patho2test 3: Demyelinating Disorders (and Alzheimer’s Disease) ppt

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Questions and Answers

What is the purpose of the myelin sheath around the axon?

To facilitate saltatory conduction along the entire length of the axon

To provide structural support to the axon

To insulate the axon and speed up transmission (correct)

To regenerate ions along the axon

What is the primary function of nodes of Ranvier?

To facilitate saltatory conduction along the axon (correct)

To regenerate the axon

To provide structural support to the myelin sheath

To slow down transmission along the axon

What is the primary difference between white matter and gray matter?

White matter is composed of phospholipid fat, while gray matter is composed of protein

White matter is myelinated axons, while gray matter is unmyelinated cell bodies (correct)

White matter is myelinated axons, while gray matter is unmyelinated axons

White matter is composed of neurons, while gray matter is composed of glial cells

What is the function of saltatory conduction?

To allow ions to move between segments of myelin getting 'regenerated' along the way Signup and view all the answers

What is the primary organization of white matter?

Into tracts that take information from the cortex to other places Signup and view all the answers

What is the primary function of oligodendrocytes in the central nervous system?

To deposit myelin within the CNS Signup and view all the answers

Which type of demyelinating disease is caused by an intrinsic, genetic defect?

Leukodystrophy Signup and view all the answers

What is the primary cause of decreased conduction velocity in demyelinating diseases?

Loss of myelin sheath Signup and view all the answers

Which of the following is NOT a symptom of leukodystrophy?

Fever Signup and view all the answers

What is the name of the enzyme deficient in Metachromatic Leukodystrophy?

Arylsulfatase-A Signup and view all the answers

What is the primary function of astrocytes in the central nervous system?

To fill spaces between neurons and surround blood vessels in the CNS Signup and view all the answers

Which type of glial cell is responsible for removing debris within the CNS?

Microglia Signup and view all the answers

What is the term for the group of rare, inherited metabolic disorders that primarily affect white matter?

Leukodystrophies Signup and view all the answers

What is the primary role of cholinesterase inhibitors in the treatment of Alzheimer's disease?

To increase the concentration of Acetylcholine and slow the progression of symptoms Signup and view all the answers

Which of the following is NOT a function of Cerebrospinal Fluid?

Producing neurotransmitters Signup and view all the answers

What is the most common cause of a Subarachnoid Hemorrhage?

Ruptured aneurysm Signup and view all the answers

Which of the following is a characteristic of Epidural Hematoma?

Bleeding between the skull and dura Signup and view all the answers

What is the approximate pH of Cerebrospinal Fluid?

7.3 Signup and view all the answers

What is the primary focus of treatment for Multiple Sclerosis?

Slowing the rate of demyelination Signup and view all the answers

Which of the following is NOT a characteristic of Cerebrospinal Fluid?

High protein content Signup and view all the answers

What is the name of the virus that causes Progressive Multifocal Leukoencephalopathy (PML)?

Polyoma virus Signup and view all the answers

What is the primary function of the Arachnoid granulations?

To reabsorb Cerebrospinal Fluid into the bloodstream Signup and view all the answers

Which layer of the meninges is loosely attached to the cerebral structures?

Arachnoid Signup and view all the answers

What is the result of rapid correction of chronic hyponatremia in the brain?

Shrinking of brain cells Signup and view all the answers

What is the approximate amount of Cerebrospinal Fluid produced daily?

600 cc Signup and view all the answers

What is the typical delay in symptoms of Central Pontine Myelinolysis (Osmotic Demyelination Syndrome)?

2-6 days Signup and view all the answers

Which of the following is a characteristic of Alzheimer's disease?

Language deficits Signup and view all the answers

What are the two pathologic hallmarks of Alzheimer's disease?

Extracellular beta-amyloid deposits and intracellular neurofibrillary tangles Signup and view all the answers

What is the result of the accumulation of beta-amyloid peptides in Alzheimer's disease?

