Brain TB

What is Brain Tuberculosis (TBM)?

TBM is the fifth most common form of extra-pulmonary TB.

It accounts for nearly 5% cases of all extra-pulmonary TB and around 1% of all reported cases of TB

The fallout, the symptoms, the signs of tubercular meningitis are less due to the infection itself but more due to immunological response provoked by the inflammatory reaction to the infection.

What are the causes of Brain Tuberculosis?

Mycobacterium tuberculosis infects lungs by droplet inhalation
- The localized infection increases and spreads to regional lymph nodes.
- At this time bacteraemia is present sending tubercle bacilli to other organs.
- Bacilli reach meninges – brain parenchyma.
- In meninges it makes small foci of metastatic caseous lesions.
- These are called Rich foci.

Rich foci increase in size.
- It ruptures into the subarachnoid space.
- Tubercles rupturing in subarachnoid space cause meningitis.
- Tubercles deeper in the brain or spinal cord cause abscesses.
- Abscesses can rupture in brain ventricle but Rich focus does not.

Pathophysiological features of TBM.
- The exudate produced due to the infection infiltrates the blood vessels of the meninges, giving rise to inflammation or obstruction as also to infarction.
- Basal meningitis accounts for dysfunction of cranial nerves (CNs) III, VI, and VII.
- This leads to obstructive hydrocephalus from obstruction of basilar cisterns.
- Subsequent neurological pathology is due to the 3 phases of adhesions, obliterative vasculitis and encephalitis.
- Formation of tuberculomas may become big but still not produce meningitis
  - If host resistance is poor it results in cerebritis or abscess formation

Symptoms of Brain TB / Meningitis?

TBM may show a very acute presentation.

Sometimes symptoms are due to cranial nerve deficits

When course is slow, it causes headache

Meningismus

Altered mental status

Vomiting

Photophobia

Fever

Cranial Nerves VI is most commonly affected, followed by Cranial Nerves III, IV, VII, less commonly the CNs II, VIII, X, XI, and XII

The duration of symptoms may range from 1 day to 9 months

Tremor is seen during course of TBM

Sometimes myoclonus and cerebellar dysfunction are observed.

Spinal involvement

Spinal meninges gets involved due to infection from intracranial meningitis
- Due to primary spinal meningitis
- Tubercular focus ruptures into the subarachnoid or transdural space
- Granulomatous exudate presses on spinal cord
- Vasculitis results in ischemic spinal cord infarction
- Most often a cold abscess develops

Progress of disease leads to increasing decalcification and erosion
- Results gradual collapse of bone and destruction of intervertebral disks
- Giving rise to kyphosis

How to confirm diagnosis?

A big diagnostic problem. To be suspicious is best strategy

To be strongly considered with the clinical picture of meningoencephalitides

Diagnostic confusions due to other forms of meningoencephalitides

Differentiate between acute and sub-acute meningitis.

Also suspect viral infections.

If leg is involved, limping is the first complaint.

Cerebral abscess is also quite likely

Diagnosis cannot be either excluded or diagnosed due to clinical findings alone

Tuberculin Test gives very limited answer

Spinal tap gives significant diagnostic confirmation

CT scan imaging of the Brain is not specific but helps to monitor complications

Treatment of Brain TB

(Prompt treatment is a must; Missed/delayed diagnoses can lead to death)

Anti-tubercular therapy is best with isoniazid, Rifampin and pyrazinamide, the fourth drug is left to local choice

The use of corticosteroids is in doubt: but they have been employed in cases of increased Intra-Ventricular pressure, due to change in consciousness, due to focal neurological findings, due to spinal block or due to tuberculous encephalopathy

Ventricular drain shunt advised in obstructive hydrocephalus and those showing neurological deterioration

Duration of Treatment
- The optimal duration of antimicrobial therapy is unclear.

The prognosis and Differential Diagnosis of Brain TB

TBM is very critical disease

Has fatal outcome, has permanent sequelae

Has fatal outcome, has permanent sequelae

Requires rapid diagnosis and treatment

Prediction of prognosis of TBM is very difficult.
- Because of variable course
- Diversity of underlying pathology
- Variation of host immunity.
- Virulence of Mycobacterium tuberculosis

Prognosis is related directly to the clinical stage at diagnosis.

Most significant variables for predicting outcome in TBM is-
- Age
- Stage of disease
- Focal weakness
- CN palsy
- Hydrocephalus

Children with advanced condition and neurological complications have poor outcomes.

Visual impairment happens very often, leads to severe disability or death.

Hydrocephalus along with positive culture leads to poorer outcome

When HIV is coexisting there is encephalopathy and lowered immunity leading to severe clinical and neuroradiological involvement

[shw_list_service icon="fa fa-check"]When HIV is coexisting there is encephalopathy and lowered immunity leading to severe clinical and neuroradiological involvement

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Brain TB

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