Diseases Of Nervous System

Diseases Of Nervous System

1. How Microbes Enter the Nervous System Skull or backbone fractures Medical procedures Along peripheral nerves Blood or lymph

2. The Nervous System Figure 22.1

3. Microbial Diseases of the Nervous System Bacteria can grow in the cerebrospinal fluid in the subarachnoid space of the CNS. The blood brain barrier (capillaries) prevents passage of some materials (such as antimicrobial drugs) into the CNS. Meningitis: Inflammation of meninges . Encephalitis: Inflammation of the brain.

4. The Meninges and Cerebrospinal Fluid Figure 22.2

5. Bacterial Meningitis Fever, headache, and stiff neck Followed by nausea and vomiting May progress to convulsions and coma Diagnosis by Gram stain or latex agglutination of CSF Treated with cephalosporins

6. Diseases of the Nervous System A. Bacterial Infections of the Nervous System 1. Bacterial Meningitis A) Although bacteria can infect the brain, spinal cord, and peripheral nerves, they more commonly infect the meninges and cerebrospinal fluids resulting in meningitis B) Bacterial meningitis is uncommon and most of its victims are children

7. Diseases of the Nervous System C) A large number of bacteria can infect the meninges, however the five leading causes are: Haemophilus influenza , Streptococcus agalactiae , Neisseria meningitidis , Listeria monocytgenes and Streptococcus pneumoniae D) Common symptoms include fever, lethargy and irritability. In older children headache, photophobia, and a stiff neck are sometimes seen

8. Haemophilus influenzae Meningitis Occurs mostly in children (6 months to 4 years). Gram-negative aerobic bacteria, normal throat microbiota Capsule antigen type b Prevented by Hib vaccine

9. Diseases of the Nervous System 2. Meningococcal Meningitis A) Greatly feared because it can result in shock and death within 24 hours after infection B) Meningococcal meningitis can occur in both adults and children C) The causative agent is Neisseria meningitidis 1) Transmission via salivary droplets

10. Diseases of the Nervous System D) The presence of N. meningitis within the nervous system causes a massive response by neutrophils resulting in inflammation, which obstructs the normal flow of fluids causing infarcts infarct – area of tissue that undergoes necrosis as a result of obstruction of local blood supply

11. Diseases of the Nervous System E) The bacteria and leukocytes metabolize the glucose normally found in cerebrospinal fluid potentially depriving the brain of nutrients F) In addition, N meningitis circulates in blood and produces an endotoxin that causes a drop in blood pressure leading to shock

12. Streptococcus pneumoniae Meningitis, Pneumococcal Meningitis Gram-positive diplococci 70% of people are healthy nasopharyngeal carriers Most common in children (1 month to 4 years) Mortality: 30% in children, 80% in elderly Prevented by vaccination

13. Diseases of the Nervous System 3. Listeriosis A) Foodborne disease associated with meningitis 1) Commonly contracted from eating Mexican cheese, soft cheeses, non-pasteurized milk, hot dogs, or coleslaw B) The causative agent is Listeria monocytogenes

14. Listeriosis Listeria monocytogenes Gram-negative aerobic rod Usually foodborne; it can be transmitted to fetus. Reproduce in phagocytes. Figure 22.5

15. Diseases of the Nervous System C) The bacteria can easily penetrate the intestinal linings and enter the bloodstream, it then crosses over into the cerebrospinal fluids where it can then infect the meninges D) The organism can grow in commercially prepared foods at refrigerator temperatures and has resulted in thousands of infections originating from a single food-processing plant

16. Tetanus Clostridium tetani Gram-positive, endospore-forming, obligate anaerobe Grows in deep wounds. Tetanospasmin released from dead cells blocks relaxation pathway in muscles. Prevention by vaccination with tetanus toxoid (DTP) and booster (dT). Treatment with tetanus immune globulin.

17. Tetanus Figure 22.6

18. Botulism Clostridium botulinum Gram-positive, endospore-forming, obligate anaerobe Intoxication comes from ingesting botulinal toxin. Botulinal toxin blocks release of neurotransmitter causing flaccid paralysis. Prevention Proper canning Nitrites prevent endospore germination in sausages.

19. Diseases of the Nervous System Botulism A) Although botulism is not a nervous system infection, it is a common type of food poisoning that can cause paralysis and be fatal

20. Diseases of the Nervous System Wound botulism occurs when C. botulinum colonizes a dirty wound especially those containing dead tissues 1) Wound botulism is rare and has been linked to the use of heroin

21. Diseases of the Nervous System C) Paralysis is the result of powerful neurotoxins which work by blocking the release of neurotransmitters 1) Initial symptoms include blurred/double vision, drooping eyelids, slurred speech, dry mouth, and muscle weakness 2) Can lead to paralysis of the arms, legs, and respiratory system leading to death if untreated

22. Diseases of the Nervous System 4. Leprosy (Hansen’s Disease) A) Once common but now a relatively minor problem in the Western world B) Caused by Mycobacterium leprae 1) An acid-fast (+) bacillus C) M. leprae is the only known human pathogen to preferentially attack the peripheral nerves, particularly of the skin

23. Diseases of the Nervous System D) The disease occurs in multiple forms: 1) Tuberculoid leprosy a) Most superficial, least severe form b) Results in skin nerve damage causing an area of sensation loss surrounded by nodules c) Generally has few complications and is the easiest form to treat d) Sometimes heals spontaneously

