Movement Disorders Sourcebook, 4th Ed.

James Chambers

• Publisher: Omnigraphics
• Year: 2021
• eBook ISBN: 9780780819146
• Topic: Medicine
• Subtopic: General Health

Consumer health information about diagnosis, treatment, and management of Parkinson disease and other hypokinetic and hyperkinetic movement disorders, along with advice for family members and caregivers.

Part 1 | Introduction to Movement Disorders

Chapter 1 | Anatomy of the Brain: How the Brain Controls the Body’s Movements

The central nervous system (CNS) consists of the brain and spinal cord, which are located in the dorsal body cavity. The brain is surrounded by the cranium, and the spinal cord is protected by the vertebrae. The brain is continuous with the spinal cord at the foramen magnum. In addition to bone, the CNS is surrounded by connective tissue membranes, called “meninges,” and by cerebrospinal fluid. The following are the major components of the brain and CNS:

• Neurons and glial cells
• Brain
• Meninges
• Spinal cord
• Cranial nerves
• Pineal and pituitary glands

Brain

Cerebrum

The cerebrum is the part of the brain that receives and processes conscious sensation, generates thought, and controls conscious

Figure 1.1. Lobes of the Cerebrum

activity. It is the uppermost and largest part of the brain and is divided into left and right hemispheres, which are joined by and communicated through the corpus callosum.

Each cerebral hemisphere is divided into five lobes, four of which have the same name as the bone over them: the frontal lobe, the parietal lobe, the occipital lobe, and the temporal lobe. A fifth lobe, the insula or island of Reil, lies deep within the lateral sulcus.

Cerebellum

The cerebellum is a cauliflower-shaped part of the brain located in the hindbrain, at the bottom rear of the head, directly behind the pons. The cerebellum is a complex system mostly dedicated to the intricate coordination of voluntary movement, including walking and balance. Damage to the cerebellum leaves the sufferer with a gait that appears drunken and is difficult to control.

Ventricles and Cerebrospinal Fluid

A series of interconnected, fluid filled cavities called “ventricles” lie within the brain. The fluid is cerebrospinal fluid (CSF), which also circulates over the outside of the brain and spinal cord.

Brainstem

The brainstem is the part of the brain continuous with the spinal cord and comprising the medulla oblongata, pons, midbrain, and parts of the hypothalamus.

Tentorium

The tentorium is a fold of the dura mater, which separates the cerebellum from the cerebrum and often encloses a process or plate of the skull called the “bony tentorium.”

Meninges

There are three layers of meninges around the brain and spinal cord. The outer layer, the dura mater, is tough, white fibrous connective tissue. The middle layer of meninges is the arachnoid, a thin layer resembling a cobweb with numerous thread-like strands attaching it to the innermost layer. The space under the arachnoid, the subarachnoid space, is filled with cerebrospinal fluid and contains blood vessels. The pia mater is the innermost layer of meninges. This thin, delicate membrane is tightly bound to the surface of the brain and spinal cord and cannot be dissected away without damaging the surface.

Spinal Cord

The spinal cord extends from the foramen magnum at the base of the skull to the level of the first lumbar vertebra. The cord is continuous with the medulla oblongata at the foramen magnum. Like the brain, the spinal cord is surrounded by bone, meninges, and cerebrospinal fluid.

The spinal cord is divided into 31 segments, with each segment giving rise to a pair of spinal nerves. At the distal end of the cord,

Figure 1.2. Meninges

Dura matter – outer layer lining skull

Arachnoid (matter) – contains blood vessels

Subarachnoid space – filled with CSF

Pia mater – covers brain

many spinal nerves extend beyond the conus medullaris to form a collection that resembles a horse’s tail. This is the cauda equina. In cross section, the spinal cord appears oval in shape.

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This chapter includes text excerpted from “Anatomy and Function Areas of the Brain and CNS,” Surveillance, Epidemiology and End Results Program (SEER), National Cancer Institute (NCI), September 7, 2016. Reviewed July 2021.

Chapter 2 | Anatomy of the Nervous System

The nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory. Together with the endocrine system, the nervous system is responsible for regulating and maintaining homeostasis. Through its receptors, the nervous system keeps us in touch with our environment, both external and internal.

