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Neuroradiology Case of the Week

Case 479

February 2010

Daniel Ginat, MD, MS and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 59-year-old female with a history of breast cancer.

Imaging Findings: Cystic lesions within expanded posterior sacral foramina are evident on CT and MRI examinations.

Figure 1: Axial CT through the level of the sacrum demonstrates two cystic lesions within expanded posterior sacral neural foramina, left larger than right.
Figure 2: Axial T1-weighted image at the corresponding level demonstrates low-signal intensity within the lesions.
Figure 3: Sagittal T2-weighted image at the level of the sacrum demonstrates a rounded lesion containing homogeneous high-signal intensity material.
Figure 4: Coronal T2-weighted image at the level of the sacrum also reveals homogeneous high-signal intensity material within bilateral (left larger than right) sacral foramina.

Diagnosis: Sacral perineural cyst

Discussion: Perineural root sleeve cysts are spinal nerve root diverticula that frequently occur in the sacrum, especially S2 and S3, where they are known as Tarlov’s cysts. These lesions contain CSF and normal nerve fibers and can cause bone erosion and significant enlargement of the posterior sacral foramina. Consequently, on CT these cysts will measure simple fluid density and on MRI, high T2 and low T1 signal intensity will be apparent. These cysts do not enhance. Although readily recognized on imaging, the differential diagnosis for Tarlov’s cysts may include meningocele, arachnoid cyst, neurofibroma, ductal ectasia, and synovial cyst. These lesions are usually asymptomatic but can occasionally provoke symptoms of sciatica.

References:

  1. Grossman RI, Yousem DM. Neuroradiology: The Requisites. 2nd Ed., Mosby. Philadelphia. 2003: 806-807.
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