Fatal familial insomnia is associated with -
What is the most common type of optic nerve glioma?
The most common site of glioblastoma multiforme is
Which tumor is characterized by the presence of Antoni A and Antoni B areas, as well as Verocay bodies?
Negri bodies are primarily found in which of the following cell types?
Explanation: ***Prion disease*** - **Fatal familial insomnia (FFI)** is a rare, inherited neurodegenerative disorder caused by a mutation in the **PRNP gene**, leading to the misfolding of the prion protein [1]. - The accumulation of these misfolded proteins primarily affects the **thalamus**, disrupting sleep and leading to progressive insomnia, autonomic dysfunction, and motor deficits. *Degenerative disease* - While FFI is a **neurodegenerative disease**, this option is too broad and does not specify the unique underlying cause, which is a prion protein [1]. - Other degenerative diseases like Alzheimer's or Parkinson's are not caused by prions and have different pathogenetic mechanisms and clinical presentations [1]. *Neoplastic disease* - **Neoplastic diseases** involve the uncontrolled growth of abnormal cells, leading to tumors (cancers). - FFI is not characterized by tumor formation or abnormal cell proliferation; instead, it is caused by protein misfolding. *Vascular disease* - **Vascular diseases** affect the blood vessels, such as stroke or atherosclerosis, leading to tissue damage due to impaired blood flow. - FFI does not involve damage to blood vessels or issues with blood supply; its pathology is centered on prion protein accumulation in brain tissue. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1284, 1288-1289.
Explanation: ***Pilocytic*** - **Pilocytic astrocytoma** is the most common histological type of optic nerve glioma, particularly in children. - These tumors are generally low-grade and have a relatively good prognosis. *Gemistocytic* - **Gemistocytic astrocytomas** are a type of astrocytoma characterized by large, plump cells with abundant cytoplasm and eccentric nuclei. - While they can occur in the central nervous system, they are not the most common subtype for optic nerve gliomas. *Fibrous* - **Fibrous astrocytomas** are another subtype of astrocytoma, but they are less common in the optic nerve compared to pilocytic astrocytomas. [1] - The term "fibrous" refers to their histological appearance, which is not the predominant form of optic nerve glioma. *Protoplasmic* - **Protoplasmic astrocytomas** are a rare subtype of astrocytoma. - Their presence in the optic nerve is extremely uncommon, making them an unlikely answer for the most common type of optic nerve glioma. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 725-726.
Explanation: ***Frontal lobe*** - The **frontal lobe** is the most common site for **glioblastoma multiforme (GBM)**, a highly aggressive primary brain tumor. - GBM frequently arises in the **cerebral hemispheres** and has a predilection for the frontal and temporal lobes. *CP angle* - The **cerebellopontine (CP) angle** is a common location for **acoustic neuromas (vestibular schwannomas)** and **meningiomas**, not typically glioblastoma. - Tumors in this region often present with **cranial nerve deficits**, particularly hearing loss and facial numbness. *Brain stem* - The **brainstem** is a common site for **gliomas in children** (e.g., diffuse intrinsic pontine glioma), but **glioblastoma multiforme** in adults rarely originates here. - Brainstem tumors often cause significant neurological deficits due to vital control centers located in this area. *Occipital lobe* - While GBM can occur in any cerebral lobe, the **occipital lobe** is **less commonly affected** compared to the frontal and temporal lobes. - Tumors in the occipital lobe typically present with **visual field defects**.
Explanation: ***Schwannoma*** - Characterized by **Antoni A** and **Antoni B patterns**, where Antoni A features densely packed cells and Antoni B areas show loosely arranged cells [1]. - The presence of **Verocay bodies**, which are palisades of nuclei, is a distinctive feature of schwannomas [1]. *Astrocytoma* - Composed primarily of **astrocytic cells** and does not present with Antoni A or B areas. - Lacks **Verocay bodies**; instead, it shows diffuse infiltrative growth patterns with varying grades. *Medulloblastoma* - Characterized by **primitive neuroectodermal cells (PNET)**, primarily affecting children, with no Antoni features. - Does not exhibit **Verocay bodies** and typically presents with high-grade tumors affecting the cerebellum. *Glioma* - A broad category that includes several tumor types, primarily arising from **glial cells**, lacking defined Antoni structures. - Does not feature **Verocay bodies**, focusing instead on a more uncontrolled proliferation of glial cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, p. 1250.
Explanation: ***Pyramidal neurons*** - **Negri bodies** are pathognomonic eosinophilic intracytoplasmic inclusions found in neurons infected with the **rabies virus** [1]. - They are **most consistently and classically** found in the **pyramidal neurons of the hippocampus (Ammon's horn)**, making this the **primary diagnostic site** [1]. - While also found in cerebellar Purkinje cells, **hippocampal pyramidal neurons** are the **gold standard location** for identifying Negri bodies in rabies diagnosis [1]. *Oligodendrocytes* - These are **glial cells** responsible for producing the **myelin sheath** in the central nervous system. - **Negri bodies** occur specifically in **neurons**, not glial cells, so they are not found in oligodendrocytes [1]. *Purkinje cells* - **Purkinje cells** are large neurons in the **cerebellar cortex** [1]. - **Negri bodies can be found** in Purkinje cells as a **secondary site** [1]. - However, they are **less consistently present** compared to hippocampal pyramidal neurons, which remain the **primary and most reliable diagnostic location**. *Microglial cells* - **Microglial cells** are the resident **immune cells** of the CNS, acting as phagocytes. - They are **glial cells**, not neurons, and do not harbor **Negri bodies**, which form only within infected neurons [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1279-1280.
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