Central nervous system

The central nervous system is composed of the brain and spinal cord. Your brain and spinal cord serve as the main "processing center" for the entire nervous system, and control all the workings of your body.

• The brain plays a central role in the control of most bodily functions, including awareness, movements, sensations, thoughts, speech, and memory. Some reflex movements can occur via spinal cord pathways without the participation of brain structures. 
  
  
   
• The spinal cord is connected to a section of the brain called the brainstem and runs through the spinal canal. Cranial nerves exit the brainstem. Nerve roots exit the spinal cord to both sides of the body. The spinal cord carries signals (messages) back and forth between the brain and the peripheral nerves.

Cerebrospinal fluid surrounds the brain and the spinal cord and also circulates within the cavities (called ventricles) of the central nervous system. The leptomeninges surround the brain and the spinal cord. The cerebrospinal fluid circulates between 2 meningeal layers called the pia matter and the arachnoid (or pia-arachnoid membranes). The outer, thicker layer serves the role of a protective shield and is called the dura matter.

The basic unit of the central nervous system is the neuron (nerve cell). Billions of neurons allow the different parts of the body to communicate with each other via the brain and the spinal cord. A fatty material called myelin coats nerve cells to insulate them and to allow nerves to communicate quickly.

Poliomyelitis

Poliomyelitis is a viral disease that can affect nerves and can lead to partial or full paralysis.

Causes, incidence, and risk factors

Poliomyelitis is a disease caused by infection with the poliovirus. The virus spreads by:

• Direct person-to-person contact
• Contact with infected mucus or phlegm from the nose or mouth
• Contact with infected feces

Symptoms

There are three basic patterns of polio infection: subclinical infections, nonparalytic, and paralytic. About 95% of infections are subclinical infections, which may not have symptoms.

SUBCLINICAL INFECTION SYMPTOMS

• General discomfort or uneasiness (malaise)
• Headache
• Red throat
• Slight fever
  
• Sore throat
• Vomiting
  

People with subclinical polio infection might not have symptoms, or their symptoms may last 72 hours or less.

Clinical poliomyelitis affects the central nervous system (brain and spinal cord), and is divided into nonparalytic and paralytic forms. It may occur after recovery from a subclinical infection.

Signs and tests

The health care provider may find:

• Abnormal reflexes
• Back stiffness
• Difficulty lifting the head or legs when lying flat on the back
• Stiff neck
• Trouble bending the neck

Tests include:

• Cultures of throat washings, stools, or cerebrospinal fluid (CSF)
• Routine CSF examination
  
• Test for levels of antibodies to the polio virus

Treatment

The goal of treatment is to control symptoms while the infection runs its course.

People with severe cases may need lifesaving measures, especially breathing help.

Symptoms are treated based on their severity. Treatment may include:

• Antibiotics for urinary tract infections
  
• Medications (such as bethanechol) for urinary retention
• Moist heat (heating pads, warm towels) to reduce muscle pain and spasms
• Painkillers to reduce headache, muscle pain, and spasms (narcotics are not usually given because they increase the risk of breathing trouble)
• Physical therapy, braces or corrective shoes, or orthopedic surgery to help recover muscle strength and function

 

Meningitis

Meningitis is a bacterial infection of the membranes covering the brain and spinal cord (meninges).

See also:

• Aseptic meningitis
  
• Meningitis - Gram-negative
  
• Meningitis - H. influenzae
  
• Meningitis - meningococcal
  
• Meningitis - pneumococcal
  
• Meningitis - staphylococcal
  
• Meningitis - tuberculous
  

Symptoms

Symptoms usually come on quickly, and may include:

• Fever and chills
• Mental status changes
  
• Nausea and vomiting
• Sensitivity to light (photophobia)
• Severe headache
• Stiff neck (meningismus)

Other symptoms that can occur with this disease:

• Agitation
  
• Bulging fontanelles
  
• Decreased consciousness
  
• Poor feeding or irritability in children
• Rapid breathing
• Unusual posture, with the head and neck arched backwards (opisthotonos)

Meningitis is an important cause of fever in children and newborns.

People cannot tell if they have bacterial or viral meningitis by how they feel, so they should seek prompt medical attention.

Treatment

Doctors prescribe antibiotics for bacterial meningitis. The type will vary depending on the bacteria causing the infection. Antibiotics are not effective in viral meningitis.

Other medications and intravenous fluids will be used to treat symptoms such as brain swelling, shock, and seizures. Some people may need to stay in the hospital, depending on the severity of the illness and the treatment needed.

Sclerosis

Sclerosis is a hardening of the organ or tissue due to an increase in connective tissue . Sclerosis is, therefore, a disease which derives from another, is an autonomous disease.

The disease usually occurs due to tissue damage as a result of inflammation, poor perfusion or also aging processes. Similarly, also an autoimmune disease can lead to sclerosis. The result is an uncontrolled production of connective tissue, which leads to a hardening. Affected organs harden and lose elasticity.

ENCEPHALITIS

Encephalitis is irritation and swelling (inflammation) of the brain, most often due to infections.

Encephalitis is a rare condition. It occurs more often in the first year of life and decreases with age. The very young and the elderly are more likely to have a severe case.

Encephalitis is most often caused by a viral infection. Many types of viruses may cause it. Exposure to viruses can occur through:

• Breathing in respiratory droplets from an infected person
• Contaminated food or drink
• Mosquito, tick, and other insect bites
• Skin contact

Symptoms

Some patients may have symptoms of a cold or stomach infection before encephalitis symptoms begin.

When a case of encephalitis is not very severe, the symptoms may be similar to those of other illnesses, including:

• Fever that is not very high
• Mild headache
• Low energy and a poor appetite

Treatment

The goals of treatment are to provide supportive care (rest, nutrition, fluids) to help the body fight the infection, and to relieve symptoms. Reorientation and emotional support for confused or delirious people may be helpful.

Medications may include:

• Antiviral medications, such as acyclovir (Zovirax) and foscarnet (Foscavir) -- to treat herpes encephalitis or other severe viral infections (however, no specific antiviral drugs are available to fight encephalitis)
• Antibiotics -- if the infection is caused by certain bacteria
• Anti-seizure medications (such as phenytoin) -- to prevent seizures
  
• Steroids (such as dexamethasone) -- to reduce brain swelling (in rare cases)
• Sedatives -- to treat irritability or restlessness
• Acetaminophen -- for fever and headache

If brain function is severely affected, interventions like physical therapy and speech therapy may be needed after the illness is controlled.

CEREBRAL TRAUMA:

Traumatic brain injury happens when a bump, blow, jolt, or other head injury causes damage to the brain. Every year, millions of people in the U.S. suffer brain injuries. More than half are bad enough that people must go to the hospital. The worst injuries can lead to permanent brain damage or death.

Half of all traumatic brain injuries (TBIs) are due to motor vehicle accidents. Military personnel are also at risk. Symptoms of a TBI may not appear until days or weeks following the injury. Serious traumatic brain injuries need emergency treatment.

Treatment and outcome depend on the injury. TBI can cause a wide range of changes affecting thinking, sensation, language, or emotions. TBI can be associated with post-traumatic stress disorder. People with severe injuries usually need rehabilitation.