Neuropathy, Myopathy & Motor Neuron Disease

Question 1

What are the two subdivisions of neuropathy?

Answer 1

MONOneuropathy and POLYneuropathy (or PERIPHERAL neuropathy)

Question 2

A. Define MONOneuropathy

B. How is diagnosis made?

C. cause?

D. pathophys

Answer 2

A. single, major, named nerve is involved (ex: median nerve, peroneal nerve, etc) with sensory or motor deficits related to its anatomical distribution

B. Diagnosis is often made from clinical findings, sometimes from nerve conduction/EMG testing, which helps localize and assess severity of the nerve lesion

C. trauma or compression

D. focal demyelination of a nerve may occur where the nerve tends to be compressed, accompanied by axonal damage if a severe lesion

• ulnar mononeuropathy form leaning or falling onthe elbow
• peroneal mononeuropathy from an injury to the lateral knee

Question 3

A. Define POLY(peripheral)neuropathy

B. pathophys

C. CP

Answer 3

A. a disorder of multiple, major and small nerves

B. early sensory loss or impairment in distal limbs (feet, with longest sensory fibers in body, then hands: “stocking and glove“

C. spontaneous tingling, “pins and needles” (paresthesia) and unpleasant sensation from non-noxious stimulus (dysesthesia)

• distal limb weakness and atrophy
• **longer sensory fibers get affected first
• early loss or decrease of muscle stretch reflexes

Question 4

A. What is the most common MONOneuropathy?

B. what causes the median nerve to be compressed

C. What are some CP?

D. Tx

Answer 4

A. MEDIAN mononeuropathy at the wrist (carpal tunnel syndrome)

B. if flexor tendons passing through the carpal tunnel get inflammed or swollen, the median nerve is compressed.

• fluid retention during pregnancy may also compress the median nerve here, in addition to rarer diseases depositing material in the carpal tunnel

C. tingling numbness of the hand may awaken the pt, thenar weakness and atrophy occur in more severe cases

D. local rest, anti-inflammatory medication, plinting, or surgical decompression of the nerve

Question 5

A. Define traumatic MONOneuropathy?

B. Where does Wallerian degeneration occur and what does it involve? When is surgery considered?

Answer 5

• effects of closed or blunt trauma range from a. only local nerve swelling, to b. damage of myelin and axons (perhaps including the supporting peri- and epineurium)
• penetrating trauma is more likely to physically disrupt all these elements of the nerve involved
• Wallerian degeneration occurs at the site of severe injury; involving myelin and axons distal to that pt
  
  • if a “framework” or “scaffolding” of peri- and epineurium remains, axonal sprouting may progess to appropriate muscle
  • sx is considered where natural re-innervation fails–when there is more space/distance to cover=less likely for axon to regrow
• neuroma-resprouting axon pile up in a bulbous neuroma (often painful)

Question 6

What are the 5 steps for the evaluation of POLY(periphery)neuropathy?

Answer 6

1. review pts history
   
   1. hereditary neuropathy suggested by same symptoms in family
   2. toxic neuropathy may be realted to certain occupations, hobbies, or medications
2. clues from clinical pattern of nerve involvement
   
   1. mulitple mononeuropathies (SLE, diabetes, others)
   2. autonomic nerve involvement (diabetes, others)
3. Blood tests for potential, especially treatable, causes
4. nerve conduction testing and electromyography (EMG)-a test of neve and muscle fxn
5. nerve biopsy in selected cases

**often the cause of POLY(peripheral)neuropathy remains unknown.

Question 7

What are the TWO pathologies of polyneuropathy as suggested by EMG testing, or shown by nerve biopsy?

Answer 7

A. DEMYELINATION

• found in some heriditary neuropathies, or in autoimmune mediated polyneuropathies (Guillain-Barre syndrome) where abnormalities are often asymmetrical or non-uniform
• if severe, can lead to secondary axonal loss

B. AXONAL DEGENERATION

• primary process in most POLY(peripheral)neuropathies, possibly from inadequate axoplasmic flow in various metabolic conditions
• DE-myelination may secondarily occur

Question 8

What are the differences between nerve conduction studies and EMG testing?

