M- CNS Infections Flashcards
What are the 3 possible categories of infection in the calverium?
What symptoms allude to each?
- meningitis- meningeal inflammation like stiff neck, headache
- encephalitis - some aspect of cerebral dysfunction
- meningoencephalitis- mixture of both
In addition to encephalitis and meningitis, infection of the brain can also form abscesses.
What are the areas where abscesses can occur?
Which areas are most likely?
Abscesses can occur in:
- parenchyma
- epidural space [more common than subdural]
- subdural space
What are the most common NON-INFECTIOUS causes of meningitis?
- neoplastic conditions
- carcinomatous meningitis from breast/lung cancers - chemical meningitis
- IVIG
What is the “triad” of infectious meningitis?
In what percent of cases does each of these symptoms present?
In what percent of cases do all 3 present?
- Fever - 77%
2, Headache- 87% - Neck stiffness- 83%
ALL 3 = 44% [too low to be used as a sensitive screen for the potentially fatal condition]
What infectious agents are known to cause meningitis?
What are the 2 most common?
- bacteria
- viruses
[most common]
- fungi
- parasites
- mycobacteria
- spirochetes
What 2 clinical exam findings are indicative of meningeal inflammation?
What is the specificity/sensitivity of these 2 findings?
- Kernig sign - flex the hip 90 degrees and extend the patients knee. + sign = pain.
- Brudzinksi’s sign - flex the patient’s neck. + sign = the patient flexes hip and knees
Data suggests that neither exam finding is sensitive nor specific [in one study 3/66 with meningitis had +Kernig/Brudzinski]
What are the steps of a lumbar puncture?
lumbar puncture :
- lateral recumbent position [seated could work, but you won’t get an opening pressure]
- align patients shoulders/pelvis to avoid rotation of the vertebral column
- insert lumbar puncture needle in the midline along a line connecting the superior border of the posterior iliac crests [L3/L4, L4/L5, L5/S1]
Diagnosis of meningitis involves clinical and paraclinical info but the most important “test” is what?
CSF analysis
At what level does the spinal cord terminate?
At what levels would it be acceptable to do a lumbar puncture?
Which level is most commonly done?
What layers must the needle penetrate to be in the area where CSF is located?
Spinal cord terminates at L1
Lumbar puncture is performed at
L3-L4
L4-L5 [most common]
L5-S1
skin–> ligamentum flavum–> dura–>arachnoid –> subarachnoid [where CSF is]
When evaluating CSF, what values correlate with normal?
- opening pressure
- WBC
- PMNs
- RBCs
- Protein
- Glucose
- less than 180 mmH2O
- less than 5
- 0
- 0
- 15-45 mg/dl
- over 50 mg/dl
When evaluating CSF what values correlate with bacterial meningitis?
- opening pressure
- WBC
- PMNs
- RBCs
- Protein
- Glucose
- over 180 [diff from normal]
2. over 1000 [normal is 40]
When evaluating CSF, what values correlate with viral meningitis?
- opening pressure
- WBC
- PMNs
- RBCs
- Protein
- Glucose
- less than 180 [normal]
- 50-500 [normal is less than 5]
- less than 50% [normal is zero]
- 0
- less than 100 [normal is 15-45]
- over 40 [normal]
When must you obtain CSF in a person suspected of meningitis?
BEFORE the administration of antibiotics because this can sterilize the CSF cultures and change the CSF parameters.
This will make it less likely that you identify the causative organism [for better treatment]
What are the relative risks of lumbar puncture that need to be evaluated before trying to obtain CSF?
Lumbar punctures in general are very safe, but there is a slight risk for life-threatening herniation.
CT should be done before a lumbar puncture in patients at high risk of herniation:
- immunocompromises
- history of CNS disease
- new onset seizure
- papilledema
- altered consciousness or focal deficit
A 6 year old boy is brought into the emergency room by his parents with 3 hours of fever, headache, rash, nausea/vomiting, and lethargy.
On exam, he is altered, somnolent, and has nuchal rigidity. There are NO localizing signs on physical exam.
Does he have meningitis, encephalitis or meningoencephalitis?
What is the order of next steps ?
He is suspicious for bacterial meningitis and due to his altered consciousness may have encephalitis too = meningoencephalitis.
- Blood Culture STAT [already giving IV for antibiotics, 50% will have + culture]
- Dexamethasone and empiric antibiotics
- CT scan
- if CT is negative [they won’t herniate] –>
- lumbar puncture
- evaulate CSF for bacterial meningitis
- gram stain and culture
A patient presents with possible bacterial meningitis.
