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"Neuropsychology is the study of how the nervous system -- the brain -- works at its most sophisticated level. That is, at the level of behavior. Our behavior is a function of how our brain operates."
Neuropsychology:
An Introduction to Differential Diagnosis
of Neurobehavioral SyndromesAnthony H. Risser, Ph.D., 1999
(copyright, 2002; all rights reserved)
LET me begin this morning with a short introduction as to neuropsychology itself. The term neuropsychology refers to the scientific study of brain-behavior relationships. Neuropsychology is the study of how the nervous system--the brain--works at its most sophisticated level. That is, at the level of behavior. Our behavior is a function of how our brain operates. I use the term behavior to mean virtually any activity you could think of--including activities in daily life, learning, emotions, and all aspects of cognition.This branch of knowledge is multidisciplinary; its foundations in the late 19th and early 20th centuries were in neurology, psychology, medicine, physiology, anatomy, and other scientific disciplines. Clinical neuropsychology represents one of the clinical neurosciences--one that is chiefly concerned with the effects of central nervous system disease on behavior. Diseases affecting the brain frequently result in alterations of behavioral experience. Clinical neuropsychology is concerned with classifying consistencies in this relation between disease state and behavioral consequence.
As a neuroscience, clinical neuropsychology is most closely allied with behavioral neurology and many of the first centers of neuropsychological expertise grew from within academic neurology departments--especially in the American Midwest. One of the first was founded in 1949 at the Neurology Department of the University of Iowa College of Medicine by Dr. Arthur Benton, arguably the first modern clinical neuropsychologist, Dr. A.L. Sahs, who was the chairman of neurology, and Dr. Russell Meyers, who was the chairman of neurosurgery. Neuropsychology also has a kinship with the field of organic psychiatry. Within the domain of psychology, neuropsychology is a recognized subspecialty with its own academic doctoral programs, such as the one I graduated from in Canada, and two-year post-graduate residency/fellowship programs, such as the one I completed in the Neurology Department of the University of Wisconsin Medical School, Milwaukee Clinical Campus.
I want to present three things about neuropsychology to you this morning:
A description of some basic features in neuropsychology service delivery.
First, I identify six basic features that define the process of neuropsychological service delivery:
[1] Higher cerebral functions are multidimensional. Therefore, the neuropsychological evaluation of cognitive functioning in known or suspected brain disease also must be multidimensional. The construct of a single (or global) measure of higher cerebral functioning is not a valid construct in clinical neuropsychology.When the brain is healthy and functioning normally, the basic dimensions of cognitive function are: Orientation; Attentional Capacity and Higher-Order Attention; New-Learning and Memory; Intellectual Functioning; Language Functioning: (Production, Understanding); Visuospatial, Visuoperceptive, and Visuoconstructive Functioning; Sensorimotor Functioning; Executive Functioning; and Personality Functioning.
[2] A differential diagnosis of neurobehavioral functioning is the primary goal of a neuropsychological consultation and the basis for neuropsychological recommendations. As normal functioning is multidimensional, observed disorders in neuropsychological functioning are many and varied.
[3] Performances during neuropsychological evaluation are interpreted in terms of quantitative scores, qualitative performances, and defective-performance patterns on tests that are standardized and objective in format, supplemented as needed with clinical measures and understood within the context of the primary medical record. A raw score on a single test is the least important part of a neuropsychological evaluation.
[4] Evaluations must be flexible, in that they should be tailored for the individual patient and the individual's presenting problems, medical history, and the clinical context in which the evaluation is requested and executed. Evidence is obtained to allow for reaching appropriate diagnostic impressions.
[5] Performances on neuropsychological evaluations are examined in terms of neurobehavioral syndromes. Syndrome evolution or change represents one key neurobehavioral measure of improvement/dissolution of function.
[6] Use of neuropsychological findings in multidisciplinary clinical settings by, for example, therapists in head-injury rehabilitation settings, requires a clinician's, rather than a technician's, viewpoint. Differential diagnosis in such settings is useful when the diagnostic process is appreciated and when differential management is feasible. It is here that neuropsychological consultation offers the most challenge to the development of effective and cost-efficient rehabilitation by (a) increasing the evidence base to document the specific nature of disorders caused by neurological disease processes and (b) by aiding in the continued refinement and fine-tuning of provided treatments.
I want to introduce to you what I consider to be the major dimensions or characteristics of normal cognition from a neuropsychological viewpoint.
