Infections on Nervous System Flashcards
Reminder: unique features of brain/spinal cord:
–________: protects from organisms, but also restricts immune system access
–________: with inflammation -> swelling & neurologic damage
Blood brain barrier
Rigid skull/vertebral canal
Leptomeningeal inflammation =
Encephalitis/cerebritis/myelitis (spinal cord) or Brain abscess =
Meningitis
Parenchymal inflammation
( When meninges and brain tissue are affected: meningoencephalitis)
Subdural or epidural inflammation =
Subdural/epidural empyemas
Routes of infection in the brain
- Hematogeneous spread: Arterial spread = Retrograde venous spread from Anastomotic connections between face veins & cerebral circulation or Paravertebral venous plexus, Batson
- Local extension – air sinuses, infected tooth
- Neural Route (Extension from PNS to CNS)
- Direct implantation - trauma, iatrogenic
Neurotropism ie special affinity for brain
What are some mechanisms?
- Viral specific Rs on brain
- Capsule proteisn adhere to meninges and have antiphogocytic properties
- Viral spread along nerves
Viral specific receptors on brain cells: what are two examples?
Poliovirus for motor neurons of anterior horns of spinal cord
Mumps virus for ependymal cells lining ventricles
Group B streptococci, E. coli subtypes modality of entering brain
Capsule proteins that adhere to meninges and possess antiphagocytic properties
Herpes simplex virus, Rabies, Varicella zoster virus enter brain:
Viral spread along nerves
Headache, photophobia, stiff neck (nuchal rigidity), clouded consciousness, fever
Meningitis
Hyperacute (<24 hrs) meningtis; see sparse inflammation, numerous organisms, congestion
– Meningococcal meningitis
Acute (2-7 days) - most common infection in CNS
– Usually bacterial
– Usually results from hematogeneous spread
Subacute/chronic (> 1 week)
– Tuberculosis, syphilis (often brain parenchyma also affected)
– Lymphocytes, plasma cells, macrophages appear in exudate
much less fulminant than bacterial meningitis & less severe symptoms
– Summer & early fall
– Lymphocytic infiltrate in meninges
“Aseptic” (usually viral) -
What do we see on histology of acute bacterial meningitis
exudate present, numerous PMNS, leukocytes in the subarachnoid spce
Complications of bacterial meningitis
Brain infarcts, secondary vasculitis, phlebitis may occur and cause infart of underlying brain tissue
Aseptic meningitis causitive organsims:
Arboviruses or Enterovirus (most common) :Echovirus and Coxsackie
- Circumscribed focus of infection
- Clinical S/S: focal deficits, raised intracranial pressure
- Usually bacterial or fungal origin
Parenchynal infections: BRAIN ABSCESSES
–liquifactive necrosis
Cause of brain abcess in immunocompetent host
Step and staph
Brain abcesses are caused by what pathogens in immunocompromised hosts?
Toxo, Listeria, gram neg bacilli, myco, fungi
DEscribe a brain abcess histologically
center is necrotic and thre are inflammatory cells and fibrous capsule
*we also see giant cell; granulomatous and early fibrous wall
Inflammation of brain
• Spinal cord-myelitis
• Meninges and brain-meningoencephalitis
• May be bacterial, viral, or fungal in origin
examples of parenchymal infections: encephalitis
Causes of bacterial mengioencephalitis
• Tuberculosis
- Syphilis
- Lyme disease
Cause of TB
Mycobacterium tuberculosis
- CNS involvement in 10-15%
- HIV infection is risk factor
Most common form of TB in CNS
What do we see in CSF levels?
Meningoencephalitis
CSF: elevated pressure & protein, decreased glucose, lymphocytic pleocytosis
Cultures for AFB are positive in 50% t**hus PCR for TB now** always performed
Sigs and symptoms of TB meningioencephalitis are simular to other meningitis; what do we see in the meninges?
Meninges contain lymphocytes, macrophages, granulomas with extension into underlying brain
Describe findings on scan and grossly in pt infected with TB mengioencephalitis
Gross; see exudate located in base of brain
scan see enhancement of meninges over brain base
Describe histological findings in pt with TB meningioencephalitis
Leptomeningeal vessels with arteritis; Hydrocephalus and infarcts may occur secondary to vessel occlusion
oh myyyy, what is this mean?
AFB + stain seen in pts with TB
- Mass lesion with central necrotic core of caseation, surrounded by fibroblasts, epithelioid histiocytes, giant cells & lymphocytes
- AFB are present in necrosis
Tuberculoma
Describe what you see on pathology of caseous necrosis in TB
see caseous necrosis with granulomatous inflammation
there are epitheliod histiocytes surrounding lesion
•Spondylitis (Pott’s disease)
- Granulomatous process involves vertebral bodies & discs
- Causes epidural abscess
- Cord compression, vertebral collapse
•Epidural extension of the granulomatous inflammation
Tuberculosis osteomyelitis