Introduction

The Parkinson's-Reversing Breakthrough

Alternative Treatment for Parkinson Disease

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Diseases with movement disorders may be difficult to diagnose, both at the onset when motor symptoms are mild and not sufficiently specific (e.g., difficulty in manipulating objects), or at the end stage when distinctive motor signs are diluted into a severe and polymorphous clinical picture (e.g., gait disorder with postural instability and cognitive decline in aged patients). Erroneous diagnoses are frequent (1,2), even in the most common idiopathic Parkinson's disease (PD) (3). Some of these errors may be avoided if the cognitive dysfunctions that often accompany these diseases are included in the diagnostic criteria.

Subtle but specific cognitive deficits can frequently be detected in patients with a variety of diseases accompanied by movement disorders. We used to say "except for essential tremor" but some cognitive changes have recently been reported even in this case (4). This is explained by the fact that the neuronal pathways connecting the basal ganglia to the cortex project not only to regions involved in the control of movements (motor, premotor, supplementary motor areas) but also to cortical areas contributing to cognitive functions (prefrontal cortex) and to emotional-processing behavior (cingu-lum and orbitofrontal cortex). In each of these diseases, the loss of different specific populations of neurons in the basal ganglia produces not only a characteristic motor syndrome, but also a recognizable pattern of neuropsychological deficits. Why not include these cognitive and behavioral changes in diagnosis decision trees? Indeed, the use of appropriate neuropsychological tests or questionnaires to detect these deficits can contribute to the diagnosis of such diseases (Table 1).

In this review, we will (1) present the different types of deficits that can be usually encountered following lesions of the basal ganglia; (2) characterize the neuropsychological pattern of the main movement disorders: idiopathic PD, multiple system atrophy (MSA), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and dementia with Lewy bodies (DLB); and (3) show that the contribution of neuropsychological deficits to diagnosis varies from one parkinsonian disorder to another.

From: Current Clinical Neurology: Atypical Parkinsonian Disorders Edited by: I. Litvan © Humana Press Inc., Totowa, NJ

Table 1

Proposed Neuropsychological Battery to Evaluate Cognitive and Behavioral Deficits in Parkinsonian Disorders

Domain of Investigation

Proposed Tool

Global cognitive efficiency Global executive syndrome Set elaboration and monitoring Set maintenance Set shifting

Inhibition of interferences Motor programming

Resistance to environmental dependency Strategic components of memory Opposition between free and cued recall Linguistic functions Gestures

Emotional behavior

Mattis Dementia Rating Scale (5)

Frontal Assessment Battery (6)

Wisconsin Card Sorting Test (7)

Lexical fluency (8)

Trail Making Test (9)

Stroop Test (10)

Graphic and motor series (11)

Imitation, prehension, utilization (12)

California Verbal Learning Test (13)

Grober and Buschke Test (14)

Boston Diagnostic Aphasia Examination (15)

Apraxia examination (16)

Neuropsychiatric Inventory (17)

WHAT ARE THE COGNITIVE AND BEHAVIORAL CHANGES CURRENTLY ENCOUNTERED IN PARKINSONIAN DISORDERS?

The neuropsychological picture of patients may vary from subtle behavioral abnormalities to florid dementia with delusions and hallucinations. The nature and severity of cognitive disorders, the type of impaired memory processes, the presence or absence of instrumental deficits, the precocity of the dysexecutive syndrome, and the frequency of behavioral disorders depend on the underlying neuronal lesions.

According to DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th ed.) criteria (18), dementia is defined by the development of multiple cognitive deficits, severe enough to interfere with social activity or personal relationships and representing a decline from a previously higher level of functioning. The term dementia needs to be used with caution in diseases in which motor impairment, mood, and behavioral disorders may be part of the clinical picture. In these patients the loss of intellectual capacities can, however, be evaluated by psychometric criteria, using global scales, such as the Mattis Dementia Rating Scale (5), which is more appropriate than the Mini Mental State Exam for predominantly subcortical degenerative diseases, given the inclusion of tests evaluating attention and executive functions. Such tools provide cutoff scores that permit a psychometric distinction between demented and nondemented patients. Dementia is usually not observed in PD with early onset (19) or in the early stages of PD (20) or MSA (21,22). Dementia may occur in patients with late-onset PD (23), PSP (24,25), or CBD (26). It is a major feature of DLB, although there may be fluctuations of intellectual functioning from one day to another (27).

