Flashcards in Infections of the Nervous System Deck (40):
What are the three cardinal findings of bacterial meningitis?
fever, headache and neck stiffness
What are two classically described physical exam findings associated with meningitis (but not specifically the bacterial form)?
What is Kernig's sign?
pain upon attempted passive extension at the knee when the hip is flexed
What is Brudzinski's sign?
an involuntary flexion of the hips when the neck is flexed
What are the most common bacteria associated with bacterial meningitis?
How do the bacteria usually reach the CNS in bacterial meningitis?
they typically reach the subarachnoid space bia hematogenous spread from the respiratory tract, but can also get there by direct extension from trauma or through the sinuses
What are the classic findings on CSF analysis for bacterial meningitis?
elevated WBC with a predominance of PMNs
low glucose (less than 2/3rds of the serum glucose)
CSF gram stain with bacterial
What are the typical antibiotics used empirically for bacterial meningitis?
Ampicillin, Ceftriaxone and Vancomycin
+ steroids in children to prevent long-term complications
How does a brain abscess present clinically?
The same way any other focal intracranial lesion presents: headache, focal neurologic signs, seizures, and potentially signs of increased ICP
sometimes fever, but not always
Solitary brain abscesses are usually caused by what? How about multiple brain abscesses?
solitary abscesses are usually from invasion of the intracranial space from neighboring areas of infection like the sinuses
multiple brain abscesses are seen as a result of hematogenous dissemination, such as from infective bacterial endocarditis
What will a brain abscess look like on MRI or CT?
a mass lesion surrounded by ring enhancement and signs of central necrosis
How will a spinal epidural abscess present?
neck or back pain with focal neurologic signs consistent with spinal cord compression or cauda equina involvement
fever is not necessarily present
What are the three ways tuberculosis can affect the CNS?
1. tuberculous meningitis
2. intracranial tuberculomas
3. Pott disease
M. tuberculosis has a predilection for what part of the CNS?
the basal meninges
How will M. tuberculosis meningitis present in comparison to other bacterial meningitides?
will have cranial nerve palsies in addition to the usual fever, HA and nuchal rigidity
can also get hydrocephalus or brain infarcts from inflammation affecting cerebral vessels at the base of the brain
also tends to have a more subacute or chronic insidious presentation than acute bacterial meningitis
What will tuberculous meningitis look like on CSF analysis?
leukocytosis with lymphocytic predominance (rather than PMNs)
CSF glucose will be very low
Acid fast bacilli staining can identify the mycobacterium and you can do PCR for mycobacterial antigens
Describe Pott disease.
It's tuberculosis of the vertebral bodies that can extend directly into the epidural space causing neurologic symptoms
note: extension through the disk spaces to adjacent vertebral bodies suggests pott disease as opposed to metastatic disease
What are some of the ways Lyme disease can affect the CNS?
cranial nerve palsies (bell's palsy particularly)
a syndrome of polyradiculopathy
What will a CSF analysis show in a lyme infection affecting the CNS?
PCR assay for spirochetal antigen
What is the typical CSF profile in a viral meningitis?
lymphocytic predominance of WBCs
negative gram stain and culture obviously
Treatment of viral meningitis is usually just supportive unless what?
unless HSV1 is suspected, in which case you give IV acyclovir
Viral encephalitis from HSV-1 has a predilection for what part of the brain?
the base, specifically the medial temporal lobes and orbitofrontal regions
Describe the clinical presentation of HSV encephalitis.
limbic dysfunction with complex partial seizures of mesial temporal lobe origin, olfactory hallucinations and memory disturbances in addition to the usual headache, fever, and altered LOC.
What will the CSF in HSV1 encephalitis show in addition to the usual leukocytosis?
elevated RBCs (and thus needs to be distinguished from a traumatic tap)
can also run a PCR for HSV1
What might an EEG show in HSV encephalitis?
periodic epileptiform discharges over one or both temporal regions
What is the CSF profile of most fungal CNS infections?
lymphocytic predominance of WBCs
How do immunocompromised patients typically pick up cryptococcal CNS infections?
inhaling the fungus (present in soil or pigeon droppings) and then disseminates hematogenously to the CNS
How can we make the diagnosis of cryptococcal CNS infection?
India ink staining of the CSF or more likely a rapid latex agglutination assay for cryptococcal antigen
What are the two main parasitic infections of the CNS?
toxoplasmosis (toxoplasma gondii)
neurocysticercosis (taenia solium)
What group of patients typically gets CNS toxoplasmosis?
How are humans usually exposed to toxoplasma gondii?
cat feces or eating undercooked meat
What will imaging show in CNS toxoplasmosis?
multiple ring-enhancing lesions in the basal ganglia or at the gray-white matter junction
(may need to do a biopsy to differentiate from primary CNS lymphoma)
How do we get taenia solium?
it's a tapework we can get by eating undercooked pork (endemic in Central and South America)
What will imaging show in neurocysticercosis?
multiple cystic lesions which can be ring-enhancing or calcified and often with surrounding edema
What's the treatment for neurocysticercosis?
albendazole and steroids to control the inflammation and edema
How does neurocysticercosis usually present?
new-onset focal seizures
List the ways HIV can affect the CNS
1. opportunistic infection with toxoplasmosis, cryptococcal meningitis, JC virus (and subsequent PML)
2. HIV-associated dementia
3. vacuolar myelopathy
4. risk for primary CNS lymphoma
Describe the dementia you get with HIV.
it's a late complication with subcortical dementia - primarily cognitive impairment and psychomotor slowing
MRI will show patchy T2 hyperintensity in the white matter with cerebral atrophy
Describe vacuolar myelopathy
It's a late complication that resembles subacute combined degeneration syndrome - patients develop posterior column signs (loss of vibration and joint position sense with sensory ataxia) and signs of corticospinal tract dysfunction (spasticity and hyperreflexia)