Nervous System Disorders

Question 1

What % of human genes are associated with the nervous system?

Answer 1

50%

Question 2

List 5 features specific to the CNS:

Answer 2

• protection of bony enclosures
• metabolic requirements
• absence of central lymphatics
• circulation of CSF
• distinctive patterns of wound healing

Question 3

What is selective vulnerability?

Answer 3

functionally related neurons may be selectively damaged
Ex: exposure to limited hypoxia or hypoglycemia will cause greatest damage to portions of the hippocampus, pyramidal cells of the cortex, Purkinje cells of cerebellum, and the basal ganglia

Question 4

Which part of the CNS is most affected by Alzheimer’s disease?

Answer 4

Hippocampus

Question 5

Which part of the CNS is most affected by the effects of mercury?

Answer 5

Cerebellar granular neurons

Question 6

Which part of the CNS is most affected by poliomyelitis?

Answer 6

Anterior horn cells

Question 7

Is repair of the injured nerve processes better in the PNS or the CNS?

Answer 7

PNS

Question 8

What are the 4 types of reactions of neuronal injury?

Answer 8

Acute neuronal injury (red neurons)
Axonal reaction (Central Chromatolysis)
Atrophy
Intra-neuronal deposits (inclusions)

Question 9

Describe acute neuronal injury.

Answer 9

Can be caused by ischemia, infection, toxicity, etc
Includes loss of Nissl bodies, increased angularity, and nuclear pyknosis appear after 12-24 hours of irreversible injury
Fragmentation occurs

Question 10

Describe the axonal reaction

Answer 10

Refers to reactions in the cell body that accompany axonal regeneration. Associated with synthesis of proteins & sprouting of axons.
Caused by axon trauma, hypoxia, etc.
Perikaryon swells and rounds up, Nissl disappears from the central cell body and nucleus moves to the periphery. With successful regeneration, the neuron recovers.

Question 11

What is “Wallerian degeneration”?

Answer 11

the changes that occur in the distal axon (seen in the axonal reaction)

Question 12

Describe neuronal atrophy.

Answer 12

common in chronic progressive degenerative disease & sometimes aging

• reduction in size, may (if severe) progress to neuronal death
• loss of a single neuron produces no reaction to glia, but can progress to selective loss of functionally related neurons (as in ALS) and reactive gliosis
• “trans-synaptic degeneration” of communicating neurons can occur

Question 13

What are the 5 types of Intra-neuronal deposits?

Answer 13

• Neurofibrillary tangles
• Lewy bodies
• Viruses
• Lipofuscins
• Metabolic Storage Diseases (Tay-Sachs and Niemann-Picks)

Question 14

Describe Neurofibrillary tangles and which type of conditions these are typical for

Answer 14

structures made of twisted cytoskeletal filaments, that contain ubiquitin (which tags abnormal proteins for removal). They are stained with silver
- typical in Alzheimer’s disease, post encephalitic Parkinsonism, Parkinson-dementia complex of Guam, dementia of boxers

Question 15

Describe Lewy bodies and which conditions these are typical for

Answer 15

Pink staining spheroids made of ubiquitin

- Idiopathic Parkinson’s disease (substantia nigra) and Lewy-body dementia (cortex)

Question 16

Describe Intracellular “inclusion bodies” (virus particles) and which types of conditions they are typical for

Answer 16

These appear in infected cells as in polio and viral encephalitis.
In rabies, known as Negri bodies

Question 17

Describe Lipofuscins

Answer 17

They are the “wear and tear” pigments that accumulate within neurons from old age and chronic hypoxia

Question 18

Describe metabolic storage diseases.

Answer 18

Contribute to accumulated intraneuronal deposits of complex lipids.
In retina, degeneration can lead to a cherry red spot in the fovea

Question 19

Does death of a neuron or loss of an axon lead to myelin degeneration?

Answer 19

Yes

Question 20

Does myelin loss lead to neuronal degeneration?

Answer 20

Not necessarily. Only if the condition is extensive or prolonged (chronic demyelinating disease)

Question 21

Are glia more or less sensitive to injury than neurons?

Answer 21

Less

Question 22

What are the most sensitive to injury type of glia?

Answer 22

Oligodendrocytes- swell when stressed

Question 23

What are the least sensitive to injury type of glia?

Answer 23

Astrocytes

Question 24

What happens in diseases of oligodendrocytes?

Answer 24

Oligodendrocytes are responsible for the production of myelin and may wrap around several axons, therefore a disease of oligodendrocytes including MS (demyelinating disease) cause oligodendrocytes and myelin to be replaced by astrocytic scars.

Question 25

What are the 3 potential causes for increased intracranial pressure?

Answer 25

- space occupying lesions - edema & swelling - hydrocephaly

Question 26

What are the 2 types of edema & swelling in the CNS?

Answer 26

Vascular (vasogenic) - Most common - Increased vascular permeability Cellular (cytotoxic) - increased cell water indicates injury

Question 27

Describe Hydrocephaly

Answer 27

The volume of CSF is increased and the ventricles are dilated- typically an increased intracranial pressure

Question 28

What is hydrocephaly ex vacuo?

Answer 28

A type of hydrocephaly in which the ventricles are expanded secondary to atrophy of the brain, in which case the CSF pressure IS NOT increased.

