Tension-type headache is a nonspecific headache, which is not vascular or migrainous, and is not related to organic disease. The most common form of headache, it may be related to muscle tightening in the back of the neck and/or scalp. There are two general classifications of tension-type headache: episodic and chronic, differentiated by frequency and severity of symptoms. Both are characterized as dull, aching and non-pulsating pain and affect both sides of the head.