Nervous System Disease

• Blood Brain Barrier

  • The blood vessels that supply blood to the brain are different from other blood vessels because it is highly selective, allowing only specific molecules like nutrients, waste, and small lipids to cross over the brain.
  • It prevents microbes and toxins from entering the brain, but also keeps some beneficial drugs from entering the brain.
• Meninges

  • 3 membrane layers cover and protect the brain and spinal cord.
  • Meningitis is inflammation of the meninges and encephalitis is inflammation of the brain
• Meningitis

  • Inflammation of the meninges which can lead to encephalitis (brain inflammation)
  • Both meningitis and encephalitis are life-threatening
  • Diagnose via a spinal tap and measure increased white blood cells in the cerebrospinal fluid.
  • Signs/Symptoms of meningitis:
  • Severe, persistent headache
  • very stiff neck
  • Nausea and vomiting
  • Sudden high fever
  • Sensitivity to light
  • Double vision and drowsiness
• Meningitis and Encephalitis

  • Inflammation of the meninges which can lead to encephalitis (brain inflammation)
  • Both meningitis and encephalitis are life-threatening
  • Diagnose via a spinal tap and measure increased white blood cells in the cerebrospinal fluid.
  • Signs/Symptoms of encephalitis:
  • All of the above
  • Disorientation and confusion
  • Change in behavior
  • Seizures
• Listeriosis

  • Caused by eating contaminated food (dairy and meat), containing Listeria monocytogenes
  • Symptoms:
  • In healthy adults, symptoms are mild flu-like.
  • In older adults, immunocompromised people, and pregnant women, the disease can be severe with signs/symptoms of:
  • Fever, muscle ache, fatigue, diarrhea, stupor and convulsion
  • Can lead to septicemia and meningitis
  • This is one reason why pregnant women are advice to avoid eating raw food and dairy
  • Treatment with antibiotics.
• Rabies

  • Viral infection is transmitted by the bite of a rabid animal (skunk, dog, bat, raccoon, fox).
  • Virus attacks the brain stem resulting in death within 3~12 weeks if timely treatment is not given
  • Signs and symptoms include:
  • Flu-like symptoms
  • Prickling or numbness at the site of the bite
  • Agitation and confusion
  • Hyper-salivation, hydrophobia, violent outbursts, paralysis, coma, and death. (hydrophobia disease-cause vomit)
  • FYI, treatment includes injection of human rabies immune globulin (HRIG) near the site of the bite, followed by 4 doses of rabies vaccine within 14 days in the arm.
• West Nile Virus

  • Transmitted by various species of Culex mosquitoes
  • Most cases are subclinical(we cannot really tell) and about 1/5 will have flu-like symptoms.
  • Less than 1% will have serious complications. Those who are immunocompromised, the very young, and elderly are most at risk
  • In serious cases, can lead to meningitis and encephalitis.
• Polio

  • Caused by a human enterovirus (gut virus) and transmitted via the oral-fecal route where the virus replicates in the neurons of the oropharynx(mouth/throat) and intestine. (comes from contaminated water/food)
  • Most (2/3) will have no symptom, some will have minor symptoms (flu-like)
  • In rare severe cases, the virus spreads to CNS and kills neurons leading to motor loss, muscle pain, and paralysis
  • Less than 1% will become paralyzed and those 5~10% die from respiratory arrest unless they use a respiratory/ventilator
  • vaccine available.
• Hansen’s Disease (Leprosy)

  • caused by Mycobacterium leprae
  • Difficult to “catch”
  • 95% of adults cannot get infected
  • Those at risk and susceptible are living in tropical countries(wet, humid), must be genetically susceptible, and live in close proximity to someone with leprosy.
  • Bacteria damages the peripheral nerve causing:
  • Loss of sensation in the infected area, so injuries go unnoticed
  • Abdominal skin growth and discoloration
  • Muscle weakness and paralysis (ex. hands and feet)
• Tetanus/Lockjaw

  • Caused by strict anaerobe Clostridium tateni that enters a deep flesh wound.
  • The bacteria produces tetanin toxin which causes a continuous overstimulation of the muscles (especially the jaw and neck) resulting in muscle pain and muscle spasms that inhibit normal muscle function.
  • The severity of muscle spasms can lead to bone breaking, but death is usually caused by respiratory failure
  • Prevention via DTaP vaccine, treated with antibiotics to kill vegetative cells and Ig-G to bind to toxins.
• Botulism

  • caused by Clostridium botulinum
  • Botulin toxin inhibits muscle contraction by inhibiting the release of acetylcholine (ACh). Without ACh, muscles are not stimulated thus resulting in paralysis and death from respiratory failure
  • 3 forms of botulism
  • Foodborne: food contains botulin (ex. canned vegetables, fermented meats, etc)
  • wound: wound infected by bacteria
  • Infant: Ingestion of spores (most common)
  • Treatment includes antibiotics, injection with Ig-G to bind to toxins, and if needed a ventilator.
• Cryptococcus neoformans

  • Causes cryptococcosis
  • Normally infects the lung, but in rare cases can cause meningitis/encephalitis, especially in immunocompromised individuals
• Coccidioides immitis

  • Causes coccidioidomycosis or Valley Fever
  • Normally infects the lung, but in rare cases can cause meningitis/encephalitis, especially in older people(60 years), pregnant women, immunocompromised individuals, and certain ethnic groups (ex. Pacific Islanders, Latinos, and African Americans, etc.)
• African Sleeping Sickness (Sleeping sickness)

  • Transmitted by the bite of tse-tse fly(blood-sucking fly) which harbor the protozoan Trypanosoma brucei.
  • The protozoan attacks the brain stem causing abnormal sleep-wake cycle, muscle weakness, tremors, paralysis, personality changes, and eventually death within a year
  • Don’t worry, so far these flies are found in only sub-Saharan Africa…
• Chagas

  • Transmitted by the bite of an insect called the kissing bug, but transmission is actually via feces of the insects…huh?
  • Inside the body, the protozoan attacks the heart and nerve that controls the GI tract leading to heart damage, megacolon/GI tract problems, and death.
• Primary Amoebic Meningoencephalitis (PAM)

  • Caused by a protozoan (amoeba) called N.fowleri, which lives in freshwater lakes. Although, infection is rare, once in the brain it is 100% fatal.

  FYI, in 2011, 2 people contracted PAM from using dirty water for their neti pot.
• Toxoplasmosis

  • Caused by a protozoan called Toxoplasma gondii, which is found in cat feces and other animals.
  • Healthy individuals are not at risk, but immunocompromised people and fetuses of pregnant women are vulnerable.
  • In susceptible people, the protozoan damages organs(eye, brain, etc) and can cause spontaneous abortion. In people with AIDS, it causes encephalitis.
• Prion diseases

  • believed to be caused by a misfolded protein that causes normal brain protein to misfold, leading to a condition known as spongiform encephalitis (sponge-like brain)
  • All cases are 100% fatal
  • The following diseases are believe to be linked to prions
  • Kuru
  • Cruzfeld-Jakob
  • Fatal Familial Insomnia
  • Scrapie (occurs in sheep)
  • Mad Cow disease