A 27-year-old man presents with gradually progressive headache, low-grade fever, vomiting and altered sensorium for the past 3 weeks. Neurological examination reveals neck stiffness and multiple cranial nerve palsies. Magnetic resonance imaging of the brain demonstrates dense basal meningeal exudates associated with hydrocephalus and multiple cerebral infarcts involving the basal ganglia region. What is the most likely diagnosis? A.Viral meningitis B.Tuberculous meningitis C.Herpes simplex encephalitis D.Cerebral malaria
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The answer is B. Tuberculous meningitis. Here is the full reasoning:
Answer: B - Tuberculous Meningitis
Why This Presentation Is Classic for TBM
Every feature in this case maps directly onto the hallmark characteristics of tuberculous meningitis (TBM):
| Clinical Feature | Explanation in TBM |
|---|---|
| Gradual onset over 3 weeks | TBM is a subacute/chronic meningitis - progression over weeks is characteristic, unlike viral meningitis (days) or HSV encephalitis (acute) |
| Low-grade fever + headache + vomiting | The classic prodrome of TBM |
| Altered sensorium | Reflects raised ICP and parenchymal involvement |
| Neck stiffness | Meningeal irritation from the basal exudate |
| Multiple cranial nerve palsies | Directly caused by the thick gelatinous basal exudate compressing cranial nerves at the base of the brain |
| Dense basal meningeal exudates on MRI | The pathological hallmark of TBM - "the brunt of the process falls on the basal meninges, where a thick, gelatinous exudate accumulates, obliterating the pontine and interpeduncular cisterns" |
| Hydrocephalus | Classic complication; the basal exudate obstructs CSF drainage through the basal cisterns |
| Cerebral infarcts in basal ganglia | TBM causes endarteritis/vasculitis of perforating vessels supplying the basal ganglia - a well-recognized complication |
Pathological Basis (from Adams and Victor's Principles of Neurology, 12th Ed.)
The basal exudate in TBM surrounds and obliterates the pontine and interpeduncular cisterns, extends to the optic chiasm, floor of the third ventricle, and undersurfaces of the temporal lobes. Microscopically it consists of fibrin, lymphocytes, plasma cells, and caseating granulomas. This same exudate:
- Encases cranial nerves III, IV, VI, VII at the base of the brain - causing the cranial nerve palsies
- Obstructs CSF flow - causing hydrocephalus
- Causes vasculitis of penetrating arteries - causing basal ganglia infarcts
The MRI finding described (gadolinium enhancement of basal meninges + hydrocephalus + cranial nerve palsies) is specifically illustrated in textbook Figure 31-3 as the typical MRI appearance of TBM.
Why the Other Options Are Wrong
- A. Viral meningitis - Acute onset (hours-days), NOT subacute over 3 weeks. Basal exudates, cranial nerve palsies, and basal ganglia infarcts are NOT typical. CSF is lymphocytic but without thick exudates.
- C. Herpes simplex encephalitis - Presents acutely with fever, seizures, and focal neurological deficits. Characteristically involves the temporal lobes and limbic system, NOT basal meninges. No cranial nerve palsies or basal exudates.
- D. Cerebral malaria - Caused by Plasmodium falciparum; presents with fever, seizures, and diffuse encephalopathy. Does NOT cause basal meningeal exudates, cranial nerve palsies, or subacute progression over weeks. Requires travel to endemic region.
The correct answer is B. Tuberculous meningitis - the subacute onset, basal meningeal enhancement, hydrocephalus, multiple cranial nerve palsies, and basal ganglia infarcts together constitute the pathognomonic constellation of TBM.
Source: Adams and Victor's Principles of Neurology, 12th Edition - Chapter 31, Tuberculous Meningitis
A 27-year-old man presents with gradually progressive headache, low-grade fever, vomiting and altered sensorium for the past 3 weeks. Neurological examination reveals neck stiffness and multiple cranial nerve palsies. Magnetic resonance imaging of the brain demonstrates dense basal meningeal exudates associated with hydrocephalus and multiple cerebral infarcts involving the basal ganglia region. What is the most likely diagnosis? A.Viral meningitis B.Tuberculous meningitis C.Herpes simplex encephalitis D.Cerebral malaria
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The answer is B. Tuberculous meningitis.
Answer: B - Tuberculous Meningitis
The MRI below is the textbook image for this exact condition - note the striking gadolinium enhancement concentrated at the base of the brain (basal cisterns), representing the thick exudate of TBM:
Figure: MRI in tuberculous meningitis showing gadolinium enhancement of the basal meninges, reflecting multiple abscesses, accompanied by hydrocephalus and cranial nerve palsies. - Adams and Victor's Principles of Neurology, 12th Ed.
Why Every Clue Points to TBM
1. Subacute onset over 3 weeks
TBM is characteristically a subacute/chronic meningitis - the 3-week progressive course is its hallmark. Viral meningitis resolves in days; HSV encephalitis presents acutely; cerebral malaria is also acute.
2. Dense basal meningeal exudates on MRI
This is the pathological signature of TBM. As Adams and Victor's states:
"The brunt of the pathologic process falls on the basal meninges, where a thick, gelatinous exudate accumulates, obliterating the pontine and interpeduncular cisterns and extending to the meninges around the medulla, the floor of the third ventricle and subthalamic region, the optic chiasm, and the undersurfaces of the temporal lobes."
3. Multiple cranial nerve palsies
The thick basal exudate encases cranial nerves III, IV, VI, VII, and VIII as they traverse the basal cisterns - directly explaining the multiple cranial nerve palsies. This is so characteristic that Adams and Victor's specifically labels cranial nerve palsies as a named complication in the MRI figure caption above.
4. Hydrocephalus
The basal exudate obstructs CSF resorption through the basal cisterns and aqueduct, causing communicating hydrocephalus. Up to 25% of advanced TBM cases require neurosurgical intervention for this complication.
5. Cerebral infarcts in the basal ganglia
TBM causes an endarteritis/vasculitis of the small perforating arteries (lenticulostriate vessels) that supply the basal ganglia - producing the ischemic infarcts seen on MRI. This is a classic and serious complication of TBM, resulting from the inflammatory exudate surrounding and invading vessel walls.
Why the Other Options Are Wrong
| Option | Why It Doesn't Fit |
|---|---|
| A. Viral meningitis | Acute onset (hours to days), self-limiting; no basal exudates, no cranial nerve palsies, no infarcts |
| C. HSV encephalitis | Acute onset; preferentially involves the temporal lobes and limbic system (not basal meninges); presents with seizures and behavioral change, not cranial nerve palsies |
| D. Cerebral malaria | Diffuse encephalopathy from P. falciparum sequestration in microvasculature; no basal exudates; no cranial nerve palsies; requires travel to endemic area |
The correct answer is B - Tuberculous meningitis.
The triad of subacute progression + dense basal meningeal enhancement + hydrocephalus + cranial nerve palsies + basal ganglia infarcts is pathognomonic for TBM and perfectly reproduced in this case.
Source: Adams and Victor's Principles of Neurology, 12th Edition, Chapter 31 - Tuberculous Meningitis
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