Cascade of events leading to neuronal cell death Signup and view all the answers

What is the primary difference between Alzheimer's disease and other forms of dementia?

Presence of beta-amyloid deposits Signup and view all the answers

What is the purpose of slowly correcting chronic hyponatremia?

To allow cells to acclimate to osmotic changes Signup and view all the answers

What is the result of the change in shape of Tau proteins in Alzheimer's disease?

Aggregation and formation of neurofibrillary tangles Signup and view all the answers

What is the primary organizing principle of the brain's response to hyponatremia?

Shift of osmolytes from intracellular to extracellular space Signup and view all the answers

What is the primary mechanism of myelin destruction in demyelinating diseases?

Immune-mediated destruction of myelin Signup and view all the answers

What is the primary function of CD4+ T-cells in the immune response?

Recognition of antigen and activation of immune response Signup and view all the answers

What is the primary role of macrophages in the pathophysiology of MS?

Phagocytosis of dead cells and debris, and presentation of antigen to T-cells Signup and view all the answers

What is the term for the scarring that occurs in MS due to astrocyte response?

Plaques Signup and view all the answers

What is the characteristic pattern of symptoms seen in relapsing-remitting MS?

Periods of relapse with periods of full or partial recovery Signup and view all the answers

What is the mechanism by which oligodendrocytes can repair themselves in the CNS?

Production of new myelin by nearby oligodendrocytes Signup and view all the answers

What is the primary role of B-cells in the pathophysiology of MS?

Production of antibodies against oligodendrocytes Signup and view all the answers

What is the term for the acute neurologic episode that is usually the first manifestation of MS?

Clinically isolated syndrome Signup and view all the answers

What is the primary function of regulatory T-cells in the pathophysiology of MS?

Release of cytokines to shut down the immune response Signup and view all the answers

What is the characteristic location of white matter lesions in MS?

In both the brain and spinal cord Signup and view all the answers

What would be the likely CSF findings in a patient with bacterial meningitis?

Elevated WBCs, decreased glucose, and presence of bacteria Signup and view all the answers

What is the primary mechanism by which the brain compensates for increased intracranial pressure?

Autoregulation of cerebral blood flow Signup and view all the answers

Which of the following is a complication of unrelieved increased intracranial pressure?

Herniation of brain tissue through the foramen magnum Signup and view all the answers

What is the primary purpose of an external ventricular drain in a patient with a space-occupying lesion?

To drain CSF and relieve pressure Signup and view all the answers

Which type of hydrocephalus is caused by overproduction of CSF?

Communicating hydrocephalus Signup and view all the answers

What is the main treatment option for obstructive hydrocephalus?

Ventriculoperitoneal shunt Signup and view all the answers

Which of the following is a characteristic of normal pressure hydrocephalus?

Adult syndrome of progressive dementia, gait disorders, and urinary incontinence Signup and view all the answers

What is the term for the compensatory enlargement of the ventricles due to loss of surrounding brain tissue?

Hydrocephalus ex vacuo Signup and view all the answers

What would be the likely CSF findings in a patient with subarachnoid hemorrhage?

Presence of RBCs or xanthochromia Signup and view all the answers

What is the term for the process by which the brain tissue is pushed through openings in the skull due to increased intracranial pressure?

Herniation Signup and view all the answers

Study Notes

Neurons and Axons

Axons are long projections from the cell body that carry nerve impulses away from the cell body
Myelinated neurons have a myelin sheath wrapped around the axon, which speeds up transmission
Nodes of Ranvier are interruptions of the myelin sheath, allowing for saltatory conduction
Saltatory conduction allows for faster transmission by jumping between nodes of Ranvier

White and Gray Matter

White matter is composed of myelinated axons, which appear white due to the phospholipid fat that makes up myelin
Gray matter is composed of unmyelinated cell bodies
White matter is organized into tracts, which bring information to the cortex or take it from the cortex to other places

