pediagenosis: Nervous
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Showing posts with label Nervous. Show all posts
Showing posts with label Nervous. Show all posts

Tuesday, April 13, 2021

NEURONAL GROWTH FACTORS AND TROPHIC FACTORS

NEURONAL GROWTH FACTORS AND TROPHIC FACTORS


NEURONAL GROWTH FACTORS AND TROPHIC FACTORS

NEURONAL GROWTH FACTORS AND TROPHIC FACTORS
Neuronal growth factors and trophic factors are signal molecules produced by neurons, glia, and target tissues that can influence neuronal differentiation, growth of neurites, establishment of contacts for signaling, maintenance of neural contacts with their central or peripheral targets, and other functions. 

Saturday, April 3, 2021

Motor Control And The Cerebellum

Motor Control And The Cerebellum

Motor Control And The Cerebellum
Motor control
Motor control is defined as the control of movements by the body. These movements can be both influenced and guided by the many sensory inputs that are received, or can be triggered by sensory events. They can also be triggered by the need to move using internal mechanisms. The major division of the body into sensory and motor functions is artificial, because almost all motor areas in the central nervous system (CNS) receive sensory inputs.
The organization and physiology of motor systems have been represented as a number of hierarchical structures, but these must be viewed with caution, as they are again artificial and, by necessity, oversimplified.
Motor Control And The Cerebellum
        Figure 59a shows the major ascending sensory inputs and descending motor outputs, and Figure 59b shows the main looped pathways within the CNS.

Tuesday, March 9, 2021

FRONTOTEMPORAL DEMENTIA

FRONTOTEMPORAL DEMENTIA

FRONTOTEMPORAL DEMENTIA

Frontotemporal dementia (FTD) is a heterogeneous spectrum of disorders marked by degeneration in the frontal and anterior temporal lobes, resulting in various symptoms of disturbed personality, behavior, and language. FTD is the third most common form of neuro- degenerative dementia, ranking after Alzheimer disease and dementia with Lewy bodies, accounting for perhaps 5% of all dementia cases. FTD generally presents at a younger age than Alzheimer disease and has a mean age at onset of 58 years.

DEMENTIA WITH LEWY BODIES

DEMENTIA WITH LEWY BODIES

DEMENTIA WITH LEWY BODIES

Dementia with Lewy bodies (DLB) is the second most common cause of dementia, accounting for 10% to 15% of dementia cases. The pathologic hallmark of DLB is the presence of Lewy bodies in neurons of the brainstem, primarily the substantia nigra, and through-out the cerebral cortex. Lewy bodies are primarily composed of abnormal aggregations of the synaptic protein alpha-synuclein. Interestingly, brain changes of Alzheimer disease (plaques and tangles) frequently co-occur with typical Lewy body pathology.

VASCULAR DEMENTIA

VASCULAR DEMENTIA

VASCULAR DEMENTIA

Vascular dementia is interesting in that many of those who do have a true vascular dementia are not diagnosed with it, while many who probably do not have a vascular dementia are diagnosed with it. The most straightfor-ward presentations are those in which an individual with normal cognition has a large stroke that causes a combination of cognitive signs, such as aphasia and a memory retrieval problem. If the patient cannot resume their prestroke day-to-day level of function because of these new cognitive deficits, the criteria for vascular dementia are met, but because the stroke so clearly caused the deficits, they are held to simply represent the consequences of a stroke (as opposed to a frank vascular dementia). On the other hand, some patients will present with a gradually progressive dementia, a retention-type memory deficit, no motor signs, no history of sensory or motor changes, and a neuroimaging study that shows subcortical changes that could be consistent with “small vessel cerebrovascular disease.” In the elderly, such patients almost always have the plaques and tangles that are expected in Alzheimer disease. In such cases, despite the neuroimaging changes, it is probably more appropriate to consider Alzheimer disease as the primary etiology. Still, the frequent association between Alzheimer disease and cerebrovascular pathology suggests these conditions may be linked in some way.

TREATABLE DEMENTIAS

TREATABLE DEMENTIAS

TREATABLE DEMENTIAS

Although in some ways cognitive performance abilities evolve throughout adulthood, many elderly people remain mentally sharp into their ninth and tenth decades. The emergence of uncharacteristic changes in an individual’s cognition that impacts their usual activities should, therefore, trigger an evaluation for possible etiologies.

Because Alzheimer disease is the most common cause of intellectual decline in later life, symptoms or signs that are unusual in Alzheimer disease should particularly alert the physician to a different diagnosis and the possibility of reversing the dementing process. Such features include early age at onset; prominent headache; disturbances of gait or incontinence early in the course of the illness; epileptic seizures; fever; precipitous decline over a period of weeks or months; alteration of consciousness, especially sleepiness, stupor or delirium; history of head trauma; focal neurologic signs, such as lateralized visual, motor, or sensory abnormalities; accompanying dysfunction of peripheral nerves characterized by paresthesias and absent distal reflexes; and known systemic cancer, collagen vascular disease, or endocrinopathy. The presence of any of these features should dictate further evaluation and consideration of the following treatable dementias.

TREATABLE DEMENTIAS


Metabolic Disease with Encephalopathy. When intellectual decline is caused by systemic metabolic disease, there are usually four associated features: diminished alertness; asterixis; a global decrease in mental function, often with a flight of ideas; and variability of intellectual function during the day. The metabolic dysfunction can be either endogenous or exogenous. An endogenous abnormality indicates too much or too little of a substance or metabolite usually found in the body, such as calcium, sodium, thyroid hormone, sugar, and so forth, may be responsible.