Orientation is basically a function of level of alertness. It represents our always-changing awareness of our place in time and space--our ability to, for example, know roughly what time of day and what day of the week it is and to know where we are, such as in Central Park or on the way to the supermarket. Accurate temporal orientation is an essential component of basic mental competence. A deficit in orientation--when observed--is a very sensitive indicator or some type of abnormal condition, although it is not specific as to the type of abnormality. No one can consistently identify time down to the exact minute, but studies indicate that roughly 95% of the normal adult population can identify the time of day to within an hour or so.
Attention as a cognitive function is itself considered to be multi-dimensional. That means it can be broken down as a system into a number of reliable cognitive subsystems. Like orientation, attention appears as a diffusely organized function in the brain and is sensitive to diffuse or multifocal brain disorders. The Reticular Activating System of the brainstem and midbrain, the Thalamus, and the Frontal Lobes are particularly important regions for normal levels of alertness and attention.
New-learning and memorization are cognitive functions that, like attention, are multidimensional systems. Although it may sound simplistic to say it, but to learn something is to remember it and to remember something implies having learned it in the first place. There are a number of ways to distinguish the different stages of learning and memory. I distinguish between immediate memory--which is quite sensitive to attentional functioning and is relatively short-term--and long-term memory, which represents our stored fund of knowledge. Learning is the process of memory and involves encoding and storage of new information. A final process in memory functioning is the retrieval of stored information, which may involve free recall, cued recall, and recognition memory.
The ability to learn new material is perhaps the single cognitive function most sensitive to any deviation from normality--the ability may be compromised in the context of brain disease; in the context of psychopathology; in the context of transiently acute stress, boredom, or fatigue; or in the context of non-neurological acute or chronic disease processes. Any cognitive problem that results in increased forgetfulness may elicit patient symptoms of memory problems. It is the cognitive area of most frequent subjective complaint.
Intellectual functioning represents a global representation of overall functioning. Intellectual functioning can be compromised by severe brain trauma and by the neurodegenerative diseases, such as Alzheimer's.
Language functioning is defined by a number of subsystems at both a cognitive and an anatomical level. These components of language include: verbal production, word-retrieval, repetition of phrases, controlled verbal association, comprehension, higher-order verbal-conceptual functioning, spelling, reading, and writing. These abilities are largely subserved by the dominant cerebral hemisphere, typically the left hemisphere.
Next, visuospatial, visuoperceptive, and visuoconstructive functioning. Visuoperception is that area of processing that deals with what an object is. Visuospatial functioning is that area of processing that deals with where we are relative to objects and the relative positions of different objects or the relative positions of different parts of objects. Finally, visuoconstruction is a psychomotor function involving our ability to create and manipulate objects. Regarding the brain, these cognitive functions appear mediated predominantly by the functioning of the right hemisphere. There appears to be an anatomical distinction between the spatial and perceptual functions, with spatial functioning mediated by areas of the right parietal lobe and perceptual functioning mediated by areas of the right temporal lobe.
Sensorimotor functioning includes basic features like psychomotor speed, fine-motor control and dexterity, and visual acuity.
Executive functioning are functions which reflect our own form of internal government, functions which allow for self-control over our behavior and emotions. For self-control, one could also say regulation, modulation, initiation, shifting, and termination. The broad expanse of the frontal lobes appear to underlie these functions, although a precise degree of localization has evaded clinical researchers for a hundred years.
Finally, the various facets that make up one's personality are not cognitive per se, but it is vital not to forget those aspects of our behavior that define us as individuals when examining cognitive functioning.
When brain trauma occurs, there is no one single neuropsychological deficit or syndrome that will result. Any of a multitude of disorders can be observed and diagnosed. These disorders vary in their complexity, their severity, their impact upon the individual, and their prognosis. The diagnostic process is complicated because the neuropsychological evaluation of a head-injured patient may reveal the presence of any of the neuropsychological disorders that I will describe, it may reveal the presence of normal functioning without any evidence of disordered functioning, it may reveal the presence of disorders that preceded the head-injury and reflect the patient's premorbid status rather than being an acquired disorder, or it may reveal the presence of a patient who is feigning or malingering problems. The diagnostic process will be influenced by the severity of the head injury and the point in time it is begun since the injury, since the return to consciousness, and since the resolution of PTA.
I want to introduce to you the major neurobehavioral disorders. The differential diagnosis of these disorders are the basic clinical practice in neuropsychology. They are:
[a] Dementia
[b] Acute Confusional State
[c] Attentional Disorders
[d] Aphasia
[e] Amnestic Syndrome
[f] Focal Visuoperceptive and Visuospatial Disorders
[g] Neurobehavioral Frontal Lobe Syndrome
[h] Organic Personality DisorderIn addition, the differential diagnosis of these disorders should also include a formal ruling out of psychiatric-personality disorders. These disorders include: Mood Disorders (such as, Depressive Episodes, Manic Episodes, and Bipolar Disorders), Thought Disorders (such as, the Schizophrenic-Spectrum Disorders and Delusional-Paranoia Disorders), Somatoform Disorders, Adjustment Disorders, Personality Disorders, and Malingering.
