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Chapter 7

Clinical Neruopsych - Chapter 7 - Neuropathology for Neuropsychologists.pdf

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University of Toronto Scarborough
Konstantine Zakzanis

Chapter 7 - Neuropathology for Neuropsychologists -In order to make diagnostic sense out of the behavioural patterns that emerge in neuropsychological assessment, the practitioner must be knowledgeable about the neuropsychological presentation of many kinds of neurological disorders and their underlying pathology -knowledge of these disorders gives the examiner a diagnostic frame of reference that helps to identify, sort out, appraise, and put into a diagnostically meaningful context the many bits and pieces of observational, scores, family reports, and medical and social history that typically make up the material of a case Neurological Disorders (exemplified) -head trauma -vascular disorders -degenerative disorders -multiple sclerosis -normal pressure hydrocephalus -toxic conditions -infectious processes Traumatic Brain Injury (TBI) -defined as an alteration in brain function, or other evidence of brain pathology, caused by an external force -generally refers to injury involving the brain resulting from some type of impact and/or acceleration/deceleration of the brain -traumatic brain injury is the most common cause of brain injury -head injuries resulting from “falls” are most likely to be incurred by infants and young children -accident involving moving vehicles account for approximately half of all head injuries in the other age groups -head injury is still synonymous with TBI, but in some cases it refers to injury of other head structures such as the face or jaw -brain damage typically occurs in two stages -primary injury: damage that occurs at time of impact -secondary injury: physiological processes set in motion by the primary injury -the primary injury -coup -the blow at the point of impact -countercoup lesions -when the brain sustains a bruise (contusion) in an area opposite the blow, occurs in most cases of occipital injury -coup and countercoup lesions account for specific and localizable behavioural behavioural changes that accompany closed head injuries -the movement of the brain within the skull puts strains on delicate nerve fibers and blood vessels that can stretch them to the point shearing -shearing effects -microscopic lesion that occur throughout the brain tend to be concentrated in the frontal and temporal lobes and the interfaces between gray and white matter -hence the diffuse damage and neuropsychological effects -the more severe the injury, the more likely it is that the patient will display deficits characteristic of frontal and temporal lobe injuries along with behavioural abnormalities and the more prominent these deficits will be -impairments in information processing speed, attention, and learning and consequent retrieval is most common neuropsychological profile in mild and moderate TBI, as well as severe TBI, although extent of executive disturbances is more prominent in these patients Closed vs Open Head Injuries -closed head injuries (CHI) are referred to as blunt head trauma or blunt injury -the skull can be fractured and the injury may still be a CHI as long as the meningeal covering of the brain itself is not breached by penetration through the skull -account for most head injuries -Penetrating head injuries (PHI) a.k.a. open head injuries (OHI) include all injuries from any source in which the skull and dura are penetrated by missiles or other objects -account for less than 10% of all documented head trauma in the civilian population -there are commonalities between CHI and PHI, the nature of the injury along with the pathophysiological processes set in motion by damage to the brain may differ in these two types of injuries -acquired brain injury (ABI) refers to just about anything that can damage brain tissue and may be applied to TBIs -concussion: considered a mild form of TBI -secondary or delayed injuries are sometimes more dangerous than the primary cause of the TBI -hemorrhage, hypoxia (insufficient oxygen), ischemia (insufficient or absent blood supply), elevated intracranial pressure (ICP), and changes in metabolic function, coagulopathy (blood clotting), and pyrexia (fever) -prevalence estimates and incidence reports in epidemiological studies vary depending on such decisions as whether to include all grades of severity, to count deaths, to limit the study to hospitalized patients, etc -for the most common type of CHI, mild TBI, many of the injured may never seek medical care -peak ages for TBI are in the 15 - 24 year range with high incidence rates also occurring in the first five years and for elderly persons -helmets have reduced head injuries in sports such as bicycling, hockey, horseback riding, and football although not all helmets reduce craniofacial injuries effectively -low socioeconomic status, unemployment, and lower educational levels are also risk factors, increasing the likelihood of TBIs due to falls or assaults more than for other groups -TBI: young working class males, limited educational attainment, lack of previous stable work prior to injury -Violent TBI: less than high school, unemployed, male, high blood alcohol level at time of injury, and african americans -the behavioural effects of all brain lesions binge upon a variety of factors, such as severity, age, site of lesions, premorbid personality, and the mechanisms of the injury Diagnosis of TBI -how a TBI is categorized depends on the injury characteristics, not some random point post status by way of “severity” of cognitive impairment -glasgow coma scale (GCS): not appropriate for many cases, and it largely meaningless without other form of supplementary material -duration of lost consciousness: good predictor for severe injuries -post traumatic amnesia: brief or no PTA associated with with mild injury with increasing PTA duration associated with more severe