Diseases of the Nervous System

Nervous System  Central nervous system – brain and spinal cord  Peripheral nervous system

Meninges  Covering of the brain and spinal cord  Three layers –Dura –Arachnoid –Pia  Infection of the fluid around the brain and spinal cord is meningitis  Infection of the brain is encephalitis

Bacterial Diseases of the Nervous System  Meningitis  Listeriosis  Tetanus  Botulism  Leprosy

Meningitis  Three species of bacteria cause 70% of the cases of meningitis  Haemophilus influenzae  Streptococcus pneumoniae  Neisseria meningitidis  Symptoms generally include fever, headache, stiff neck, nausea, vomiting, convulsions, coma  Antibiotic treatment  High mortality without treatment

Haemophilus influenzae  Most common in children under 5, especially at 6 months  The use of the Hib vaccine has reduced the incidence of this type of meningitis  Haemophilus influenzae is now not a leading cause of the disease as it once was

Neisseria meningitis  Causes disease in children under 2 years of age  10% of the population are carriers and reservoir for the disease  Generally begins as throat infection that leads to meningitis  Vaccine is available but not widely used

Streptococcus pneumoniae  Leading cause of bacterial meningitis  Common in children, with high mortality rate  Bacteria is carried in the general population is the nasopharynx  Vaccine is available  Increased antibiotic resistance

Viral Meningitis (aseptic meningitis)  Most common from of meningitis  25,000-50,000 hospitalization per year  Cause - many different viruses involved, Enteroviruses most common  Symptoms - fever, severe headache, stiff neck, sensitivity to bright lights, nausea, vomiting  Serious but rarely fatal. Disease course is usually 7-10 days, full recovery typical  Spread generally through direct contact with respiratory droplets  No specific treatment

Listeriosis  Listeria monocytogenes  G+ coccobacillus  Commonly found in soil, water, vegetation, and GI tract of animals  Generally mild infection that can lead to meningitis  2500 cases in US per year  500 deaths  Dangerous to pregnant woman due to potential fetal damage or death  Food and vegetable sources of the bacteria, cook food well!  Bacteria can grow at cold temperatures and increase in number even in the refrigerator

Listeria infection continued  Symptoms - fever, muscle aches, GI symptoms. Nervous system - headache, stiff neck, confusion, convulsions  Pregnant women - 20 times more likely to get listeriosis!

Tetanus (Lockjaw)  Causative agent is G+ anaerobic spore former - Clostridium tetani  Symptoms of the disease are the result of a powerful neurotoxin that is released when the organism multiplies  Toxin blocks relaxation of muscles causing a rigid paralysis  Deep puncture wound – “ rusty nail ”  Rarely seen today because of the DPT vaccine  Vaccine in a TOXOID, made from inactivated toxin

Prevalence of Tetanus

Botulism  Form of food poisoning caused by the G+ anaerobic spore former - Clostridium botulinum  Bacteria produces a powerful neurotoxin that blocks muscle contraction leading to a flaccid paralysis  Spore contamination of canned food  Food eaten uncooked as in a salad cause the toxic poisoning  Cooking will inactivate the toxin

Infant Botulism  “ Floppy “ baby syndrome  Under 1 year of age  cases per year in the US  5% cases from honey spores  95% unknown cause

Botox (poison those wrinkles)

Other medical uses of BOTOX  Cervical dystonia –Involuntary contraction of neck muscles  Strabismus –Cross-eyed  Blepharospasm –Uncontrolled muscles contraction of eyelids  Severe axillary hyperhidrosis –Excessive “ arm-pit ” sweating. Also the hands and feet.

Hansen’s Disease (Leprosy)  Caused by the acid-fast bacteria Mycobacterium leprae  Slow growing bacteria that affects the PNS and tissues of the body periphery, fingers, nose, ears, feet  Two forms of the disease –Tuberculoid – mild form of the disease –Lepromatous – more serious form that can lead to loss of body tissue  Leprosy is treated with antibiotics and is not highly contagious

Leprosy

Incidence of Leprosy

Viral Diseases of the Nervous System  Polio  Rabies

Polio  Best known cause of paralysis  Only 1% of cases of polio resulted in paralysis  Primary mode of transmission is fecal-oral  “ Flu-like ” symptoms and immune system may stop the disease at this point  Virus can infect motor neurons and cause paralysis

Polio vaccines  Humans are the only reservoirs of the disease so it can be eradicated by vaccination  1954 Salk IPV vaccine introduced. Made from inactivated virus, given by injection  1963 Sabin OPV introduced. Made from live, weaken virus, given orally  Few cases of polio from the OPV vaccine. No longer recommended by the CDC  Polio has largely been eliminated from developed areas of the globe

Global Polio Incidence

Dr. Jonas Salk ( )

Dr. Albert Sabin ( )

The “King” and Polio

Rabies  Fatal encephalitis caused by the bite of infected animal  Slow growing virus, long incubation period  Virus spreads from the bite to the CNS  Once the symptoms appear the disease is always fatal  Rabies is carried in the wild mainly by raccoons, skunks, and bats

Rabies virus

How rabies spreads

Distribution of Reservoirs for Rabies

Rabies Treatment  If bitten by an animal:  1. If the animal can be located have it tested for rabies  2. If the animal cannot be found then  3. Wash the wound with soap and water  4. Begin the vaccination series to prevent the disease  REMEMBER: the disease is ALWAYS fatal once the symptoms appear

Negri bodies

Prion Diseases  Infectious protein  Progressive fatal encephalitis  Examples of prion diseases –Scrapie –Mad cow disease –Kuru –Variant CJD (Creutzfeldt-Jacob disease)