Internal Medicine - Infectious Diseases - CNS Infections

Question 1

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?

Answer 1

Meningitis

Question 2

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?

Answer 2

Encephalitis

Question 3

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?

Answer 3

Abscess

Question 4

What is the most likely offending bacterial agent in a patient presenting with meningitis following recent neurosurgery?

Answer 4

Staphylococcus

Question 5

A patient with HIV presents with CD4 count of <100 along with signs of meningitis. What is the most likely causative bacterial agent?

Answer 5

Cryptococcus

Question 6

A patient who was recently camping/hiking presents with a rash and a meningitis-like presentation. What is on your differential?

Answer 6

Lyme disease

Rocky Mountain Spotted Fever (Rickettsia)

Question 7

A patient with a recent history of camping/hiking presents with joint pain and facial palsy. What is the most likely diagnosis?

Answer 7

Lyme disease

Question 8

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?

Answer 8

Rocky Mountain Spotted Fever (Rickettsia)

Question 9

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?

Answer 9

Tuberculosis

Question 10

An adolescent presents with meningitis-like symptoms. What one finding on exam would clue you into suspecting Neisseria as the causative agent?

Answer 10

Petechial rash, especially on lower extremities

Question 11

What is the best initial and most accurate test in diagnosing meningitis?

Answer 11

LP

Question 12

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?

Answer 12

Bacterial meningitis

Question 13

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?

Answer 13

Tuberculous meningitis

Question 14

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?

Answer 14

Viral meningitis

Question 15

What is the characteristic finding for Guillain-Barre syndrome on CSF studies?

Answer 15

Cytoalbuminologic dissociation: normal WBC count but high protein count.

Question 16

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?

Answer 16

1. 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.
2. 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.

Question 17

An ophthalmic exam reveals a blurred, fuzzy disc margin. What medical condition is this describing?

Answer 17

Papilledema

Question 18

When is a bacterial antigen/latex agglutination test indicated? (Hint: answer is not “when Cryptococcus neoformans is suspected.”)

Answer 18

When patient received antibiotics prior to LP (to prevent worsening of infection during delay of management) and culture is likely to be falsely negative.

Question 19

Following LP, what is the most accurate diagnostic test for suspected tuberculosis meningitis?

Answer 19

Acid fast stain and culture of CSF

Question 20

Following LP, what is the most accurate diagnostic test for suspected Lyme or Rickettsia-related meningitis?

Answer 20

Specific serologic testing, ELISA, western blot, or PCR (buncha’ genetic stuff) of CSF

Question 21

Following LP, what is the most accurate diagnostic test for suspected Cryptococcus-related meningitis?

Answer 21

India ink or cryptococcal antigen

Note: cryptococcal antigen testing is more sensitive and specific than India ink.

Question 22

When all other tests on the LP come back negative, what is the most likely causative agent of meningitis?

Answer 22

Viral

Question 23

Three components of best treatment for bacterial meningitis?

Answer 23

Ceftriaxone
Vancomycin
Steroids (dexamethasone) (especially if WBCs are in the thousands)

Question 24

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?

Answer 24

Ampicillin to cover Listeria

Question 25

What two other components would you add to the treatment of meningitis caused by Neisseria meningitidis?

Answer 25

1. Respiratory isolation for the patient

2. Rifampin (or ciprofloxacin or ceftriaxone) prophylaxis to close contacts

Question 26

What is the most common neurologic deficit of untreated bacterial meningitis?

Answer 26

CN 8 deficit or deafness.

Question 27

What is the most common cause of encephalitis?

Answer 27

Herpes simplex

Question 28

What is the first step in management of a patient who presents with acute onset of fever and confusion?

Answer 28

Head CT (confusion = get a CT!)

Question 29

What is the most accurate test of herpes encephalitis?

Answer 29

PCR of CSF

Question 30

What is the best initial therapy for herpes encephalitis?

Answer 30

Acyclovir

Question 31

Why are famciclovir and valacyclovir not used for treatment of herpes encephalitis even though they can be used to treat genital herpes?

Answer 31

Famciclovir and valacyclovir are not available as IV formulations and herpes encephalitis must be treated as quickly as possible (thus with IV meds).

Question 32

A patient has acyclovir-resistant herpes encephalitis. What is the next best management?

Answer 32

Foscarnet

Question 33

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?

Answer 33

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).