Sciatica and femoral head osteonecrosis complicating a gluteal hydatid cyst: A case report

INTRODUCTION AND IMPORTANCE: Hydatid disease is an endemic echinococcal infestation in Tunisia. Only 4% of hydatid cysts are located in the muscle. The gluteal localization is a very rare entity. The present case illustrates a gluteal hydatid cyst resulting in sciatica and osteonecrosis of the femoral head, an exceptional entity. CASE PRESENTATION: A 49-year-old man of urban origin, with free medical history, presented to our outpatient clinic with left sciatica and mechanical hip pain, that have been ongoing for 2 years. Pelvic radiograph showed femoral head osteonecrosis and lytic lesions of the ischium. MRI scan identified an extra-articular vesicular cyst in the left gluteal region involving the gluteus maximus. It suggested the diagnosis of musculo-skeletal echinococcosis. The patient underwent surgery and intraoperative findings showed a gluteal vesicular cyst with direct compression of the sciatic nerve, it also revealed femoral head necrosis. The cyst was drained and the pericyst excised. Total hip arthroplasty was postponed and the patient received a course of anthelmintic chemotherapy. CLINICAL DISCUSSION: Muscular involvement of hydatid cysts is rare and seen only in 4% of cases. Neurological complications from sciatic nerve compression can present as sciatica, with a principal differential diagnosis of nerve root compression. Aseptic femoral head osteonecrosis, an exceptional complication of an extra-articular gluteal hydatid cyst, can result from three mechanisms: a direct mechanical compression, an ischemic process due to vessel obstruction or a cellular process mediated by osteoclasts. Treatment is based on surgical excision combined with anthelmintic chemotherapy, the latter reduces the number of live cysts and the risk of recurrence. CONCLUSION: Although gluteal cysts are extremely rare with different clinical symptoms, surgery associated with anthelmintic treatment has a good functional outcome.