22 The Role of Neuropsychology in the Evaluation and Treatment of Geriatric Patients

Thomas Swirsky-Sacchetti and Caterina B. Mosti

Introduction

What Is Neuropsychological Assessment?

Neuropsychology is the science of brain–behavior relationships. Neuropsychological assessment is the objective measure of brain functioning in which a person’s performance is compared with individuals in that person’s normative group (i.e., similar age and educational backgrounds). Although brief and/or computerized batteries are now available, a comprehensive battery measures all major domains of neurocognitive functioning, including overall intelligence, learning and memory, expressive and receptive language, sensory and motor function, and complex problem solving/executive function. A good neuropsychological evaluation should also include a measure of personality/emotional functioning. Fixed batteries (e.g., the Halstead–Reitan neuropsychological battery) are becoming less popular in the wake of flexible batteries, in which the test composition is dictated by the particular needs of the patient and the specific referral question. A full comprehensive battery can sometimes require up to 6 hours of testing, but most batteries developed for the geriatric population are of necessity briefer but with every attempt made to evaluate all of the aforementioned cognitive domains to some extent. Although briefer computerized batteries such as ImPACT (ImPACT Applications, Inc., Pittsburgh, PA) have gained popularity in the assessment of sports-related concussions, many of these batteries have limited use with the elderly due to inadequate norms, the inherent discomfort many elderly have with computerized assessment, and the limited ability of the clinician to clearly understand and adequately diagnose the patient’s problems with only 20 to 30 minutes’ worth of data. Even one of the most widely used neurological screens in clinical practice, the Mini-Mental State Examination (MMSE), has been shown to have limited utility in a white matter dementia,¹ underscoring its limited utility with common forms of dementia, such as vascular dementia, which predominantly affects white matter.

Abbreviated batteries have their utility in a screening capacity, but referral questions are often complicated in the elderly and require “pattern analysis” (i.e., an inspection of the individual’s strengths and weaknesses across the aforementioned modalities). These strengths and weaknesses are identified within a context of the patient’s overall intelligence and educational/occupational background. For example, one would have higher expectations for someone of superior intelligence, such that even a technically average or low average score on a memory task might have implications for the onset of an incipient dementia. Given the prevalence of depression and other emotional issues in the elderly, the neuropsychologist must also factor in the contribution of emotional variables. This is also done by pattern analysis, wherein various subtypes of dementia present with differing patterns, each of which differ from normal aging changes in the brain and/or a primary emotional etiology. To do pattern analysis, a more comprehensive evaluation covering intelligence, learning and memory, receptive and expressive speech, sensory/motor functions, and executive functions is required.

Neuropsychological Functioning in the Elderly

There are a host of well-documented changes in brain functioning as a result of normal aging. The brain slows in information processing speed and is less adept at “fluid” measures of cognition, which require quick adaptation and adjustment to unfamiliar tasks. In contrast, “crystallized” intelligence, such as one’s long-term knowledge base for occupationally related material, vocabulary, or the rules of grammar, may continue to increase with age, depending on one’s intellectual curiosity. There is a wide range of normal variation in the cognitive aspects of aging, similar to physical aging, which is why norms based on age and education are crucial in interpretation of testing results.

Mild cognitive impairment (MCI) is defined as the diminution of one domain of cognitive functioning with other domains remaining intact. Subtypes of MCI have been identified, with the amnestic subtype (i.e., predominant memory impairment) being the one subtype more likely to convert to dementia. Petersen et al reported that the prevalence of MCI in a nondemented population of older adults ages 70 to 89 is ~ 16%.2 Considering that many of these individuals will convert to dementia, the importance of the potential contribution of cognitive issues in the elderly cannot be underestimated. Given increased longevity and better medical treatment, the prevalence of various forms of dementia is increasing.

Dementia is an umbrella term under which many subtypes of cognitive decline may fall. Rates of dementia in those ages 71 and older are at ~ 13.5%. Incidence of dementia among adults ages 71 to 79 falls at ~ 5% but jumps to 37% in adults ages 90 and over.³ Although Alzheimer disease is perhaps the most widely discussed dementia, there are several other dementia subtypes, including multi-infarct (vascular) dementia, frontotemporal dementia, and subcortical dementias. Alzheimer disease is characterized by progressive and diffuse cognitive decline with prominent memory decline, often without a clearcut onset. Vascular dementia presents with more isolated domains of cognitive impairment, and is usually characterized by deficits in executive functioning with relatively intact aspects of memory. Frontotemporal dementia is characterized by atrophy of the frontal and/or temporal lobes of the brain responsible for planning and judgment and understanding and production of speech, respectively. Hallmark symptoms of frontotemporal dementia can include increasingly erratic or impulsive behavior, which may be the first signs of a problem, as well as changes in language. Subcortical dementias, such as those associated with Parkinson and Huntington diseases, tend to result in slower speed of processing or inability to initiate activities and are in contrast to the forgetfulness or language difficulties associated with cortical dementias (e.g., Alzheimer disease).

