-
CNS Infections: Meningitis
- Acute purulent type
- Chronic types: tuberculosis, syphilis, fingal
- Viral
-
Meningitis: clinical features
- Fever
- headache
- nuchal rigidity
- Kernig sign: thigh at 90, can't extend leg without pain
- Brudzinski sign: neck flexion causes pain and knees to flex
-
Normal values for CSF exam
- clear to inspection (like water)
- opening pressure: 80-180 mm/H2O
- protein: 20-40 mg/dL
- Glucose: 45-65 mg/dL (60% blood glucose)
- Cells: 0-5 lymphocytes
-
Bacterial meningitis: pathogenesis of brain injury
- Proinflammatory cytokines: vasodilatation - NO, PGI2, PAF; brain edema (C3a, C5a, histamine)
- Tissue invasion: brain and ventricles; blood vessels
-
Acute purulent meningitis
- Exudate in meninges
- ploys in subarachnoid space
- vascular dilatation part of acute inflammation
- Brain edema
- ventriculitis and abscess formation - if meningitis is untreated
- Infection spread to vessels with vasculitis may lead to
- Multiple small infarcts
-
Tuberculous meningitis
- Declining incidence in US except AIDS patients
- infection begins in the lung: reinfection TV with spread via blood
- Dx using CSF exam and/or PCR
- Complications are those of chronic basilar fibrosing meningitis (like cryptococcus and syphilis)
-
Tb Meningitis
- thick exudate at base of brain leading to meningeal fibrosis
- Tuberculoma: extension from meninges - can get a Tb infiltration of brain
-
Tb meningitis: what are complications of fibrosing meningitis at the base of the brain?
obstruction of Luschka, decreased reabsorption of CSF in arachnoid villi
-
CNS Syphilis
- Occurs in tertiary disease
- Meningovascular syphilis: chronic fibrosing meningitis; obliterative arteritis with infarcts
- Tabes dorsalis: dorsal root disease
-
Meningovascular syphilis
- Chronic fibrosing meningitis: especially over the convexities
- Infarcts due to obliterative arteritis
-
Tertiary syphilis destroys lumbosacral sensory roots
tabes dorsalis
-
Tabes dorsalis
- dorsal root disease with loss of axons in posterior columns
- Spirochetes seldom seen in tertiary syphilis
- Impaired proprioception (+Romberg) and loss of sensation in lower extremities
-
Cryptococcal meningitis
- Caused by fungus cryptococcus: found in bird excreta, rotting vegetation
- Underlying debilitating disease, 50% cases - but not just in the immunocompromised
- Primary focus in the lung
- Headache, low grade fever, cranial nerve palsies
- CSF exam important in Dx
- Chronic, progressive course
-
Cryptococcal Meningitis Histo
- Chronic fibrosing meningitis at the base of the brain
- Meningeal fibrosis traps cranial nerves causing cranial neuropathies
- Meningitis may etend along Virchow-Robin spaces,but organisms do not invade the brain
- Noncommunicating hydrocephalus due to chronic meningitis
- Meningitis obstructs foramina and restricts subarachnoid CSF flow
- Organisms with thick unstained capsule
- Capsule around organisms stained with mucin stain
- CSF showing organisms outlined by India ink
-
Aseptic Meningitis
- Usually viral in origin, culture negative
- Patients present with clinical findings of meningitis
- Causes: Enterovirus 80%; HSV-2, LCM
- Often no definite Dx is made
- Infection is usually self-limited: no treatment is given
-
Brain Abscess
- Sources: local or distant infection
- Etiology usually bacterial - mixed flora
- Signs of mass lesion with fever: headache, seizures, elevated WBC
- CSF exam not useful: 10% mortality; 50% morbidity
-
Brain abscess
- early abscess without a capsule
- may also have an early abscess with unilateral edema
- Early abscess without capsule; necrotic tissue with many ploys
- Two week old abscess with early capsule formation shown in trichrome stain for collagen (blue)
- Mature abscess: with fibrous capsule
- Abscess with ring enhancement
- this is the only instance ein which there's a fibrous scar forms in the brain - with an abscess
- will get a ring-enhancing lesion and a lot of edema around the abscess
-
Embolic infection
- Mycotic aneurysms: involve small arteries beyond circle; due to bacteria, less often fungi - origin often endocarditis
- Septic infarcts: infected emboli from heart; infarcts are small, multiple cortical
-
Mycotic aneurysms
- wall of aneurysm with inflammation
- multiple hemorrhagic septic infarcts
- septic infarct with numerous ploys and clusters of bacteria
-
Aspergillosis
- Opportunistic infection: HIV, cancer, immunosuppression
- Invasive disease
- May originate from pneumonia
- Angiocentric infection: and hemorrhagic infarction
-
Angiophilic infections: other characters in the cast
- bacteria: meningococci, pseudomonas, leptospira
- Rickettsiae
- Fungi: aspergillus, mucomycosis
- viruses: HIV, varicella/zoster
-
Aspergillosis
- Typical lesion deep, can have multiple lesions
- with a deep hemorrhagic infarct
- organisms can be seen invading vessel wall
- Silver stain showing acute angle branching hyphae
-
Toxoplasmosis
- Opportunistic infection, esp. AIDS
- Caused by parasite T gondii
- Reactivated from dormant sites
- Presents as massl lesion or infection
- ring-enhancing lesion by imaging
-
Toxoplasmosis: histo
- toxoplasma abscess
- abscess with necrotic cells and numerous ploys
- cyst containing many bradyzoites
- also looks like trypanosome cruzii
-
Typical viral encephalitis: arbovirus infections
- represents the typical viral encephalitis: actually CNS viral infection is meningoencephalitis
- many agents usually in summer, warmer weather
- sudden onset, fever, headache, drowsiness, stupor, coma
- Course variable
-
Viral encephalitis
- Brain is diffusely swollen and congested
- lymphocytic perivascular cuffing b/c started in the blood
- death of neurons are phagocytized (not specific, can also be caused by apoptosis or be seen in Rickettsial disease
- Glial nodules: primarily of microglial cells and lymphocytes - scattered
-
West Nile fever
- was confined to Middle East
- First US case in summer of 1999
- Reservoir in crows and other birds
- Culex mosquito
- Dx: based on IgM Ab in CSF
- Sudden onset, fever, headache:rash, muscle weakness, myalgia
- most cases are mild - 15-20% mortality with encephalitis, risk greater after age 50
|
|
