Infective and Vascular CNS Pathology MCQs

Pilocytic astrocytomas are relatively benign tumors that typically affect children and young adults. Most commonly located in the cerebellum , they also may involve the third ventricle, the optic pathways, the spinal cord, and occasionally the cerebral hemispheres. Reference: Robbins Basic Pathology, 10 th ed, Pg: 883

The consequences of traumatic brain injury may be internal and subtle. The parasagittal cortex is anchored to arachnoid villi, whereas the lateral aspects of the cerebrum move more freely. This anatomical feature, together with the differential density of gray and white matter, permits generation of shearing forces between different brain regions, leading to diffuse axonal shearing injuries, particularly in vehicular accidents. Shearing injuries can distort or disrupt axons, causing them to retract into "spheroids", as well as lose myelin. This type of injury typically occurs in parasagittal white matter and may be accompanied by multiple small hemorrhages. Duret hemorrhage (choice b) occurs in the uncus during transtentorial herniation. Reference: Robbins & Cotran Pathologic Basis of Diseases 10 th edition, Chapter – 28 pg 1249

Most common brain tumour is Metastatic tumour and the most common primary brain tumour is meningioma. Reference: Robbins Basic Pathology, 10 th ed, Pg: 885

In most patients with AIDS encephalopathy, the disease is attributable to an active infection of the CNS by the virus itself. Macrophages and microglial cells in the CNS are productively infected by HIV-1. Although neurons and astrocytes may interact with the virus, they do not seem to be infected but are injured indirectly by cytokines or other neurotoxic factors released by macrophages. Also only microglia cells express both CD 4 co-receptor and chemokines receptor (CCR5 and CXCR4) that are required in combination for efficient infection by HIV. Reference: Robbins & Cotran Pathologic Basis of Diseases 10 th edition, Chapter – 28 pg 1267

Like the lymphoid system, the nervous system is a target of HIV infection. Macrophages and microglia, cells in the CNS that belong to the macrophage lineage, are the predominant cell types in the brain that are infected with HIV. Microglial nodules are a well-known phenomenon in viral encephalitis, in which perineuronal aggregation of activated microglia/macrophages indicative of neuronal phagocytosis is often observed. Reference: Robbins and Cotran Pathologic Basis of Diseases, 10 th ed, Pg: 177.

Atypical meningiomas (WHO grade II) are recognized by the presence of either an increased mitotic rate, or prominent nucleoli, increased cellularity, patternless growth, high nucleus-to cytoplasm ratio, or necrosis. These tumors demonstrate more aggressive local growth and a higher rate of recurrence and may require therapy in addition to surgery. Some histologic patterns-clear cell and chordoid-also correlate with more aggressive behavior, as does the presence of brain invasion. Reference: Robbins and Cotran Pathologic Basis of Diseases, 10 th ed Pg: 885

Explanation: Glioblastoma is designated as Grade IV astrocytoma in the WHO system, representing the most aggressive type. It is associated with necrosis, vascular proliferation, and marked pleomorphism and carries a poor prognosis. Explanation of other options: Grade I (Option A): Pilocytic astrocytoma, benign, common in children, slow-growing, favourable prognosis. Grade II (Option B): Diffuse astrocytoma, slow growing, lacks necrosis or high mitotic activity. Grade III (Option C): Anaplastic astrocytoma, with cellular pleomorphism and mitotic activity but no necrosis. Key Takeaways: WHO grading system classifies gliomas based on malignancy and prognosis. Glioblastoma (Grade IV) is the most malignant astrocytoma. Features include necrosis, vascular proliferation, and rapid progression.

Hypoxic and hypoglycemic injury leads to "red" neurons as the initial reaction. The larger pyramidal neurons are the most sensitive, particularly in the hippocampus with hypoglycemia, as well as neocortical Betz cells and cerebellar Purkinje cells. Astrocytes proliferate in reaction to brain injury in the process called gliosis. Endothelial cells are most likely to proliferate in neoplasms. Microglia respond to brain injury with a macrophage-like function. Oligodendroglial cells provide myelination for brain neuronal axons. Reference: Robbins & Cotran Pathologic Basis of Diseases 10 th edition, Chapter – 28 pg 1242