Ch. 12 - Infections of CNS Flashcards
Common organisms causing bacterial meningitis in neonates/infants? Adults?
Neonates - GBS, E. coli
Infants - GBS, Strep pneumo
Kids/adults - Strep pneumo, Neisseria meningitides
3 main routes of infectious spread to meninges and CSF
- Hematogenous
- Retrograde via infected thrombi from infections adjacent to CNS (sinusitis, otitis, mastoiditis)
- Direct spread into subarachnoid space from skull or paranasal sinus infections
Why is phagocytosis impaired in CSF?
Has low opsonic activity
Major presenting features of meningitis
High fever + meningismus (HA, neck stiffness, photophobia, vomiting, AMS)
Often preceded by URI
How does meningitis presentation differ in infants, elderly, and immunocompromised?
Neck stiffness and fever are often absent; usually present with irritability, confusion, obtundation
CSF features in bacterial meningitis
Cloudy CSF, elevated WBC (esp. PMNs), elevated protein, low glucose, positive Gram stain in over 70%
Which abx is the mainstay of bacterial meningitis tx?
Ceftriaxone; add a penicillin as needed for appropriate coverage
Major complications of bacterial meningitis
Cerebral edema, seizures, communicating hydrocephalus, subdural effusion (esp. in kids), subdural empyema (rare), brain abscess (rare)
Where do brain abscesses arising by hematogenous dissemination frequently develop?
Usually multiple at the junction of white and grey matter; specific region is proportional to blood flow - most occur in distribution of MCA (i.e. parietal lobe)
What is the most common pathogen isolated from brain abscesses?
Streptococcus (80%); Staph aureus when infection results from trauma or postoperatively
CT appearance of brain abscess
Contrast-enhancing ‘ring’ lesion
What is the most sensitive imaging modality for diagnosing a brain abscess?
MRI
When should surgical excision of brain abscesses be considered?
Persistent reaccumulation of pus despite repeated aspirations, in accessible site, well-formed fibrous capsule, cerebellar location
What abx should you use for postoperative brain abscess?
Vancomycin
Clinical features of epidural brain abscess?
Primarily those of osteomyelitis (acute localizing pain, pitting edema of scalp)
Pott’s puffy tumor
Localized pitting edema of scalp over area affected by epidural abscess
Classic presentation of subdural abscess
Patient with history of acute frontal sinusitis who develops severe headaches and high fever, has rapid neurological deterioration with seizures
What will CSF show in TB meningitis?
Lymphocytic pleocytosis, elevated protein, low glucose, low chloride, acid-fast bacilli in 20%
Definitive diagnosis of TB meningitis
Culture of M. tuberculosis which can take up to 6 weeks
Tx of TB meningitis
Isoniazid, rifampin, ethambutol, pyrazinamide
How does intracranial tuberculoma present?
Similar to intracranial tumor (raised ICP, focal neurologic signs, seizures)
Systemic sxs of TB in less than 50%
Preoperative dx is usually appreciated only after recognition of TB foci ELSEWHERE
How does cerebral cryptococcosis present?
Patient with underlying condition (AIDS, IV drug use, sarcoidosis) hung out with pigeons
Dx of Cryptococcus
Cryptococcus seen on India ink prep
Positive latex cryptococcal agglutination test
Cryptococcus tx
Amphotericin B, 5-fluocytosine, or fluconazole
Why should great care be taken when excising intracerebral hydatid cysts?
Spilled contents can induce anaphylactic shock
Medical tx of hydatid cyst
Albendazole
How is cerebral toxoplasmosis treated?
Sulfadiazine and pyrimethamine
Common cerebral infections in AIDS?
Toxoplasmosis > Cryptococcus > TB, Candida, HSV, progressive multifocal leukoencephalopathy
Most common parasitic dx of CNS
Neurocysticercosis caused by Taenia solium (tapeworm)
CSF appearance in neurocysticercosis
Lymphocytosis, eosinophilia, positive complement fixation test, occasionally see cysts
Tx of neurocysticercosis
Surgical intervention + albendazole or praziquantel
Presentation and causative organism of herpes simplex encephalitis
HSV-1; acute necrotizing encephalitis (meningitis, progressive deteriorating neurologic state, seizures)
EEG in herpes simplex encephalitis
Focal slowing, periodic spikes or sharp and wave patterns
What is seen on MRI with herpes simplex encephalitis? In CSF?
Signal changes within temporal lobe with edema and hemorrhage
CSF with mononuclear cells and viral DNA
Herpes simplex encephalitis tx
Acyclovir
Identify the lesion
Ring-enhancing cerebral abscess with surrounding edema
Identify the lesion
Herpes simplex encephalitis in right temporal lobe
