Chapter 26 Pt 2

Question 1

In what process are myelin ovoids formed?

Answer 1

Axonal neuropathies: Wallerian degeneration => Schwann cells will catabolize myelin => unravel and disintegrate into spherical structures.

Question 2

What do we see on histology in demyelinating neuropathies?

Answer 2

Onion bulbs: excess proliferation of Swchwann cells => concentric layers of cytoplasm of Schwann cells and redundant BM wrapped around thinly myelinated axons, like an onion

Question 3

Type 1 Muscle Fibers

1. Color
2. Action
3. Strength
4. Physiology

Answer 3

1. Red
2. Sustained force
3. Weight-bearing
4. Slow-twich

Question 4

Type 2 Muscle Fibers

1. Color
2. Action
3. Strength
4. Physiology

Answer 4

1. White
2. Sudden movements
3. Purposeful motion
4. Fast-twitch

Question 5

What causes Type 2 Fiber Atrophy (group atropgy)?

Answer 5

1. Inactivity or disuse (limb fracture, degeneration of pyramidal tract)
2. Neurodegenerative disease
3. Corticosteroids => steroid myopathy

Question 6

What type of reactions do muscle fibers undergo?

Answer 6

1. Segmental necrosis
2. Vacuolization
3. Regeneration
4. Hypertrophy

Question 7

When a muscle fiber undergoes segmental necrosis, briefly describe the process?

Answer 7

1. Necrosis of segment
2. Myophagocytosis
3. Replaced with collagen and fat

Question 8

Characteristics of muscle fibers that are regenerating

Answer 8

1. Centrally located nuclei
2. Cytoplasm is red with trichrome stain because alot of RNA

Question 9

Characteristics of muscle fibers that are undergoing hypertrophy

Answer 9

Muscle fiber splitting: cell membrane splits it down middle with adjacent nuclei

Question 10

What can cause a neurogenic bladder? (6)

Answer 10

1. MS
2. Parkinsons
3. DB
4. Infection of brain/SC
5. Spina bifida

Question 11

Course of Bells Palsy

Answer 11

• Occurs 48-72 hours after a URI/DM and resolves spontaneously in pts who are 15 - 60YO

Question 12

Inflammatory neuropathies: how do we differentiate them?

Answer 12

1. Guillian Barre Neuropathy
2. Chronic Inflammatory Demyelinating Polyradiculoneuropathy

Differentiate by: time course and whether htey respond to steroids.

Question 13

MC AQUIRED Inflammatory Peripheral Neuropathy

Answer 13

Chronic Inflammatory Demyelinating Peripheral Polyradiculoneuropathy

Question 14

2/3’s of Guillain-Barre Syndrome cases are preceded by what; which etiologies have been implicated?

Answer 14

Acute, influenza-like illness

1. Campylobacter
2. CMV,
3. EBV,
4. Mycoplasma penumoniae,
5. Prior vaccination

Question 15

How is CIDP and AIPD different from one another?

Answer 15

CIDP

1. Chronic: persists more than 2 months and has remissions and relapses
2. Responds to steroids

Question 16

Pathophysiology of CIDP?

Answer 16

IgM and IgG Ab on myeling sheath

Question 17

Infectious Polyneuropathies (5)

Answer 17

1. Leprosy (Hansen Disease)
2. Diptheria
3. Varicella-Zoster Virus
4. Lyme Diseae
5. HIV

Question 18

MC Viral Infection of the PNS

Answer 18

1. Varicella Zoster

Question 19

What is Leprosy, Hanson Disese?

Answer 19

Mycobacterium Leprea invades Schwann cells and other cells => symmetric polyneuropathy in COOL extrememties

Question 20

In lepromatous leprosy (Hansen Disease) Schwann cells are invaded by Mycobacterium leprae and what pattern of peripheral nerve damage will be seen?

Answer 20

1. Segmental demyelination and remyelination
2. Loss of myelinated AND unmyelinated fibers
3. Endoneurial fibrosis
4. Multi-layered thickening of perineural sheaths.

Question 21

What are the clinical symptoms of Leprosy (Hansen Disease)?

Answer 21

1. Symmetric polyneuropathy of pain fibers COOL extremeties => loss of sensation in hands and toes, but nose is often affected first.
2. Large, traumatic ulcers => pt does not feel it.

Question 22

Leprosy Findings

Answer 22

• AFB (+): multuple uniform-staining acid-fast slender baccili

Question 23

More localized nerve involvement + granulomatous nodules in the dermis is characteristic of what form of leprosy?

Answer 23

Tuberculoid leprosy = TH1 (cell-mediated) response

Question 24

Peripheral nerve dysfunction as a result of Diptheria is due to what; what are the early sx’s and later findings?

Answer 24

Result of diptheria exotoxin

1. Early loss of proprioception and vibratory sensation
2. Bulbar and respiratory muscle dysfunction -> dealth or long-term disability due to suffocation.

Question 25

Lesion seen in peripheral nerves due to **Diptheria**

Answer 25

1. **_Selective demyelination_** that extends to the **_anterior/posterior roots_** and into the **_mixed sensorimotor nerves_**

Question 26

**Diptheria** is MC due to what?

Answer 26

1. **Incomplete immunization** 2. **Waning adult immunty**

Question 27

MC viral infection of PNS

Answer 27

Varicella-Zoster Virus

Question 28

What damage to nerves occurs in Varicella-Zoster?

