Lambert-Eaton myasthenic syndrome

In Lambert-Eaton myasthenic syndrome, myasthenia refers to muscle weakness, and Lambert-Eaton refers to Edward Lambert and Lealdes Eaton, the two physicians who first described the condition.

Lambert-Eaton myasthenic syndrome is a rare autoimmune disease that attacks the peripheral nervous system, causing muscle weakness, and actually improves temporarily after repeated use of the muscle.

The nervous system is divided into the central nervous system, which is the brain and spinal cord, and the peripheral nervous system, which includes all the nerves that connect the central nervous system to the muscles and organs.

The peripheral nervous system can then further be divided into the somatic nervous system, which controls voluntary movement of our skeletal muscles, and the autonomic nervous system, which is even further divided into the sympathetic and the parasympathetic, and controls the involuntary movement of the smooth muscles and glands of our organs.

Now, to better understand Lambert-Eaton myasthenic syndrome, let’s review normal skeletal muscle contraction at the cellular level.

First you’ve got your motor neurons, which have voltage-gated calcium channels in their membranes.

Whenever a motor neuron receives an electrical impulse from the brain, these channels open up and let calcium inside.

The increased intracellular calcium concentration triggers the release of small vesicles that contain the neurotransmitter acetylcholine into the neuromuscular junction.

Acetylcholine goes from the neuron over to the nicotinic receptors on muscle cell membranes.

When acetylcholine binds the nicotinic receptors it leads to muscle contraction.