Answer 8

Nerve conduction studies:

• sensory and motor nerves are electrically stimulated and their responses are measured
• a primary slowing of nerve conduction velocity suggests a DE-myelination problem
• primary loss of amplitude suggests axonal loss

EMG testing [pt 1]: nerve conduction studies; uses electrodes taped to the skin (surface electrodes) to measure the speed and strength of signals traveling between two or more points.

EMG testing [pt 2]: needle electromyography; (using needle electrodes) the electrical activity of muscles within individual motor units is assessed for evidence of denervation, reinneration or muscle disease

Question 9

What are the findings of a sural-nerve biopsy and how are they interpreted?

Answer 9

• a loss of myelinated nerve fibers indicated a demyelinating type of neuropathy
• If the clinical picture or EMG suggest a chronic polyneuropathy is due to inflammatory, immune-mediated, or vasculitic causes it is confirmed by sural (sensory nerve) biopsy

Question 10

What are the 4 components of POLY(peripheral) nueropathy treatment?

Answer 10

1. tx of its primary, underlying cause (eg control of diabetes, abstince from alcohol)
2. orthotic device to allow for safe ambulation
3. PT to maintain jt ROM
4. meds to relieve painful sensory disturbances (paresthesia [pins and needls/tingling and pricking], dysesthesia [abnormal sensation])–neuropathic pain
   
   1. topical creams or ointments
   2. oral anti-convulsants or anti-depressants
      
      1. ​all interact wtih NT

Question 11

**Poly-Guillain-Barre Syndrome**

A. characteristics

B. pathophys

B1. path

C. epidemiology

D. Associated symptoms

E. HD

F. Diagnosis

G. Prognosis

H. Tx

Answer 11

A. very acute POLY(peripheral) neuropathy, weakness progressing over hours to days, at its worst by FOUR weeks

B. an ASCENDING (legs first), AREFLEXIC PARALYSIS

• generalized (including respiratory) paralysis may occur
• some paresthesia (pins and needles), little objective sensory loss

B1. pathologically: inflammation and demyelination of peripheral nerves or roots (if severe, secondary axonal loss)

C. occurs at any age

D. 50% of pts (in US) had recent viral respiratory infection

E. misdirection of the immune system to attack nml peripheral nerve myelin (antigen modification by the recent virus?)

F.– evidence of demyelination (slowing of nerve conduction) by EMG testing of nerves

–elevated protein in CSF, with few if any WBCs

G. overall good with optimal healthcare

H. plasmapheresis or immunoglobulin infusions (IVIG) may shorten the illness and hasten recovery

Question 12

CHRONIC, acquired polyneuropathies

A. time of evolution

B. 7.5 possible causes

Answer 12

A. evolve over months to years

B. several possible causes:

• Diabetes mellitus
  
  • other metabolic or endocrine (uremia, hypOthyroid)
• rheumatological (rheumatoid arthritis, lupus)
• nutritional (B vitamin deficiencies)
• toxins (alcoholism, lead exposure)
• cancer, myeloma
• infection (leprosy, most common cause WORLDWIDE)
• unknown

**look at the pt’s meds

Question 13

Hereditary Neuropathies

A. epidemiology

B. CP

C. pathophys

D. tx

Answer 13

A. onset usually by childhood, may be subte

B.

–distal sensorimotor deficits, little ot no paresthesia or dysesthesia

–typical orthopedic deformities present since neuropathy begain in a growing child:

>>scoliosis [abnml lateral curvature of the spine]

>>hammertoes [toe that is bent permanently downward, typically as a result of pressure from footwear]

>>pes cavus [fixed plantar flexion of the foot; high arch]

C. caused by known or unknown metabolic mechanisms or genetic disorders

D. no curative tx available; give assistive devices or orthotics as needed

Question 14

A. What is myopathy?

B. CP

C. Diagnosis

D. Sarcoid myopathy

Answer 14

A primary disease of muscle

B. CP

• symptoms of weakness, fatigue, sometimes cramps
• proximal limb weakness and atrophy (shoulders, hips, thighs)
• late loss of reflexes (after significant atrophy present)
• intact sensation

C. Diagnosis

• review of family history (muscular dystrophy)
• serum muscle enzymes (CK) are often elevated–if ongoing muscle fiber breakdown
• EMG demonstrates a disorder of muscle
• muscle biopsy

D. Sarcoid myopathy-homeboy with swagger walk; weak hip girld

Question 15

A. What is an inflammatory myopathy?

B. epidemiology

C. which cause is most common in the USA

D. Diagnosis

E. Tx

Answer 15

A. polymyositis-inflammation and weakness of multiple muscles (and associated blood vessels) may occur from viral infections or drug rxns.

