Neuroradiology has found evidence of a possible original activation of cluster headache from the portion of the brain called hypothalamus. Furthermore, an activation of the parasympathetic nervous system through the sphenopalatine ganglion, which may also explain some of the one-sided involuntary symptoms, is suspected in cluster headache. Injection of Botulinum toxin type A (BTA) inhibits secretion of synaptic acetylcholine resulting in nerve signals being blocked. The duration of such a blockade is believed to be 3-9 months.