Electromyographic abnormalities associated with symptomatic sacral Tarlov cysts

Tarlov or perineural cysts (TC) are commonly overlooked as a cause of sacral and ischial pain, and urogenital and bowel problems. TC can be seen on MRI, but are often considered asymptomatic. This is especially true for smaller cysts. Moreover, there are only few diagnostic characteristics that can be used to confirm that the cysts are the cause of the symptoms. As a consequence, a lot of controversy remains regarding the clinical importance of TC. Because of this underdiagnosed condition, patients often suffer for several years from unrecognized chronic neuropathic pain and neurological conditions. In this article, case reports of three patients with giant and smaller symptomatic sacral cysts are presented, in which electromyographic testing was performed to demonstrate nerve damage. We suggest that electromyography of the sacral nerve roots can be a reasonable tool for the diagnosis of symptomatic TC, as well as for the differentiation from other pathological entities causing sacral and ischial pain. Moreover, using electromyography it was also documented that smaller cysts of < 1 cm can cause nerve damage. Therefore incidence of symptomatic TC may be higher than initially thought.