Dementia reflects a generalized impairment in intellectual (mental) functioning. Dementia typically is a consequence of a diffuse and/or multifocal disease process, such as Alzheimer's Disease and the other neurodegenerative disease processes, multiple cerebrovascular events, and severe traumatic head injury. Dementia, if due to a neurodegenerative disease process such as Alzheimer's, shows a progressive loss of mental functioning over time. If due to an acute event, such as severe head injury, then the post-traumatic dementia may be most pronounced early and then show some degree of resolution over time. The neuropsychological status of a demented individual typically indicates a level of intellectual functioning significantly below premorbid expectation and reveals impairments in the ability to learn and remember new information. Associated features may also be present, such as language and visuoperceptive disorders, which will vary on an individual basis. Dementia is particularly common in severe head injuries with the mechanical characteristics of acceleration-deceleration and rotation--characteristics that are most commonly seen in motor-vehicle accidents and which result in diffuse, widespread damage to the brain. Dementia is a particularly common outcome when coma is extended or when there has been a prolonged period of increased intracranial pressure.
The Acute Confusional State typically results from a toxico-metabolic derangement and can frequently occur in the context of neurological disease but also in the context of chronic system illness, such as diabetes and renal disease, acute febrile illnesses, in alcohol-withdrawal, or as a side-effect of prescription medications. Acute confusional states are especially common in the elderly and may frequently be misdiagnosed as a dementia. Unlike most forms of dementia, however, acute confusional states usually resolve with treatment or management of the underlying etiology. The neuropsychological profile of an acutely confused patient will typically reveal significant disorientation and impaired new-learning abilities. In head injury, Post-Traumatic Amnesia or PTA is a form of confusional state that may be observed during the period between return of consciousness and ending with the return of continuous memory functioning.
Attentional Disorders are very common in neurological disease, but also are frequently observed in the context of the major psychopathologies, such as the Schizophrenic and Mood Disorders. The neuropsychological profile of these individuals typically reveal a very specific cognitive impairment of attention and concentration. Tests used during neuropsychological exams are very sensitive to the presence of attentional disorders but, of themselves, may not afford great specificity as to etiology; specificity is aided by examining the attentional disorder within the clinical context, by assuring the receipt and a careful review of the medical record, and by obtaining a good history on interview with the patient.
Aphasia reflects a neurologically based linguistic disorder and presents in a number of different subtypes, each with characteristic features. The most common features in the language of aphasic patients are the presence of paraphasic errors and anomia (the name for word-finding difficulties). The neuropsychological profile of aphasic individuals will vary with the aphasic subtype. When seen in the context of vascular etiologies, these subtypes typically reflect the distribution of the involved vessel(s). The neuropsychological profiles of the aphasic individual also show some change over the course of recovery and reveal, when present, the presence of any associated language-related or non-language deficits. In head-injured patients, isolated language deficits, such as a residual anomia, are much more frequent than are frank aphasias.
The Amnestic Syndrome reflects a global inability to learn and remember new information. Unlike the demented patient, an amnestic's intellectual functioning is not defective. Amnesias may take different forms and an important distinction needs to be made between organic and psychogenic (i.e., of psychological origin) amnesias. Specific organic etiologies, such as anoxic encephalopathy after cardiac arrest, sometimes produce global amnestic syndromes. Psychogenic amnesias and complaints of memory loss are quite frequent in the context of psychopathology, but do not necessarily imply the presence of an organic deficit in memory. Feigning of memory loss is sometimes observed in patients who are malingering.
Focal damage to either the left or the right hemispheres may result in selective (and sometimes very rare) neuropsychological deficits. In head injury, focal damage typically refers to those areas of brain tissue that have been contused and the presence of focal disorders may reflect the location, size, number, and depth of contusions. When Focal Neurobehavioral Deficits of the Right Hemisphere occur, they typically involve aspects of visuoperceptual functioning. There is a general tendency for spatial disorders to be observed with right parietal lobe damage and for visuoperceptual disorders to be observed with right temporal lobe damage.
The rare clinical disorder of Prosopagnosia is an example of the visuoperceptive disorders. In prosopagnosia, an individual loses the ability to recognize familiar faces--faces of friends, family members, celebrities. This phenomenon is observed without intellectual, memory, linguistic, or visual acuity losses. Lesions in the mesial temporo-occipital region of the right hemisphere or bilaterally can produce the disorder.
