Infections of the CNS
Meningitis
Pachymeningitis:Epidural and subduralinfections
Leptomeningitis-Subarachnoid
Cerebral abscess-focal inflammation
Encephalitis-diffuse inflammation

Formation,circulation,function of CSF
Formation-500 ml/day
Ultrafilteration & secretion –choroid plexus, ependymal lining of ventricles
Circulation: ventricular system-foramina-subarachnoid space

Function of CSF
Protects, lubricates the brain
Provides nutrients, removes waste
90-150 ml adult
10-60 ml in newborn
Blood brain barrier –homeostasis;electrolytes
Urea,glucose ,protein,creatinine passively along concentration gradient

Normal CSF
Thin, colourless, clear fluid
Pressure 90-180mm WATER (10-100 neonates)
0-5 WBC’s /mm3 (neonates 0-30/ mm3 )
Lymphocytes & monocytes
Occasional ependymal or choroid plexus cells
Protein 15-45mg/dl
Glucose 50-80mg/dl
Chloride 113-130 mEq/L
Sterile

Pyogenic meningitis pathogenesis
Blood borne
Direct-sinuses,mastoid,middle ear,dural venous sinuses,direct trauma,fracture skull
Neonates:E Coli,Strep pneumoniae,
Adolescents: N Meningitides, H influenzae
Adults: N Meningitides, Strep pneumoniae type 3
Elderly :Listeria monocytogenes,strep pneumoniae type 3

Gross pathology
Pus in the subarachnoid space
Meningeal vessels engorged
Location-Pneumococcal-convexities
Tracks along vessels, ventriculitis
Microscopy
PMN in SA space,> meningial vessels
Thrombosis of superficial vessels &
Cerebral ischemic damage

Tubercular meningitis
Hematogenic spread
Gross:Thickening & opacity of leptomeniges
Basal meningitis, encasing cranial N’s
Discrete white granules on the meninges +/-
Microscopy-granulomas, lympho-plasmacytic infiltrate
Obliterative endarteritis..

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