Intoxications and Infections of the Nervous System Flashcards by Maggie Musso

MOA tetanus toxin?

Tetanospasmin binds to cortical, brain stem, and spinal interneurons, preventing the release of inhibitory glycine and GABA

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Presentation of tetanus?

Motor neuron disinhibition begins days to 2 weeks after exposure

Severe, prolonged, painful muscle spasms - may be local or diffuse; trismus (lockjaw), risus sardonicus (grimacing smile), opisthotonus (arching back)

Generalized convulsive seizures

Impaired swallowing or breathing

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Management of tetanus?

ICU care with mechanical ventilation, sedation, pharmacologic neuromuscular blockade, anticonvulsants

Human tetanus IG (neutralize toxin)
ABX for wound infection

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MOA botulism?

Exotoxin binds to presynaptic nerve terminals and prevents the release of ACh from LMNs and parasympathetic nerves

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Presentation of botulism?

Paralysis of skeletal muscle, bowel, bladder, salivary glands within 12-48 hours of ingestion

Ptosis, diplopia, pupillary paralysis -> dysphagia, facial and limb weakness, possible respiratory paralysis

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DDx of botulism?

MG
Brain stem infarction
GBS variant

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Dx botulism?

MRI and EMG may help exclude other causes of paralysis

Toxin may be detected by bioassay in food samples or fecal testing

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Manage botulism?

ICU monitoring
Antitoxin
Guanidine - facilitates ACh release form motor nerve endings and may improve clinical strength

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Presentation of lead poisoning in adults?

Peripheral neuropathy, often with prominent focal neuropathies like wrist drop

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Presentation of lead poisoning in children?

Encephalopathy and abdominal pain

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Rx lead poisoning?

Chelating agents

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Presentation of CO poisoning?

Headache, vomiting, blurry vision, can progress to coma, seizures, and CP arrest

Survivors may have residual memory or cognitive deficits; some may shown signs of parkinsonism (basal ganglia is sensitive to CO)

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Rx CO poisoning?

Inhalation of 100% O2

Hyperbaric chamber

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What causes Wernicke-Korsakoff syndrome?

Deficiency of thiamine (B1)

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Presentation of Wernicke’s encephalopathy?

Nystagmus, ophthalmoplegia, gait ataxia, and confusion; may resolve within hours to days of thiamine administration

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Presentation of Korsakoff’s psychosis?

Chronic memory deficit or amnestic memory with frequent confabulation

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Cause and presentation of alcoholic cerebellar degeneration?

Lesion in the anterior-superior vermis

Ataxic gait and dysmetria of the lower limbs

What causes central pontine myelinosis?

Demyelination of the CST and corticobulbar tacts in the pons, often due to overly rapid correction of severe hyponatremia

Presentation of meningitis?

Evolves over hours to days with symptoms that may be severe including fever, headache, stiff neck, malaise, lethargy, N/V

Bacterial - serious, may be fatal
Viral - usually milder, resolves spontaneously

On exam - lethargy to coma, nuchal rigidity, Kernig or Brudzinski signs

Petechial rash in the setting of meningitis suggests what cause?

Meningococcal (N. meningitidis)

Management of meningitis?

Cx blood, CSF, other infected material
Start broad spectrum ABX immediately - initial coverage typically consists of ceftriaxone (or other newer generation cephalosporin) + vancomycin; add ampicillin if Liseria is a concern (elderly or neonates)

In adults, IV dexamethasone (0.15 mg/kg) reduces neurological complications and lower mortality

LP as soon as possible

Sequelae of meningitis?

Hydrocephalus if pus develops and obstructs CSF pathways

Meningoencephalitis if pus accumulates over the cortical subarachnoid space

Infarction of brain or spinal cord if local vessels become inflamed and thrombose

Deafness (young children)

Suspected organisms causing bacterial meningitis in neonates (0-4 weeks old)

GBS

E. coli

Suspected organisms causing bacterial meningitis in children (<15 y/o)

N. meningitidis

S. pneumoniae

Suspected organisms causing bacterial meningitis in adults (>15 y/o)

S. pneumoniae N. meningitidis E. coli

Reasons to delay an LP?

Thrombocytopenia Clotting factor deficiency Infection along the skin of the back Concern for elevated ICP (unconscious, papilledema) or intracranial mass with edema (new onset seizure, focal neuro deficit, history of stroke, cerebral mass lesion or infection, immunocompromised)

Typical CSF profile of bacterial meningitis?

>500-1000 WBCs, PMN predominance High protein Low glucose Gram stain/culture

Typical CSF profile of viral, tuberuculous, fungal, syphilitic meningitis?

All: <500 WBCs, lymphocytic predominance Protein high in all, except viral which can be normal or high Glucose normal in viral, low in TB/fungal, and normal to low in syphilis

Normal CSF profile?

No WBCs <45 mg/dL protein >50% blood glucose

Presentation of chronic meningitis?

More subtle symptoms over weeks or months Typically infect elderly, malnourished, immunocompromised Confusion, low grade fever, mild headache, may not have obvious nuchal rigidity

Typical causes of chronic meningitis?

TB, fungus, syphilis, some parasites

Presentation of encephalitis?

Symptoms evolve over hours to days Involve fever and headache with signs and symptoms of brain involvement, such as seizures, focal deficits, behavioral changes, impaired consciousness

Work-up of encephalitis?

CSF (lymphocytic pleocytosis, normal or slightly decreased glucose) Antibody titers for suspected viruses (CSF and serum), especially HSV-1 MRI

Herpes simplex encephalitis is important to recognize since it is non-epidemic, non-seasonal, and carries a high mortality rate when not treated. What causes it, what parts of the brain does it tend to affect, how does it present, and how should it be treated?

HSV-1 Inferior frontal and medial temporal lobes (often bilaterally and asymmetrically) Aphasia, behavioral changes, memory deficits IV acyclovir

Unique presentation of WNV encephalitis?

Significant weakness -> affects peripheral nerves (like GBS) or anterior horn cells (like polio)

Presentation of polio?

Acute febrile illness, with a preferential viral invasion and destruction of anterior horn cells and brain stem motor nuclei LMN signs, often asymmetric Chronic joint or back pain, fatigue, imbalance

Presentation and Rx of shingles?

Eruption of a vesicular rash with severe neuralgic pain along one or two adjacent dermatomes on the torso or limb; acyclovir or other anti-viral

Describe nervous system manifestations of HIV/AIDS.

Early: acute, aseptic meningitis, myopathy or inflammatory polyneuropathy Late: chronic, painful sensory neuropathy, cognitive changes, HIV dementia, myelopathy akin to subacute combined degeneration Primary cerebral lymphoma Opportunistic infections: cerebral toxoplasmosis, cryptococcal meningitis, CMV retinitis or encephalitis, PML (reactivation of JC virus)

Presentation of abscesses?

Fever, headache Seizures and focal signs Brain edema with mass effect, increased ICP Abscess may rupture -> meningitis

Dx abscess?

CT or MRI with and without contrast

Presentation of CJD?

Very rapidly progressive dementia with cerebellar, CST, LMN, or EPS signs and symptoms; myoclonus is usually present

Dx CJD?

Brain biopsy with spongiform changes (cytoplasmic vacuoles in neurons and astrocytes, neuronal loss without inflammation) Periodic sharp wave discharge on EEG