Answer 28

1. **Loss of affected ganglia and neurons**: mononuclear infilrate, regional necrosis and hemorrohage 2. **Death of sensory neurons** =\> causes **death of axons of peripheral nerves** 3. Focal destruction of **large motor neurons in anterior horns** or **CN motor nuclei** at affected level

Question 29

**_Lyme Disease_** 1. Causes what damage to peripheral nerves? 2. Clinical symptoms

Answer 29

1. **Polyradiculopathy** 2. **Unilateral/bilateral facial N palsy**

Question 30

**_HIV_** 1. Causes what damage to peripheral nerves? 2. Clinical symptoms

Answer 30

1. **Mononeuritis multiplex** 2. Late stages =\> **demyelinating disorder** that resembles **GB** or **CIDP** 1. _Distal_ _sensory_ neuropathy

Question 31

MCC of peripheral neuropathy

Answer 31

**DB**

Question 32

**MCC** of _symmetrical_ neuropathy that involves _dista***l sensory + motor***_ nerves

Answer 32

**DB**

Question 33

What is the most common pattern of **peripheral neuropathy** seen with **Diabetes**?

Answer 33

**Ascending** distal **symmetric** **sensorimotor** **polyn**europathy

Question 34

Prevalence of peripheral neuropathy associated with **diabetes** is dependent on what?

Answer 34

**_Duration_** of the disease; 80% of ppl with DM for over 15 years

Question 35

Clinical symptoms of Diabetees

Answer 35

1. **Ascending distal symmetric sensorimotor polyneuropathy =\>** 1. Numbing 2. Loss of pain 3. Paresthesias and dysthesias =\> pain 4. Balance 2. **ANS sx:** 1. Postural hypotension 2. Incomplete bladder emptying =\> IC risk of infections

Question 36

**Lesion** in DB

Answer 36

1. **Segmental demyelination** =\> _thin_ myelinated fibers 2. **Loss** of _small_ myelinated and unmyelinated fibers 3. **Endoneurorial arterioles** =\> thick, hyalinzed and PAS +

Question 37

* **Uremic neuropathy** seen in setting of **renal failure** is a causes what type of neuropathy? * Symptoms?

Answer 37

1. **Distal symmetric neuropathy** 2. Asymptomatic in some; or 1. **Muscle cramps** 2. **Distal dysthesias** 3. **DEC DTR**

Question 38

Lesion is Renal failure (uremic syndrome)

Answer 38

1. **Axonal degeneration, t**hen **regeneration** after recovery after dialysis

Question 39

**Thyroid dysfunction** can cause what type of neuropathy?

Answer 39

1. **HypOthyroidism** =\> carpal tunnel compression neuropathy 2. **HypERthyroidism** =\> GB

Question 40

Other toxic neuroapthies

Answer 40

Pb (lead) Chemo

Question 41

Which type of neuropathy is the **most common paraneoplastic syndrome** and which malignancy is it most commonly associated with?

Answer 41

**Small cell lung cancer =\> _Sensorimotor_ neuronopathy**

Question 42

What is a a distinctive presentation of neuropathy associated with **monoclonal gammopathies (B-cell neoplasms)?**

Answer 42

* Paraprotein deposts in between non-compacted myelin lamalle * **POEMS:** Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal gammopathy, and Skin changes

Question 43

**"Saturday night palsy"** is due to compression of which nerve?

Answer 43

**Radial nerve i**n the **upper arm**

Question 44

Which nerve is affected in **Morton neuroma** and what histologic finding is seen?

Answer 44

**- Interdigital nerve** at **intermetatarsal sites** --\> **_metatsalgia_** =\> * =\> ball of foot is **painful/inflamed** and feels like "walking on a marble" - **Histologically** = _perineural fibrosis_

Question 45

What is the **MC inherited peripheral neuropathy,** which should ALWAYS be in a DDX of someone with a peripheral neuoropathy?

Answer 45

**Charcot -Marie Tooth (CMT)**

Question 46

What is **CMT**?

Answer 46

Hereditary demyelination of **_MOTOR_** + **_SENSORY_** nerves that is slowly progressive, presenting in early 20s.

Question 47

What is the **most common subtype** of hereditary motor and sensory neuropathy (CMT) disease, what is the inheritance pattern, when and how does it present?

Answer 47

**CMT1** = _AD_ mutation of _PMP22_ (peripheral myelin protein 22) on _Chr 17._ * -Presents in 20s: w/ slowly progressive **_distal_** demyelinating motor and sensory neuropathy

Question 48

Which structures are injured in the **CMT2** variant of CMT disease and when does it present?

Answer 48

_AD_ mutation of _MDN2_ gene _mitochondrial fusion_ **Axonal injury**; typically severe w/ early childhood onset

Question 49

Clinical Sx of **Charcot Marie Tooth**

Answer 49

1. Presents in **20s** 2. **Peroneal neuropathy =\> clumsy child that has problems walking/runniing**: lower leg atrophy =\> deformed LE (looks like inverted bottle) 3. **Foot deformitie**s: pes cavus and hammer toe 4. **DEC or no DTR** 5. **Foot drop** 6. **EMG = slowing of motor nerve conduction velocity**

Question 50

What is **Familal Amyloid Polyneuropathy?**

Answer 50

**Amyloid deposition** in the peripheran nerve

Question 51

How do **traumatic neuromas** aka **pseudotumors** grow?

Answer 51

**Despite misalignment**, axons contineu to grow into small swirls that are randomly oriented, but surrouned by ORGANIZED layers of Schwaanc cells, fibroblasts and perineural cells