Definition : inflammation of the meninges covering the brain and spinal cord due to invasion of the subarachonid space by TB bacilli .
TB meningitis : 3 stages (1)The prodromal stage of invasion with non specific symptoms (2) The stage of clear cut meningeal manifestations (3) The terminal stage of paralysis and coma . Diagnostic criteria : the diagnosis depends on high index of clinical suspicion : - Previous history of pulmonary or extrapulmonary TB or - Contact to a tuberculous patient - Long insidious history of non specific complaint like headache .- Irritability ,loss of weight ,altered sensorium ,,signs of increase intracranial pressure - signs of cranial nerve affection .
First prodromal stage : diagnosis remains in doubt for 2-3 weeks .
-Non specific symptoms: restless sleep,drowsines
s, loss of appetite ,low grade fever ,headache,vomiting . Second (meningeal stage) : signs of meningeal irritation ,stiff neck and back ,positive kernig;s and Bruidsinski's signs ,bulging anterior fontanel in young children ,exaggeration of deep tendon reflexes sensorium is clouded ,temperature is increased ,vomiting becomes more frequent .
Fundus examination : papilloedema , peripherally located choroidal tubercles may be present , cranial nerve palsies ,(this stage lasts 7-10 days )
Third stage : stupor progresses to coma ,pupils become dilated and fixed ,corneal reflex is absent ,deep tendon reflexes disappear ,emaciation and scaphoid abdomen are notable ,irregular respiration develop .Investigations :(1) CSF : WBCs : variable(10-1000 cells/ul) <500 cells/
ul,predominance of lymphocytes , initial stage PMN predominance changed later to lymphocytic predominance , Glucose: <40mg/dl low
Protein : (moderate to marked increase (50-500mg/dl), (2) CSF culture (87% diagnostic ) (3) PCR : 60% SENSTIVE. (4) Adenosine deaminase : Positive test in patients with meningeal syndrome strongly supports the diagnosis of TBM and permits the commencement of antiTB treatment (5) Tuberculin skin test : in the absence of symptoms usually the only sign of TB infection in children is a positive TB skin test .(6) CBC: anemia with high sedimentation rate . (7) imaging : Chest x-ray (may be associated pulmonary TB) (8) Brain CT with contrast or MRI with gadolinium may show meningeal enhacement ,areas of infarction and hemorrhage may be seen, also single or disseminated tuberculomata may be seen