Tarlov Cyst Causing Sacral Insufficiency Fracture.

Background And Importance: Tarlov cysts, also known as perineural cysts, have been described as meningeal dilations of the spinal nerve root sheath between the peri- and endoneurium at the dorsal root ganglion. Most often they are found in the sacrum involving the nerve roots. Normally asymptomatic, they have been reported to present with radiculopathy, paresthesias, and even urinary or bowel dysfunction. Sacral insufficiency has not been a well-documented presentation.

Clinical Presentation: The patient is a 38-year-old female who started to develop left low back pain and buttock pain that rapidly progressed into severe pain with some radiation down the posterior aspect of her left leg. There was no recent history of spine or pelvic trauma. These symptoms prompted her initial emergency department evaluation, and imaging demonstrated a large Tarlov cyst with an associated sacral insufficiency fracture. She was noted to have a normal neurological examination notable only for an antalgic gait. She was taken to surgery via a posterior approach and the cyst was identified eccentric to the left. The cyst was fenestrated and the nerve roots identified. Given her large area of bone erosion and insufficiency fractures, fixation of the sacroiliac joints was deemed necessary. Fusion was extended to the L5 vertebral body to buttress the fixation. She tolerated the procedure well and was discharged from the hospital on postoperative day 3.

Conclusion: Tarlov cysts of the sacrum can lead to significant bone erosion and subsequent insufficiency fractures, requiring fenestration and in some cases, complex sacropelvic fixation.