ALZHEIMER DISEASE: CLINICAL MANIFESTATIONS, PROGRESSIVE PHASES

ALZHEIMER DISEASE: CLINICAL MANIFESTATIONS, PROGRESSIVE PHASES

ALZHEIMER DISEASE: CLINICAL MANIFESTATIONS, PROGRESSIVE PHASES

The earliest stages of Alzheimer disease are generally marked by cognitive changes in multiple domains of cognition, including memory, executive function, language, and visuospatial function. Of importance, these cognitive changes are often well-compensated, and individuals may still be independent in many activities in the community, and their symptoms may not be readily apparent in casual conversation. Observations from an attentive family member, relative, or friend describing cognitive changes interfering even mildly with the subject’s usual function is a sensitive indicator of the earliest stages of AD.

Thursday, February 18, 2021

PYELOPLASTY AND ENDOPYELOTOMY

PYELOPLASTY AND ENDOPYELOTOMY

PYELOPLASTY AND ENDOPYELOTOMY

A pyeloplasty or endopyelotomy may be performed to treat an obstruction of the ureteropelvic junction (UPJ, see Plate 6-6). A pyeloplasty consists of surgical reconstruction of the UPJ, whereas endopyelotomy consists of intraluminal, endoscopic incision of the obstruction.

ALZHEIMER DISEASE: PATHOLOGY

ALZHEIMER DISEASE: PATHOLOGY

ALZHEIMER DISEASE: PATHOLOGY

Alzheimer disease (AD) is the most common neurodegenerative disorder and affects 10% of people older than age 65 years and nearly 50% of those 85 years and older. The brain affected by AD has gross changes of brain atrophy accompanied by microscopic changes of amyloid plaques and neurofibrillary tangles.

Wednesday, February 17, 2021

NONDOMINANT HEMISPHERE HIGHER CORTICAL DYSFUNCTION

NONDOMINANT HEMISPHERE HIGHER CORTICAL DYSFUNCTION

NONDOMINANT HEMISPHERE HIGHER CORTICAL DYSFUNCTION

When it comes to stroke-induced lateralized deficits, patients with left-sided hemiplegia caused by damage to the nondominant right cerebral hemisphere frequently do not recover as well as patients with similar left hemisphere lesions, despite the fact that they are not aphasic. Return to the work place and previous home and family participation occur less frequently after a stroke causing left-sided hemiplegia. Although disturbances of higher cortical function and behavior in patients with right hemisphere disease are more subtle, they are equally or more functionally disabling than the more obvious aphasia caused by left hemisphere disease. Deficits in right hemisphere disease include the following.

DOMINANT HEMISPHERE LANGUAGE DYSFUNCTION

DOMINANT HEMISPHERE LANGUAGE DYSFUNCTION

DOMINANT HEMISPHERE LANGUAGE DYSFUNCTION

Aphasia, a disorder of language usage and comprehension, should be distinguished from dysarthria, impaired articulation, and mutism, the absence of speech. Usually, the presence of aphasia accurately localizes dysfunction to the cerebral hemisphere concerned with speech.

AMNESIA

AMNESIA

AMNESIA

The term “amnesia” is used generally to describe impairment or loss of memory. It is often subclassified as being either retrograde or anterograde. With retro- grade amnesia, memories that had previously been stored are no longer available. With anterograde amnesia, information occurring in real time does not enter long-term storage. Memory is a complex process comprising three different functions: (1) registration of information, (2) storage by reinforcement, and (3) retrieval.

MEMORY CIRCUITS

MEMORY CIRCUITS

MEMORY CIRCUITS

Long-term memory is a term that encapsulates the brain’s ability to store information. It is subdivided into two main types: explicit memory (also known as declarative memory) and implicit memory (also known as nondeclarative memory). Explicit memory refers to the acquisition of information about objects, stimuli, and information that is consciously noted and recallable. The mesial temporal lobe, which includes the hippocampal formation (CA1, CA3, and dentate gyrus) and ento- rhinal cortex, is the region responsible for this process. While the hippocampal formation stores memories, the entorhinal cortex mediates learning and memory via its interaction with the hippocampus and neocortex. For instance, neocortical information from a visual stimulus is translated via the entorhinal cortex to higher-order complex memory representations such that an emotion can trigger a visual memory. Layer II of the entorhinal cortex is the first region affected in Alzheimer disease (AD). The memory circuit that integrates the mesial temporal lobe and hippocampal formation includes several pathways: the perforant pathway (input to the hippocampus from the entorhinal cortex), Mossy fiber pathway (dentate gyrus to CA3 region), Schaffer collateral/associational commissural pathway (from CA3 to CA1 region), and CA1-subiculum-entorhinal cortex pathway (the principal output of the hippocampus).

TESTING FOR DEFECTS OF HIGHER CORTICAL FUNCTION

TESTING FOR DEFECTS OF HIGHER CORTICAL FUNCTION

TESTING FOR DEFECTS OF HIGHER CORTICAL FUNCTION

It is useful to test functions that can be localized to individual brain regions because abnormalities on these tests can help localize a neuroanatomic defect and thereby suggest a specific etiology. Screening for disorders of higher cortical function can be completed within the context of an office visit, whereas extensive examinations can take up to several hours.

ASTROCYTES

ASTROCYTES

ASTROCYTES

Astrocytes provide structural isolation of neurons and their synapses and provide ionic (K+) sequestration, trophic support, and support for growth and signaling functions to neurons. Oligodendroglia provide myelination of axons in the CNS. Microglia are scavenger cells that participate in phagocytosis, inflammatory responses, cytokine and growth factor secretion, and some immune reactivity in the CNS. Perivascular cells participate in similar activities at sites near the blood vessels. Schwann cells provide myelination, ensheathment, trophic support, and actions that contribute to the growth and repair of peripheral neurons. Activated T lymphocytes normally can enter and traverse the CNS for immune surveillance for a period of approximately 24 hours.

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