<prompt> A 25-year-old lady presented with fever of one month duration, ataxia and headache. Brain imaging showed dilated ventricles with basal exudates. Which among the following is the most likely CSF finding?Lymphocytosis, low glucose, low proteinLymphocytosis, normal glucose, high proteinLymphocytosis, low glucose, high proteinPolymorphonuclear pleocytosis, normal glucose, high protein  <response>: Ans. c. Lymphocytosis, low glucose, high protein Ref: Harrison 19e p1111, 18e p3414Presence of significant basal exudates, together with dilated ventricles hydrocephalus in a young female with prolonged history of fever and headache suggests a diagnosis of tubercular meningitis. Tubercular meningitis is characterized by lymphocytic pleocytosis Pleocytosis is the presence of both neutrophils and lymphocytes in CSF, low glucose and high proteins within the CSF.The pathological hallmark of Tubercular Meningitis is predominant involvement of basal cisterns that are observed by the presence of basal inflammatory tissue exudate.CSF changes in Infection of CNSParameters Normal valuesBacterial MeningitisTuberculous MeningitisViral MeningitisPressureRaisedQRaisedQRaisedQGross appearanceTurbidQClear may clotClearQProtein Normal: 20-50 mgdLHighQVery highQSlightly highQGlucose 40-70 mgdLVery LowQLowQNormalQChloride 116-122 mgdLLowQVery LowQNormalQCells 5mLNeutrophilsQPleocytosisQLymphocytosisQTubercular MeningitisClassic CSF Abnormalities in Tubercular Meningitis Elevated opening pressure Elevated protein concentration Range of 1 to 5 gL or 10 to 500 mgdL Decreased glucose concentration Range of 1.1 to 2.2 mmolL or 20 to 40 mgdL Lymphocytic pleocytosis 10-500 cellsmL Mononuclear cells except early infection when PMN cells are seen Chloride level: usually reducedThe pathological hallmark of Tubercular Meningitis is predominant involvement of basal cisterns that are observed by the presence of basal inflammatory tissue exudate.Classical Radiological Features CTMRI in Tubercular Meningitis Basal exudatesObliteration of Basal cisternsQ Tubercular exudates are primarily located in the vicinity of basal cisterns that are obscured by presence of inflammatory tissue exudate. Subarachnoid space is involved by the exudate i.e. subarachnoiditis is presentQ Abnormal leptomeningeal enhancement Usually most pronounced in the basal cisterns Involvement is mainly of the leptomeninges i.e. Pia- arachnoid: Duramater is usually sparedQ. Hydrocephalus Usually communicating although non-communicating may also be seen IschemicVasculitic infarcts Basal ganglia andor Internal capsule Tuberculomas Granulomas Calcification is commonly seen in the meninges at the base of the brain. Ventriculitis may be seen, but it is not common 