Master the board step 3

Neurology
Diagnostic Testing
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Best initial test: Head CT scan
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Most accurate test: PCR of the CSF
The most common wrong answer on questions dealing with the diagnosis of
encephalitis is “brain biopsy.” A brain biopsy is not necessary. Do a PCR instead.
Treatment
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Best initial therapy: Acyclovir
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For acyclovir-resistant patients: Foscarnet
Basic Science Correlate
Mechanism of Acyclovir
Acyclovir, valacyclovir, famciclovir, and ganciclovir all have the same
mechanism, which is to inhibit tyrosine kinase. This is why ganciclovir cannot
be used to treat acyclovir-resistant herpes and why foscarnet, which has a
different mechanism, is used instead.
Brain Abscess
A brain abscess presents with fever, headache, and focal neurological deficits.
A CT scan finds a “ring,” or contrast-enhancing, lesion. Contrast (“ring”)
enhancement basically means either cancer or infection.
Brain Abscess
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