Multiple Sclerosis – Literally, “many hardenings,” MS is a disease of unknown cause that manifests as multiple hard plaques of degeneration of the insulating layer of nerve fibers in the central nervous system. The loss of insulation allows “short circuiting” of nerve impulses. Depending upon where the degeneration occurs, patients may suffer paralysis, sensory disturbances or blindness.
Cerebrovascular accident (CVA) - the fancy name for a “stroke”. A blood vessel in the brain may burst causing internal bleeding. Or, a clot may arise in a brain blood vessel (a thrombus), or arise elsewhere (embolus) and travel to get stuck in a brain vessel which then deprives brain tissue of oxygen. Depending upon the area of the brain involved, the patient may suffer paralysis, loss of speech or loss of vision.
Transient Ischemic Attack (TIA) - “Ischemia” was introduced previously in the circulatory diseases module referring to the heart. It literally means “not quite enough blood”. A short period of insufficient blood supply to the brain can have the same signs and symptoms as a stroke such as weakness in an arm, a partial loss of vision, but the problem lasts less than 24 hours. People who get TIA’s are at increased risk of having a stroke in the future.
Epilepsy - a Greek word for “seizure.” Convulsions is another term used. Seizures may have many causes and not all seizures are epilepsy. High fevers in young children may trigger seizures which are short in duration, easily controlled and, typically, have no permanent aftereffects. Epilepsy is a specific condition which may occur at any age, seizures are more intense, longer lasting in duration, and recur with some frequency. The condition may be controlled with medication, or if unresponsive to drugs, may require surgery.
Aphasia - loss of speech. The speech centers are located on the left side of the brain in a majority of people. If someone suffers a “stroke” (cerebrovascular accident-CVA), or traumatic brain injury, and it involves the left side of the brain, they may suffer speech impediments that vary over a spectrum of problems from difficulty in finding the right word, speaking slowly and with difficulty, or complete loss of speech. Actually, there are two speech centers. Injury described above involves the motor speech area, the area of the brain that produces language by integrating thoughts of speech with the movements of the larynx, lips and tongue. There is a second speech area, the receptive or sensory area, that enables us to understand speech. Injury to the latter results in still fluent speech, but the individual does not understand what they are hearing.
Neurologist - a physician specializing in diseases of the brain, spinal cord and nerves. He/she may refer a patient to a neurosurgeon. Neurologists do not do surgery.
Lumbar (spinal) puncture or tap (LP) - introducing a needle between the lower bony vertebrae of our spinal column allows a physician to sample the fluid, cerebrospinal fluid (CSF), surrounding the brain and spinal cord. Lab tests on the fluid are used for diagnostic purposes such as presence of bacteria in meningitis, special proteins in multiple sclerosis, or blood cells.
Brain scan - introducing a radioactive element into the blood can image possible tumors in the brain. The radioactive dose is very low and detectable only with special, very sensitive instruments that are much more sophisticated than the old Geiger counters.
Electroencephalography (EEG) - Wow, what a mouthful, but take it apart. Starting at the end of the word: an image (in this case a written recording) of the brain’s electrical activity. EEGs are used to diagnose different types of seizure disorders such as epilepsy, brain tumors, and are used in sleep research to identify stages of sleep.
Computed tomography (CT) - a specialized X-ray machine that takes multiple images of a body area from different angles and has a computer that integrates the multiple images into “slices” of the body. The resolution is much better than standard X-rays and there is better differentiation of types of tissue (bone, air, solid organ).
Magnetic Resonance Imaging (MRI) – Although the image produces the “slices” through the body seen by CT (see above), no X-rays are involved. The patient’s body is placed in a strong magnetic field. Radio pulses affect the resonance or “spin” of atoms in the tissues. A computer analyzes this information to show subtle differences in tissue molecular structure producing very high resolution and better differentiation of soft tissue, such as a tumor within the liver.
What is the nervous system?
The nervous system is a complex, sophisticated system that regulates and coordinates body activities. It is made up of two major divisions, including the following:
- Central nervous system. This consists of the brain and spinal cord.
- Peripheral nervous system. This consists of all other neural elements.
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In addition to the brain and spinal cord, principal organs of the nervous system include the following:
- Eyes
- Ears
- Sensory organs of taste
- Sensory organs of smell
- Sensory receptors located in the skin, joints, muscles, and other parts of the body
What are some disorders of the nervous system?
