthria, apraxia of speech (AOS), and aphasia. These deficits may be the first sign of a degenerative neurological condition, and their recognition can contribute to the localization of pathologic changes and the neurologic diagnosis (Duffy, 1995).

Corticobasal degeneration (CBD; also called cortico-basal-ganglionic degeneration or cortico-striatal-nigral degeneration) * is a neurodegenerative disease characterized by asymmetric cortical and extrapyramidal signs, often with progressive asymmetric limb rigidity and apraxia as the core syndrome. Clinical diagnosis of probable CBD or CBD syndrome is made when these signs are present and do not respond to drugs used to treat Parkinson disease, such as levodopa. Other common signs that may appear during the course of CBD include alien limb phenomena, aphasia, apraxia of speech, dysarthria, cognitive and/or memory deficits, frontal release signs, and postural instability (Boeve et al., 2000; Kompoliti et al., 1998; Lang, Riley, & Bergeron, 1994; Litvan, 1997; Litvan et al., 1997; Rinne, Lee, Thompson, & Marsden, 1994). Symptoms usually appear insidiously in the sixth to eighth decade, with gradual progression over 5 to 15 years until death (Boeve, 2000; Muller et. al., 2001).

Characteristics of the speech and language deficits that may occur in CBD are not well described, although they commonly are commented on. In a literature review conducted by searching the Medline database from 1990 to April 2000 using the keyword "corticobasal degeneration," 66 reports were identified that provided behavioral descriptions of a total of 504 cases, the majority of which had clinically diagnosed CBD (as opposed to biopsy or autopsy-confirmed CBD). Speech or language characteristics were described in 60 of the 66 articles, representing 457 of the 504 cases. Twelve cases were known to be duplicated in multiple articles (Frattali, Grafman, Patronas, Makhlouf, & Litvan, 2000; Frattali & Sonies, 2000), and thus were counted only once in the total, leaving 457. Table 1 summarizes the speech and language problems noted within these 60 articles.

Speech disorders (i.e., dysarthria or AOS) were identified in 55% of the 457 cases (253/457). Diagnoses of these disorders were made by neurologists in the majority of cases and by a speech-language pathologist in 26 cases. Dysarthria was reported in 191 patients (42% of the 457 cases) within 34 of the 60 articles. Dysarthria--type using Darley, Aronson, and Brown's (1975) method of categorization--was reported in only one study. In that study, Frattali and Sonies (2000) identified hypokinetic dysarthria in 5 of their 13 patients, mixed dysarthria in 7 patients, and spastic dysarthria in 1 patient. Although limb apraxia is a hallmark of the CBD syndrome, AOS was reported present in only 3.9% of all cases cited (18/457), within 7 of the 60 articles. Four percent of patients (20/457 in 19 of 60 articles) were reported to have nonverbal oral apraxia (NVOA).

Deviant speech characteristics or observations of the oral mechanism frequently were described. Terms and phrases used to describe verbal output characteristics included slurred speech, slow rate, hypophonia, dysphonia, aphonia, articulation errors, hoarse voice, echolalia, palilalia, hesitant speech, anarthria, reduced verbal output, monotone voice, prosodic deficits, scanning speech quality, monosyllabic responses, and unintelligible responses. At least 17 of the 457 patients with speech disorders became mute or anarthric at some point during the course of the disease. Other observations of the speech mechanism included motor impersistence, orolingual dyskinesia, facial dystonia, and reduced facial and/or tongue movements.

The time of onset of speech/language symptoms within the course of the neurologic disease was noted in 119 cases and were the first sign of disease in 19 of these individuals (16%). They appeared as early signs (less than 1 year after onset of other clinical signs) in an additional 17 cases (14%).

