Ch 26 Nervous System Infections Flashcards
What does the Cerebrum control?
Voluntary Muscles
Perception
Thinking
Speech
What does the Cerebellum control?
Involuntary body movements
What does the brain stem control?
Breathing, heart rate, BP
What does the spinal cord extend from? Where does it go to?
It extends from the brain stem to the lumbar region
The nerves that transfer commands from the CNS to the muscles and glands make this up =
The Peripheral Nervous System
The cranial nerves and spinal nerves both are a part of the-
Peripheral Nervous System
These nerves carry signals toward the CNS =
Sensory Nerves
These nerves carry signals away from the CNS =
Motor Nerves
These nerves carry signals away and towards the CNS =
Mixed Nerves
This cell of the nervous system provides support, insulation, & nutrients. They also phagocytize microbes =
Neuroglia
These cells of the nervous system carry nerve impulses + lie in a region called the cell body =
Neurons
This is a collection of many neurons’ cell bodies =
Ganglion
These are chemical signals between cells and they may be either stimulatory or inhibitory =
Neurotransmitters
What are the 3 layers of the Meninges?
The Dura Mater
The Arachnoid Mater
The Pia Mater
The outer most layer of the meninges, protects bones from spreading infections =
Dura Mater
The layer of the meninges that contains numerous branchlike fibers creating the subarachnoid space =
Arachnoid Space
The inner most layer of the meninges, the blood vessels on top of this layer supply the CNS with blood =
Pia Mater
The walls of the blood vessels on top of the CNS are composed of tightly joined cells that form the-
Blood-Brain Barrier
What is the function of the Blood-Brain Barrier?
To prevent pathogens + large molecules in the blood from entering the subarachnoid space
Do blood infections easily spread to the CNS?
No
Are CNS infections very easy to treat?
No, because Antimicrobials don’t easily spread to the CNS
The fluid that leaks from the blood to the subarachnoid space is called the-
Cerebrospinal Fluid (CSF)
What does the CSF do?
It circulates throughout the brain + spinal cord to act as a shock absorber, removes wastes
Provides nutrients, electrolytes & oxygen to nervous tissues
How does one sample Cerebrospinal Fluid?
By performing a Lumbar Puncture
If you do a lumbar puncture, what does it mean if the CSF looks cloudy?
There’s likely an infection
How can pathogens access the CNS?
Breaks in the bones & meninges
Medical procedures
Travel in peripheral neurons to the CNS
Infect + kill cells of the meninges, causing meningitis
Inflammation can alter the permeability of the blood-brain barrier
How can bacteria cause disease?
Infecting cells of the nervous system (Meningitis)
Bacteria growing elsewhere release toxins that affect neurons (Botulism / Tetanus)
What are the signs and symptoms of Bacterial Meningitis?
Sudden high fever, severe meningeal inflammation, and increased white blood cells in the CSF
Encephalitis
Systemic Inflammation
Infection of the brain =
Encephalitis
What are the manifestations of Encephalitis?
Behavioral Changes
Coma
Death
What are the manifestations of Systemic Inflammation?
Hemorrhaging and reddish/purplish lesions on the skin, shock, convulsions, coma and death can occur in a span of just a few hours
What type of bacteria causes Meningococcal Meningitis?
Neisseria meningitidis
What five species of bacteria cause 90% of bacterial meningitis?
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae
Listeria monocytogenes
Streptococcus agalactiae
How does Meningococcal Meningitis work?
A release of endotoxin and other factors causes an immune response that produces the characteristic rash. The inflammation that results causes blood to leak out of the blood vessels and into the tissue.
This blood leakage/hemorrhaging also occurs in the brain and elsewhere in the body leading to sepsis, rapid organ failure, and death
How does Meningococcal Meningitis spread?
Can infection people of any age.
(Most at risk = Infants, Young Children, Young Adults).
N. meningitidis can spread via respiratory droplets when there is prolonged contact with a carrier.
N. meningitidis is one of the most common causes of bacterial Meningitis.
Meningococcal meningitis can become an-
Epidemic
Military barracks & College Dorms are both at risk for-
Meningococcal Meningitis
How is bacterial meningitis diagnosed?
Based on signs and symptoms + Culturing of bacteria from CSF
With meningococcal meningitis, a characteristic rash often occurs and can be indicative of infection with N. meningitidis
How is bacterial meningitis treated?
IV Antimicrobial Drugs
How is bacterial meningitis prevented?
There are vaccines available for N. meningitidis, usually only recommended for high risk groups
Even with the use of antibiotic treatment, what percentage of people usually end up dying?
What percentage usually end up with long term disabilities?
~10% die
~20% suffer longer term disabilities
What long term disabilities can bacterial meningitis cause?
Deafness, Brain Damage, Loss of Limbs (Due to Tissue Necrosis)
What does the bacteria called Listeria monocytogenes cause?
Listeriosis
How does Listeria enter the body?
Enters the body in contaminated food or drink that are usually contaminated with soil or animal manure
What foods can carry Listeria?
Fresh fruits and vegetables, frozen vegetables, processed meats, soft cheeses, and raw milk
Can Listeria grow in low temperatures?