B. blk women, 30s-50s

C. AUTOIMMUNE cause=most common in USA:

• proximal weakness over weeks to months
• rash around the eyes or fingers may occur (dermatomyositis-inflammation of the skin and underlying muscle tissue, involving degeneration of collagen, discoloration, and swelling)
• rarely related to underlying cancer

D. Dx confirmed by EMG testing, and presence of inflammation and muscle fiber necrosis on biopsy

–biopsy: H&E stain-infiltration by mononuclear inflamm cells with fiber necrosis

E. tx: corticosteroids or other immunosuppressive drugs

Question 16

Muscular dystrophy

Answer 16

I. hereditary myopathies of variable progression and severity

II. Duchenne’s muscular dystrophy (X-linked):

• virtual absence of dystrophin (critical structural protein in muscle)
• involves respiratory and cardiac muscles as well
• proximal weakness begins in boys of childhood age
• calf pseudohypertrophy from muscle replaced by fat, connctive tissue
• cardiorespiratory death by third decade
• have to crawl into push-up position, and use thighs to stand up-weak hip girdle (also muscles of hips and thighs)

III. other milder, more restricted muscular dystrophies

Question 17

What is motor neuron disease (MND)

Answer 17

• disorder (occasionally hereditary) where degeneration of UMN and LMN (or both)
• occurs with varying severity and rate of progression

Question 18

Spinal muscular atrophy (MND)

A. what part of the grey matter does it involve?

B. What are the LMN signs

C. What is the name of the infantile onset condition

Answer 18

A. involves anterior horn cell

B. weakness, atrophy, areflexia, fasciculations

C. Werdnig-Hoffman–a terminal condition due to rapid development of diffuse weakness, no current currative tx

-milder childhood and adult onset types exist, creating chronic diability, but are not fatal

Question 19

Amyotrophic lateral sclerosis (ALS)-MND (and SC)

A. CP

B. epidemiollogy

C. prognosis

D. diagnosis

E. tx

Answer 19

A.

• progressive degeneration of ALL motor neuron subgroups: UMN (corticobulbar AND corticospinal tracts; pyramial neurons) and LMN (anterior horn cells, brain stem (cranial nerve) motor nuclei)
• frequently begins with regional/asymmetrical weakness and atrophy of a limb (eg severe shoulder and upper limb)…spreads and becomes BILAT
  
  • –OR–
• initial weakness of swallowing or speech

• later, more generalized LMN signs, diffuse fasciculations may be prominent
• nml sensation
• hyper-reflexia, spasticity or babinski signs
• weakness eventually affects speech, chewing, swallowing, and breathing
• atrophc interosseus muscles of L. hand
• due to coexistence of UMN signs, may first seem to be a cervical SC lesion

B. rarely familial

C. worst prognosis of all motor neuron disorders (50% die within THREE yrs, with respiratory failure or complications of profound weakness)

D. Dx: clinical picture and EMG testing

E. Tx: RILUZOLW (glutamate antagonist) prolongs survival by months (glutamate may “overly excite” motor neurons)…no curative tx

Question 20

neuropathies and history

Answer 20

• clinical pattern of nerve involvement=clue for underlying cause
• most mon: trauma
• ultiple mono: systemic illness
• non-acute poly:
  
  • current or recent medications (chemotherapy)
  • malnutrition and vitamin deficienes
  • test with blood tests/”screening”
• hereditary neuropathy: positive family hx
• toxic neuropathies: exposure to neurotoxins (at work) or social habits (alcoholism)