Chapter 27: Diseases of Peripheral Nerves

Question 1

Which painful nodule composed of non-neoplastic haphazard whorled proliferation of axonal processes and assoc. Schwann cells results from failure of axons to find their distal target during regeneration ?

Answer 1

Traumatic neuroma aka “pseudotumor”

Question 2

What is the electrophysiologic hallmark of axonal neuropathies vs. demyelinating neuropathies?

Answer 2

• Axonal neuropthay = a reduction in signal strength
• Demyelinating neuropathy = slowed nerve conduction velocity

Question 3

What are the primary targets of damage in demyelinating neuropathies?

Answer 3

Schwann cells w/ their myelin sheaths

Question 4

Why is the peripheral nerve dysfunction caused by neuronopathies equally likely to affect proximal and distal parts of the body?

Answer 4

Damage at the level of neuronal cell body

Question 5

Mononeuritis multiplex describes a disease process that damages several nerves in a haphazard fashion and is commonly due to what?

Answer 5

Vasculitis i.e., polyarteritis nodosum

Question 6

Characteristic “stocking and glove” distribution of sensory deficits is seen with what anatomic pattern of peripheral neuropathies?

Answer 6

Polyneuropathies

Question 7

Histologic features of Guillain-Barre Syndrome are characterized by what?

Answer 7

Inflammation** and **demyelination of spinal nerve roots and peripheral nerves = radiculoneuropathy

Question 8

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

Answer 8

• Acute, influenza-like illness
• Campylobacter, CMV, EBV, and Mycoplasma penumoniae, or prior vaccination

Question 9

Morphologically what is the most prominent lesion seen in Guillain-Barre Syndrome?

Answer 9

Segmental demyelination affecting peripheral nerves

Question 10

Clinical presentation of Guillain-Barre Syndrome is dominated by what signs/sx’s; what characteristic CSF finding will there be?

Answer 10

• Ascending paralysis and areflexia
• DTR’s lost early in the process
• ↑ CSF protein levels w/ little or no CSF pleocytosis (inflammatory cells remain confined to the roots

Question 11

How is Guillain-Barre Syndrome managed clinically?

Answer 11

Plasmapheresis and IV Ig

Question 12

What is the most common acquired inflammatory peripheral neuropathy?

Answer 12

Chronic inflammatory Demyelinating Poly(radiculo)neuropathy

Question 13

Chronic inflammatory Demyelinating Poly(radiculo)neuropathy is characterized by what type of neuropathy?

Answer 13

Symmetrical mixed sensorimotor polyneuropathy that persists for 2 months or more

Question 14

Which 2 features of Chronic inflammatory Demyelinating Poly(radiculo)neuropathy distinguish it from Guillain-Barre?

Answer 14

Time course (presence at least 2 months) and response to steroids

Question 15

How is Chronic inflammatory Demyelinating Poly(radiculo)neuropathy treated?

Answer 15

Glucocorticoids + IVIg + plasmapheresis

Question 16

Upon sural nerve biopsy in patient with Chronic inflammatory Demyelinating Poly(radiculo)neuropathy what is a characteristic finding?

Answer 16

Onion-bulbs: excessive proliferation –> multiple layers of Schwann cells wrap around an axon like the layers of an onion

Question 17

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

Answer 17

Segmental demyelination and remyelination + loss of both myelinated and unmyelinated axons

Question 18

Which type of neuropathy is seen with lepromatous leprosy (Hansen Disease) and which sensory fibers will be lost?

Answer 18

• Symmetric polyneuropathy affected cool distal extremities and face
• Involves pain fibers, loss of sensation = injury; since pt’s are rendered unaware of injurious stimuli –> large traumatic ulcers

Question 19

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

Answer 19

Tuberculoid leprosy = T_H1 (cell-mediated) response

Question 20

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

Answer 20

• Result of diptheria exotoxin
• Early loss of proprioception and vibratory sensation
• Acute peripheral neuropathy assoc. w/ prominent bulbar and respiratory m. dysf.

Question 21

If VZV is reactivated it travels along sensory nerves and leads to what?

Answer 21

Painful, vesicular skin eruption (shingles) in a sensory dermatomal distribution

Question 22

Which dermatomes are commonly affected by VZV reactivation; what kind of damage is seen?

Answer 22

• Thoracic or trigeminal nerve dermatomes
• Neuronal destruction and loss of affected ganglia
• Axonal degeneration of periphral nerves after death of sensory neurons

Question 23

Focal destruction of which neuronal structures may be seen with reactivation of VZV?

Answer 23

Large motor neurons in anterior horn or cranial nerve nuclei

Question 24

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

Answer 24

Ascending distal symmetric sensorimotor polyneuropathy

Question 25

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

Answer 25

**_Duration_** of the disease

Question 26

Biopsies of the affected peripheral nerves/arterioles in diabetes will show what finding and with what stain?

Answer 26

**Endoneurial arterioles** show _thickening_, hyalinization, and intense **PAS-(+)** of their walls + extensive _reduplication_ of basement membranes

Question 27

Diabetic peripheral neuropathy is characterized by a relative loss of which size and type of nerve fibers?

Answer 27

**_Small_** myelinated _and_ unmyelinated fibers

Question 28

What are "positive sx's" associated with diabetic peripheral neuropathy?

Answer 28

**_Paresthesias_** and **_dyesthesias_** = **painful sensations**

Question 29

Other than peripheral neuropathy, what is another manifestation of diabetic nervous system dysfunction that is often seen?

Answer 29

**Autonomic dysfunction**: postural hypotension, incomplete bladder emptying (↑ infections) and sexual dysfunction

Question 30

Uremic neuropathy seen in setting of renal failure is a distal, symmetric neuropathy often associated w/ what signs and sx's?

Answer 30

**Muscle cramps** + **distal dysesthesias** + ↓ **DTRs**

Question 31

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

Answer 31

**Sensorimotor neuronopathy** in setting of **Small cell lung cancer** = **_most common_**

Question 32

What is a a distinctive presentation of neuropathy associated with monoclonal gammopathies?

Answer 32

**POEMS:** **P**olyneuropathy, **O**rganomegaly, **E**ndocrinopathy, **M**onoclonal gammopathy, and **S**kin changes

Question 33

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

Answer 33

**Radial nerve** in the **upper arm**

Question 34

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

Answer 34

- **Interdigital nerve** at **intermetatarsal sites** --\> **foot pain**; "walking on a marble" - **Histologically** = perineural fibrosis

Question 35

Demyelinating forms of Charcot-Marie-Tooth (CMT) disease are associated with what morphological features?

Answer 35

- **Demyelination** and **remyelination** including **Schwann cell hyperplasia** ---\> **Onion-bulb formation** - Hyperplasia may be so _severe_ that involved nerve is **palpably enlarged**

Question 36

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 36

- **CMT1** = group of **autosomal _dominant_** disorders - Presents in **_2nd decade_** w/ _slowly_ progressive **distal demyelinating motor** and **sensory** neuropathy

Question 37

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

Answer 37

**Axonal injury**; typically **_severe_** w/ **early childhood onset**

Question 38

Familial amyloid polyneuropathies are mainly due to germline mutations in which gene?

Answer 38

**Transthyretin** gene