Clinical Signs of TB Meningitis
TB meningitis presents with a characteristic subacute course over weeks with fever, headache, and altered mental status, but the classic triad of fever, neck stiffness, and altered mental status occurs in only 41-51% of cases, making absence of these signs unreliable for excluding the diagnosis. 1, 2
Temporal Pattern and Prodromal Phase
- The hallmark feature is a subacute presentation with symptoms persisting for weeks before diagnosis, distinguishing it from acute bacterial meningitis 3, 4
- Initial phase consists of nonspecific symptoms including malaise, low-grade fever, headache, personality changes, listlessness, and failure to thrive 4, 5
- A clinical history exceeding 5 days has 93% sensitivity for TB meningitis and strongly differentiates it from acute bacterial causes 2
- A subacute course of more than 3 weeks strongly favors TB meningitis over other bacterial etiologies 2
Primary Clinical Manifestations
Neurological Signs
- Headache is the predominant symptom, typically protracted and progressive over 2-3 weeks 4, 5
- Altered mental status progressing from confusion to stupor or coma if untreated 4, 5
- Fever present for more than 7 days is characteristic 6
- Neck stiffness and meningismus develop as disease progresses 4, 6
Associated Features
- Vomiting is common 4, 6
- Focal neurological deficits develop due to tuberculous vasculitis causing ischemic brain injury 4
- Cranial nerve palsies result from basal meningitis, which is the predominant pattern in TB meningitis 4
- Seizures may occur 5
Critical Diagnostic Pitfall
Do not exclude TB meningitis based on absence of classic meningeal signs, as neck stiffness has only 31% sensitivity in adults and classic signs have poor diagnostic accuracy. 7, 8, 1 The absence of fever, neck stiffness, or altered mental status cannot rule out the diagnosis, as these findings are frequently absent even in confirmed cases 7, 1
Complications and Advanced Disease
- Hydrocephalus develops from basal exudates obstructing CSF flow 4, 6
- Stroke occurs secondary to tuberculous vasculitis 4
- Progressive mental status deterioration from confusion to coma represents advanced disease 4, 5
- Hyponatraemia frequently accompanies TB meningitis 9
Special Populations
- In HIV-positive individuals, TB meningitis often presents atypically with higher rates of extrapulmonary manifestations 3, 6
- Children may present with more subtle symptoms including irritability, poor feeding, and failure to thrive 4
Clinical Decision-Making
Treatment should be initiated based on clinical suspicion supported by CSF findings, not microbiological proof, as delay in starting antitubercular therapy significantly increases mortality and neurological morbidity. 2 The subacute presentation over weeks combined with characteristic CSF findings (lymphocytic predominance, elevated protein, low glucose with CSF/plasma ratio <0.5) should prompt immediate empiric therapy 2, 3, 4