Possible causes of arm numbness that affects one or both arms and worsens at night include inadequate blood supply to a particular area, nerve damage, infection and inflammation, according to Healthgrades. Other conditions, such as malignancy and trauma, can also lead to arm numbness.
Arm numbness mostly occurs due to harmless conditions, notes Healthgrades. It can be accompanied by a burning or prickling sensation known as paresthesias, particularly when the numbness occurs at night. Arm numbness resulting from very cold temperatures diminishes quickly when a person shifts to a warmer place. In some cases, arm numbness indicates an underlying condition that requires prompt medical care. People who experience accompanying symptoms such as slurred speech, arm weakness or paralysis should call a doctor immediately.