Cns disorders

1. •CNS DISORDERS

2. Structure of the Nervous System
•Divided into two parts
–Central nervous system (CNS)
–Peripheral nervous system (PNS)
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4. Structure of the Nervous System
•Composed of the brain and spinal cord
–Brain has several main parts
–Cerebrum controls voluntary muscles, perception,
and “thinking”
–Cerebellum controls many involuntary body
movements
–Brain stem controls breathing, heart rate, blood
pressure
–Spinal cord
– Extends from the brain stem to the lumbar region
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5. Structure of the Nervous System
•Structures of the Peripheral Nervous System
–Nerves transfer commands from CNS to muscles
and glands
–Cranial nerves extend from brain through holes in
the cranial bones
–Spinal nerves extend from spinal cord through
vertebral gaps
–Three types of nerves
–Sensory nerves – carry signals toward the CNS
–Motor nerves – carry signals away from the CNS
–Mixed nerves – carry signals toward and away from
the CNS
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6. Structure of the Nervous System
•Cells of the Nervous System
–Two basic cell types
–Neuroglia
–Provide support, insulation, nutrients; phagocytize
microbes
–Neurons
–Carry nerve impulses
–Nucleus lies in a region called the cell body
–Ganglion is collection of many neurons’ cell bodies
–Dendrites and axons extend from the cell body
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7. Structure of the Nervous System
•Portals of Infection of the Central Nervous
System
–CNS is an axenic environment
–It has no normal microbiota
–Pathogens may access the CNS several ways
–Breaks in the bones and meninges
–Medical procedures
–Travel in peripheral neurons to the CNS
–Infect and kill cells of the meninges, causing
meningitis
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8. Factors Important to Understanding Nervous System
Pathology
1. The nervous system consists of highly specialized functional
units called neurons. Damage to neurons is irreversible because
neurons cannot regenerate. Injury to certain areas of the brain
result in loss of function to that particular area. A loss of vision
center in the occipital lobe causes blindness. Lesions of the
respiratory centers in the medulla oblongata causes death.
2. The central nervous system (CNS) is protected from
mechanical injury by the bones of the skull and vertebrae. If the
vertebrae were detached from one another or dislocated, the
spinal cord may be severed.

9. 3. The CNS is separated from the remainder of the body by
meninges and by a bloodbrain barrier. The brain is protected from
harmful substances in that the blood or cerebral spinal fluid (CSF)
acts as filters.
Examples:
Bilirubin does not enter the CNS compartment, even in the most
severe forms of jaundice.
Glucose concentration in the CSF is at a level that is one-half
that of the blood concentration.
Factors Important to Understanding Nervous
System Pathology

10. 4. The brain and the spinal cord are surrounded by CSF.
CSF separates the brain from the meninges and serves as a
mechanical buffer (cushion) between the brain and bones of the
skull
CSF serves as a venue to remove metabolites and waste
products from the brain
CSF remains constant under normal circumstances in regards
to rate of production, flow and reabsorption
Factors Important to Understanding Nervous
System Pathology

11. 5. Neurons do not divide, but supporting glial cells are capable of
dividing. The brain contains billions of neurons, all of which were
formed during prenatal, intrauterine life.
Neurons are long-lived cells. Nevertheless, every hour of our lives,
we lose thousands of neurons due to natural death. Since neurons
cannot divide, neurons cannot become tumors.
However, support structures such as the meninges or blood
vessels are capable of proliferation and/or malignant
transformation
Glial cell tumors are called gliomas
 Meningiomas are tumors of meninges
 Hemangioblastomas are tumors of blood vessels
Factors Important to Understanding Nervous
System Pathology

12. 6. The CNS may be affected by diseases that involve other
organs, but also by diseases that are unique to the CNS.
Examples:
 Atherosclerosis of the coronary arteries and aorta is often
accompanied by CerebroVascular Accidents (CVA).
 Uremia or hepatic encephalopathy eventually would cause a
coma
 Prions, minute infectious particles, survive only in nerve cells
(kuru, mad cow disease, Creutzfeldt-Jacob disease)
Factors Important to Understanding Nervous
System Pathology

13. 7. The symptoms of CNS diseases result from dysfunction or loss
of function of neurons.
Examples:
 Headaches are a result of brain tumors, and increased
intracranial pressure from massive bleeding causes generalized
paralysis, coma, and death if vital centers in the brain are
compressed.
 Loss of neurons in Alzheimer’s disease causes loss of memory
 Abnormal function of neurons in Parkinson’s disease causes
rigidity of muscles.
 Abnormal excitation of neurons causes convulsions in epilepsy
Factors Important to Understanding Nervous
System Pathology

14. Bacterial Diseases of the Nervous System
•Bacteria cause disease in two ways
–Infect cells of the nervous system
–Meningitis
–Leprosy
–Bacteria growing elsewhere release toxins that
affect neurons
–Botulism
–Tetanus
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15. Bacterial Diseases of the Nervous System
•Bacterial Meningitis
–Signs and symptoms
–Sudden high fever and severe meningeal
inflammation
–Encephalitis can result in behavioral changes,
coma, and death
–Can develop rapidly
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16. Bacterial Diseases of the Nervous System
•Bacterial Meningitis
–Pathogens and virulence factors
–Five species cause 90% of bacterial meningitis
cases
–Neisseria meningitidis
–Streptococcus pneumoniae
–Haemophilus influenzae
–Listeria monocytogenes
–Streptococcus agalactiae
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17. Diplococci of Neisseria meningitidis

