Filarial dance sign
Citation, DOI and article data
The filarial dance sign refers to a twirling motion of microfilariae (e.g. W. bancrofti) in dilated lymphatic channels. It is identified as a characteristic sign of scrotal filariasis.
The dilated channels are identified with the absence of color flow on color Doppler study and the microfilariae as curvilinear echogenic undulating structures within it. Generally, 5-6 microfilariae are seen per channel.
It is important to note that this sign is highly characteristic of filarial infection in the right clinical context but is by no means pathognomonic. It has also been reported on scrotal ultrasound in individuals with no history of exposure to filariae, but who clinically have epididymal obstruction. Indeed in a large published series from the UK, a country in which filariasis is not endemic, most of the affected patients had undergone a vasectomy 4.
Histopathologically, the randomly moving echogenicities in one of these reported cases comprised multiple macrophages admixed with partially-broken down clumped together spermatozoa 2; although other explanations have also been posited as the origin of these appearances 4.
History and etymology
The filarial dance sign was first described by Fernando Amaral (fl. 2019), a Brazilian radiologist, and colleagues in 1994, in the scrota of 14 patients infected by Wuchereria bancrofti 3.
- 1. Chaubal NG, Pradhan GM, Chaubal JN et-al. Dance of live adult filarial worms is a reliable sign of scrotal filarial infection. J Ultrasound Med. 2003;22 (8): 765-9. J Ultrasound Med (full text) - Pubmed citation
- 2. Wang Z, Yang Z, Lei YY, Zhang YD, Chen LD, Xie XY, Lu MD, Wang W. Who Is Doing the Dance in Epididymis: The Principle of Moblile Echogenicities Without Filarial Infection: Case Report. (2015) Medicine. 94 (34): e1418. doi:10.1097/MD.0000000000001418 - Pubmed
- 3. Amaral F, Dreyer G, Figueredo-Silva J, Noroes J, Cavalcanti A, Samico SC, Santos A, Coutinho A. Live adult worms detected by ultrasonography in human Bancroftian filariasis. (1994) The American journal of tropical medicine and hygiene. 50 (6): 753-7. doi:10.4269/ajtmh.1994.50.753 - Pubmed
- 4. Adejolu M, Sidhu PS. The "filarial dance" is not characteristic of filariasis: observations of "dancing megasperm" on high-resolution sonography in patients from nonendemic areas mimicking the filarial dance and a proposed mechanism for this phenomenon. (2011) Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine. 30 (8): 1145-50. Pubmed