24. Diseases of the Nervous System 2) Lepromatous leprosy a) Widespread dissemination of the bacteria b) Responsible for the disfiguring nodules associated with the disease c) Generally affects cooler regions of the body (nose, ears, eyebrows, chin, and testes) d) Loss of sensation & necrosis also occurs

25. Diseases of the Nervous System e) May alternate between stages of remission and rapid deterioration f) Secondary infections include blindness, and kidney or respiratory failure 3) Borderline leprosy a) An intermediate form of the disease b) Can progress either direction c) Early nerve damage is most severe effect

26. Diseases of the Nervous System B. Viral Diseases of the Nervous System 1. Viral meningitis A ) Much more common than bacterial meningitis, it causes similar but much milder symptoms with recovery in 7 to 10 days B) Most cases result from members of the picomavirus family C) The viruses are transmitted via the fecal-oral route, respiratory secretions or saliva

27. Diseases of the Nervous System 2. Viral Encephalitis (inflammation of the brain) A) Whereas viral meningitis is usually a benign illness, viral encephalitis is much more likely to cause death or permanent disability B) Viral encephalitis can be sporadic (a few widely scattered cases all the time) or it can be epidemic

28. Diseases of the Nervous System C) Epidemic encephalitis has multiple causative agents but all are arboviruses and are transmitted by mosquitoes 1) West Nile encephalitis falls into this family and gets much publicity but LaCrosse encephalitis is the most commonly reported form of the disease in the U.S. D) Sporadic encephalitis is usually due to HSV-1

29. Diseases of the Nervous System 3. Poliomyelitis (Polio) A) Poliomyelitis is the focus of an international campaign to rid the Earth of the disease B) Poliomyelitis is caused by polioviruses 1, 2, and 3 1) All are members of the picornavirus family

30. Diseases of the Nervous System C) Poliovirus enters the body orally (fecal-oral), infects the throat and intestinal tract, invades the bloodstream, and then crosses the blood-brain barrier D) The virus selectively destroys motor nerve cells of the brain and spinal cord leading to paralysis, muscle wasting, failure of normal bone development and death

31. Diseases of the Nervous System E) Post-polio syndrome occurs years (15-50 years later) after acute poliomyelitis infection, and is probably caused by the death of nerve cells that had taken over for the one’s killed initially 1) Symptoms include fatigue, slowly progressive muscle weakness and, at times, muscular atrophy 2) Joint pain and increasing skeletal deformities such as scoliosis are also common

32. Diseases of the Nervous System F) Prevention includes the use Salk’s inactivated, injectable vaccine in most areas or Sabin’s orally administered attenuated vaccine in areas of epidemic or endemic diseases

33. Diseases of the Nervous System 4. Rabies A) slow, progressive, disease characterized by fatal meningoencephalitis B) Caused by the rhabdovirus 1) A RNA virus with a distinctive bullet shape

34. Diseases of the Nervous System C) The virus is spread to humans from wild and domestic reservoirs via bites, scratches, and sometimes inhalation of respiratory droplets D) The virus initially stays at the entry site and multiplies before moving along sensory nerves to the CNS

35. Diseases of the Nervous System E) Viral replication in the CNS is followed by migration to structures such as the eye, heart, skin, and salivary glands (which completes the cycle) F) The disease progresses through identifiable stages

36. Diseases of the Nervous System 1) Incubation – 20-90 days a) Occurs at the wound site b) Some feel pain, burning, & tingling 2) Prodromal Stage – 2-10 days a) Characterized by fever, anorexia, nausea, vomiting, headache, and fatigue

37. Diseases of the Nervous System 3) Acute neurological phase – 2-7 days a) Furious form i) Agitation, disorientation, seizures, and twitching ii) Hydrophobia also is seen because of the pain involved with swallowing b) Dumb form i) Patient us usually paralyzed & disoriented

38. Rabies Virus (Rhabdovirus) Figure 22.12

39. Negri Bodies

40. Diseases of the Nervous System 4) Coma – 0-14 days 5) Death – forever  G) Diagnosis is difficult because symptoms of rabies often mimic other diseases 1) Often occurs postmortem H) There is no known effective treatment once symptoms develop 1) Pre-symptom individuals are given rabies immune globin immediately and a series of 5 vaccinations over 28 days

41. Diseases of the Nervous System C. Other Nervous System Infections 1. Cryptococcal meningoencephalitis A) This is a fungal disease which originates as a lung infection after a person inhales dust laden with pigeon droppings B) Caused by the fungus Filobasidiella neoformans 1) F. neoformans is an encapsulated yeast that resists phagocytosis

42. Diseases of the Nervous System C) Fungi rarely invade the nervous system of healthy people but they can be a threat to the life of individuals with underlying diseases such as diabetes, cancer, and immunodeficiency D) Person-to-person transmission does not occur

43. Naegleria fowleri Protozoan infects nasal mucosa from swimming water. Figure 22.17

44. Transmissible Spongiform Encephalopathies Caused by prions Sheep scrapie Creutzfeldt-Jakob disease Kuru Bovine spongiform encephalopathy Transmitted by ingestion or transplant or inherited. Chronic and fatal