The nervous system is vulnerable to various disorders. It can be damaged by the following:
- Trauma
- Infections
- Degeneration
- Structural defects
- Tumors
- Blood flow disruption
- Autoimmune disorders
Disorders of the nervous system
Disorders of the nervous system may involve the following:
- Vascular disorders, such as stroke, transient ischemic attack (TIA), subarachnoid hemorrhage, subdural hemorrhage and hematoma, and extradural hemorrhage
- Infections, such as meningitis, encephalitis, polio, and epidural abscess
- Structural disorders, such as brain or spinal cord injury, Bell's palsy, cervical spondylosis, carpal tunnel syndrome, brain or spinal cord tumors, peripheral neuropathy, and Guillain-Barré syndrome
- Functional disorders, such as headache, epilepsy, dizziness, and neuralgia
- Degeneration, such as Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis (ALS), Huntington's chorea, and Alzheimer's disease
Signs and symptoms of nervous system disorders
The following are the most common general signs and symptoms of a nervous system disorder. However, each individual may experience symptoms differently. Symptoms may include:
- Persistent or sudden onset of a headache
- A headache that changes or is different
- Loss of feeling or tingling
- Weakness or loss of muscle strength
- Sudden loss of sight or double vision
- Memory loss
- Impaired mental ability
- Lack of coordination
- Muscle rigidity
- Tremors and seizures
- Back pain which radiates to the feet, toes, or other parts of the body
- Muscle wasting and slurred speech
The symptoms of a nervous system disorder may resemble other medical conditions or problems. Always consult your doctor for a diagnosis.
Doctors who treat nervous system disorders
Doctors who treat nervous system disorders may have to spend a lot of time working with the patient before making a probable diagnosis of the specific condition. Many times, this involves performing numerous tests to eliminate other conditions, so that the probable diagnosis can be made.
Neurology. The branch of medicine that manages nervous system disorders is calledneurology. The medical doctors who treat nervous system disorders are called neurologists.
Neurological surgery. The branch of medicine that provides surgical intervention for nervous system disorders is called neurosurgery, or neurological surgery. Surgeons who operate as a treatment team for nervous system disorders are called neurological surgeons orneurosurgeons.
Rehabilitation for neurological disorders. The branch of medicine that provides rehabilitative care for patients with nervous system disorders is called physical medicine and rehabilitation. Doctors who work with patients in the rehabilitation process are calledphysiatrists.
Nervous System: Facts, Function & Diseases
The nervous system is a complex collection of nerves and specialized cells known as neurons that transmit signals between different parts of the body. Vertebrates — animals with backbones and spinal columns — have central and peripheral nervous systems.
The central nervous system is made up of the brain, spinal cord and retina. The peripheral nervous system consists of sensory neurons, ganglia (clusters of neurons) and nerves that connect to one another and to the central nervous system.
Description of the nervous system
The nervous system is essentially the body’s electrical wiring. It is composed of nerves, which are cylindrical bundles of fibers that start at the brain and central cord and branch out to every other part of the body.
Neurons send signals to other cells through thin fibers called axons, which cause chemicals known as neurotransmitters to be released at junctions called synapses. A synapse gives a command to the cell and the entire communication process typically takes only a fraction of a millisecond.
Sensory neurons react to physical stimuli such as light, sound and touch and send feedback to the central nervous system about the body’s surrounding environment. Motor neurons, located in the central nervous system or in peripheral ganglia, transmit signals to activate the muscles or glands.
Glial cells, derived from the Greek word for "glue," support the neurons and hold them in place. Glial cells also feed nutrients to neurons, destroy pathogens, remove dead neurons and act as traffic cops by directing the axons of neurons to their targets. Specific types of glial cells (oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system) generate layers of a fatty substance called myelin that wraps around axons and provides electrical insulation to enable them to rapidly and efficiently transmit signals.
Diseases of the nervous system
There are a number of tests and procedures to diagnose conditions involving the nervous system. Aside from MRIs and CT scans, an electroencephalogram (EEG) is often used to record the brain's continuous electrical activity by attaching electrodes to the scalp. Positron emission tomography (PET) is a procedure that measures the metabolic activity of cells.
A spinal tap places a needle into the spinal canal to drain a small amount of cerebral spinal fluid that is tested for infection or other abnormalities.
A number of nerve disorders can affect the nervous system, including vascular disorders such as:
- stroke
- transient ischemic attack (TIA)
- subarachnoid hemorrhage
- subdural hemorrhage and hematoma
- extradural hemorrhage
The nervous system can also experience functional difficulties, which result in conditions such as:
- epilepsy
- Parkinson's disease
- multiple sclerosis
- amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease
- Huntington's chorea
- Alzheimer's disease
Infections such as meningitis, encephalitis, polio, and epidural abscess can also affect the nervous system.