18. Cells of Streptococcus pneumoniae

19. The pleomorphic bacili of Haemophilus influenzae
Pleomorphisms

20. Bacterial Diseases of the Nervous System
•Bacterial Meningitis
–Pathogenesis
–S. agalactiae acquired during birth
–Listeria transmitted via contaminated food
–Other species transmitted via respiratory droplets
–Epidemiology
–S. pneumoniae present in throat of 75% of
humans
–Not spread by casual contact
–Meningococcal meningitis can become epidemic
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21. Bacterial Diseases of the Nervous System
•Bacterial Meningitis
–Diagnosis, treatment, and prevention
–Diagnosis based on symptoms and culturing of
bacteria from CSF
–Treated with intravenous antimicrobial drugs
–Vaccines available for S. pneumoniae, H.
influenzae type b, and N. meningitidis
–Individuals at risk for listeriosis should avoid high-
risk foods
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22. Bacterial Diseases of the Nervous System
•Hansen’s Disease (Leprosy)
–Signs and symptoms
–Tuberculoid leprosy – nonprogressive
–Lepromatous leprosy – progressive tissue
destruction
–Pathogen and virulence factors
–Mycobacterium leprae is the causative agent
–Gram-positive bacillus with mycolic acid in cell wall
–Pathogenesis
–M. leprae grows best in cooler regions of the body
–M. leprae can live inside infected cells for years
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23. Lepromatous leprosy

24. Bacterial Diseases of the Nervous System
•Hansen’s Disease (Leprosy)
–Epidemiology
–Transmitted by person-to-person contact or
breaks in the skin
–Diagnosis, treatment, and prevention
–Diagnosis based on the signs and symptoms
–Confirmed by presence of acid-fast bacilli in
samples
–Treated with multiple antimicrobials
–BCG vaccine provides some protection
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25. Bacterial Diseases of the Nervous System
•Botulism
–Signs and symptoms
–Caused by intoxication from ingested toxin
– Three forms
–Foodborne botulism
–Infant botulism
–Wound botulism
–Pathogen and virulence factors
–Clostridium botulinum is the causative agent
–Different strains produce one of seven neurotoxins
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26. Botulism toxin-overview

27. Bacterial Diseases of the Nervous System
•Botulism
–Epidemiology
–~50 cases of foodborne and wound botulism per
year in U.S.
–Infant botulism most common form in U.S.
–Diagnosis, treatment, and prevention
–Three approaches to treatment
–Washing of intestinal tract to remove Clostridium
–Administration of botulism immune globulin
–Treatment with antimicrobial drugs
–Prevented by destroying endospores in
contaminated food
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28. Bacterial Diseases of the Nervous System
•Tetanus
–Signs and symptoms
–Lockjaw
–Spasms and contractions may spread to other
muscles
–Pathogen and virulence factors
–Clostridium tetani is causative agent
–Produce neurotoxin called tetanospasmin
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29. A patient with tetanus

30. Tetanus toxin-overview

31. Bacterial Diseases of the Nervous System
•Tetanus
–Pathogenesis
–Can acquire through break in skin or mucous
membrane
–Distance of infection from CNS determines incubation
period
–Epidemiology
–Mortality rate is ~50% if left untreated
–Diagnosis, treatment, and prevention
–Diagnosis based on characteristic muscle contraction
–Treated with passive immunotherapy, antimicrobials,
active immunization
–Vaccine available against tetanus
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32. Viral Diseases of the Nervous System
•Viruses more readily cross the blood-
brain barrier
•Occur more frequently than bacterial and
fungal infections
•Include meningitis, polio, rabies, and
encephalitis
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33. Viral Diseases of the Nervous System
•Viral Meningitis
–Signs and symptoms
–Similar to those of bacterial meningitis
–Usually milder than those of bacterial or fungal
meningitis
–Pathogens and virulence factors
–90% of cases caused by viruses in the genus
Enterovirus
–Pathogenesis
–Damage to cells in the meninges triggers
meningitis
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34. Viral Diseases of the Nervous System
•Viral Meningitis
–Epidemiology
–More common than bacterial and fungal
meningitis
–Spread via respiratory droplets and feces
–Diagnosis, treatment, and prevention
–Diagnosed by characteristic signs and
symptoms in the absence of bacteria in the CSF
–No specific treatment exists
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35. Viral Diseases of the Nervous System
•Poliomyelitis
–Signs and symptoms
–Asymptomatic infections – almost 90% of cases
–Minor polio – nonspecific symptoms
–Nonparalytic polio – muscle spasms and back pain
–Paralytic polio – produces paralysis
–Pathogen and pathogenesis
–Poliovirus is the causative agent
–Transmitted most often by drinking contaminated
water
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