Nummular headache.

Nummular headache is a rare primary headache disorder characterized by focal and well-circumscribed pain fixed within a round-, oval-, or elliptical-shaped region of the head. The pain is usually mild to moderate in intensity but may be severe. Nummular headache is most common in women in the fourth to fifth decade of life. The temporal pattern may be chronic and continuous since onset, chronic evolved from episodic, or episodic. These headaches typically are unilateral, side-locked, and fixed in location, commonly affecting the parietal region. Many patients experience superimposed exacerbations of pain, lasting from seconds to days. Sensory phenomena, such as paresthesias, allodynia, and dysesthesias, are frequently reported in the region of the pain. Treatment with gabapentin, tricyclic antidepressants, or botulinum toxin may be helpful.