The Central Nervous System (Part 2)

This set of flashcards covers key vocabulary and concepts related to the central nervous system, including various diseases, infections, and tumors associated with CNS pathology.

Cerebrospinal Fluid (CSF)

A clear fluid found in the brain and spinal cord that acts as a cushion, provides buoyancy, and aids in the circulation of nutrients.

Meningitis

Inflammation limited to the meninges and CSF within the subarachnoid space, often resulting in symptoms such as headache and neck stiffness.

Acute Pyogenic Meningitis

A bacterial form of meningitis usually resulting from bacteria spreading from the nasopharynx to the bloodstream.

Encephalitis

An inflammation of the brain, which can be caused by infections, autoimmune responses, or other pathological processes.

Rabies

A severe encephalitis caused by the rabies virus, transmitted through the bite of an infected animal, leading to CNS excitability and severe symptoms.

Multiple Sclerosis (MS)

An autoimmune demyelinating disorder characterized by inflammation and the loss of myelin in the central nervous system.

Alzheimer’s Disease (AD)

A neurodegenerative condition marked by the accumulation of amyloid plaques and neurofibrillary tangles, leading to progressive dementia.

Parkinson Disease (PD)

A neurodegenerative disease characterized by motor symptoms such as tremors, rigidity, and bradykinesia due to the loss of dopaminergic neurons.

Oligodendroglioma

A brain tumor that resembles oligodendrocytes, characterized by a 'honeycomb' or 'fried egg' pattern in histopathology.

Meningioma

A predominantly benign tumor arising from the meningothelial cells of the arachnoid, often attached to the dura mater.

Cerebrospinal Fluid (CSF)

A clear, colorless fluid primarily produced by the choroid plexuses within the brain's ventricles. It circulates through the ventricular system and subarachnoid space, performing several vital functions: acting as a hydraulic cushion for the brain and spinal cord against trauma, providing buoyancy to significantly reduce the effective weight of the brain within the skull, aiding in the transport of nutrients to the CNS, removing metabolic waste products, and helping to maintain intracranial pressure and chemical stability for optimal brain function.

Meningitis

An inflammatory condition specifically limited to the meninges—the protective membranes (dura mater, arachnoid mater, pia mater) surrounding the brain and spinal cord—and the cerebrospinal fluid (CSF) within the subarachnoid space. It is commonly identified by a triad of symptoms: severe headache, fever, and nuchal rigidity (stiff neck), often accompanied by photophobia (sensitivity to light), phonophobia (sensitivity to sound), and altered mental status. Meningitis can be caused by bacterial, viral, fungal, or parasitic infections, as well as non-infectious causes.

Acute Pyogenic Meningitis

A severe and rapidly progressive form of bacterial meningitis, often considered a medical emergency due to its high mortality and morbidity rates if untreated. It is typically caused by common bacterial pathogens such as Streptococcus pneumoniae, Neisseria meningitidis, or Haemophilus influenzae type b. The infection usually originates from bacterial colonization in the nasopharynx, which then spreads to the bloodstream (bacteremia) and subsequently invades the central nervous system, leading to an intense inflammatory response, purulent exudate (pus) in the subarachnoid space, and rapid onset of meningeal symptoms.

Encephalitis

An acute inflammation of the brain parenchyma itself, indicating a direct infection or autoimmune attack on the brain tissue. Unlike meningitis, its symptoms often include more profound neurological deficits such as seizures, focal neurological signs (e.g., limb weakness, speech difficulties), personality changes, and altered consciousness (ranging from confusion to coma), in addition to fever and headache. The most common causes are viral infections (e.g., Herpes Simplex Virus, West Nile Virus, Japanese Encephalitis Virus), but it can also result from autoimmune conditions, bacterial infections, or other inflammatory processes.

Rabies

A severe, typically fatal viral encephalitis caused by the rabies virus, a neurotropic RNA virus from the Rhabdoviridae family. Transmission to humans primarily occurs through the bite of an infected, rabid animal (e.g., bats, raccoons, skunks, foxes, dogs, cats) when the virus in the animal's saliva enters the wound. The virus then travels retrogradely along peripheral nerves to the central nervous system, causing widespread inflammation, and leading to characteristic neurological symptoms like hydrophobia (fear of water), aerophobia (fear of drafts), muscle spasms, aggression, confusion, paralysis, and ultimately death through respiratory failure if post-exposure prophylaxis is not administered promptly.

Multiple Sclerosis (MS)

A chronic, unpredictable, autoimmune inflammatory demyelinating disorder affecting the central nervous system (CNS), specifically the brain, spinal cord, and optic nerves. In MS, the body's immune system mistakenly attacks the myelin sheath—the fatty substance that insulates nerve fibers and aids in rapid signal transmission. This attack leads to inflammation, demyelination, and ultimately axonal damage, forming characteristic lesions or 'plaques' that impair nerve signal conduction. Symptoms are highly varied and can include motor weakness, numbness, tingling, vision problems (optic neuritis), fatigue, balance issues, and cognitive dysfunction, often occurring in relapsing-remitting patterns or progressive deterioration.

Alzheimer’s Disease (AD)

The most common neurodegenerative cause of dementia, characterized by a progressive decline in cognitive function, memory, and behavior. Pathologically, AD is defined by two hallmark proteinopathies: the accumulation of extracellular amyloid plaques, composed primarily of aggregated amyloid-beta (Aβ) peptides; and the formation of intracellular neurofibrillary tangles (NFTs), made of hyperphosphorylated tau protein. These pathological changes lead to neuronal dysfunction, synaptic loss, widespread brain atrophy, and ultimately result in severe memory loss, disorientation, language impairment, and inability to perform daily activities.

Parkinson Disease (PD)

A chronic, progressive neurodegenerative disorder primarily affecting the motor system, characterized by a specific set of symptoms known as 'parkinsonism.' These include resting tremors (involuntary rhythmic shaking), rigidity (stiffness of limbs and trunk), bradykinesia (slowness of movement), and postural instability (impaired balance and coordination). The cardinal neuropathological feature of PD is the progressive loss of dopaminergic neurons in the substantia nigra pars compacta of the midbrain, combined with the presence of abnormal intracellular protein aggregates called Lewy bodies, which are primarily composed of alpha-synuclein protein.

Oligodendroglioma

A relatively rare type of primary brain tumor that originates from oligodendrocytes or their precursor cells in the central nervous system. These tumors typically occur in the cerebral hemispheres, particularly the frontal and temporal lobes. Histopathologically, oligodendrogliomas are characterized by a distinctive 'fried egg' appearance of the cells (due to perinuclear halos after tissue processing) and a 'honeycomb' or 'chicken wire' capillary network. A significant prognostic and predictive biomarker for these tumors is the co-deletion of chromosome arms 1p and 19q, which is often associated with a better response to chemotherapy and longer survival.

Meningioma

A common type of primary central nervous system tumor that arises from the meningothelial cells of the arachnoid mater, one of the three meningeal layers covering the brain and spinal cord. Meningiomas are typically slow-growing and, in the vast majority of cases, are histologically benign (WHO Grade I). They often grow outward from the meninges and exert pressure on the adjacent brain tissue or spinal cord, rather than invading it directly. They are frequently attached to the dura mater and can occur in various locations within the cranium or spinal canal. Characteristic histological features may include whorling patterns of cells and psammoma bodies (concentric calcifications).