Neuro Week 1

Question 1

Segmental Demyelination

Answer 1

Loss of myelin along a segment of nerve fiber between 2 nodes of ranvier

Question 2

Onion Bulbs

Answer 2

proliferation of multiple schwann cells around one axon. Indicates repeated re/de-myelination.

Typically seen in hereditary motor neuropathyies (Charcot-Marie-Tooth) and chronic inflammatory demyelinating neuropathies.

Question 3

Axonal Degeneration

Answer 3

Typically caused by traumatic/metabolic damage. Both axon AND myelin sheath undergo degeneration.

Denervation atrophy of myocytes within the motor units

Question 4

Wallerian Degeneration

Answer 4

Axonal degeneration distal to point of axonal damage/cell body damage.

Question 5

the result of Axonal Reinnervation of myocytes after denervation

Answer 5

Adjacent uninjured axons sprout to innervate the de-nervated myocytes. As a result the myocytes may switch types.

Question 6

Spinal Muscular Atrophy (SMA)

Answer 6

Group of autosomal RECESSIVE motor neuron diseases beginning in childhood or adolescence. the LEADING inherited cause of infant mortality.

Question 7

Werdnig-Hoffman Disease

Answer 7

Example of spinal muscular atrophy disease… therefore DUE TO MOTOR NEURON DISEASE**

Presents within first 4 months of life as a degeneration of LMNs and clinically as a “floppy baby” with generalized muscle weakness/hypotonia, muscular wasting and tongue fasciculations.

Gross pathology = atrophic ventral horns/roots

Question 8

Amyotrophic Lateral Sclerosis

Answer 8

Both UMN and LMN degeneration

Age of onset = 50+

10% inherited (auto dom)

Clinically = UMN lesion symptoms (hyperreflexia, +Babinski) and/or LMN dysfunction

Causes denervation atrophy of affected muscles

Pathology: Gross = ant. horn atrophy

Microscopic = wallerian degeneration

Question 9

Guillian-Barre syndrome (acute inflamm demyelinating polyradiculoneuropathy)

Answer 9

PERIPHERAL NERVE problem

immune-mediated (likely initiated by illness)

Clinically = ascending paralysis

Path = Chronic inflammation; segmental De-myelination

Question 10

Charcot-Marie-Tooth Disease

Answer 10

Age of onset = child; early adulthood

PERIPHERAL neuropathy (auto dom inheritance)

Clinically = distal muscle weakness with inverted champagne bottle leg appearance (aka atrophy of calf muscles) and pes cavus (aka pathologically high arch foot), also sensory problems also hammertoes are common

Path = ONION bulb formation with segmental demyelination

Question 11

Diabetic Neuropathy

Answer 11

Most common form is ascending symmetric polyneuropathy

Pathogenesis = micovascular changes due to non-enzymatic glycosylation of proteins etc. due to hyperglycemia ultimately resulting in a decreased ability to respond to reactive oxygen species

Question 12

Lead Toxicity

Answer 12

PURE motor neuropathy… includes segmental demyelination

Question 13

Myasthenia Gravis

Answer 13

immune-mediated loss of ACh receptors on postsynaptic terminal in muscle. (NMJ disorder)

Circulating AChR antibodies are almost always present

Extraocular muscles usually present first clinically

electrophysiology shows decreased motor response with repeated stimulation**

Question 14

Negri Bodies

Answer 14

inclusion bodies composed of viral particles housed within cytoplasm or nucleus of neuron in RABIES specifically

Question 15

Lewy Bodies

Answer 15

large spherical inclusions in neuron cytoplasm characteristic in Parkinson’s

Question 16

Neurofibrillary tangles

Answer 16

accumulation of abnormal neurofilaments in cytoplasm of neurons in pts. with Alzheimers

Question 17

Gliosis

Answer 17

fibrosis and scar tissue formation during neuro-repair due to proliferation of astrocytes.

