Manual of Botulinum Toxin Therapy: Use of botulinum neurotoxin in the treatment of piriformis syndrome

Introduction Piriformis syndrome is entrapment of the sciatic nerve by the piriformis muscle, causing sciatica. One estimate puts the incidence of sciatica of non-disc origin as equal to or greater than that of herniated disc, based on comparison of the number of lumbar MRI scans versus the number of subsequent surgery for lumbar disc problems in 239 subjects in 2002 (Filler et al ., 2005). The same study found intensive MRI evidence that piriformis syndrome accounted for a full 67% of sciatica of non-disc origin. Regardless of exact incidence, it seems fair to say that sciatica of non-disc origin is common and that in some circumstances the diagnosis of piriformis syndrome is controversial. Some investigators (Halpin and Ganju, 2009; Miller et al ., 2012) find the syndrome undefined and infrequent. In the 25-year period from 1987 to 2012, our own experience has included over 17 000 patients referred or self-referred for piriformis syndrome, approximately half of whom ultimately had the diagnosis confirmed. Since we are a referral center for the condition, our data cannot be used as a suitable sample from which to derive incidence or prevalence figures. However, the average length of time that our patients have had the pain related to piriformis syndrome has fallen from 6.5 years (Fishman et al ., 2002a,b) to well below 2 years, suggesting, at least, that the syndrome is being recognized and treated more quickly than in the past, and that although recognized incidence is rising, prevalence is declining.