Neuroglia (Glial Cells)

Neuroglia are non-neuron cells that make up the support system of the nervous system
Types of neuroglia:
- Oligodendroglia (oligodendrocytes): deposit myelin within the CNS
- Astrocytes: fill spaces between neurons and surround blood vessels in the CNS
- Microglia: remove debris within the CNS
- Ependymal cells: line CSF-filled cavities in the CNS and create CSF

Demyelinating Diseases

Classification of demyelinating diseases:
- Leukodystrophies: diseases of myelin formation or maintenance due to an intrinsic (genetic) cause
- Myelinoclastic: diseases of normally formed myelin caused by an extrinsic cause (toxins, chemicals, autoimmune disorders)
Pathophysiology of demyelinating diseases:
- Loss of the myelin sheath leads to impaired signal conduction
- Decreased conduction velocity means the signal cannot travel as far and is lost before it reaches its target
- Can affect both sensory and motor functions, as well as cognition

Leukodystrophies

Intrinsic disorders of myelin formation or maintenance
Caused by mutations of genes responsible for myelin protein or enzymes involved in myelin lipid metabolism
Leads to an inability to form or maintain the myelin sheath
Examples: Metachromatic Leukodystrophy

Multiple Sclerosis

Demyelinating disease caused by autoimmune destruction of the myelin sheath
Pathophysiology:
- Macrophages present antigens to T-cells, which recognize the antigens as foreign and attack the myelin sheath
- T-cells cross the blood-brain barrier and recognize the protein on oligodendrocytes as non-self
- Cytotoxic T-cells attack oligodendrocytes, and B-cells produce antibodies against the oligodendrocytes
- Macrophages phagocytose the oligodendrocytes, leading to demyelination
Clinical manifestations:
- Multifocal symptoms, such as paresthesia, weakness, and visual changes
- Lesions on the brain and spinal cord
- Patterns of symptoms:
  - Relapsing/remitting
  - Primary progressive
  - Secondary progressive
Treatment:
- Corticosteroids
- Immunomodulators
- Interferons
- "-mab" drugs

Other Demyelinating Diseases

Progressive multifocal leukoencephalopathy (PML):
- Caused by polyoma virus infection
- Seen in immunocompromised patients
- Leads to destruction of oligodendrocytes
Central pontine myelinolysis (Osmotic demyelination syndrome):
- Caused by rapid correction of chronic hyponatremia
- Leads to demyelination in the brain

Alzheimer's Disease

Neurodegenerative disease
Pathologic hallmarks:
- Extracellular beta-amyloid deposits (plaques)
- Intracellular neurofibrillary tangles
Clinical manifestations:
- Memory impairment
- Executive functioning impairment
- Impairments in other cognitive domains
- Behavioral and psychological symptoms
Treatment:
- Cholinesterase inhibitors
- Increase concentration of acetylcholine, slow progression of symptoms

Meninges and Cerebrospinal Fluid

Anatomy of the meninges:
- Dura mater
- Arachnoid
- Pia mater
Meningeal spaces:
- Epidural space
- Subdural space
- Subarachnoid space
Cerebrospinal fluid (CSF):
- Produced by ependymal cells of the choroid plexus
- Flows through the ventricular system and into the subarachnoid space
- Roles:
  - Exerts pressure within the brain and spinal cord
  - Protects against trauma
  - Transports hormones
  - Removes metabolic waste
Clinical correlation: +Normal CT brain
- Hematomas/hemorrhage
- CSF analysis

Hydrocephalus

Accumulation of excess CSF in the ventricular system
Types:
- Obstructive: blockage of CSF flow within the ventricular system
- Communicating: blockage of CSF absorption outside the ventricular system
- Normal pressure: adult syndrome of progressive dementia, gait disorders, and urinary incontinence
Treatment:
- VP shunt

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Explore the structure and function of axons, including myelination, Nodes of Ranvier, and the differences between white and gray matter.