Lambert-Eaton Syndrome

Question 1

Causes

Answer 1

Lambert-Eaton myasthenic syndrome is seen in association with small cell lung cancer and to a lesser extent breast and ovarian cancer.

It may also occur independently as an autoimmune disorder. Lambert-Eaton myasthenic syndrome is caused by an antibody directed against PRESYNAPTIC VOLTAGE-GATED CALCIUM CHANNELSin the peripheral nervous system.

Question 2

Clinical Features

Answer 2

• repeated muscle contractions lead to increased muscle strength (in contrast to myasthenia gravis)
• limb-girdle weakness (affects lower limbs first)
• hyporeflexia
• autonomic symptoms: dry mouth, impotence, difficulty micturating

ophthalmoplegia and ptosis not commonly a feature (unlike in myasthenia gravis)

Question 3

Diagnosis

Answer 3

EMG- incremental response to repetitive electrical stimulation

Question 4

Management

Answer 4

AMIFAMPRIDINE allows more acetylcholine to be released in the neuromuscular junction synapses. It works by blocking voltage-gated potassium channels in the presynaptic cells, which in turn prolongs the depolarisation of the cell membrane and assists calcium channels in carrying out their action. This improves symptoms in Lambert-Eaton syndrome.

Other options:

• Immunosuppressants (e.g. prednisolone or azathioprine)
• IV immunoglobulins
• Plasmapheresis