Discussion
Encephalitis is caused by inflammation of the brain parenchyma causing neurological dysfunction. The major criterion of encephalitis is an altered mental status that remains for more than 24 hours without an alternative diagnosis. Then, there are six minor criteria such as (1) fever >38oC within 72 hours before or after symptom onset, (2) new onset of focal neurologic disorder, (3) abnormality on electroencephalography consistent with encephalitis and not secondary to another etiology, (4) CSF white blood cells count > 5 mm2, (5) acute onset of neuroimaging abnormality consistent with encephalitis, (6) seizures not associated with a pre-existing seizure disorder. The presence of 2 minor criteria indicates possible encephalitis and the presence of more than 3 minor criteria indicates probable or confirmed encephalitis (if the etiologic agent is confirmed by polymerase chain reaction, serology, or brain biopsy)8. This case met 2 minor criteria of fever of 38oC 24 hours after symptom onset and the presence of new onset of focal neurologic disturbances of dysarthria, dysphagia, and involuntary movements.
Clinical overlap between encephalitis and encephalopathy may occur in which encephalopathy leads to a clinical condition of altered mental status that can manifest as disorientation, confusion, or other cognitive impairment, with or without evidence of brain tissue inflammation. Encephalopathy can be triggered by some toxic or metabolic conditions but sometimes occurs in response to infectious agents such as the influenza virus and Bartonella henselae 9,10.
Patients with neurotuberculosis have few specific symptoms. Delay in diagnosis must be considered, usually due to a mild initial neurologic presentation in most cases, if compared with other infectious encephalitis11. Based on a report in France, only 20% of patients had a previous history of tuberculosis. Besides, only 20% of patients had respiratory symptoms12. In this case, the patient came with a mild initial neurologic presentation and had no respiratory symptoms indicated by no history of cough.
Brain MRI is the best device for the diagnosis of encephalitis. CT scan is used only when MRI is not possible13. There are no specific features for encephalitis except in brain abscess or granulomatous lesions cases. A study in France revealed that CT scan and MRI scan were normal in 8 of 17 patients. It means that there is a possibility of a diagnosis of tuberculosis being ruled out in cases of normal imaging12.
There are no conventional lymphatics in the brain, but physiological studies showed immunologically significant drainage from the brain to cervical lymph nodes. Perivascular lymphatic drainage from the central nervous system has an important role in neuroimmunological reactions on autoimmune diseases and the same mechanism also plays a role in infection of the central nervous system14–16.
Specific antituberculosis therapy can be associated with the prolonged onset of action, especially in patients with severe brain damage17. The standard recommended therapy is fixed-dose combinations of 4 drugs (isoniazid, rifampicin, ethambutol, and pyrazinamide) for 6 months intensively. Sudden discontinuation of treatment is an independent risk factor for mortality in patients with central nervous system tuberculosis11.