The most common form of dementia is Alzheimer disease. Most agree that histopathologically confirmed Alzheimer disease constitutes around 45% of the dementia population, with vascular dementia, representing roughly another 25%. Of course, these two forms are not mutually exclusive and can co-occur in roughly another 20%. Frontotemporal dementia, with an estimated prevalence rate between 2 and 15%,⁴ and Parkinson dementia, estimated to affect less than 1% of adults ages 65 and older,⁵ are some of the more common “rare” dementias.

Neuropsychological assessment is useful in helping to differentially diagnose normal aging and the dementias, documenting response to treatment, helping the patient/family with decisions regarding needed level of care, and setting up appropriate expectations for the patient (i.e., determining if the patient is capable of managing finances or driving an automobile).

Cognitive Rehabilitation with the Elderly

Cognitive rehabilitation refers to any activity designed to improve cognitive functioning. Li et al⁶ and Reijnders et al⁷ provide excellent reviews on cognitive interventions in older adults, those with MCI, and even those with mild dementia. The use of computerized brain training programs and video games to stimulate brain functioning in the elderly is becoming more popular, although more research is needed to objectively measure any beneficial effects. There is increasing research support for using various cognitive interventions in the elderly population,⁸ with more success obviously realized in those with MCI or mild dementia as opposed to moderate–severe dementia groups. Rehearsal-based techniques for memory enhancement have demonstrated efficacy. Compensatory techniques take two forms (i.e., external and internal). External compensatory techniques simply change or rearrange the environment with the use of external crutches, so that the same function (e.g., remembering tomorrow’s appointment), is done with the use of a crutch (e.g., a calendar notebook or smart phone). Internal compensatory strategies involve rehearsal based strategies or to using different physiological pathways to accomplish the same task in an effort to avoid or to minimize reliance on dysfunctional areas. Multimodal imprinting is the technique of using more than one sensory modality for memory encoding (e.g., a list of shopping items can be encoded by auditory verbal rehearsal or by forming a mental picture of those items on the checkout counter) thereby using vastly different brain regions.

Neuropsychology and Presbycusis

One illustrative example of the intersection between neuropsychology and geriatric otolaryngology is presbycusis, which will be treated in more detail because there is a growing body of evidence supporting the association between presbycusis and cognitive decline in the elderly.^9,10 In evaluating the potential contributing factors of brain involvement in presbycusis, it is not just the assessment of receptive (and expressive) language that is more germane to central presbycusis, but also the assessment of other brain functions such as memory, executive functions, and processing speed, which are increasingly seen to be not only relevant, but of crucial importance in diagnosis and treatment.

It is increasingly clear that the comprehensive evaluation and treatment of older adults with presbycusis is based on a model in which several levels of etiology, such as peripheral functioning, central auditory processing, and cognitive functioning, are included.11 Some prefer a simplified classification system of peripheral versus central etiologies. Central presbycusis has been defined by Humes et al as “age related changes in the auditory portions of the central nervous system negatively impacting auditory perception, speech-communication performance, or both.”⁹ Humes et al studied older and young adults, the vast majority (90%) of whom had not worn hearing aids.⁹ They administered 6 cognitive measures, 17 psychophysiological measures, and 9 different measures of speech understanding. Of the 12 measures in which older adults performed significantly worse than younger adults, 6 were cognitive measures. This further underscores the importance of considering cognitive functioning in working with the elderly with presbycusis. Pichora-Fuller and Singh noted two conceptual models for describing the relationship between cognitive and central auditory processing components with peripheral etiologies, and argue for an integration of these models.¹² The “site of lesion” approach holds that distinct anatomical sites are organized hierarchically from the bottom up (i.e., peripheral, central auditory processing, and cognitive processes, respectively). This system has proven useful for differential diagnosis of conductive, sensorineural, retrocochlear, or central hearing loss. However, Pichora-Fuller and Singh argue that this schema doesn’t account for overlapping systems, which are guided by afferent encoding as well as efferent feedback. The other model described is a “processing view” model, in which a bidirectional influence and the interaction of lower-level sensory and higher-level cognitive processes is the schema for understanding the functions of hearing, listening, comprehension, and communication. The processing view model necessitates the involvement of cognitive functions of attention and memory as well as language. The authors argue that understanding how sensory and cognitive domains interact is an important precursor to remediation. Pichora-Fuller and Singh also include the role of social-emotional factors because both perceptual stressors (noise) and cognitive stressors (memory loss) can affect the social well-being.¹³ Cox et al also highlight the importance of the emotional functioning of the older individual, which can have a reverberating effect on the perceived success of treatment.¹⁴

Cognitive Domains of Importance in Presbycusis

Whereas one can argue that all domains of cognitive and emotional functioning are relevant to the evaluation and treatment of presbycusis, the areas of attention, memory, and executive function have thus far been most researched.

The role of attention takes on more salience as one moves from the relatively artificial context of listening to one stimulus source in a quiet background to the more realistic, everyday-life. Inunctional hearing required in noisy environments with more than one source of speech or other competing demands, the listener has to focus not only on the “what” of speech but also on the “where” and sometimes the “when.”¹² Selective attention refers to focusing on one source of stimuli and inhibiting others. Alain and Woods demonstrated that older adults’ difficulty hearing in a noisy context may reflect a decline in the ability to inhibit irrelevant stimuli.¹⁵

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