Bulbar palsy is a syndrome that affects the lower motor neurons of the brain and can be caused by genetic, vascular, degenerative, and inflammatory diseases, malignancy, and bacterial toxins. It affects the lower cranial nerves of the brain and can result in weakness in muscles responsible for chewing, swallowing, speaking, breathing, and facial movement.
Bulbar palsy is a syndrome that affects the lower motor neurons of the brain. There are several causes of bulbar palsy, including genetic, vascular, degenerative, and inflammatory diseases; malignancy; and bacterial toxins. It occurs when the lower cranial nerves of the brain are damaged due to trauma to the cells or motor control center of the brainstem, or from other injuries to the lower cranial nerves in the brainstem. “Bulbar” refers to the area of the lower brainstem, or medulla oblongata, that controls cranial nerves seven through 12, and “paralysis” is a form of bodily weakness, so bulbar palsy is any weakness caused by injury, trauma or defect to these nerves or the area that controls them.
Genetic causes of bulbar palsy include Kennedy disease, which is a neuromuscular disease, and acute intermittent porphyria, a metabolic disorder that can lead to disease of the neurons. A stroke that affects this lower area of the brainstem is called a medullary infarction. This damage to the vasculature can affect lower motor function of the lower cranial nerves. Motor neuron disease, which is caused by toxins; and other degenerative diseases, including syringobulbia, which is a complication in neurological pathways that causes the inside of the brain to dilate; it can also cause bulbar palsy.
Lower motor neurons can be damaged by infection leading to inflammation, such as in cases of Guillan-Barré syndrome, polio and Lyme disease, and in the case of a brain tumor. Guillan-Barré syndrome provides an example of how nerve centers are damaged by an inflammatory disease. In this case, the progressive weakness causes initial peripheral paralysis, or weakness of the arms and legs, which eventually travels back to the bulbar centers of the brain. This progressive paralysis creates disorder within the motor neurons of the brain, causing loss of muscle control.
Bulbar palsy can also be caused by a malignant tumor, such as a brain tumor. If the brainstem develops a tumor, or glomia, it can override normal brain and motor functioning. Motor function may be permanently impaired, even if the tumor is found and removed. The bacterial toxin that causes botulism creates muscle paralysis through the body’s bloodstream and affects lower motor functioning. Cases of botulism are rare in developing countries, making it the least likely cause of bulbar palsy.
Bulbar palsy is a degenerative disease. The cranial nerves affected by bulbar palsy control the muscles responsible for chewing, swallowing, speaking and, in some cases, breathing and facial movement. If one of these nerves is damaged, the lower motor neurons are affected and paralysis results. It is often confused with pseudobulbar palsy, which shares many of the same symptoms as bulbar palsy, but is caused by upper motor neuron damage resulting from strokes and affects different areas of the cerebral cortex.
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