Pathology
Central Nervous System
Central nervous system pathology for MBBS and NEET-PG: meningitis and CSF patterns, cerebrovascular disease and CNS tumours, mapped to NMC codes PA35.1 to PA35.3.
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Central Nervous System
Central nervous system pathology for MBBS and NEET-PG: meningitis and CSF patterns, cerebrovascular disease and CNS tumours, mapped to NMC codes PA35.1 to PA35.3.
This chapter covers central nervous system pathology. It includes meningitis and its cerebrospinal fluid patterns, cerebrovascular disease including infarction and haemorrhage, and the classification and differentiating features of central nervous system tumours.
High-yield: Central Nervous System
- Bacterial (pyogenic) meningitis shows a neutrophil-rich cerebrospinal fluid with high protein and low glucose.
- The common causes of bacterial meningitis vary with age, including Streptococcus pneumoniae and Neisseria meningitidis in adults.
- Tuberculous meningitis is a basal meningitis with lymphocytes, high protein, low glucose and a fibrin web.
- A cerebral infarct is usually caused by thromboembolic occlusion and shows liquefactive necrosis.
- Intracerebral haemorrhage is most often caused by hypertension, typically in the basal ganglia.
- Subarachnoid haemorrhage is usually due to a ruptured berry aneurysm and causes a sudden thunderclap headache.
- Berry aneurysms occur at the branch points of the circle of Willis, most often the anterior communicating artery.
- Gliomas arise from glial cells; glioblastoma multiforme is the most common and most aggressive primary brain tumour in adults.
- Glioblastoma shows areas of necrosis with pseudopalisading tumour cells and microvascular proliferation.
- Meningioma is a benign extra-axial tumour arising from arachnoid cells, showing whorls and psammoma bodies.
- Medulloblastoma is a malignant small round blue cell tumour of the cerebellum in children.
- Metastases are the most common intracranial tumours in adults and are often multiple and at the grey-white junction.
- The blood-brain barrier limits many pathogens and drugs from entering the central nervous system.
- Cerebral oedema and raised intracranial pressure can cause fatal herniation of brain tissue.
CNS tumour essentials
- **Glioblastoma:** Commonest and most aggressive adult primary tumour; pseudopalisading necrosis.
- **Meningioma:** Benign extra-axial tumour; whorls and psammoma bodies.
- **Medulloblastoma:** Malignant cerebellar tumour of children; small round blue cells.
- **Metastases:** Most common intracranial tumours in adults; often multiple.
NMC competencies in this chapter
- **PA35.1:** Aetiology, pathogenesis, pathology and CSF findings in meningitis
- **PA35.2:** Pathology and differentiating features of CNS tumours
- **PA35.3:** Aetiology, types, pathogenesis and pathology of cerebrovascular disease
Frequently Asked Questions
How does cerebrospinal fluid differ in bacterial and tuberculous meningitis?
Bacterial meningitis shows neutrophils with high protein and low glucose, while tuberculous meningitis shows lymphocytes with high protein, low glucose and a fibrin web.
What causes subarachnoid haemorrhage?
Most commonly a ruptured berry aneurysm at a branch point of the circle of Willis, producing a sudden severe thunderclap headache.
What is the most common primary brain tumour in adults?
Glioblastoma multiforme, a highly aggressive glioma with pseudopalisading necrosis and microvascular proliferation.
Where does hypertensive intracerebral haemorrhage usually occur?
Most often in the basal ganglia, due to rupture of small penetrating arteries damaged by chronic hypertension.
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