Learning disorders in neurodegenerative diseases may be assessed by tools, such as the California Verbal Learning Test (13) or the Grober and Buschke Test (14) that make it possible to analyze specific memory processes and distinguish between storage and retrieval difficulties. The key for understanding the relationship between memory disorders and degenerative diseases implicates the functional "mediotemporal vs frontal dissociation." Encoding deficits, loss of information after a delay, low effect of cuing on recall, high number of extralist intrusions, and false positives in recog

Dementia

Memory nition characterize diseases associated with lesion of hippocampal and perihippocampal areas such as Alzheimer's disease (AD) (28). By contrast, predominant retrieval deficits, manifested by the opposition between impaired free recall and correct cued recall and recognition, are present in diseases associated with dysfunction of striatofrontal neuronal circuits such as PSP or PD with dementia (PDD) (29). Milder deficient activation of the frontal component of memory processes occurs in PD (30,31), MSA (22), and CBD (32,33). Little has been published on learning disorders in DLB, but a study with autopsy-confirmed cases show that they are less severe than in AD (34). Clinical evidence suggests that although cued recall is less efficient in DLB than in PD or PSP, it is better preserved than in AD. A similar contrast between a true loss of information in AD and retrieval deficits in PDD also applies to retrograde amnesia.

Instrumental Activities

Instrumental dysfunction, suggestive of temporoparietal lesions, include aphasia, apraxia, and visuospatial deficits. Aphasia and apraxia may be investigated by clinical batteries, such as the Boston Diagnostic Aphasia Examination (15) or the Heilman and Gonzalez Rothi battery for apraxia (16). Visuospatial deficits are less clearly defined and do not allow the differential diagnosis of the different diseases, since various cognitive abilities, such as visuospatial perception, drawing, or constructive aptitude, and conceptual thinking may affect performance (35). Impairment of instrumental activities is specific to neurodegenerative diseases with a cortical involvement. Aphasia may be observed in DLB (27), whereas apraxia is more characteristic of CBD (32,36). In contrast, instrumental functions are mildly disturbed in PSP (37) and PDD (38) and are preserved in PD (39) and MSA (22).

Executive Functions

Executive functions, namely the mental processes involved in behavioral planning, particularly when the environment requires adaptation to a new situation, are under the control of striatofrontal circuits. These functions may be investigated at the patient's bedside (6) (see video) or by a neurop-sychological evaluation assessing the main processes mediated by striatofrontal loops such as set elaboration, set maintenance, and set shifting, inhibition of interferences, motor programming, and environmental autonomy (Table 1). These functions are impaired at an early stage of all parkinsonian disorders, but are much less severe in PD and MSA than in the other parkinsonian syndromes (25,40).

Behavioral Disorders

Delusions and hallucinations, as diagnosed in accordance with the DSM-IVcriteria (18), are common at early stages of DLB (27). They occur in PD, particularly in demented patients or as a result of treatment with anticholinergic or dopaminergic drugs, but are not characteristic of MSA, PSP, or CBD (41). Apathy and disinhibition may also be observed in parkinsonian disorders (42). Apathy has been defined as a lack of motivation and responsiveness to both positive and negative events in the absence of emotional distress or negative thoughts. It can be distinguished from depression using new scales, such as the Neuropsychiatric Inventory (17). Apathy is particularly frequent in PSP (43) and DLB (44), whereas irritability predominates in CBD (45) and depression in PD (44) (see Chapter 11).

WHICH NEUROPSYCHOLOGICAL PATTERN CHARACTERIZES EACH OF THE MAIN PARKINSONIAN DISORDERS?

Well-characterized neuropsychological profiles can be drawn from the clustering of the cognitive and behavioral characteristics found in each parkinsonian disorder (Table 2). The absence of marked cognitive or behavioral changes makes more probable the diagnosis of PD or MSA, whereas a severe dysexecutive syndrome suggestive of a striatofrontal dysfunction reinforces the diagnosis of PSP and specific deficits related to a cortical involvement contribute to the diagnosis of CBD or DLB.

Table 2

Neuropsychological Pattern of Each Disease

Table 2

Neuropsychological Pattern of Each Disease

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