Although not as common as motor speech disorders, language disorders also were frequently reported in individuals with CBD. Aphasia or "language difficulties" were observed in 20% of patients (93/457) in 38 of the 60 articles. It is noteworthy that this percentage is substantially lower than that reported in two recent studies. Fifty-three percent of 15 patients described by Frattali et al. (2000) were scored as aphasic on the Western Aphasia Battery (Kertesz, 1982). Boeve et al. (2000) reported that 70% of their 20 patients exhibited aphasia at some point during the course of the disease. The majority of affected individual in these two studies were evaluated by a speech-language pathologist, which likely increased the potential for identifying aphasic language disorders. Across all studies, modalities that were affected by aphasia included verbal and written expression and auditory and reading comprehension. Verbal output characteristics of individuals with aphasia included word-finding or naming deficits, reduced verbal/word fluency, paraphasias, perseveration, meaningless speech or jargon, difficulties with repetition, agrammatic speech, stereotypic utterances, and reduced speech output. Terms used to describe aphasia type included expressive motor, global/total, amnestic, nonfluent, anomic, Broca's, and transcortical motor aphasia. Frattali et al. (2000) reported a high frequency (53%) of nonfluent aphasia types in their sample of 15 CBD patients. Specific aphasia types identified in their study included Breca's, anomic, and transcortical motor aphasia.

This review illustrates that speech and language deficits frequently appear among the clinical manifestations of CBD and that they may be the first or among the first signs of the disease. However, only recently have there been careful descriptions of the types of speech and language disorders associated with CBD (e.g., Frattali et al., 2000; Frattali & Sonies, 2000). Almost all of these prior studies have described patients with CBD diagnosed clinically. However, we now know that several neurological disorders present with signs and symptoms similar to CBD, and a clinical diagnosis of CBD may be confirmed as another disorder on postmortem examination. The purpose of the current study was to characterize the speech and language disorders in 13 adults with autopsy-confirmed CBD who had undergone a detailed analysis of speech and language.

METHOD

Sample

Medical records were reviewed for 23 consecutive patients with autopsy-confirmed CBD who had been evaluated at the Mayo Clinic in Rochester, MN. The full range of clinical neurological findings and the methods used for pathological diagnosis for this group of patients are described in Boeve et al. (under revision). In two patients, the pathological analysis revealed cellular changes consistent with both CBD and progressive supranuclear palsy (PSP); these two cases were excluded from subsequent analyses, leaving a sample of 21 individuals diagnosed with isolated CBD. Eight additional cases were excluded because information about speech and language abilities was insufficient. Speech and language characteristics and diagnoses for the remaining 13 cases were carefully reviewed, and these cases form the basis for this report. Information was obtained from speech pathology reports for 9 of the 13 patients. The remaining 4 were not evaluated by a speech-language pathologist, but sufficient information regarding speech and language characteristics was available in neurology and neuropsychology reports.

Reliability of Clinical Observations and Diagnoses

Inter- and intrarater reliability of judgments about speech and language characteristics and diagnoses were assessed through examination of audio- or videotapes that were available for 4 of the 13 patients. The tapes contained conversational speech samples and various elements of a formal speech-language evaluation such as auditory comprehension, confrontation naming, picture description, word and sentence repetition, word definitions, word fluency, oral reading and spelling, and speech alternating and sequential motion rates (AMRs and SMRs). Full speech-language evaluations were not recorded for any of the 4 patients, but each tape contained at least some of these tasks. For the purposes of this reliability assessment, diagnoses were made based on the speech-language Samples that were available.

The first and second authors separately viewed or listened to the taped samples and independently identified the most salient speech and language abnormalities in an open-ended manner (i.e., without any a priori checklist of characteristics of interest). Decisions about the presence and type of dysarthria were based on Darley et al.'s (1975) definition and description of patterns of speech characteristics associated with various dysarthria types. Aphasia and apraxia (AOS and NVOA) diagnoses were guided by definitions and clinical descriptions by McNeil (1988) and Duffy (1995). Terms used to describe speech characteristics (e.g., strained vocal quality, irregular AMRs, etc.) were taken from these original sources to facilitate the comparisons of judgments made by the two authors. The second author has had extensive experience diagnosing speech and language disorders using these criteria. The first author gained clinical experience through an intensive postdoctoral fellowship under the supervision of the …