Question 18

Alzheimer Type II astrocytes

Answer 18

found in gray matter in pts. with liver disease or matabolic disorders (urea cycle). Cells have very large nucleus NO association with Alzheimers though…

Question 19

Role of Ependymal cells

Answer 19

line ventricles in brain and central canal of spinal cord… specialized forms of these cells act as part of choroid plexus and are thus responsible for CSF secretion

Question 20

Vasogenic Cerebral Edema

Answer 20

Most common form

Increased permeability of small VESSELS (BBB disruption)

Escape of proteins, fluids into EXTRAcellular space (especially in white matter)

Question 21

Cytotoxic Cerebral Edema

Answer 21

Increased perm of cell MEMBRANES secondarily to cell INJURY

INTRAcellular accumulation of excess fluids (more severe in gray matter)

Question 22

Hydrocephalic (interstitial) Edema

Answer 22

fluid flows from CSF into brain through ventricular lining in cases of hydrocephalus

Question 23

Neural response to Ischemia

Answer 23

betw 6-12 hrs… acute shrinkage, angularity, and EOSINOPHILIC appearance in cytoplasm

Question 24

Central chromatolysis

Answer 24

in response to physical damage…

1) cell body swells
2) Nissl bodies disperse peripherally
3) Nucleus displaces peripherally
4) ^ protein synthesis for axon repair

Question 25

Main goal of microglia

Answer 25

macrophages of the brain, spinal cord… primary immune defense to CNS

Question 26

Multiple Sclerosis

Answer 26

De-myelination of CNS ONLY…. due to auto-immunity of self-reactive T-cells to self-myelin antigen… Results in recuitment of leukocytes (Th17)and macrophages (Th1)

MUST find presence of 2 separate lesions!!!

CSF shows increase IgG as well as oligoclonal IgG

Commonly presents with visual problems either with optic nerve or MLF

Question 27

Neuromyelitis optica

Answer 27

development of optic neuritis and spinal cord de-myelination are similar points in time (MS-like)

Question 28

acute disseminated encephalomyelitis

Answer 28

rapidly progressing de-myelinating disease developing 1-2 weeks after viral infection. (MS-like)

Question 29

acute necrotizing hemorrhagic encephalomyelitis

Answer 29

severe CNS de-myelination following upper resp. infection

Question 30

central pontine myelinolysis

Answer 30

de-myelination of pontine tegmenum

Question 31

Charcot-Marie-Tooth disease. CMT 1/3 vs CMT 2

Answer 31

CMT 1 & 3 are de-myelinating and x-linked have onion bulbs (CMT1 is peripheral myelin protein 22 overexpression and typically presents in childhood)

CMT 2 is axonopathy NO onion bulbs. Is autosomal also

Question 32

Amyloid Neuropathy

Answer 32

selective pain and temp sensory loss and autonomic problems

pathogenesis due to amyloid deposits in endoneurial and pervascular areas

Tx = LIVER transplant (because transthyretin is over-produced in the liver of those effected)

Question 33

Summary: Name 4 primary neuropathies (aka inherited) and 6 secondary (aka acquired)

Answer 33

Inherited:
1) Amyotrophic later sclerosis 2) spinal muscular atrophy (werdnig-hoffman) 3) CMTs 4) Amyloid neuropathy

Acquired

1) Guillain Barre
2) Chronic inflammatory de-myelinating polyneuropathy (CIDP)
3) Metabolic (ie diabetic neuropathy)
4) Infection (leprosy/diptheria)
5) Toxicity
6) Trauma

Question 34

IMPORTANT difference between primary and secondary neuropathies

Answer 34

primary cannot be treated while secondary can be treated/managed

Question 35

Leprosy induced neuropathy

Answer 35

***tend to affect extremities with lower temperature (ie nose and ear lobes… nose tip falls off)

• widespread infection of schwann cells and skin
• “tuberculoid” with granulomatous inflammation in endoneurium, epineurium, and skin

Question 36

Diptheria induced neuropathy

Answer 36

non specific axon and myelin loss

the G+ rods actually produce and exotoxin that prevents protein synthesis

Question 37

Varicella-Zoster neuropathy

Answer 37

painful dermatomally organized skin rash

neuron loss in gangia somewhat unique

Question 38

Poilio neuropathy

Answer 38

straight kills motor neurons

Question 39

Rabies

Answer 39

retrograde transport from site of entry back to CNS to cause damage

Question 40

Vincristine and Vinblastine (“vinca alkaloids”) neuropathy

Answer 40

common chemo agents!!! prevent axoplasmic transport…

slowly progressing bilaterly symmetric weakness

Question 41

lead neuropathy

Answer 41

“pure” neuropathy

Question 42

uremic neuropathy

Answer 42

strongly associated with renal insufficiency to clear the toxin