Filarial dance sign

A 35-year-old man presented with right-sided scrotal pain. Clinically, the right epididymis was thickened. High resolution ultrasound (10MHz) examination showed four cystic spaces in the right epididymal region and one in the left epididymal region measuring 2 mm to 8 mm with multiple small (<1mm) objects exhibiting peculiar random movements as described by the Filarial Dance Sign.

• Lymphatic filariasis is a major health problem in India with most infections caused by Wuchereria bancrofti. The presence of adult worms of Wuchereria bancrofti in the infected individuals is confirmed by detecting microfilariae or filarial antigens in the patient's blood .
• Ultrasound scans have been used to detect living adult W. bancrofti on account of the characteristic pattern of adult worm movements, known as the filarial dance sign in dilated intrascrotal juxtatesticular lymphatics (worm nests) of approximately 80% of microfilaremic but asymptomatic men residing in endemic areas.
• Ultrasound is a valuable tool in the diagnosis of cases of lymphatic filariasis. Amaral et al  had first reported the use of ultrasound to visualize adult worms of W. bancrofti in the scrotal area of infected men. They described a continuous, distinctive and specific pattern of worm movement called the "Filarial dance" sign. In patients who exhibited this sign, nests of adult W. bancrofti were found in the lymphatic vessels of the spermatic cord on surgery.
• The typical movement of these filariae, called the filarial dance sign (FDS), provides an opportunity to observe the adult worms in vivo.
• The characteristic movements of adult filarial worms are called the filarial dance sign (FDS) and are a reliable diagnostic finding.

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