LAUSR

A 38-year-old woman presented with a 3-year history of intermittent diffuse pain and discomfort located in the right lower abdominal quadrant, followed by sudden severe exacerbation of sciatica with right-sided sensory deficit in the distribution of the S1 dermatome. These symptoms were accompanied by muscle cramps and weakness of the right leg; walking was only possible for a duration of 5–10min. Neither bladder or bowel dysfunction nor sexual dysfunction was reported. MRI of the abdomen performed 6 months prior to the onset of severe pain exacerbation revealed large Tarlov cysts along the nerve roots L5 and S1 on both sides (Fig. 1a, b); acute pain exacerbation led to repeat MRI, which demonstrated T1-weighted (T1w) and T2-weighted (T2w) signal alterations, and fluid-fluid levels within the right-sided S1 cyst (Fig. 1c, d) consistent with organized hematoma. Additional MR neurography of the sciatic nerve revealed pathologically increased intraneural T2 signal strictly localized to the posterior tibial portion of the sciatic nerve Fig. 1i, j) This topographical-somatotopical lesion distribution on the nerve cross section corresponds closely to fascicles emerging from the injured S1 root, as demonstrated previously [1]. The patient decided against hematoma evacuation and chose conservative treatment. MRI follow-up examinations 4 (Fig. 1e, f) and 11 (Fig. 1g, h) weeks later revealed signal alterations within the cyst consistent with chronic hematoma conversion accompanied with a reduction in cyst size. The symptoms of the patient improved. T2 signal alterations in the S1 portion of the sciatic nerve, however, remained unchanged.