Intoxications and Infections of the CNS Flashcards
Where does the tetanus toxin come from?
Tetanus is an exotoxin produced from Clostridium tetani
It is either produced anaerobically in dirty wounds or from a non-sterile needle or drug abusers
How does the tetanus toxin produce an effect?
After hours to weeks, the exotoxin binds to interneurons of the CNS, preventing release of inhibitory glycine and GABA —> motor disinhibition
(generalized seizures, painful spasms etc)
How is a tetanus diagnosis made?
Clinically
How is tetanus treated?
ICU care, neuromuscular blockade, sedation, anticonvulscents, tetanus immune globulins and antibiotics
Where does the botulism toxin come from?
Exotoxin of clostridium botulinum- produced anaerobically in improperly canned or prepared food.
How does the botulinum toxin produce an effect?
The botulinum exotoxin binds to presynaptic nerve terminals preventing the release of ACh
Administration of what aids in the release of ACh from the pre-synaptic cleft?
Guanidine
How is botulism diagnosed?
Clinical picture, EMG tests, bioassay
How does lead poisoning manifest in adults?
Peripheral neuropathy
How does lead poisoning manifest in children?
Encephalopathy, abdominal pain
How does organic solvent toxicity manifest in patients?
Encephalopathy or peripheral neuropathy
What are symptoms associated with CO poisoning?
Early: headache, vomiting, blurred vision
Later: coma, seizures, or cardiopulmonary arrest
Survivors of CO poisoning may have what lasting effects?
Amnesia and parkinsonianism
What drugs cause stroke syndromes in atypical patients?
Cocaine (most common), amphetamines, PCP, and LSD
What are the neurological symptoms caused by acute alcohol intoxication?
social disinhibition, impaired consciousness, cerebellar dysfunction
secondary head trauma
very high levels may lead to coma, death
What are the neurologic symptoms caused by alcohol withdrawal?
early, hypersympathetic stage (tremulous, sweaty, tachycardic);
limited number of convulsive seizures 12 hrs-3 days after drinking stopped;
later stage of delirium tremens, 3-4 days after drinking stopped, with fluctuating motor and autonomic activity, confusion, hallucinations
How do we treat alcohol withdrawal?
treat with benzodiazepines for sedation and seizure control, provide hydration and metabolic support, thiamine
What is acute Wernicke Encephalopathy?
nystagmus, ophthalmoplegia, gait ataxia, confusion…acute phase of Wernicke-Korsakoff syndrome
How is wernike encephalopathy corrected?
thiamine supplimentation
What is korsakoff psychosis?
Korsakoff psychosis (amnesia, confabulation) is the chronic phase of Wernicke-Korsakoff syndrome.
Where does alcoholic cerebellar degeneration occur?
Anterior superior cerebellar vermis
What are the symptoms of alcoholic cerebellar degeneration?
gait ataxia and dysmetria of the lower limbs (inability to judge distance/scale –> discoordination)
Define meningitis
Inflammation of the leptomeninges due to blood, foreign material, or infection within the subarachnoid space.
What agents cause acute meningitis vs chronic meningitis?
Acute: bacterial, viral
Chronic: unusual organisms
How are the CSF white counts and glucose affected by typical bacterial meningitis?
White count; increased neutrophils
Glucose: decreased
How should the patient be treated if bacterial meningitis is suspected?
1) Look for primary source of infection
2) Give broad spectrum antibiotics
3) Narrow antibiotics once culprit is identified
4) Observe for complications +/- DEX to minimize risk of complications
Name 4 complications of bacterial meningitis
1) Hydrocephalus (from pus obstructive CSF pathway)
2) Secondary inflammation and edema of cortex (meningoencephalitis)
3) Infarction from thrombosis of inflamed superficial vessels
4) Deafness (monitor hearing in children)
who is most susceptible to chronic meningitis?
Elderly, malnourished, and immunosuppressed patients
What are the symptoms of chronic meningitis?
subtle symptoms of mild headache, confusion, no obvious meningeal signs
What usually causes encephalitis?
Viral infection
How do you usually acquire viral encephalitis?
Viral transmission by seasonal arthropods (ticks, mosquitoes), inhalation or reactivation (herpes simplex)
What are the symptoms of encephalitis?
High fever and headache (like with meningitis)
Seizures, focal neurologic deficits, changes in behavior and consciousness (more specific for encephalitis)
Which strain of herpes causes herpes encephalitis?
HSV-1 (cause of oral herpes)
The herpes virus has a predilection for which lobes of the brain? How does this correlate to neurologic symptoms?
Frontal and temporal
* aphasia, behavioral changes and memory impairment
What is the treatment for herpes encephalitis?
acyclovir: reduces mortality from 40-70% to 20%
What are the symptoms of west nile virus?
Encephalitis –> fever, headache, rash
Weakness from affected peripheral nerves or anterior horn cells
Which cells are targeted by the polio virus?
motor neurons in the brain stem, spinal cord
Survivors of polio suffer from what long term effects?
Asymmetrical atrophy and weakness in one limb
What are shingles?
Reactivation of chicken pox (varicella zoster), which lies latent in the dorsal root ganglia
Causes a vesicular rash in 1 or 2 dermatomes
HIV destroys which WBCs?
T4 helper lymphocytes
HOw is the nervous system affected by HIV?
Direct viral invasion (dementia, meningitis)
Indirect damage from cell lysis, inflammation
Complications of an immunodeficient state
How is AIDS dementia diagnosed?
Clinical diagnosis of exclusion
MRI shows nonspecific atrophy or white matter alterations
Progressive Multifocal Leukoencephalopathy (PML) is an opportunistic infection in immunodeficient patients caused by what virus?
papovavirus
What cells of the CNS are infected by the papovavirus in PML? What is the outcome?
Oligodendrocytes
Leads to patchy demyelination in the CNS and focal deficits. It is untreatable
What is the causative agent in prion disease?
Infectious protein
What is the most common prion disease?
Creutzfeldt-Jakob Dementia (CJD)
How is prion disease transferred?
human graft tissue or neurosurgical instruments
Other prion diseases are hereditary in nature
How do prions cause disease?
Infectious proteins induce conformational changes in normal proteins –> neuronal death WITHOUT inflammation
What is the timing of Creutzfeldt-Jakob Disease?
Rapidly progressive, untreatable, fatal in weeks to months
What are the symptoms of Creutzfeldt-Jakob Disease?
Dementia with prominent myoclonus
Often corticospinal, extra-pyramidal, cerebellar or LMN signs