Structural disorders such as brain or spinal cord injury, Bell's palsy, cervical spondylosis, carpal tunnel syndrome, brain or spinal cord tumors, peripheral neuropathy, and Guillain-Barré syndrome also strike the nervous system.
Study of the nervous system
The branch of medicine that studies and treats the nervous system is called neurology and doctors who practice in this field of medicine are called neurologists. Once they have completed medical training, neurologists complete additional training for their specialty and are certified by the American Board of Psychiatry and Neurology.
Neurosurgeons perform surgeries involving the nervous system and are certified by the American Association of Neurological Surgeons.
There are also physiatrists, who are physicians who work to rehabilitate patients who have experienced disease or injury to their nervous systems that impact their ability to function.
Some milestones in the study of the nervous system include:
- Ancient Egypt: Documents describe the meninges, membranes that envelop the central nervous system; the external surface of the brain; the cerebrospinal fluid; and the intracranial pulsations.
- Ancient Greece: Medical practitioners dissect the nervous system. Aristotle distinguishes between the cerebrum and the cerebellum.
- 1543: Andreas Vesalius published his "De humani corporis fabrica." It includes detailed images depicting the ventricles, cranial nerves, pituitary gland, meninges, structures of the eye, the vascular supply to the brain and spinal cord, and an image of the peripheral nerves.
- 1664: Thomas Willis publishes his "Anatomy of the Brain," followed by “Cerebral Pathology” in 1676. He removed a brain from the cranium, and was able to describe it more clearly, setting forth the circle of Willis — the circle of vessels that enables arterial supply of the brain. He describes epilepsy, apoplexy and paralysis.
- 1837: J.E. Purkinje (1787–1869) provides the first description of neurons, a very early description of cells of any kind.
- 1878: William McEwen (1848–1924) removes a meningioma — a brain tumor — and the patient survived for many years.
- 1886: Victor Horsley (1857–1916) develops a surgical procedure for medically intractable epilepsy.
- 1906: Sir Charles Scott Sherrington publishes "The Integrative Action of the Nervous System," which describes the synapse and motor cortex.
- 1909: American surgeon Harvey Cushing (1869–1939) successfully removes a pituitary adenoma. Treating endocrine hyperfunction by neurosurgery was a major neurological landmark.
- 1960: Oleh Hornykiewicz shows that brain dopamine is lower than normal in Parkinson's disease patients.
- 1974: M.E. Phelps, E.J. Hoffman and M.M. Ter Pogossian develop the first PET scanner.
- 1986: Stanley Cohen and Rita Levi-Montalcini share the Nobel Prize for Physiology and Medicine for their work on the control of nerve cell growth.
Nervous System Diseases Program
The HSCI Nervous System Diseases Program focuses on neurodegenerative and traumatic diseases of the brain and spinal cord. In particular this collaborative, inter-institutional research program studies amyotrophic lateral sclerosis, often referred to as "Lou Gehrig's Disease”; spinal cord injury; Alzheimer’s disease; narcolepsy, and--by extension--corticobasal degeneration; Huntington's disease; and Parkinson’s disease. The aim is to understand exactly which neurons degenerate and why, and how to interfere with the degenerative process to provide a therapy.
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Key Research Questions
The HSCI Nervous System Diseases Program is pursuing cell-based and chemical-based approaches that answer the following questions:
- Are adult stem cells present in the nervous system and can we identify the molecules and genes that control the differentiation of these cells?
- How can the differentiation of adult progenitors and/or embryonic stem cells be directed into the specific types of neurons that can replace diseased or injured cells?
- Are there chemicals that could direct the differentiation of desired cells among the many types of neurons, and chemicals that could be used therapeutically in neurodegenerative diseases?
Key Scientific Results
Scientific findings from the HSCI Nervous System Diseases Program include:
- The derivation of ALS disease-specific human embryonic stem cell lines.
- The identification of compounds, through chemical screening, that: activate oligodendrocyte progenitors important in multiple sclerosis and cerebral palsy; and promote survival of amyotrophic lateral sclerosis embryonic stem cell-derived motor neurons.
- The identification of several different pathways involved in spinal muscular atrophy that regulate the levels of the protein defective in the disease.
- The identification of small molecule signaling modulators that effectively turn mouse embryonic stem cells into dopaminergic neuron progenitor cells (important in Parkinson’s disease) and into medium spiny neuron progenitor cells (affected in Huntington’s disease).
- The generation of pain neurons from human embryonic stem cells as a platform for discovering new pain medications.