L8peripheral Nerve Disease

Question 1

Most peripheral neuropathies can be subclassified as?

Answer 1

either axonal or demyelinating

Question 2

Axonal neuropathies:

Answer 2

• caused by insults that directly injure the axon.
• entire distal portion of an affected axon degenerates
• Axonal degeneration is associated with secondary myelin loss,(Wallerian degeneration)

• Regeneration takes place through axonal regrowth and subsequent remyelination of the distal axon.
• morphologic hallmark of axonal neuropathies is a decrease in the density of axons
which correlates with a decrease in the strength of amplitude of nerve impulses

Question 3

Demyelinating neuropathies:

Answer 3

1-damage to Schwann cells or myelin with relative axonal sparing results in
slow nerve conduction velocities.

2- occurs in individual myelin internodes randomly
( this process is termed segmental demyelination ).

3- relatively normal density of axons and features of
segmental demyelination and repair.

4- presence of axons with abnormally thin myelin sheaths and short internodes.

Question 4

Polyneuropathies ?

Answer 4

1- affect peripheral nerves in a symmetric length-dependent fashion.

2- Axonal loss is diffuse and more pronounced in the distal segments of the longest nerves.

3- loss of sensation and paresthesias that start in the toes and spread upward to the knees and then involve the hands in a “stocking-and-glove” distribution

Question 5

Mononeuritis multiplex ?

Answer 5

1- damage randomly affects portions of individual nerves (right radial nerve palsy and wrist drop and at separate point in time, left foot drop) -Asymmetric-
2- caused by vasculitis

Question 6

Simple Mononeuropathy ?

Answer 6

1- involve only a single nerve most commonly is the result of
traumatic injury or entrapment (e.g., carpal tunnel syndrome).

Question 7

Disorders Associated with Peripheral Nerve Injury (Guillain-Barré Syndrome):

Answer 7

1-most common life threatening diseases of the peripheral nervous system.

2-rapidly progressive acute demyelinating disorder affecting motor axons that results in ascending weakness that may lead to death from failure of respiratory muscles over a period of only days.

3-triggered by an infection or a vaccine that breaks down self-tolerance thereby leading to an autoimmune response

4- injury most extensive in the nerve roots and proximal nerve segments and is associated with mononuclear cell infiltrates rich in macrophages

5- Both humoral and cellular immune responses are believed to play a role in the disease process.

Question 8

-Associated infectious agents in Guillain-Barré Syndrome include ?

Answer 8

-Campylobacter jejuni
-Epstein-Barr virus
-cytomegalovirus
-HIV and Zika virus.

Question 9

Guillain-Barré Syndrome Treatments

Answer 9

1- Plasmapheresis
2- immunoglobulin
3- Supportive care
اللي يعدي من الحالة الacute بيتشافى

Question 10

most common chronic acquired inflammatory
peripheral neuropathy?

Answer 10

Chronic Inflammatory Demyelinating Polyneuropathy

Question 11

Chronic Inflammatory Demyelinating Polyneuropathy :

Answer 11

1- symmetrical mixed sensorimotor polyneuropathy that persists for 2 months or more.
2-Both motor and sensory abnormalities (walking, weakness, numbness, and pain or tingling sensations)
3-immune- mediated Like GBR
4-in patients with other immune disorders (SLE and HIV)
5-relapsing-remitting or progressive course عكس الثاني
6-chronically regenerating Schwann wrap around axons onion-skin pattern
7- treated by plasmapheresis and administration of immunosuppressive agents.
8-recover completely but recurrent
9-bouts of symptomatic disease lead to permanent loss of nerve function.
10-peripheral nerves show segments of demyelination and remyelination.

Question 12

most common cause of peripheral neuropathy?

Answer 12

Diabetes

Question 13

Diabetic Peripheral Neuropathies ?

Answer 13

• Autonomic neuropathy
• Lumbosacral radiculopathies
• Distal symmetric sensorimotor polyneuropathy ( mostly )

Question 14

• Autonomic neuropathy is characterized by?

Answer 14

changes in bowel, bladder, cardiac, or sexual function.

Question 15

• Lumbosacral radiculopathy usually manifests with?

Answer 15

asymmetric pain that can progress to lower extremity weakness and muscle atrophy.

Question 16

• Distal symmetric sensorimotor polyneuropathy ?

Answer 16

1-most common form of diabetic neuropathy
2-Sensory axons are more severely affected
3-paresthesias and numbness.
4-results from the length-dependent degeneration of peripheral nerves

(it does not fit into the axonal or demyelinating category but instead often exhibits features of both)

Question 17

pathogenesis of diabetic neuropathy includes?

Answer 17

1. Accumulation of advanced glycosylation end products resulting from hyperglycemia
2. Increased levels of reactive oxygen species
3. Microvascular changes
4. Changes in axonal metabolism

Strict glycemic control is the best form of therapy

Question 18

Toxic, Vasculitic and Peripheral Neuropathy:

Answer 18

-toxins interfere with axonal transport or cytoskeletal function
-longest axons are most susceptibl
-symptoms mostly in distal extremities

-Peripheral nerves are often damaged in many different types of vasculitis seen in third of all patients with vasculitis
-most common clinical picture is that of:
mononeuritis multiplex with a painful asymmetric mixed sensory and motor peripheral neuropathy.
- Patchy involvement appear as singlenerves may considerable interfascicular variation in damage

Question 19

Inherited diseases of peripheral nerves ?

Answer 19

heterogeneous group of disorders

-can be demyelinating or axonal.
-manifest in adulthood
-slowly progressive as polyneuropathies
-most common cause is mutations in the PMP22 gene
(protein of myelin sheath)

Question 20

Disorders of Neuromuscular Junction

Answer 20

1-Myasthenia Gravis
2-Lambert-Eaton Syndrome
3-Infections

Question 21

1-caused by autoantibodies that inhibit the function
of presynaptic calcium channels which reduces ACH

2-patients experience improvement in weakness with repetitive stimulation

3-Cholinesterase inhibitors are not effective

4- Therapy is reduce causative antibodies, through either plasmapheresis or immunosuppression

Answer 21

Lambert-Eaton Syndrome

Question 22

1-caused by autoantibodies that block the function of postsynaptic acetylcholine
2-depletion of the receptors.
3-more common in females
4- 60% of cases peculiar reactive hyperplasia of intrathymic B cells (thymic hyperplasia)
5-20% are with thymoma a tumor of thymic epithelial cells.

• thymic lesions perturb tolerance to self antigens, setting the stage for
generation of autoreactiveT and B cells

Answer 22

Myasthenia Gravis

Question 23

Clinical Features In MG

Answer 23

-ptosis
-diplopia
-weakness in the extraocular muscles.
-repetitive use or electrophysiologic stimulation of muscles
makes the weakness more severe

-administration of cholinesterase inhibitors improves strength markedly

Question 24

Infections in NMJ:

Answer 24

1-associated with defects in neural transmission and muscle contraction.
2-Clostridium tetani and Clostridium botulinum release neurotoxins
3- Tetanus toxin blocks the action of inhibitory neurons
3- inc. ACH > spasm (tetanus) ( spastic)
4-Botulinum toxin inhibits acetylcholine release, producing a flaccid paralysis ( flaccid )