Listeria can grow at low temperatures and can therefore grow in refrigerated foods
How does Listeriosis work?
Infection usually begins in the GI tract producing classic food poisoning-like symptoms such as diarrhea and fever, but Listeria has virulence factors that allow it to cross into other body systems and eventually the brain and CSF
Listeriosis is rarely pathogenic in-
Healthy adults
This can cause spontaneous abortion in pregnant women because it can cross the placenta =
Meningitis
Listeriosis causes Meningitis in what percentage of cases?
~20%
These are surface proteins that help Listeria attach to and enter host cell cytoplasm =
Internalins
Production of this protects Listeria from phagocytic digestion =
Listeriolysin O
What is Listeria?
A rare, but deadly germ
Listeria infection can cause pregnant women to-
Have a miscarriage, stillbirth, or cause death of the newborn
How is Listeria diagnosed?
Bacteria are cultured from CSF samples or blood
How is Listeria treated?
Treatment involves antibiotic therapy
Treatment involves antibiotic therapy prevented?
No vaccine available
Behavioral changes like avoiding unpasteurized soft cheeses, other unpasteurized foods/drinks, and some refrigerated foods like deli meats can help those at greatest risk of infection
What is Botulism?
Botulism is an intoxication with three manifestations
What are the 3 manifestations of Botulism called?
Foodborne Botulism
Infant Botulism
Wound Botulism
What are the manifestations if Foodborne Botulism?
Blurred vision, drooping eyelids, difficulty swallowing, stomach cramps, nausea, vomiting, constipation or diarrhea
Progressive muscle weakness and paralysis on both sides of the body
Can be terrifying because person is fully mentally alert
Paralysis of respiratory muscles leads to respiratory failure and death
Slow recovery from growth of new nerve cell endings
What are the manifestations if Infant Botulism?
Results from the ingestion of endospores
Notable signs include weak cry, decreased suckling, limpness in head or body
What are the manifestations if Wound Botulism?
Contamination of a wound by endospores
Symptoms similar to Foodborne Botulism
Flaccid Paralysis is caused by-
Botulism
What bacteria causes Botulism?
Clostridium botulinum
This is the most common form of Botulism in the US =
Infant Botulism
This is a neurotransmitter that promotes muscle contraction =
Acetylcholine
How does Botulism cause flaccid paralysis?
Stops the release of Acetylcholine
How can you diagnose Botulism?
Symptoms are diagnostic
Can test for toxin in fecal specimens, blood, or suspected foods
PCR and ELISAs available
What are the 4 approaches used to treat Botulism?
Maintain open and functional airways, may require a ventilator
Wash intestinal tract to remove Clostridium
Administer botulism antitoxin to stop the progression of the disease
Treat with antimicrobial drugs
How can you prevent Botulism?
Prevented by destroying endospores in contaminated food
Children under 1 year old should not consume honey which can contain endospores
What are signs and symptoms of Tetanus?
Tightening of the jaw (lockjaw)
Spasms and contractions may spread to other muscles resulting in a rigid paralysis
Irregular heartbeat and blood pressure and profuse sweating may occur
Interferes with ability to breathe in more serious cases
What bacteria causes Tetanus?
Clostridium tetani
Where is Clostridium tetani found?
Soil, dust, and the intestines of humans and animals
Clostridium tetani can produce neurotoxins called-
Tetanospasmin
How can you acquire Clostridium tetani?
Through breaks in the skin or mucous membrane
The symptoms of Tetanus are due to-
Tetanospasmin
What does Tetanus result in? How?
Normally, inhibitory neurotransmitters block nerve impulses so muscles can relax
Tetanus toxin blocks the inhibitory transmitter, resulting in continuous muscle contractions
What is the mortality rate of Tetanus if left untreated?
~50%
How is Tetanus diagnosed?
Diagnosis is based on characteristic muscle contraction
How is Tetanus treated?
Treatment involves several steps:
Thorough wound cleaning, administration of antitoxin, administration of antimicrobials, active immunization
How is Tetanus prevented?
Vaccine is available against tetanus
Example: DTaP combination vaccine protects against Diphtheria, Tetanus and Pertussis
Given multiple times during childhood; Booster recommended every 10 years for adults
Why are viruses able to cross the blood brain barrier easier than bacteria?
They’re smaller
Between viral diseases, fungal diseases, and bacterial diseases of the Nervous System, what is more frequent?
Viral Diseases
What is the incubational period for Rabies?
Can be long, 30-50 days or even up to a year
Once symptoms develop, Rabies is -
Always fatal
Is treatment of Rabies during the incubation period possible?
Yes
What are the initial symptoms of Rabies?
Discomfort at the site of the bite, fever and headache
What are the signs and symptoms of Furious (Classical) Rabies?
Agitation, hyperactivity, fear of water, excess salivation, desire to bite, foaming at mouth (all to increase the likelihood of transmission to next host). Death occurs after a few days due to cardiac/respiratory failure
What are the signs and symptoms of Paralytic Rabies?
Paralysis at infection site, spreads throughout body eventually causing coma and death. Slower course of disease compared to classical rabies
What causes rabies?
