CNS Infections- Polio Virus Flashcards
(34 cards)
Poliomyelitis (myelitis = inflammation of spinal chord) is an acute systemic infectious disease.
In its rare, severe form, it affects CNS, destroying motor neurons in spinal cord, which results in a _____________.
flaccid, ascending, asymmetrical paralysis. Old name is infantile paralysis
Another name for Polio virus is
Human Enterovirus C
Polio is an enterovirus - Human Enterovirus C- description
-Polio viruses
-a non-enveloped
+sense RNA virus
-3 serotypes designated as PV1, PV2, and PV3
infection with one serotype results in lifelong immunity but they __________
An adequate vaccine must contain __________.
do not cross neutralize
all three types (i.e., is trivalent)
Polio is rare today in US due to vaccination. Polio was thought to be primarily a disease of _________. Most cases occurred in slightly __________ who manifested with more serious disease.
developed/industrialized countries
older, susceptible children and young adults
Paralytic polio is a significant concern in ____________
underdeveloped countries
Infection is acquired from an infected or diseased person, primarily by the ____________.
fecal-oral route via contaminated food and water; virus is present in stool 3-6 weeks.
-less so by respiratory secretions/aerosol droplets and saliva (oral-oral transmission)
Host of Polio
Humans are the sole host (the virus only infects humans). Transmission occurs most frequently by persons with inapparent infections.
Reservoirs of Polio
humans AND water
How communicable is Polio?
Highly communicable: Poliovirus is highly infectious, with seroconversion rates in susceptible household contacts of children nearly 100% and of adults over 90%
Populations affected by Polio (list)
- children less than 3 are primarily affected (in utero, neonatal, infant infections DO NOT normally occur)
- adolescents and young adults, esp. pregnant women are also susceptible.
- the elderly
- Younger pt have less severe manifestations. The likelihood of developing paralytic polio increases with age, as does the extent of paralysis (one limb vs quadriplegia)
Seasonality/temporal pattern
Summer-fall (in temperate zone, i.e., Northern hemisphere), little seasonality occurs in the tropics
Common pathogenesis/presentation
S/S: no symptoms (majority) or mild malaise
Polio is a _____ virus. After virus enters the mouth or nose, the virus infects cells and then spreads to _____________, first in pharynx and later in the intestinal tract where infection can persist for _________ and the patient may manifest with signs and symptoms. The virus is shed in _______ for several weeks and in the feces for several months. A viremia will also occur. Rarely, the viremia is ______.
lytic
draining lymph nodes along the GI tract
weeks to months
oral secretions
high
Rarely, the virus enters the CNS by:
- crossing the blood-brain barrier
- travels by neural routes (infects skeletal muscle, then travels up innervated nerves of skeletal muscles) and along the PNS via retrograde axoplasmic flow as per herpes, and/or rabies viruses to CNS
Once in the CNS, poliovirus spreads along certain nerve fiber pathways, preferentially replicating in and destroying motor neurons within ___________. This leads to the development of _________, the various forms of which (spinal, bulbar, and bulbospinal) vary only with the amount of neuronal damage and inflammation that occurs, and the region of the CNS that is affected.
the spinal cord, brain stem, or motor cortex
paralytic poliomyelitis
Spread through CNS results in
lower motor neuronal damage (FLACCID PARALYSIS) with NO sensory loss (unlike GBS)
Inapparent/Asymptomatic infection is the most common (90→95%); however disease form manifests in 4-8% of people with these S/S:
- Minor illness/gastroenteritis/abortive poliomyelitis is most common
- fever, malaise, fatigue, drowsiness,
- headache, muscle aches
- sore throat/pharyngitis
- nausea and vomiting, abdominal pain, constipation, rarely diarrhea
- Lasts 72 hours or less
Polio also manifest as Aseptic meningitis without paralysis/non-paralytic
(Abortive illness/Abortive polio (3rd most common form) — Signs and Symptoms of aseptic meningitis described earlier plus:
-Pain in front part of neck
-Back pain or backache
-Muscle stiffness, Leg pain (calf muscles)
-Muscle tenderness and spasm in any area of the body
-Pain or stiffness of the back, arms, legs, abdomen
Symptoms usually last 1 - 2 weeks
Least (0.1 →2%) common form of diease is paralytic poliomyelitis, S/S:
Initially Signs and Symptoms of aseptic meningitis without paralysis, but is FOLLOWED BY an asymmetric flaccid paralysis that is
ascending, acute onset, with a fever.
During the rare paralytic poliomyelitis, paralysis begins 1→ 10 daysafter the early symptoms began. It progresses for two to three days and is usually complete by the time the fever breaks. S/S are:
- Severe muscle aches or spasms, muscle pain
- Loss of superficial and deep reflexes (Diminished deep-tendon reflexes/areflexic leg weakness).
- EMG velocity studies demonstrate axonal-type polyneuropathy affecting anterior horn cells or their axons vs. demyelination
Sensory involvement of paralytic poliomyelitis is
abnormal sensations (but not loss of sensation) in an area; sensitivity to touch, paresthesia.
3 forms of paralytic poliomyelitis – 3 Different types of paralysis may occur, depending on the nerves involved:
- Spinal
- Bulbar polio
- Bulbospinal polio
- for some patients, paralysis is temporary, lasting weeks
Post-polio Syndrome manifests as:
- unaccustomed fatigue
- new or recurrent muscle weakness and pain
- progressive muscle atrophy
- Peak incidence is 30 → 40 years following acute polio
- Disease develops when patient’s remaining motor units/motor neurons start to respond poorly due to their overuse throughout many years. NOT due to activation of latent poliovirus
