Internal Medicine - Infectious Diseases - CNS Infections Flashcards
All CNS infections may present with fever, headache, nausea, and vomiting. If the question stem mentions stiff neck, photophobia, and meningismus along with signs of infection, what is the most likely diagnosis?
Meningitis
All CNS infections may present with fever, headache, nausea, and vomiting. If the question stem mentions confusion along with signs of infection, what is the most likely diagnosis?
Encephalitis
All CNS infections may present with fever, headache, nausea, and vomiting. If the question stem mentions focal neurologic findings along with signs of infection, what is the most likely diagnosis?
Abscess
What is the most likely offending bacterial agent in a patient presenting with meningitis following recent neurosurgery?
Staphylococcus
A patient with HIV presents with CD4 count of <100 along with signs of meningitis. What is the most likely causative bacterial agent?
Cryptococcus
A patient who was recently camping/hiking presents with a rash and a meningitis-like presentation. What is on your differential?
Lyme disease
Rocky Mountain Spotted Fever (Rickettsia)
A patient with a recent history of camping/hiking presents with joint pain and facial palsy. What is the most likely diagnosis?
Lyme disease
A patient with a recent history of camping/hiking presents with a rash that moves from arms/legs to the trunk. What is the most likely diagnosis?
Rocky Mountain Spotted Fever (Rickettsia)
A patient who presents with meningitis-like symptoms has a history of a cavitary lesion found on a previous chest x-ray. What is the most likely cause of their current presentation?
Tuberculosis
An adolescent presents with meningitis-like symptoms. What one finding on exam would clue you into suspecting Neisseria as the causative agent?
Petechial rash, especially on lower extremities
What is the best initial and most accurate test in diagnosing meningitis?
LP
A CSF study in a patient with suspected meningitis returns with elevated WBCs, elevated protein, and decreased glucose. Which type of meningitis does the patient likely have?
Bacterial meningitis
A CSF study in a patient with suspected meningitis returns with mildly elevated WBCs, markedly elevated protein, and normal to low glucose. Which type of meningitis does the patient likely have?
Tuberculous meningitis
A CSF study in a patient with suspected meningitis returns with mildly elevated WBCs, and normal protein and glucose levels. Which type of meningitis does the patient likely have?
Viral meningitis
What is the characteristic finding for Guillain-Barre syndrome on CSF studies?
Cytoalbuminologic dissociation: normal WBC count but high protein count.
A patient with meningitis presents with the following symptoms: papilledema, seizures, focal neurologic abnormalities, and/or confusion that interferes with neurologic examination. What are your next two steps in managing this patient?
- START TREATMENT! When there is going to be a delay in getting the LP for a patient, it is better to start broad treatment with ceftriaxone, vancomycin, and dexamethasone.
- Get CT to rule out mass before performing LP!
Note: you’d still want to get an LP on this patient even with the high chances of getting a false negative due to treatment; there are other tests you can do on the CSF to figure out what the causative agent is.
An ophthalmic exam reveals a blurred, fuzzy disc margin. What medical condition is this describing?
Papilledema
When is a bacterial antigen/latex agglutination test indicated? (Hint: answer is not “when Cryptococcus neoformans is suspected.”)
When patient received antibiotics prior to LP (to prevent worsening of infection during delay of management) and culture is likely to be falsely negative.
Following LP, what is the most accurate diagnostic test for suspected tuberculosis meningitis?
Acid fast stain and culture of CSF
Following LP, what is the most accurate diagnostic test for suspected Lyme or Rickettsia-related meningitis?
Specific serologic testing, ELISA, western blot, or PCR (buncha’ genetic stuff) of CSF
Following LP, what is the most accurate diagnostic test for suspected Cryptococcus-related meningitis?
India ink or cryptococcal antigen
Note: cryptococcal antigen testing is more sensitive and specific than India ink.
When all other tests on the LP come back negative, what is the most likely causative agent of meningitis?
Viral
Three components of best treatment for bacterial meningitis?
Ceftriaxone
Vancomycin
Steroids (dexamethasone) (especially if WBCs are in the thousands)
If you have a patient who is either/or: Elderly Neonate Steroid use AIDS/HIV Immunocompromised or alcoholic Pregnant
What other component would you add to the treatment of their meningitis? Why?
Ampicillin to cover Listeria
What two other components would you add to the treatment of meningitis caused by Neisseria meningitidis?
- Respiratory isolation for the patient
2. Rifampin (or ciprofloxacin or ceftriaxone) prophylaxis to close contacts
What is the most common neurologic deficit of untreated bacterial meningitis?
CN 8 deficit or deafness.
What is the most common cause of encephalitis?
Herpes simplex
What is the first step in management of a patient who presents with acute onset of fever and confusion?
Head CT (confusion = get a CT!)
What is the most accurate test of herpes encephalitis?
PCR of CSF
What is the best initial therapy for herpes encephalitis?
Acyclovir
Why are famciclovir and valacyclovir not used for treatment of herpes encephalitis even though they can be used to treat genital herpes?
Famciclovir and valacyclovir are not available as IV formulations and herpes encephalitis must be treated as quickly as possible (thus with IV meds).
A patient has acyclovir-resistant herpes encephalitis. What is the next best management?
Foscarnet
A patient has been receiving IV acyclovir for herpes encephalitis for the past few days. Today, their creatinine levels begin to rise. What is the cause of this? How would you manage this patient?
Acyclovir can cause renal toxicity; the treatment is the most likely cause of the patients rise in creatinine.
Lower the dose of acyclovir (but keep them on the med!) and hydrate (to help renal function).
