Pathophysiology and neurostimulation for cluster headache and other TACs
The trigeminal autonomic cephalalgias (TACs) are highly debilitating headache problems. The activation of trigeminal–autonomic reflex and ipsilateral hypothalamic activation play a pivotal role, but there are various concerns that remain unresolved in understanding of the pathophysiology of TACs.
The knowledge of central role of hypothalamus led to its utilization as a therapeutic target. Other peripheral neuromodulation targets were tried in the management of refractory cluster headache (CH) and other TACs after the good results procured with hypothalamic stimulation.
As per a study, in chronic cluster headache (CCH) patients, hypothalamic deep brain stimulation (DBS) produced a decrease in attack frequency of more than 50% in 60% of patients. Favorable outcomes were depicted in the Occipital nerve stimulation (ONS) with a reduction of more than 50% attacks in around 70% patients with medically intractable CCH. In 68% patients, stimulation of sphenopalatine ganglion (SPG) with a miniaturized implanted stimulator caused clinically significant improvement. The number of attacks decreased when vagus nerve stimulation (VNS) with a portable device was used in conjunction with standard of care in CH patients. DBS and ONS have been applied eminently in some cases of other TACs, plus hemicrania continua (HC) and short-lasting unilateral headache attacks (SUNHA).
DBS showed good consequences, although it is more invasive method and can cause serious adverse events. ONS had frequently good outcomes with no serious adverse events. In the acute and prophylactic treatment of refractory cluster headache, SPG stimulation (SPGS) produced the desired results. At this moment, ONS and SPG stimulation techniques were suggested as the first line therapy in refractory cluster patients. Recently, new non-invasive approaches like non-invasive vagal nerve stimulator (nVNS) have shown efficacy in a few trials and could be an interesting alternative in CH management except it entails more testing and positive randomized controlled trials.