They have many possible causes directly resulting from high or low pH or substrate concentrations in the blood, including hormonal imbalances, dehydration, low levels of magnesium, potassium, or calcium (evidence has been mixed), side effects of medication, or, more seriously, diseases such as amyotrophic lateral sclerosis and neuropathy. They are also a common complaint during pregnancy.
Charley horse
Hairball
Crutch
Wellbee
Greenpilot
Cowlick
Squawk 
White cane