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Cognitive disorders. Disorders of motor function. Disorders of peripheral nerves. Alterations in coordination of muscle movements
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Cognitive disorders
Cognitive disorders can be caused by any disorder that permanently damages large cortical or subcortical areas of the hemispheres. The most common cause of dementia is Alzheimer’s disease, which is a major health problem among the elderly. It is characterized by cortical atrophy and loss of neurons, the presence of neuritic plaques, granulovacuolar degeneration, and cerebrovascular deposits of amyloid. The disease follows an insidious and progressive course that begins with memory impairment and terminates in an inability to recognize family or friends and the loss of control over bodily functions.
Multi-infarct dementia is associated with vascular disease and Pick’s disease with atrophy of the frontal and temporal lobes.
Creutzfeldt-Jakob disease is a rare transmissible form of dementia. Wernicke-Korsakoff syndrome results from chronic alcoholism. Huntington’s disease is a rare hereditary disorder characterized by chronic and progressive chorea, psychological change, and dementia.
Disorders of motor function
Disorders of motor function include disorders of the skeletal muscle, the neuromuscular junction, and the peripheral nerves.
Muscular dystrophy is a number of disorders that produce progressive degradation of skeletal muscle. Muscle necrosis is followed by fat and connective tissue replacement. Duchenne muscular dystrophy, is inherited as a X-linked trait and transmitted by the mother to her male offspring.
Myasthenia gravis is a disorder of the neuromuscular junction resulting from a deficiency of functional acetylcholine receptors, which causes weakness of the skeletal muscles. Because the disease affects the neuromuscular junction, there is no loss of sensory function. The most common manifestations are weakness of the eye muscles, with ptosis and diplopia; the jaw muscles, which make chewing and swallowing difficult; and proximal muscles and extremities, which make climbing stairs and lifting objects difficult.
Disorders of peripheral nerves
include mononeuropathies and polyneuropathies.
Mononeuropathies involve a single spinal nerve, plexus, or peripheral nerve trunk. Carpal tunnel syndrome, a mononeuropathy, is caused by compression of the medial nerve that passes through the carpal tunnel in the wrist.
Polyneuropathies involve multiple peripheral nerves and produce symmetric sensory, motor, and mixed sensorimotor deficits.
Guillain-Barre syndrome is a subacute polyneuropathy of uncertain origin. It causes progressive ascending motor, sensory, and ANS manifestations. Respiratory involvement may occur and necessitate mechanical ventilation.
Alterations in coordination of muscle movements
Alterations in coordination of muscle movements and abnormal muscle movements result from disorders of the basal ganglia and cerebellum. The basal ganglia organize basic movement patterns into more complex patterns and release them when commanded by the motor cortex, contributing gracefulness to cortically initiated and controlled skilled movements. Disorders of the basal ganglia are characterized by involuntary movements, alterations in muscle tone, and disturbances in posture. These disorders include tremor, tics, chorea, athetosis, dystonias, and dyskinesias.
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Parkinsonism, a disorder of the basal ganglia, is characterized by destruction of the nigrostriatal pathway, with a subsequent reduction in striatal concentrations of dopamine.
This results in an imbalance between the inhibitory effects of dopaminergic basal ganglia functions and an increase in the excitatory cholinergic functions. The disorder is manifested by of slowness of movement (i. e. , bradykinesia), increased muscle tonus and rigidity, rest tremor, gait disturbances, and impaired autonomic postural responses.
The cerebellum is responsible for smoothing of rapid movement in the body. The cerebellum also to have a role in learning both motor and cognitive tasks in which skilled responses are developed through repeated practice. Cerebellar disorders include vestibulocerebellar dysfunction, cerebellar ataxia, and cerebellar tremor.
Spinal cord injury
Spinal cord injury is a neurologic condition most commonly caused by motor vehicle accidents, falls, and sports injuries. Dysfunctions of the nervous system after SCI comprise various degrees of sensorimotor loss and altered reflex activity. Depending on the level of injury, the physical problems of SCI include spinal shock; ventilation and communication problems; next, autonomic nervous system dysfunction, that predisposes to the vasovagal response, autonomic hyperreflexia, impaired body temperature regulation, and postural hypotension; impaired muscle pump and venous innervation leading to edema of dependent areas of the body and risk of deep vein thrombosis; altered sensorimotor integrity that contributes to uncontrolled muscle spasms, altered pain responses, and threat to skin integrity; alterations in bowel and bladder elimination; and impaired sexual function.
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