Neuropsychology provides an important contribution to the management of patients with PD. Neuropsychological evaluation delineates the nature and extent of cognitive changes, if any, and a profile of relative neuropsychological strengths and weaknesses. Such knowledge is helpful in:
■ the determination of the most probable etiology of mild- and new-onset cognitive changes;
■ development and formulation of strategies or treatments to ameliorate the impact of cognitive deficits on functioning;
■ guidance of the patient and family in making and requesting adaptive changes in the patient's home, leisure, and work environments, which enhance functioning and minimize handicap;
■ decision making about the appropriateness of medical and neurosurgical interventions for a patient;
■ assessment of competence to consent to treatment;
■ financial, legal, placement planning.
Given the prevalence of cognitive and behavioral changes in PD, every patient would, in ideal circumstances, receive a baseline evaluation when first diagnosed with PD. Such a baseline neuropsychological evaluation would facilitate the accurate detection and diagnosis of subsequent neurobehavioral changes and permit the evaluation of treatment effects. This, however, occurs rarely and probably reflects cost-effectiveness issues in a managed care environment and the reluctance of many patients to contemplate in the early disease stages the threat of later, possibly significant, cognitive compromise. In the absence of an early baseline evaluation, a neuropsychological evaluation in the context of cognitive morbidity relies on a less accurate, probabilistic estimation of premorbid functioning to detect and estimate the extent of impairments.
Accordingly, if a full evaluation is not indicated or cannot be achieved soon after diagnosis, a cognitive screening should be contemplated as an alternative. Such screening can be readily achieved in the neurologist's office using the Mattis Dementia Rating Scale (7), or comparable instruments. Likewise, the administration of brief self-report measures of mood state and quality of life [e.g., the Beck Depression (8) and Anxiety Inventories (9), and Parkinson's Disease Questionnaire 8-item short-form (10)] are invaluable, in screening for mood disturbance and the extent to which treatments are impacting quality of life. Affective disturbances are crucial to screen for on a regular basis, considering the high prevalence of anxiety and depression in patients with PD (11), and the high likelihood of these entities going undiagnosed (12) or undertreated (13) in routine neurologic practice. The optimization of quality of life, from the patient's perspective, facilitates a patient-physician collaboration and treatment adherence.
A more comprehensive neuropsychological evaluation that supplements screening should be strongly considered under the following circumstances:
■ if the patient, caregiver, and/or clinician suspect changes in the patient's ability to carry out fundamental and/or instrumental activities of daily living, which are unlikely to be related to motor dysfunction;
■ if there is concern regarding a possible evolving dementia related to depression, PD, Alzheimer's disease (AD), or any other medical and/or psychiatric condition;
■ if the neurologist suspects that brief cognitive screening tests [e.g., the Mini Mental State Exam (14)] are not sufficiently sensitive to detect possible changes in cognitive functions; indeed, screening measures designed to detect cognitive decline in AD are typically poorly sensitive to mild subcortical dementias as often seen in PD (15).
■ if the patient is being considered for surgical treatment of PD. In fact, recently published guidelines emphasize the need for neuropsychological evaluation in this regard (16,17). Such evaluation facilitates patient selection and provides a baseline against evaluating potential postsurgical neurobehavioral changes and their implications.
■ if a patient experiences difficulties at work likely unrelated to motor symptoms and signs;
■ when issues and questions arise regarding a person's competence to: manage financial affairs, prepare an advanced directive or living will, or consent to treatment (18);
■ when questions arise about the most appropriate environment for the continued care of the patient;
■ when the patient and/or family report that the patient experiences emotional changes and/or is withdrawing from social roles;
■ once a patient has experienced delirium or hallucinations, given that such phenomena may be harbingers of dementia (19).
Prior to making a referral for neuropsychological evaluation, it is important to determine whether neuropsychological evaluation is appropriate to address the specific question the clinician or patient might have. Of equal importance is that the referring clinician carefully articulates the referral question, which allows the neu-ropsychologist to tailor evaluative procedures accordingly, and that the neuropsy-chologist clearly communicates the findings and their possible implications to the referring clinician, patient, and family, while specifically addressing the referral question.
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