injury -neuroimaging -neuropsychological testing -retrograde amnesia (RA) usually involving the minutes, sometimes hours and more rarely days immediately preceding the accident, frequently accompanies PTA -frontal and temporal regions, as well as the anterior cingulate gyrus implicated in RA -visual field defects are stone indicators of severity -anosmia (loss of smell) can be a marker of not only damage to olfactory regions but also the orbitofrontal damage Severity Classifications and Outcome Prediction -patients whose injuries seem mild, as measured by most accepted methods, may have relatively poor outcomes both cognitively and socially -patients classified as moderately to severely injured have enjoyed surprisingly good outcomes Glasgow coma scale (GCS) -classification system based on elcation of depth and duration of altered consciousness -good predictor of injury outcome Mild Traumatic Brain Injury -GCS: 13 - 15 -duration of lost consciousness corresponds to less than 20 minutes -post traumatic amnesia corresponds to less than 24 hours -Islands of memory -temporal/continuous memory -no evidence of intracranial injury on neuroimaging examination -Complicated Mild Traumatic Brain Injury: same as above, except THERE IS intracanial injury present Moderate Traumatic Brain Injury -GCS: 10 - 12 -duration of lost consciousness corresponds to greater than 20 minutes and less than 36 hours -duration of post traumatic amnesia is greater than 24 hours and less than seven days Severe Traumatic Brain Injury -GCS: 9> -duration of lost consciousness is greater than 36 hours -duration of post traumatic amnesia is greater than seven days Penetrating Head Injuries -injuries reported from a diverse array of objects -gunshot wounds to the head are the leading cause of PHI -focal lesions, usually produce relatively circumscribed and predictable cognitive losses -PHI can also result from a tangential injury in which an object glances off the skull, fracturing it along with the fragments driven into the brain although the object does not actually penetrate the brain -PHI mortality higher than CHI -rapid gains in the first 1-2years -further improvement is possible, however it is a very slow process -more likely a result of learned accommodations and compensations than of return of renewal of function -certain cognitive functions improve quicker than others, some never return to premorbid levels of efficacy -although focal effects are typically more pronounced than diffuse ones -patients with open head injuries may also show impairments consistent with diffuse injury -information processing deficits -attention and concentration -memory Predictors of Recovery from TBI Positive Prognosis Negative Prognosis -younger than 35 years old -older than 45 years older -no previous brain injury -previous brain injury -no history of substance abuse -history of substance abuse -good academic achievement -history of academic achievement -stable work history -erratic work history -strong social support networks -poor social support networks -no history of legal difficulties -criminal history -premorbid independence -no history of independence Closed Traumatic Brain Injuries -mild traumatic brain injury accounts for about 90% of traumatic brain injuries -traumatic brain injury of any severity can result in cognitive disorder characterized by difficulties in: -behavioural expressions, memory, concentration, decision making, mood, etc -outcome is largely dependent on a number of factors. also defined by injury characteristics, defined by initial GCS, duration of lost consciousness, post traumatic amnesia and the presence or absence of intracranial injury on neuroimaging examination taken against the duration that has elapsed post status Outcome from mild TBI -evidence based -cumulative research on the outcome of a single, uncomplicated mild traumatic brain injury shows that neuropsychological impairments may persist for up to three months, but the norm is full recovery with no long-term residual deficits -meta analyses -when using an evidence based approach in a recent meta analytic publication it was found that persons with mild traumatic brain injury essentially returned to a baseline level of normal cognitive performance within one to three months post-trauma -there was a 97% overlap of control and mild traumatic brain injury test performance by one month post-trauma and the 95% confidence intervals of effect size estimates at both 30- 89 days and more than 89 days post-trauma included zero. -the authors of this study interpreted the data as showing that the overall cognitive test performance of those with mild traumatic brain injury was essentially indistinguishable from that of matched controls by one-month post-trauma -the maximum prevalence of persistent neuropsychological deficit after three months is likely to be little to none and as such, the neuropsychological assessment is likely to have positive predictive value of less than 50% -one will more likely be correct when not diagnosing brain injury when diagnosing brain injury when diagnosing a brain injury in cases with chronic disability after mild traumatic brain injury Outcome from Moderate TBI (and complicated mild TBI) -cumulative research on the outcome of a single uncomplicated moderate traumatic brain injury demonstrates the severe disability does occur after moderate traumatic brain injury, although it is uncommon -that is, some reports indicate that no moderately injured patients remained with severe disability at 6 months post-injury, whilst others found that 6% to 14% had severe disabililty -moderate disability is a more common outcome and is seen about 25% of patients at 6 months post injury -good recovery is by far the most common outcome after moderate traumatic brain injury, with 53% to 73% of cases showing good recovery Outcome from a severe TBI -for survivors of severe TBI, the vast majority of neurobehavioural recovery is made
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