Abstract
Given that cluster headache is a rare but nevertheless devastating disease, we read the recent published case series of Wolter et al. (1), proposing spinal cord stimulation (SCS) in cluster headache with interest. It is beyond dispute that alternative and sometimes invasive therapies are needed especially in patients with refractory chronic cluster headache. Neuromodulatory approaches have are increasingly employed with promising results. However, we herewith comment on two points: the definition of refractory cluster headache and major adverse events.
There is no commonly accepted definition of refractory cluster headache, but high-dose verapamil and additional drugs are recommended before a patients with cluster headache should be called medically intractable (2,3). These recommendations help to define patients where indeed more invasive methods should be considered. In the case series of Wolter et al., only one out of seven patients was treated with verapamil >480 mg and only two out of seven were treated with topiramat >100 mg. This may be due to side effects with higher doses but this is not even discussed. It remains vague whether combinations of two or more drugs were used. For future trials the criteria by Leone et al. (2004) designed for the selection of hypothalamic deep brain stimulation should be adopted (3,4).
Adverse effects such as lead migration, battery depletion and local infections are inherent in neuromodulatory approaches and have been reported in hypothalamic brain stimulation (3), occipital nerve stimulation (5), and stimulation of the sphenoid ganglion (6).
However, the rate reported in this case series of only seven patients is exceedingly high and resulted in repetitive invasive procedures:
patient 1: lead revisions because of dislocation after 6 months and 12 months patient 2: lead revisions because of dislocation after 3 months patient 4: lead revision because of breakage after 6 weeks patient 5: lead revision because of dislocation after 2 days and 9 months and revision because of lead breakage after 3 month, paddle lead after 12 month patient 6: lead revision because of breakage after 2 days and 7 months.
We agree, that the additional operations needed for battery replacement (patients 1, 2, and 5) and side shift of the cluster headache (which is reported in two of the seven patients) should not be perceived as major adverse events. However, a lead revision in five out of seven patients raises the question whether the concluding statement, “There were no major adverse events”, is too enthusiastic. Given that a dislocation of the lead is an inherent problem in spinal cord stimulation especially in parts of the spinal cord with high mobility such as the upper cervical spine, less invasive methods such as the occipital stimulation should be preferred.