The Neurobehavioral Frontal Lobe Syndrome is really a family of ill-defined syndromes at this time, reflecting the fact that the great size of the frontal lobes relative to the rest of the brain and the various pathologies that damage them often produce diffuse (rather than focal) damage. Facets of these presentations can include increased distractibility, impulsiveness and decreased recognition of errors once made, deficits in being able to sequence information in either time or space, and Lhermitte's Utilization Behavior--wherein patients tend to use objects that they see, regardless as to whether it is appropriate. One of Lhermitte's patient's, for example, whenever she would come in for her examination, would take his stethoscope from around his neck and his reflex hammer from his coat pocket and begin examining him. Another patient, upon seeing any painting or photograph on an office wall would react as if he were in an art museum and want to engage people (such as other patients in the waiting room, the receptionist) in formal art critiques.
Changes in an individual's character and personality are common after significant frontal lobe damage, and when present, a diagnosis of an Organic Personality Syndrome needs to be considered. Head-injured patients with OPS may be characterized by organically based persistent disturbances in self-control. OPS patients may show marked instability in their affect, some going from tears to laughter to anger in seconds. They may show recurrent belligerence and explosive outbursts of aggression or of rage that are grossly out of proportion to any psychosocial or environmental stressors. They may be markedly impaired in their social (interpersonal) judgment. They may show marked apathy called abulia.
The natural history of organic personality features subsequent to head injury is still being charted by research. Clinically, one might expect that the severity of these features would slowly subside over time, making management easier. However, in many cases of severe head injury, psychosocial symptoms may not improve, and may even worsen with lengthening time since the original injury. It has been accepted that moderating variables which can influence behavioral outcome include normal premorbid personality functioning, but perhaps less so with more severe damage. One one-year and five-year follow-up study, which interviewed close relatives of severely head-injured patients, reported persisting behavioral impairments. Aggressive aspects of post-traumatic behavior (i.e., threats or gestures of violence, striking a family member) were reported to be on-going problems by 15% of the interviewees one year after the injury, but were reported to be on-going problems by 54% of the sample at five years. Another study, examining severely head injured patients 10-to-15 years post injury, found that patients with documented brainstem and/or anterior (i.e., frontal lobe) lesions continued to have significant psychosocial impairments. While some patients improved when compared to earlier evaluation at approximately six years after the accident, others were found to be more aberrant in their psychosocial functioning at 10-to-15 years than earlier. Reasons for this can be: (a) increasing frustration and failure in attempting to return to premorbid levels of functioning, (b) increasing alienation of friends, family, work peers and supervisors as a result of behavioral excesses, and (c) increasing social isolation caused by divorce and an inability to keep a job.
Understanding the Abulic-Hypokinetic Syndrome, a variant of OPS, is of particular interest to me. The syndrome is attributable to frontal lobe lesions in, or underlying to, the mesial aspect of the first (superior) frontal gyrus. Some neurologists attribute this syndrome to damage to fronto-diencephalic connections as much as to frontal lobe damage.
Abulia refers to a loss of drive and initiative. It has been described as a loss of purposeful striving. It can be interpreted as either apathy, indifference, and equanimity, depending upon the situational circumstances in which the patient is observed. Hypokinesia refers to the motor complement of the mental phenomenon; that is, patients with this disorder do not initiate motor behavior. Even the normal (unconscious) spontaneous levels of motor activity, such as minor postural adjustments, variations in position, gesturing, are absent or greatly reduced. In the acute phase (or in severe forms) of this disorder, the patient may fail to respond to commands. Mutism is present. In less acute (or less severe) presentations, long delays in initiating responses and slowness in response performance (once initiated) are seen. Upon the return of speech, it may be hypophonic (e.g., whispered) before resuming normal volume. Nevertheless, spontaneous speech is absent or limited. Speech tends to occur only in response to questions or other's speaking in the background. Counterintuitively, occasional and brief periods of excitement or agitation are often reported to occur in this disorder.
When this disorder occurs following unilateral vascular lesions, resolution or near recovery can occur. Persisting abulic-hypokinetic states are almost always attributed to bifrontal vascular or traumatic lesions. If the lesions are discrete, intellectual capacity is retained along with memory. If the patient can cooperate with and respond to memory testing, then performance is usually normal. However, such situations also contain high levels of situational demands (cues) to retain and retrieve information. On the other hand, in everyday situations the patient with this disorder may fail to initiate the retrieval of memories (sometimes referred to as "forgetting to remember").
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