Infectious Diseases of CNS

Question 1

Define hydrocephaly.

Answer 1

Hydrocephaly

• Communicating hydrocephaly: an accumulation of cerebrospinal fluid due to deficient resorption
• Internal: an obstruction of the flow pathway through the brain
• Hydrocephaly ex-vaccuo: brain shrinks and CSF replaces it.

Question 2

Define meningismus.

Answer 2

Meningismus is resistance to neck flexion due to pain when inflamed meninges are stretched.

Question 3

What is Kernig’s sign?

Answer 3

Kernig’s sign is involuntary flexion of the knee when the lower limb is flexed at the hip.
- This occurs because the inflamed meninges are stretched by stretch of the sacral nerve roots.

Question 4

What is pleocytosis?

Answer 4

Pleocytosis is the presence of an excessive number of white blood cells in the spinal fluid.

Question 5

What is Brudzinski’s sign?

Answer 5

Brudzinski’s sign is involuntary flexion of the knees when the neck is flexed.
- This occurs because the inflamed meninges are stretched by flexing the neck and tension can be relieved somewhat by taking tension off of the sacral nerve roots by flexing the knees.

Question 6

What does “parameningeal” refer to?

Answer 6

Parameningeal refers to processes (particularly infections) that occur outside of the dura but which are adjacent to it (producing some signs - particularly in the CSF) of inflammation.

Question 7

What are the 4 broad classes of meningitis?

Answer 7

1) Acute
2) Chronic
3) Bacterial
4) Viral/Aseptic

Question 8

What are the most common causes of acute meningitis?

Answer 8

Most acute meningitis is bacterial or viral (chemical meningitis is rarer).

Question 9

What are the most common causes of acute bacterial meningitis?

Answer 9

The most common cause of acute bacterial meningitis are strep pneumonia, Neisseia meningitides, group B strep, Listeria monocytogenes, Hemophilus influenzae.

Question 10

Which bacterial would you suspect in adults? 
In older children/adolescents? 
In young children?
In infants? 
In the elderly?

Answer 10

• Adults: strep pneumonia (especially in adults)
• Children/adolescents: Neisseria meningitis
• Young children: H. influenzae
• Infants: group B strep
• Elderly/immunosuppressed: Listeria

Question 11

What are the signs and symptoms of acute bacterial meningitis?

Answer 11

• Headache, fever, meningismus, confusion progressing to stupor, elevated intracranial pressure.
• Young children and particularly infants may not have fever or neck stiffness.
• Infants may have a bulging fontanelle.

Question 12

What are some potential complications of meningitis?

Answer 12

Potential complications of meningitis include: cranial nerve palsy, hydrocephalus, stroke, seizure, abscess.

Question 13

What is the most critical diagnostic procedure for suspected meningitis?

Answer 13

Lumbar puncture is critical for diagnosis and for determining the best treatment.
- Analyze CSF

Question 14

What are the findings in the CSF in acute bacterial meningitis?

Answer 14

• Increased protein
• PMNs are numerous with most bacterial meningitis
• Glucose (as a percentage of systemic blood glucose) may be low with bacteria

Question 15

What are the principles of treatment of acute meningitis?

Answer 15

Do not wait for cultures - empiric antibiotics are used to cover potential organisms.

• A third generation cephalosporin + vancomycin are most common, but you should consider adding ampicillin if over 55 or immunocompromised.
• Steroids may be useful in children to cut down on complications

Question 16

What is the most common cause of aseptic meningitis?

Answer 16

Most aseptic meningitis is viral.

Question 17

What are the symptoms of aseptic meningitis?

Answer 17

The symptoms of aseptic meningitis include:

- Headache, neck stiffness, photophobia, viral syndrome.

Question 18

What are the CSF findings in aseptic meningitis?

Answer 18

• The CSF usually shows fewer than 500 WBC - some polys early then lymphocytes.
• There may be slight elevation of protein
• Glucose is usually normal.

Question 19

What are causes of chronic meningitis?

Answer 19

The causes of chronic meningitis include:

• Atypical bacteria (mycobacteria)
• Fungi
• Spirochetes (syphilis, Lyme)
• Parasites.
• Neoplasm (carcinomatous meningitis) - especially lymphoma.

Question 20

What are the signs and symptoms of chronic meningitis?

Answer 20

• Headache and mental status change.
• The patients are usually debilitated and have constitutional symptoms although
• Damage to cranial nerves
  
  • Can cause hydrocephaly and stroke.
• NO meningismus.

Question 21

What is the key to diagnosis of chronic meningitis?

Answer 21

CSF is critical to diagnosis of chronic meningitis.

Question 22

What are parameningeal infections?

Answer 22

Parameningeal infections are outside the dura but adjacent to it (sinuses, otitis, mastoiditis, epidural empyema, epidural abscess - including the spine, osteomyelitis).
- These often result in elevated protein and mononuclear pleocytosis in the CSF.

Question 23

What are the features of acute viral encephalitis?

Answer 23

Patients with acute viral encephalitis may have meningeal signs but patients are more encephalopathic (sleepy, stuporous, not thinking clearly).

Question 24

What are the potential complications of acute viral encephalitis?

Answer 24

Potential complications of acute viral encephalitis include:

- Increased intracranial pressure and seizures.

Question 25

What are the potential causes of acute viral encephalitis?

Answer 25

• Arboviruses (seasonal and some in epidemics)
  
  • Several types of equine encephalitis and West Nile virus.
• Herpes simplex (most common)

Question 26

What are the potential causes of chronic encephalitis?

Answer 26

• HIV
• Myxovirus (progressive multifocal leukoencephalopathy)
• Subacute sclerosing panencephalitis (the measles virus).

Question 27

What are the causes of brain abscesses?

Answer 27

Brain abscesses may follow focal infections such as otitis media, sinusitis, mastoiditis, but it may also result from hematogenous spread (teeth, bacterial endocarditis, etc).

Question 28

What are the symptoms of brain abscess?

Answer 28

• Headache and focal deficits.
• The patient may or may not show signs of systemic illness.
• Seizures may develop

Question 29

What are the most common organisms in brain abscess?

Answer 29

Brain abscess are usually mixed infection including anaerobes.
- There is a cerebritis stage, encapsulation stage, and potential rupture (sometimes fatal).

Question 30

What is the treatment for brain abscesses?

Answer 30

• Empiric antibiotics are used in the cerebritis stage of brain abscess
  
  • Third generation cephalosporin and metonidazole or chloramphenacol
• The patient requires close observation and may require surgical drainage or aspiration when capsule forms.

Question 31

What is the role of lumbar puncture in brain abscesses?

Answer 31

Spinal taps are extremely dangerous in brain abscesses due to potential herniation when pressure is released below.