Types and treatment of LMN disorders

Question 1

What is the most common cause of inflammatory myopathy?

Answer 1

dermatomyositis

Question 2

How will dermatomyositis present?

Answer 2

• Gottron papules, periorbital oedema, heliotrope rash, V-sign, shawl sign, mechanic’s hands
• Acute (days) or subacute (weeks) proximal weakness, myalgia

Question 3

How is dermatomyositis treated?

Answer 3

acute - steroids
longterm - methotrexate
if not tolerated ciclosporin
3rd line rituximab

Question 4

What are the most common autoimmune NMJ disorders?

Answer 4

• MG (most common by far)
• Lambert Eaton myasthenia syndrome
• Organophosphate poisoning
• Botox

Question 5

What is the most common autoantibody in MG?

Answer 5

antibodies for AChR

can also have antibodies to MuSK but AChR far more common

Question 6

What test can be used for MG?

Answer 6

• test for autoantibodies (takes a long time to get back)

- can do Ice test or tension test in mean time (which will improve muscle strength)

Question 7

How is Myasthenia Gravis managed?

Answer 7

1) pyridostigmine
2) steroids then methotrexate then rituximab
3) MG crisis use IV immunoglobulin

Question 8

What are the exacerbating factors for MG?

Answer 8

• infection
• stress
• withdrawal of cholinesterase inhibitors
• rapid intro of steroids
• electrolyte imbalance (dec K+ and dec phosphate)
• anaemia
• drugs

Question 9

How will myasthenic crisis present?

Answer 9

• increasing muscle weakness and diplopia
• respiratory failure
• O2 sats and blood gases normal
• but FVC 1L requiring ICU support

Question 10

How are myasthenia crisis treated?

Answer 10

IV Immunglobulins
plasma exchange
ventilation
NBM and NG feeding

Question 11

How are different neuropathies distinguished?

Answer 11

nerve conduction studies

1) axonal - conduction velocity preserved but amplitude reduced
2) demyelinating - conduction slower but amplitude preserved

Question 12

What type of LMN lesion is GBS?

Answer 12

polyradiculopathy

Question 13

What type of LMN lesion is GBS?

Answer 13

polyradiculoneuropathy (acute inflammatory and demyelinating)

Question 14

How will patients with GBS present?

Answer 14

• progressive weakness
• arefelxia
• peak within 4 weeks of onset
• symmetrical
• more motor than sensory symptoms + pain
• autonomic dysfunction
• 50% have facial involvement

Question 15

What are the investigations for GBS?

Answer 15

CSF for elevated protein
Nerve conduction study
Imaging (to show no structural changes)
CK (check for muscle disease)
TFT, K+, bone - (no metabolic cause)

Question 16

How to treat GBS?

Answer 16

• urgent (recovery takes years)
• IV immunoglobulin
• supportive airway care
• enoxaparin

Question 17

What are the common mononeuropathies?

Answer 17

• carpal tunnel
• ulnar
• radial
• foot drop (common perineal nerve)

Question 18

What are the common mononeuropathies?

Answer 18

• carpal tunnel (median)
• ulnar
• radial
• foot drop (common perineal nerve)

Question 19

What is the most common presentation of MND?

Answer 19

• amyotrophic lateral sclerosis (mix of UMN & LMN signs)

Question 20

What are the clinical findings in MND?

Answer 20

• painless and progressive weakness and wasting
• lower CN nerves affected (jaw weakness, facial weakness and gag reflex reduced, tongue fasciculation’s)
• head drop
• cachexia
• sensation normal
• ## cognition impaired

Question 21

What differential diagnosis should be excluded when diagnosing MND?

Answer 21

• multifocal motor neuropathy
• cervical myeloradiculopathy
• MG (MND no ocular involvement)
• inherited motor neuropathies (MND more rapid progression)

Question 22

What are the investigations necessary for MND?

Answer 22

MRI spine

Nerve conduction study

Question 23

Ho wis MND managed?

Answer 23

• no treatment
• palliative care
• possible ventilation
• need dietician or gastroenterology