Question 29

What is the pathogenesis of hydrocephaly?

Answer 29

- an imbalance exists between the rates of production (choroid plexus) and absorption (arachnoid granulations)

Question 30

What are the potential causes of hydrocephaly?

Answer 30

- Overproduction of CSF - Decreased transport and/or absorption of CSF - Obstructive/ non-communicating (CSF doesn't reach subarachnoid space) - Communicating (CSF enters subarachnoid space, but circulation or absorption is blocked)

Question 31

What are 3 examples of obstructive hydrocephalus?

Answer 31

- congenital anomalies - tumors, abscesses - scarring in the ventricular system, obstruction at foramina of Magendie and Luschka

Question 32

What are 3 examples of communicating hydrocephalus?

Answer 32

- scars of the arachnoid granulations and/or meninges - thrombi, neoplasms - severe CHF- venous congestion & pooling

Question 33

What are the 3 areas that are most vulnerable for hydrocephalus obstruction?

Answer 33

- aqueduct of silivius - foramina of magendie and luschka - subarachnoid space between midbrain & forebrain

Question 34

What are often the first symptoms of hydrocephalus?

Answer 34

- headache, mental dullness, nausea & vomiting

Question 35

What are the 2 manifestations of hydrocephalus?

Answer 35

Papilledema (chocked dis) Herniation- the rigid skull and dural reflections force the brain to be squeezed through openings and around partitions like putty when it is displaced or undergoes swelling (examples= cingulate, uncal, or tonsillar herniation)

Question 36

Can vascular tears or hemorrhage cause nervous system disorders?

Answer 36

Yes

Question 37

What is a contusion?

Answer 37

Interstitial bleeding due to blunt trauma

Question 38

What is a laceration when referring to brain trauma?

Answer 38

Tearing of brain tissue with bleeding into surrounding region, can contribute to edema and swelling

Question 39

Describe a concussion and its effects

Answer 39

It is a closed head injury, usually doesn't have bleeding. Effects include loss of consciousness, alterations in reflexes Unclear pathogenesis, but may be associated with disturbances to midbrain reticular activating system Recovery is common

Question 40

What is a contrecoup injury?

Answer 40

Head trauma that causes damage to parts of the brain opposite the site of impact

Question 41

Explain cord trauma

Answer 41

Can be caused by penetrating or crushing injuries, vertebral dislocations -effects may be exaggerated when stenosis of the vertebral canal

Question 42

What are the two major classes of CNS infections?

Answer 42

Meningitis & Encephalitis

Question 43

What is meningitis?

Answer 43

Infection of meninges and CSF winch may present with systemic signs such as stiff neck, headache, or photophobias In survivors, scarring and obstruction of CSF may producer complications

Question 44

What are the 3 types of meningitis?

Answer 44

``` Acute pyogenic (bacterial) Acute lymphatic (viral) Chronic ```

Question 45

Explain acute pyogenic meningitis

Answer 45

Purulent educates in the meninges - high mortality Causes include - neisseria meningitidis- most common in adolescents and young adults - E.coli, h. Influenza, streptococcus pneumonia and other opportunistic infections in young and immunodeficient CSF findings - elevated polys, reduced glucose, elevated protein, bacteria present

Question 46

explain acute lymphatic meningitis

Answer 46

More common and less severe than acute pyogenic Causes include - mumps, ECHO viruses, Epstein-Barr, herpes CSF findings - elevated lymphocytes, moderately elevated protein, normal glucose

Question 47

Explain chronic meningitis

Answer 47

May have insidious origin progressive headaches, malaise, vomiting are common Causes include - TB, fungi, brucellosis Subarachnoid space becomes fibrosis CSF has increased mononuclear cells, markedly elevated proteins

Question 48

What are the 3 categories of encephalitis?

Answer 48

Viral diseases "Slow virus" diseases "Unconventional agent encephalopathies" (prion diseases)

Question 49

What are the general features of viral encephalitis?

Answer 49

Mononuclear cell infiltrates Intracellular inclusion bodies (except for rabies which were intracytoplasmic) Latency Tropics (selectivity) determines which neurons or parts of the brain are affected Effects can be mild to lethal

Question 50

What are examples of viral encephalitis?

Answer 50

Arbor viruses- most common sore equine types, exs= St. Louis encephalitis and West Nile Childhood infections such as measles, rubella, and chicken pox Herpes simples types 1 & 2 Polymyelitis (nearly gone in west hemisphere) Rabies HIV

Question 51

What % of AIDS patients develop neurological disorders?

Answer 51

60%

Question 52

Explain the slow virus diseases of encephalitis

Answer 52

They have a long incubation period send prolonged relentlessness to illness SSPE (subsume sclerosing panencephalitis) - may follow childhood measles - gives rise to dementia and motor disturbances, death Progressive multifocal leukoencephalopathy - in immunosuppressed - oligodndroglia infected

Question 53

What are the hallmarks of prion diseases?

Answer 53

Microscopic vacuolization of brain tissue (known as spongiform degeneration) and the accumulation of abnormal forms of prion proteins

Question 54

What are two types of prion diseases?

Answer 54

Creutzfeld Jacob disease (subacute spongiform encephalopathy) Kuru