The Nervous System

The Parkinson's-Reversing Breakthrough

Diets for Parkinsons

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As the debility increases and the influence of the will over the muscles fades, the tremulous agitation becomes more vehement. It now seldom leaves him for a moment; but even when exhausted nature seizes a small portion of sleep, the motion becomes so violent as not only to shake the bed-hangings, but even the floor and sashes of the room. The chin is now almost immovably bent down upon the sternum. The slops with which he is attempted to be fed, with the saliva, are continually trickling from the mouth. The power of articulation is lost. The urine and faeces are passed involuntarily; and at the last, constant sleepiness, with slight delirium, and other marks ofextreme exhaustion, announce the wished-for release.

James Parkinson (1755-1824)

General Considerations

By the second century ce, Galen had already described the cerebral ventricles, 7 of the 12 cranial nerves, and the cerebral convolutions. There was, however, little further interest in the anatomy and physiology of the neurologic system until the 16th century. In 1543, Andreas Vesalius illustrated the basal ganglia, and in 1552, Bartolommeo Eustachius described the cerebellar peduncles and the pons.

In the 17th century, Thomas Willis published descriptions and illustrations of the cerebral circulation, the ''striate body,'' and the internal capsule. Caspar Bartholin and others thought that the function of the cerebral cortex was to protect the blood vessels, whereas other investigators believed that the cerebrum possessed higher functions. Francois Pourfour du Petit stressed that the cortex was responsible for motor activity. This concept lay dormant until the end of the 19th century.

Careful anatomic descriptions of the tracts, nuclei, and gyri were contained in the writings of scientists of the 18th and early 19th centuries. Johann Christian Reil and Karl Friedrich Burdach provided names for the many gross anatomic structures that had been illustrated by others in previous centuries. Reil has been credited with the naming of the insula, capsule, uncinate and cingulate fasciculi, and tapetum. The uncus, lenticular nucleus, pulvinar, and gyrus cinguli were named by Burdach. During this same period, Samuel von Soemmering, Felix Vicq d'Azyr, Franz Josef Gall, Louis Gratiolet, and Luigi Rolando made many detailed illustrations of the cerebral convolutional patterns.

In the early 19th century, the first descriptions of several disease states were published. In 1817 James Parkinson wrote an essay describing the ''shaking palsy'' that now bears his name. In 1829 Charles Bell wrote:

The next instance was in a man wounded by the horn of an ox. The point entered under the angle of the jaw and came out before the ear____ He remains now a singular proof of the effects of the loss of function in the muscles of the face by this nerve being divided. The forehead of the corresponding side is without motion, the eyelids remain open, the nostril has no motion in breathing, and the mouth is drawn to the opposite side.

This is the classic description of facial nerve (seventh cranial nerve) palsy, also known as Bell's palsy.

In the mid-19th century, an interest in microscopic neuroanatomy developed. Jan Purkinje, Theodor Schwann, and Hermann von Helmholtz were a few of the many neuroanatomists who contributed valuable information about the intricacies of the nervous system. However, not until the late 19th century were specific staining techniques developed by Camillo Golgi, Vittorio Marchi, and Franz Nissl, which led to the current understanding of neuronal disease. The nerve cell had finally been discovered.

The 20th century was a period of further progress in the description of the cerebral cortex, anterior commissure, thalamus, and hypothalamus. A major advance came from the work of Santiago Ramon y Cajal in 1904. His histologic exploration clarified the complexities of the neuron. Not until 1925 were the hypophysial-hypothalamic connections described, and even today, the function of the hypothalamus is not fully understood.

It has been suggested that more than 40% of patients who present to internists have symptoms referable to neurologic disease. The internist must be able to identify the early signs and symptoms of neurologic disease and initiate the appropriate therapy. All too often, subtle signs and symptoms may be ignored, and a diagnosis is not made until advanced disability is apparent.

Cerebrovascular disease is one of the most devastating diseases of our time. It remains the third leading cause of death in the United States. More than 700,000 Americans suffer a stroke yearly, and it is the number one cause of disability;more than 3 million Americans currently live with permanent brain damage caused by such an event. On average, someone in the United States suffers a stroke every 53 seconds, and every 3.3 minutes, someone dies of one. In 2007, there were 151,147 deaths from cerebrovascular disease, and 5.2 million noninstitu-tionalized adult Americans have had a stroke. In addition, 8.1% of all hospital inpatient deaths are related to stroke and cerebrovascular disease. The debilitating consequences of stroke and the economic impact on society are enormous.

The generalist or internist holds an important position because a patient with a neurologic problem usually seeks help from that physician first. A thorough knowledge of basic neuro-anatomy and physiology is the cornerstone of neurologic diagnosis.

Structure and Physiology

The brain, which is enclosed in the cranium and surrounded by the meninges, is the center of the nervous system. The brain can be divided into paired cerebral hemispheres, basal ganglia, diencephalon (thalamus and hypothalamus), brain stem, and cerebellum.

The two cerebral hemispheres make up the largest portion of the brain. Each hemisphere can be subdivided into four major lobes named for the cranial bones that overlie them: frontal, parietal, occipital, and temporal. The fissures and sulci divide the cerebral surface. A deep midline, longitudinal fissure separates the two hemispheres. The convolutions, or gyri, lie between the sulci. A lateral view of the left cerebral hemisphere is pictured in Figure 21-1. Figure 21-2 is a medial view of the right cerebral hemisphere. A basal view of the cerebral hemispheres is pictured in Figure 21-3.

The cerebrum is responsible for motor, sensory, associative, and higher mental functions. The primary motor cortex is located in the precentral gyrus. Neurons in this area control voluntary movements of the skeletal muscles on the opposite side of the body. An irritative lesion in this area may cause seizures or changes in consciousness. Destructive lesions in this area can produce contralateral flaccid paresis or paralysis.

The primary sensory cortex is located in the postcentral gyrus. Irritative lesions in this area may produce paresthesias (''numbness'' or a "pins-and-needles" sensation) on the opposite side. Destructive lesions produce an impairment in cutaneous sensation on the opposite side.

The primary visual cortex is located in the occipital lobe along the calcarine fissure, which divides the cuneus from the lingual gyri. Irritative lesions in this area produce visual symptoms

Central sulcus Precentral gyrus

Postcentral gyrus

Frontal lobe

Parietal lobe

Central sulcus Precentral gyrus

Postcentral gyrus

Parietal lobe

Frontal lobe

Occipital lobe

Cerebellum

Lateral sulcus

Temporal lobe

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