Neuromuscular Disorders

Question 1

definition of lower motor neuron: what happens if this is messed up?

Answer 1

LMN: its axon and all the muscle fibers innervated by it. If there is no synchronized contraction of the muscles, weakness develops

Question 2

what is the definition of the motor unit?

Answer 2

alpha motor neuron, the axon, and all the muscle fibers innervated

Question 3

What are 3 important upper motor neuron signs?

Answer 3

Hyperreflexia, pathological reflexes (babinski, hoggman, clonus), spasticity

upper motor neurons are inhibitory, so if theyre damaged, you get an increase in activation

Question 4

3 important lower motor neuron signs

Answer 4

weakness, atrophy, fasciculations

Question 5

What are the 2 bulbar signs?

Answer 5

Dysarthria, dysphagia (speech usually first)

Question 6

which motor neurons do ALS involve?

Answer 6

It is a multi system involvement, so the combined involvement of upper and lower motors unit injury will lead to classical features of the disease.

Question 7

In terms of dx for ALS< what is the clinical presentation/course? What is supporitve lab data?

Answer 7

• no biomarker, no definitive radiological markers
• EMG/NCS, TMS, MRI
  note: Mini-Mental State Examinations is a poor screening tool

Question 8

Describe the onset of ALS

Answer 8

FOCAL

• limb onset (80%):
  
  • upper: asymmetric distal (split hand
  • lower: foot drop, wasting in anterior tibialis
• bulbar onset (20%)
  
  • tongue atrophy, fasciculation

Question 10

for ALS, what is the key points in differential dx?

Answer 10

• spinal muscular atrophy (childhood disorder, LMN only)
• Myasthenia gravis: proximal weakness, fluctuating, bulbar and eye findings, mestinon may cause fasciculations, no UMN
• cervical spondylosis: nothing above the neck
• multifocal motor neuropathy: antibody testing GM1 triad EMG

Question 11

What are thre 3 ways to classify polyneuropathies (peripheral nerve)?

Answer 11

1. FIBER INVOLVED: pure sensory, sensory motor, pure motor, autonomic
2. PATHOLOGY/ELECTRODIAGNOSTIC: demyelinating, axonal, mixed
3. SPEED OF PRESENTATION: acute, subacute, chronic

Question 12

explain difference between mononeuropathy, mononeuritis multiplex, and polyneuropathy (peripheral neuropathy).

Answer 12

Mononeuropathy: pattern of weakness and sensory loss at single nerve (i.e. carpal tunnel syndrome)

Mononeuritis multiplex: multiple nerves affected in random pattern; acute onset, frequently painful (DM, vasculitis)

Polyneuropathy: distal, symmetric

Question 13

What are the sensory signs of a polyneuropathy?

positve and negative symptoms?

Answer 13

• start in feet, move proximally
• hand symptoms appear when LE symptoms progress up to knees
• positive: pins and needles, tingling, burning
• negative: numbness, deadness, rubbery soles, “like i’m walking with thick socks on”

Question 14

Describe the motor polyneuropathy symptoms

Answer 14

• weakness first in feet: tripping, turn ankles
• progress to weakness in hands: trouble opening jars, trouble turning key in lock

Question 15

What is the most common pathophysiology of polyneuropathy

Answer 15

AXONAL: reflexes spared longer until muscle spindles involved; amplitude reduction on EMG

less common is demyelinating: early reflex loss

Question 16

What NM disorder is a neuromuscular emergency and why?

Answer 16

Acute polyneuropathies (guillain barre syndrome, prphyria, toxins)

respiratory involvement, can have problems breathing

Question 17

pathophysiology of Guillain Barre Syndrome and treatment (2)

Answer 17

immune mediated, may be post infectious (C. jejuni molecular mimicri)

treatment: plasma exchange if severe; IV immunoglobulin

Question 18

5 forms of subacute polyneuropathies

Answer 18

1-vasculitis

2-paraneoplastic

3-chronic inflammatory demyelinating polyneuripathy

4-toxins

5-drug induced

Question 19

clinical patterns: disease

acute/subacute onset

Answer 19

Guillan Barre syndrome, chronic inflammatory demyelinating polyneuropathy, paraneoplastic

Question 20

clinical patterns: disease

proximal weakness

Answer 20

chronic inflammatory demyelinating polyneuropathy

Question 21

clinical patterns: disease

asymmetry

Answer 21

vasculitis, CIDP, paraneoplastic, diabetic amyotrophy

Question 22

sensory ataxia (lack of voluntary movement)

Answer 22

paraneoplastic, sjogrens, chronic immune sensory polyradiculopathy

Question 23

clinical patterns: disease

onset in hands and feet together

Answer 23

CIDP, B12 deficiency

Question 24

clinical patterns: diseases

small fiber, autonomic, cardiac/renal disease

Answer 24

DM, amyloidosis

Question 25

What does DM, cancer (small cell lun ca), sjogrens, dysproteinemia, AIDS, and B12 deficiency all ahve in common regarding their neuropathies?

Answer 25

they are purely SENSORY

Question 26

What are the 6 major neuropathies with facial nerve involvement?

Answer 26

1, GBS (can be bilateral)

2. CIDP
3. Sarcoid
4. HIV
5. Leprosy

Question 27

What is Charcot-Marie Tooth? What is the gene?

Answer 27

Hereditary neuropathy: demyelinating or axonal

CMT1A: PMP22 duplication

Question 28

What is the difference between Lambert-Eaton syndrome, botulism, and myasthenia gravis in terms of where the problem occurs regarding the neuromuscular junction?

Answer 28

LE syndrome and botulism: pre synaptic dysfunction

MG: post synaptic dysfunction

Question 29

NMJ anatomy: where are the Ach receptors located? where is AchE prominent?

Answer 29

Receptors - at top of secondary clefts

AChE prominent in secondary clefts

Question 30

In terms of release of Ach, descripte the difference between MEPP and EPP

Answer 30

• _small _quanta released spontaneously give rise to miniature end plate potentials
• nerve impulse AP cause huge quantal release, depolarizing the post-synaptic membrane giving rise to endplate potential
• EPP trigged excitation-contraction coupling and muscle contraction

Question 31

is autonomic involved in GBS?

Answer 31

yes, acute.

Question 32

what is the problem in lambert eaton myasthenic syndrome?

Answer 32

• presynaptic disorder of NMJ
• voltage gated Ca channel antibodies impede release of ach
• results in weakness, more lower extremities, autonomic involvement

Question 33

what is LEMS associated with?

Answer 33

underlying cancer (paraneoplastic), usually small cell lung cancer

Question 34

dx of MG:

most specific:

most sensitive:

Answer 34

specific: antibody testing
sensitive: single fiber EMG