Cognitive Effects of Brain Injury and Disease
The care of patients with brain injury and diseases has improved substantially over the last thirty years. Nonetheless, the acute cognitive effects caused by brain injury are still a problem for the survivors. Such impairments are substantial contributors to functional disability after brain injury and reduce quality of life for affected persons and their families (Schultza, Cifub, McNameea, Nicholsb; Carneb, 2011). Accordingly, it is important for clinicians providing care to persons with brain injury to be familiar with the cognitive squeal of such injuries, their neuropathophysiologic bases, the treatment options that may alleviate such problems, and their effects on functional ability and quality of life.
Literature Review: Cognitive Effects
The anatomy, pathophysiology, and cognitive sequel of brain injury and diseases vary as a function of cause of brain injury. Accordingly, identification of the specific cause of injury and other relevant factors (e.g., age, injury severity, comorbid conditions, etc.) is needed to understand the cognitive sequel of brain injury. For the survivors of severe brain injury, 30 -- 60% will develop persistent cognitive, behavioral, and/or other neurological problems (Howard, Holmes, Koutroumanidis, 2011).
These problems may be functionally debilitating and severely affect quality of life for patients and their families. Common elementary neurological impairments include parkinsonism, dystonia, chorea, tremor, tics, athetosis, seizures, and myoclonic syndromes (Schultza, Cifub, McNameea, Nicholsb; Carneb, 2011). Cognitive impairments include disturbances of arousal (e.g., coma, vegetative states), awareness and attention (e.g., minimally conscious state, delirium), and higher-level cognitive functions, most commonly including disturbances of processing speed, memory, and executive function. Additionally, as many as 35% of these individuals experience depression within the first 3 months following brain injury and more than 30% are depressed at 12 months post-injury (Howard, Holmes, Koutroumanidis, 2011).Cognitive impairment is among the more fully characterized neurobehavioral sequel of brain injury, and one that neurologists and neuro-rehabilitation specialists are often asked to evaluate, to make recommendations regarding their management, and to opine on prognosis for recovery both in the early post-resuscitation period and thereafter. In the service of providing information that may be of use to clinicians performing these and related tasks, the present work reviews and summarizes the literature describing cognitive impairments due to brain injury. Studies published and indexed in Medline/PubMed were identified (Schultza, Cifub, McNameea, Nicholsb; Carneb, 2011).
Post-Brain Injury And Brain Disease Cognitive Impairments
Among patients whose severities of injury permit recovery to a level above MCS, a variety of other cognitive impairments may develop and produce substantial interference with functional independence and quality of life (Aaro, Smedler, Leis, Emanuelson, 2009). The cognitive effects of brain injury like attention, speed of processing, memory, and executive function are discussed below:
Attention and Processing Speed Impairments
Although the word 'attention' is often used as if it referred to a unitary cognitive function, attention actually denotes a collection of interrelated processes that detect, select, and sustain focus on one or more external or internal stimuli. Included in this set of processes are: cortical orientation, the process by which primary sensory cortices detect novel stimuli; selective attention, which refers to the selection from among the many sensory events processed simultaneously in the brain the one that will be admitted into consciousness for further processing; sustained attention (also referred to as concentration or vigilance), which refers to the maintenance of attention on a selected target; and divided attention, which refers to the selection and sustained processing of two or more stimuli simultaneously (Aaro, Smedler, Leis, Emanuelson, 2009
Working memory is closely related to attentional processes, and involves the temporary maintenance and manipulation of information 'off-line' (i.e., keeping one or a small set of words, numbers, images, sounds, etc. 'in mind' briefly after they are presented) . Closely related to attention is processing speed, which refers to the rate at which information is processed in the brain; this process is manifested clinically as reaction time or response latency. Attention and processing speed are supported by several large-scale selective distributed networks. These networks include: primary and secondary sensory cortical areas; tertiary (heteromodal parietal) cortical areas cross-linking information between primary and secondary sensory cortices; quaternary (heteromodal frontal) cortical areas that elaborate, organize, modulate, and permit interpretation of information processed elsewhere; the frontal-subcortical circuits required for higher-level attentional processing and working memory; and multiple white matter bundles connecting the cortical-cortical and cortical-subcortical areas comprising these networks (Piros et al. 2012).
Injury to any of these areas may affect attention and processing speed; in general, injury to or dysfunction of cortical areas disrupts one or more aspects of attention whereas injury to or dysfunction of their...
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