Saliva from an infected animal (bite)
How does Rabies work?
Virus replicates in muscle cells and then moves into neurons
Travels up the neurons into the ganglia in the spinal cord
From here, the virus gets access to the brain
The virus can travel down the nerves from the brain to infect other tissues (like salivary glands)
Progression of disease depends on where the bite is relative to the brain
What are the most common reservoirs for Rabies in the US?
Raccoons (30%)
Bats (30%)
Skunks(26%)
Foxes (4%)
How do you diagnose Rabies?
Diagnosis by unique neurological symptoms
No tests can confirm rabies virus at the time of bite or shortly thereafter
Once virus begins replicating, before symptoms occur, virus can be detected using fluorescent tests on nerves at the base of hair follicles
Saliva can also be tested using PCR
How do you treat Rabies?
Treated by injecting human rabies immunoglobulin, giving vaccine injections, and cleansing infection site
What are the manifestations of Poliomyelitis?
Asymptomatic in ~90% of cases.
4 Possible Variations.
What are the 4 variations of Poliomyelitis?
Minor Polio
Nonparalytic Polio
Paralytic Polio
Postpolio Syndrome
What are the manifestations of Minor Polio?
Nonspecific symptoms, mild intestinal disease
What are the manifestations of Nonparalytic Polio?
Muscle spasms and back pain
What are the manifestations of Paralytic Polio?
Produces flaccid paralysis
What are the manifestations of Postpolio Syndrome?
It can be debilitating:
years after polio, slowly progressive muscle weakness/atrophy, joint degeneration can occur.
Rarely life-threatening.
1 in 200 cases of this kind of polio can be reversible =
Paralytic Polio
What is the cause of Poliomyelitis?
Poliovirus
How is Poliovirus transmitted?
Most often transmitted by drinking contaminated water
Polio is an Endemic in-
Pakistan + Nigeria
How is Poliomyelitis diagnosed?
Diagnosed by identification of virus in the throat or feces
How is Poliomyelitis treated?
No specific treatment exists
How is Poliomyelitis prevented?
Two effective vaccines are available (Salk Vaccine + Sabin Vaccine)
Inactivated Polio Vaccine (IPV) =
Salk Vaccine
Attenuated, Oral Polio Vaccine (OPV) =
Sabin Vaccine
What are the advantages of the IPV vaccine?
Effective; inexpensive; stable during transport and storage; poses no risk of vaccine-related disease
What are the advantages of the OPV vaccine?
Provides lifelong immunity without boosters; triggers secretory antibody response similar to natural infection; easy to
administer; results in herd immunity
What are the disadvantages of the IPV vaccine?
Requires booster to achieve lifelong immunity; must be injected; requires higher community immunization rate than
does OPV
What are the disadvantages of the OPV vaccine?
Less stable than IPV; can mutate to disease-causing form; poses risk of development of polio in immunocompromised
contacts of vaccinated individuals
What Polio vaccine does America use?
US uses Salk vaccine (IPV):
4 doses in childhood, ages at 2, 4 months, 6-18 months and 4-6 yo
Primary Amoebic Meningoencephalopathy can also be called-
Brain-Eating Amoeba
What are the signs and symptoms of Brain-Eating Amoeba?
Headaches, fever, symptoms progress rapidly to confusion, seizures, inflammation of the brain, coma and death
What is Primary Amoebic Meningoencephalopathy caused by?
Naegleria fowleri + Species of Acanthamoeba
How does Naegleria fowleri + Species of Acanthamoeba enter the body?
Skin Abrasions
Eyelid
Inhalation of Contaminated Water
How do Brain-Eating Amoeba get to the brain?
They travel up olfactory nerves to gain access to the brain
Problems caused by Brain-Eating Amoeba are-
Rare but almost always fatal (Most cases occur in Texas, Florida, & Arizona)
Where can Brain-Eating Amoeba be found?
In warm freshwater and soil environments
What are the 3 forms of Brain-Eating Amoeba?
Cyst
Trophozoite
Flagellated
Resistant, inactive amoeba stage =
Cyst
Active feeding amoeba stage =
Trophozoite
This amoeba stage is an active but non-feeding stage, occurs when environment is not favorable, gives it a chance to find a new environment before progressing to cyst form =
Flagellated
Who are the people most at risk for acquiring Brain-Eating Amoeba?
People that enjoy water-related activities, such as swimming underwater, diving, and watersports
This is the Trophozoite stage of amoeba is considered to be the-
Infectious form, infectious form, it can use its pseudopods to travel from the nose up the olfactory nerves and get access to the brain
Occasionally, what form of amoeba can be found in the CSF?
The Flagellated Form
How can Primary Amoebic Meningoencephalopathy be diagnosed?
Detect amoebae in sample from the eye or brain or in CSF
Usually diagnosis is made during autopsy
How can Primary Amoebic Meningoencephalopathy be treated?
Drugs have limited success
How can Primary Amoebic Meningoencephalopathy be prevented?
Prevented by avoiding contaminated water supplies or swimming in stagnant bodies of water during peak summer months, using nose clips to avoid inhalation of water can also be helpful
