Central Nervous System Pathology – Meningitis & Space-Occupying Lesions

Vocabulary flashcards covering essential terms from the lecture on central nervous system infections, space-occupying lesions, and related pathology.

Central Nervous System (CNS)

Anatomical division consisting of the brain and spinal cord.

Peripheral Nervous System (PNS)

Nerves and ganglia outside the CNS that connect it to the body.

Somatic Nervous System

Functional division governing conscious, voluntary skeletal-muscle movement.

Autonomic Nervous System

Functional division regulating involuntary internal-organ activity; includes sympathetic and parasympathetic branches.

Sympathetic Nervous System

Autonomic subdivision producing rapid ‘fight-or-flight’ responses to stress or danger.

Parasympathetic Nervous System

Autonomic subdivision that supports ‘rest-and-digest’ functions not requiring quick action.

Meninges

Three protective connective-tissue layers (dura, arachnoid, pia) that surround the brain and spinal cord.

Dura Mater

Outermost, tough fibrous meningeal layer adjacent to the skull.

Arachnoid Mater

Middle meningeal layer with web-like trabeculae overlying the subarachnoid space.

Pia Mater

Delicate innermost meningeal layer adherent to brain and spinal cord surfaces.

Subarachnoid Space

CSF-filled interval between arachnoid and pia mater; site of many CNS infections and hemorrhages.

Neuron

Primary excitable cell of the nervous system specialized for signal transmission.

Dendrite

Branched neuronal process receiving synaptic inputs.

Axon

Long neuronal projection that conducts action potentials away from the cell body.

Myelin Sheath

Lipid-rich insulating layer around many axons, produced by oligodendrocytes or Schwann cells, enhancing conduction speed.

Neuroglia

Collective term for non-neuronal supporting cells in nervous tissue.

Astrocyte

Star-shaped CNS glial cell involved in metabolic support and reactive gliosis.

Oligodendrocyte

CNS glial cell that forms myelin sheaths around multiple axons.

Microglia

Resident macrophage-like immune cells of the CNS.

Ependymal Cell

Ciliated glial cell lining cerebral ventricles and central canal; participates in CSF movement.

Schwann Cell

PNS glial cell that myelinates a single peripheral axon segment.

Meningitis

Inflammation of the leptomeninges, usually due to infection.

Encephalitis

Inflammation of brain parenchyma, most often viral in origin.

Meningoencephalitis

Concurrent inflammation of both meninges and brain tissue.

Bacterial (Purulent) Meningitis

Acute neutrophil-rich leptomeningeal infection commonly caused by organisms such as N. meningitidis or S. pneumoniae.

Viral (Aseptic) Meningitis

CSF lymphocyte-predominant meningeal inflammation typically due to enteroviruses, HSV, or arboviruses.

Tuberculous Meningitis

Subacute/chronic basilar meningeal infection caused by Mycobacterium tuberculosis.

Virchow-Robin Space

Perivascular sleeve where lymphocytes accumulate in viral encephalitis.

Space-Occupying Lesion

Any intracranial mass that displaces neural tissue and may raise intracranial pressure.

Cerebral Abscess

Localized collection of pus and necrotic tissue within the brain, often surrounded by a fibrous capsule.

Liquefactive Necrosis

Type of tissue necrosis characterized by enzymatic digestion into a liquid mass, seen in brain infarcts and abscesses.

Fibrous Capsule (of abscess)

Granulation-tissue-derived wall around a brain abscess separating it from surrounding parenchyma.

Reactive Gliosis

Proliferation and hypertrophy of astrocytes in response to CNS injury.

Brain Infarct

CNS tissue death caused by ischemia from vascular occlusion or hypoperfusion.

Red Neuron

Eosinophilic shrunken neuron characteristic of acute ischemic injury.

Foamy Macrophage

Lipid-laden phagocyte that clears necrotic debris in subacute brain infarct.

Raised Intracranial Pressure (ICP)

Pathologic elevation of pressure within the skull leading to headache, papilledema, nausea, and possible herniation.

Epidural Hematoma

Arterial hemorrhage between skull and dura, often from middle meningeal artery trauma.

Subdural Hematoma

Venous bleeding between dura and arachnoid, usually from torn bridging veins.

Subarachnoid Hemorrhage

Bleeding into the CSF-filled subarachnoid space, classically from ruptured berry aneurysm.

Intracerebral Hemorrhage

Bleeding within brain parenchyma, commonly due to hypertension.

Brain Tumor

Neoplastic space-occupying lesion within the cranial vault; may be primary or metastatic.

Glioma

Primary brain tumor arising from glial cells; includes astrocytoma, oligodendroglioma, and ependymoma.

Astrocytoma

Glial tumor derived from astrocytes; ranges from low-grade diffuse to high-grade glioblastoma.

Glioblastoma

WHO grade IV astrocytoma characterized by necrosis with pseudopalisading cells and vascular proliferation.

Pilocytic Astrocytoma

WHO grade I astrocytoma typically occurring in children, often cerebellar, with Rosenthal fibers.

Oligodendroglioma

Slow-growing glioma with ‘fried-egg’ cells and delicate capillary network.

Ependymoma

Tumor of ependymal cells lining ventricles; may form perivascular pseudorosettes.

Medulloblastoma

Highly malignant embryonal cerebellar tumor, common in children.

Meningioma

Extra-axial tumor arising from arachnoid cap cells of meninges; usually benign and compressive.

Meningothelial Meningioma

Most common meningioma subtype with syncytial cells forming whorls and possible psammoma bodies.

Psammoma Body

Concentric calcific spherule frequently seen in meningiomas and other tumors.

Pseudo-palisading Necrosis

Histologic pattern of tumor cells lining up around necrotic centers, typical of glioblastoma.

Papilledema

Optic-disc swelling due to raised intracranial pressure.

Purulent Exudate

Thick, neutrophil-rich inflammatory fluid seen in bacterial meningitis, often coating brain base.