Tuberculous Meningitis

A 3-year-old patient presented to the emergency department after developing epileptic seizures. The patient’s guardians also referred the patient had a low-grade fever and headache for a week. Physical evaluation revealed neck stiffness. An MRI scan was ordered for further evaluation. CSF analysis showed mildly increased leucocytes without neutrophilia, decreased glucose and increased proteins.

MRI evaluation showed hydrocephalus and increased signal intensity in the subarachnoid space in fluid attenuation images. Meningeal enhancement was demonstrated in post-gadolinium sequences.

Tuberculosis is a highly prevalent disease in low-income countries. The increase in cases of HIV and conditions leading to decreased immunity has made it hard for it to be eradicated. Extrapulmonary TB accounts for about 14% of tuberculosis cases. It affects mainly pediatric and HIV-positive patients [1]. Tuberculous meningitis represents about 1% of all tuberculosis cases, and it is the most severe form of extrapulmonary tuberculosis. It affects mainly patients between 2 and 5 years [2]. Vaccination with Bacillus Calmette– Guérin (BCG) vaccine in endemic areas is performed mainly to protect especially against tuberculous meningitis, preventing it´s development in up to 84% of cases [3,4]. Our patient was not vaccinated and lived in an endemic area (Mexico).

Symptoms are often non-specific. They include cough, low-grade fever, malaise and headache. Neurological status alteration can present later in the course of the disease, particularly those reflecting an increase in intracranial pressure [5].

CSF evaluation shows a mild increase in leucocytes (mainly lymphocytes, as neutrophils usually represent less than 50%), decrease in glucose, and increase in proteins. Mycobacterium tuberculosis can rarely be isolated from CSF (about 60%) [2]. Real-time PCR can increase sensitivity to up to 71.4 % [6]. Our patient’s CSF analysis showed leukocytosis, low glucose and increased proteins; real-time PCR was positive for M tuberculosis.

On imaging, enhancing exudate in the basal cisterns (more sensitive on MRI) has been found in up to 90% of cases. In later stages, there may be widening of subarachnoid spaces [7]. Complications from the presence of exudate in the basal cisterns are hydrocephalus (due to occlusion of CSF flow), ischemic infarct (due to necrotizing arteritis of lenticulostriate and thalamoperforating arteries), venous infarct (due to dural venous thrombosis) and cranial nerve involvement (due to vascular compromise or nerve entrapment in the basal exudates) [8]. 

Clinical guidelines emphasize the importance of starting antituberculosis medications early, postulating isoniazid and rifampicin as key in the management as they have better CNS penetration. In multidrug-resistant cases fluorquinolones are being used with positive results. The regimen should be continued for 9 months, as most complications present within the first 3 months from diagnosis [2].

Tuberculous meningitis carries a poor prognosis with a mortality of about 50%. Most patients (about 80%) will develop complications, particularly if treatment initiation is delayed, or stopped within the first 2 months [9].

Conclusion

Imaging evaluation of patients with tuberculous meningitis is key for starting the appropriate management early. MRI features are generally more sensitive and specific than clinical evaluation or CSF analysis.  

Written informed consent from the patient’s parents for publication has been obtained.