L4

Question 1

Most diseases of myelin are?

Answer 1

white matter disorders.

Question 2

CNS Diseases of Myelin:

Answer 2

1-Demyelinating diseases of the CNS.
-acquired
-damage to previously normal myelin (multiple sclerosis ).

2-Dysmyelinating diseases (Leukodystrophy).
- myelin is not formed properly
- has abnormal turnover kinetics.
-mutations that disrupt the function of proteins

Question 3

most common disease in Demyelinating Diseases
result from immune-mediated injury?

Answer 3

multiple sclerosis (MS).

Question 4

Multiple Sclerosis

Answer 4

-autoimmune against components of myelin sheath.

-episodes of neurologic deficits,

-white matter lesions separated in space

-shows relapsing and remitting episodes of
neurologic impairment.

-related to genetic susceptibility and undefined
environmental triggers.

-Polymorphisms in the genes encode( IL-2 and IL-7 )

Question 5

Pathogenesis of Multiple Sclerosis

Answer 5

1. initiated by TH 1 and TH 17 T cells react against myelin antigens and secrete cytokines
2. TH 1 cells secrete (INF- gamma ) which activate
   macrophages.
3. TH 17 promote the recruitment of leukocytes.
4. demyelination caused by activated leukocytes and their injurious products.

Question 6

Morphology in MS

Answer 6

1-multifocal white matter disease.
2-discrete, gray-tan plaques.

3-infiltrate in plaques consists of T lymphocytes
(CD4+ and CD8+) and macrophages.

4-commonly arise near the ventricles and then others sites (optic nerve,chiasma, brain stem)

5-Active plaque contains:
(abundant macrophages containing myelin debris) Lymphocytes present, mostly as perivascular cuffs.

6- quiescent plaques (inactive plaques):
inflammation mostly disappears, leaving behind little to no myelin

Question 7

Clinical Features Of MS

Answer 7

-CSF
mildly elevated protein level with an increased
proportion of ((immunoglobulin))

-pleocytosis
-Oligoclonal bands
-antibodies

Question 8

two general patterns of postinfectious autoimmune reactions to myelin?

Answer 8

• Acute disseminated encephalomyelitis
• Acute necrotizing hemorrhagic encephalomyelitis

الاول
symptoms develop a week or two after an antecedent infection and are non localizing (headache, lethargy, and coma).
الثاني
devastating related disorder which typically affects young adults and children.

Question 9

1- antibody mediated demyelinating disease centered on the optic nerves and spinal cord
2-presence of antibodies against aquaporin-4
3- show loss of aquaporin-4.
4-antibodies injure astrocytes through complement dependent mechanisms.

Answer 9

Neuromyelitis optica (NMO)

Question 10

1-non-immune process
2-loss of myelin involving the center of the pons, most often after rapid correction of hyponatremia
3-oligodendroglial cell injury uncertain (edema induced by
sudden changes in osmotic pressure)
4-quadriplegia

Answer 10

Central Pontine Myelinolysis

Question 11

1-inherited dysmyelinating diseases caused by abnormal myelin synthesis or turnover.
2-mutation affect lysosomal enzymes and peroxisomal enzymes.

Answer 11

Leukodystrophies
Most are of autosomal recessive inheritance نوعه

• X-linked diseases may also occur .

Question 12

Morphological Features of Leukodystrophies

Answer 12

1. Loss of white matter
2. brain atrophic
3. ventricles enlarge
4. Infiltration of macrophages
   (which often become stuffed with lipid).

Question 13

Clinical features of leukodystropathy:

Answer 13

-children are normal at birth but begin to miss developmental milestones during infancy and childhood.
-Diffuse involvement of white matter
-deterioration in motor skills, spasticity, hypotonia, or ataxia.

Question 14

Thiamine Deficiency (beriberi)

Answer 14

-confusion, abnormalities in eye movement, and ataxia (Wernicke encephalopathy)

Wernicke encephalopathy:
1-foci of hemorrhage and necrosis mostly in (mammillary bodies) but also adjacent to the (ventricles) especially the third and fourth ventricles

2dilated capillariesmwith prominent endothelial cells

3-As the lesions resolve, a cystic space appears along
with hemosiderin-laden macrophages
-
memory disturbances (Korsakoff syndrome):
Lesions in the medial dorsal nucleus of the thalamus

(((This occur in Patients with chronic alcoholism, carcinoma and, chronic gastritis persistent vomiting ))))

Question 15

Vitamin B12 Deficiency.

Answer 15

-neurologic deficits associated with changes in the spinal cord, collectively termed subacute (combined degeneration of the spinal cord)

-ascending and descending tracts affected
-slight ataxia
-lower extremity numbness and tingling
-spastic weakness
-paraplegia may occur

Question 16

are particularly susceptible to hypoglycemic injury?

Answer 16

Hippocampal neurons

Question 17

Not-controlled diabetes mellitus can
be associated with ?

Answer 17

ketoacidosis
hyperosmolar coma.

Question 18

Hyperglycaemic Patients develop confusion, stupor, and eventually coma associated with ?

Answer 18

intracellular dehydration caused by the hyperosmolar state

Question 19

Hepatic Encephalopathy

Answer 19

-depressed levels of consciousness and sometimes coma.
- “flapping” tremor (asterixis)

-Elevated levels of ammonia
-Ammonia metabolism only in astrocytes and in hyperammonemia, astrocytes in the cortex and basal ganglia develop swollen, pale nuclei
(called Alzheimer type II cells)