MRI investigation of radiating pain in the lower limbs: value of an additional sequence dedicated to the lumbosacral plexus and pelvic girdle.

OBJECTIVE: In some cases, sciatica-like symptoms radiating through the buttock, anterior thigh, or leg result from spinal root compression in an extraspinal location or from injury to the pelvic girdle. It has been suggested that adding a coronal STIR sequence dedicated to the lumbosacral plexus and pelvis to the routine MRI protocol can provide a good depiction of disorders of this type.

MATERIALS AND METHODS: Two hundred nine patients with sciatica-like symptoms of suspected lumbar origin were included in the study. Disorders responsible for symptoms involving extraspinal compression of the lumbosacral plexus or pelvic girdle were retrospectively noted and correlated with age, sex, location of pain, referring physician, presence of discoradicular impingement liable to explain symptoms, and history of neoplasia.

RESULTS: An extraspinal cause of symptoms was depicted in 12 cases (5.7%), including three cases of extraspinal compression and nine differential diagnoses in the pelvic region. Prevalence of an extraspinal cause of pain was significantly correlated with the absence of discoradicular impingement in the spine (p=0.046). A higher prevalence of extraspinal compression of the lumbosacral plexus (p=0.029) was seen in patients 60 years old or older, whereas no other feature was statistically associated with an extraspinal cause of pain.

CONCLUSION: Because of its short acquisition time and subsequent low cost, the additional coronal STIR sequence should be performed in the routine MRI investigation of sciatica-like symptoms when no discoradicular impingement is seen in the spine to depict an extraspinal cause of symptoms.