Like other systems in the body, the nervous system is composed of organs, principally the brain, spinal cord, nerves, and ganglia. These, in turn, consist of various tissues, including nerve, blood, and connective tissue. Together these carry out the complex activities of the nervous system.

The various activities of the nervous system can be grouped together as three general, overlapping functions:

• Sensory
• Integrative
• Motor

Millions of sensory receptors detect changes, called “stimuli,” which occur inside and outside the body. They monitor such things as temperature, light, and sound from the external environment. Inside the body, the internal environment, receptors detect variations in pressure, pH, carbon dioxide concentration, and the levels of various electrolytes. All of this gathered information is called “sensory input.”

Sensory input is converted into electrical signals called “nerve impulses” that are transmitted to the brain. There the signals are brought together to create sensations, to produce thoughts, or to add to memory; decisions are made in each moment based on the sensory input. This is integration.

Based on the sensory input and integration, the nervous system responds by sending signals to muscles, causing them to contract, or to glands, causing them to produce secretions. Muscles and glands are called “effectors” because they cause an effect in response to directions from the nervous system. This is the motor output or motor function.

Nerve Tissue

Although the nervous system is very complex, there are only two main types of cells in nerve tissue. The actual nerve cell is the neuron. It is the “conducting” cell that transmits impulses and the structural unit of the nervous system. The other type of cell is neuroglia, or glial, cell. The word “neuroglia” means “nerve glue.” These cells are nonconductive and provide a support system for the neurons. They are a special type of “connective tissue” for the nervous system.

Neurons

Neurons, or nerve cells, carry out the functions of the nervous system by conducting nerve impulses. They are highly specialized and amitotic. This means that if a neuron is destroyed, it cannot be replaced because neurons do not go through mitosis. The image below illustrates the structure of a typical neuron.

Each neuron has three basic parts: cell body (soma), one or more dendrites, and a single axon.

Dendrites

Dendrites and axons are cytoplasmic extensions, or processes, that project from the cell body. They are sometimes referred to as fibers.

Figure 2.1. Structure of a Typical Neuron

Dendrites are usually, but not always, short and branching, which increases their surface area to receive signals from other neurons. The number of dendrites on a neuron varies. They are called “afferent processes” because they transmit impulses to the neuron cell body. There is only one axon that projects from each cell body. It is usually elongated and because it carries impulses away from the cell body, it is called an “efferent process.”

Axon

An axon may have infrequent branches called “axon collaterals.” Axons and axon collaterals terminate in many short branches or telocentric. The distal ends of the telocentric are slightly enlarged to form synaptic bulbs. Many axons are surrounded by a segmented, white, fatty substance called “myelin” or the “myelin sheath.” Myelinated fibers make up the white matter in the CNS, while cell bodies and unmyelinated fibers make the gray matter. The unmyelinated regions between the myelin segments are called the “nodes of Ranvier.”

In the peripheral nervous system, the myelin is produced by Schwann cells. The cytoplasm, nucleus, and outer cell membrane of the Schwann cell form a tight covering around the myelin and around the axon itself at the nodes of Ranvier. This covering is the neurilemma, which plays an important role in the regeneration of nerve fibers. In the CNS, oligodendrocytes produce myelin, but there is no neurilemma, which is why fibers within the CNS do not regenerate.

Functionally, neurons are classified as afferent, efferent, or interneurons (association neurons) according to the direction in which they transmit impulses relative to the central nervous system. Afferent, or sensory, neurons carry impulses from peripheral sense receptors to the CNS. They usually have long dendrites and relatively short axons. Efferent, or motor, neurons transmit impulses from the CNS to effector organs such as muscles and glands. Efferent neurons usually have short dendrites and long axons. Interneurons, or association neurons, are located entirely within the CNS in which they form the connecting link between the afferent and efferent neurons. They have short dend...

Table of contents

• Cover
• Halftitle
• Title
• Copyright
• Table of Contents
• Part 1. Introduction to Movement Disorders
• Part 2. Hypokinetic Movement Disorders
• Part 3. Hyperkinetic Movement Disorders
• Part 4. Cerebellar Disorders and Ataxias
• Part 5. Childhood Movement Disorders
• Part 6. Diagnosis and Treatment of Movement Disorders
• Part 7. Living with Movement Disorders
• Part 8. Additional Help and Information
• Index