He is not immunocompromised, has no prior history of CNS disease, does not have seizure, papilledema, focal neurological deficits or altered consciousness.
What is the order in which you diagnose/treat?
- Blood cultures STAT at the same time as lumbar puncture
- dexamethasone + empiric antibiotics
- if the CSF shows bacterial meningitis do a gram stain
- positive ID of organism–> dex + targeted antibiotic; neg ID of organism–> dex + empiric antibiotic
What is the best predictor or morbidity and mortality in a patient with bacterial meningitis?
The time to antibiotic treatment [longer = worse outcome]
Therefore, even though it may compromise CSF content, possible cultures a little bit, you need to start them right away when the patient presents with possible meningitis
What is the time frame in which antibiotics change components of the CSF?
- loss of gram stain and culture w/in hours
- cell count and protein won’t change for 24-48hrs
- differential and glucose are the first to change
What are the guidelines for administration of steroids before antibiotics when treating bacterial meningitis?
What is the effect on morbidity and mortality?
Steroids are recommended prior to empiric treatment with antibiotics because a lot of the bacteria that cause meningtis are encapsulated and when the antibiotic lyse them, there is a secondary inflammatory response that can damage CNS and CNs.
Steroids reduce morbidity [especially hearing loss] but there is no reduction in mortality
What is the most common sequelae of meningitis [esp. pneumococcal meningitis]?
hearing loss
What is the treatment for viral meningitis?
Supportive care
If a patient presents with meningitis, what are you to assume until proven otherwise?
You need to assume that it is bacterial meningitis until proven otherwise because it has the highest level of morbidity/mortality
How do you differentiate bacterial vs. viral meningitis?
There are not specific ways to differentiate.
You need to delve into the patient history b/c the presentation will be the same, and even the lab results can be the same.
The CSF content would be a little different, but a bacterial meningitis that had been preemptively treated with antibiotics can have viral-like CSF content
What % of patients will die from meningitis?
What % that survive will have neuropsychological changes?
35% die, 50% will live but with neuropsych changes
What is encephalitis defined as?
What is the clinical presentation?
What mst be evident on pathology?
It is inflammatory condition of the brain.
Clinical = some form of cerebral dysfunction [altered consciousness, seizures, focal deficits, encephalopathy
Pathology = evidence that dysfunction is caused by inflammation [infectious or not]
What causes the majority of infectious encephalitides?
viruses- arbo [WNV], HSV, entero, herpes [CMV, varicella, EBV]
What is the only bacterial meningitis that gives RBCs in the CSF?
anthrax
A 23 year old is transferred to the MICU after a 3 day hospitalization. He has a fever and mental status changes.
Lumbar puncture reveals 125 lymphocytes, no RBCs, normal glucose, and protein of 85.
He is obtunded and started having seizures.
Does he have meningitis, meningoencephalitis, or encephalitis?
What are potential causes of this?
Encephalitis
He lacks the headache/neck stiffness associated with meningitis
The DDx is endless and includes infectious and non-infectious causes.
- infectious
- autoimmune
What can WBC tell you about the underlying cause of encephalitis?
Absolutely nothing.
They can range from 0-13000 in both infectious AND non-infectious causes
What percent of patients that present with encephalitis do not obtain a diagnosis?
2/3
What autoimmune issue was recently discovered to play a role in eliciting encephalitis-like symptoms?
Who is mostly affected?
How do they present clinically?
What are 2 possible associations with this autoimmune problem?
Anti-NMDA Receptor Ab encephalitis
It can affect children or adults and they present with:
- seizures
- psychosis
- catatonia
It can be associated with:
- benign teratomas
- post-infection from HSV encephalitis [it is thought that the infection may elicit immune response that recognizes and targets a native antigen]
Are the following more likely to be found in the brain or spinal cord?
- parenchymal abscess
- subdural abscess
- epidural abscess
- in the brain [extremely rare in the cord]
- calvarium following procedures on subdural hematomas that get infected
- spinal column
What is the most common route by which bacterial abscesses form in the brain?
How will they present?
local extension from the sinuses/nasopharynx
Abscesses present with focal neuro symptoms, seizures, and complications of increased ICP
What is treatment for bacterial abscesses?
- drainage
2. empiric antibiotics
What are risk factors for the development of epidural abscesses on the spinal column?
How will they present?>
- alcohol
- diabetes
- cancer
- procedures
- IV drug use
They can present with:
- focal pain/tenderness
- radicular or myelopathic symptoms
