• Isaacs syndrome arises in childhood or adult life either in association with polyneuropathy or an inherited type of episodic ataxia
• Characterized by muscle twitching, spasms, generalized stiffness which persist through sleep. May affect any muscle group.
• Continuous muscle activity is a result of hyperexcitability of terminal parts of motor nerve fiber. An inherited form is believed to be associated with a peripheral nerve K channel abnormality.