Peripheral Neuropathies

Question 1

Describe the normal function of the neuromuscular junction. (3)

Answer 1

1. Pre-synaptic nerve ending is the same as a synapse:
   - AP arrives
   - Opens voltage gated Ca2+ channels
   - Ca2+ influx causes neurotransmitter release
2. Muscle cell contains ligand gated Na+ channels
   a. These are opened by neurotransmitters
   b. This causes depolarisation of the muscle cell
3. Muscle cell contains voltage gated Ca2+ channels, which are opened by depolarisation
   a. This causes muscle contraction

Question 2

Describe the features of a motor neuropathy. (3)

Answer 2

Weakness
Muscle atrophy
Reduced reflexes

Question 3

Describe the features of a sensory neuropathy. What if the nerve fibres affected are:

a) Large, myelinated fibres? (4)
b) Small, unmyelinated fibres? (5)

Answer 3

LARGE FIBRES:
Sensory ataxia
Loss of vibration sense
Numbness/tingling
Reduced reflexes

SMALL FIBRES:
Loss of pinprick sense
Loss of temperature sense
Painful, burning numbness
Tinging
Reduced reflexes

Question 4

Describe the clinical features of autonomic neuropathies. (4)

Answer 4

Postural hypotension
Erectile dysfunction
GI disturbance
Abnormal sweating

Question 5

What are the 2 main types of peripheral polyneuropathy?

Answer 5

Length-dependent axonal neuropathy

Guillain-Barré syndrome (acute inflammatory demyelinating neuropathy)

Question 6

List 11 causes of length-dependent axonal neuropathy.

Answer 6

Diabetes
Alcohol abuse
B12/folate deficiency
Immune related (e.g. RA, lupus, vasculitis)
Metabolic/endocrine (e.g. hypothyroidism)
Drug induced
Infections
Congenital conditions
Malignancy
Paraneoplastic disease
Critical illness

Question 7

Give 4 examples of drugs that can cause length-dependent axonal neuropathy.

Answer 7

Amiodarone
Isoniazid
Gold
Cisplatin

Question 8

Give 2 examples of congenital causes of length-dependent axonal neuropathy.

Answer 8

Charcot-Marie-Tooth syndrome

Hereditary neuropathy with liability to pressure palsy (HNPP)

Question 9

Describe the clinical features of length-dependent axonal neuropathy. (5)

Answer 9

Gloves and stockings distribution
Symmetrical 
Slow progression
NO significant sensory ataxia
Possible mild weakness

Question 10

What is Guillain-Barré syndrome caused by? (1)

List 3 examples.

Answer 10

Infection (cross-reactivity), e.g.

• Campylobacter
• CMV
• EBV

Question 11

Describe the clinical features of Guillain-Barré syndrome. (6)

Answer 11

Progressive ascending weakness
Rapid progression (over days)
Flaccid tetraparesis
Absent reflexes
Respiratory paralysis
Autonomic involvement

Question 12

How would you treat Guillain-Barré syndrome?

Answer 12

IV immunoglobulin

Apheresis