Cauda equina mass: An Approach

-      CLINICAL PRESENTATION &FINDINGS

      57 yr male with h/o low back pain with no h/o trauma presents for MRI lumbar spine which shows – Large relatively well defined , regular, intradural, subtly & heterogeneously enhancing SOL, seen from lower L3 border to middle of body of L5 with compression of cauda equina fibers, displaying mostly soft tissue signals on all sequences / normal meningeal  enhancement, with no significant hemorrhage / fat / cystic / necrosis/ MR demonstrable calcification  components / sugarcoating / scalloping or enlargement of the posterior neural elements/ dumbbell shaped extension across the neural foramina / marrow signal abnormality / soft tissue collections  -intradural neoplastic etiology is possible like astrocytoma (though no significant enhancement) / gangliogloma (though no calcification) / unusual epidermoid (though no cyst ) etc. may need consideration. Other etiology like myxopapillary ependymoma or neuroenic etiologies less likely, in view of enhancement pattern. Case Submitted by Dr MGK Murthy, Dr GA Prasad.

Tumors of cauda equina & filum terminal region -

Myxopapillary ependymomas  are the most common tumor of the conus medullaris and filum terminale, representing more than 90% of tumors in this region  seen in young adults  and usually show marked homogeneous enhancement & may have hemorrhagic areas ( cap sign)  & calcifications. Cord edema &  nontumoral cysts  are common findings. Also may show scoliosis, canal widening & vertebral scalloping.

Schwannomas -  arise from nerve roots of cauda equine & show marked enhancement with occasional cystic & necrotic areas & fatty degeneration at times. Hemorrhages are less common.

Other less frequent tumors -

Astrocytoma   can show bone erosion, scoliosis, interpedicular distance widening and eccentric disposition. T1-weighted MRI reveals a lesion with multiple vertebral involvement and poorly defined margins . Cysts are also common in astrocytomas without a cap sign.

Meningioma – well defined isointense lesions on T1 & T2 with variable homogenous enhancement & may show calcifications. Hemorrhages are uncommon.

Metastasis of the intradural spine are rare & usually seen from lung, breast, melanoma, lymphoma, leukemia.  Post-contrast study can show  leptomeningeal enhancement & thickening suggesting drop metastasis or leptomeningeal carcinomatosis also known as “sugar coating” or “Zuckerguss.  Cystic structures are rarely associated with spinal metastasis, however bone erosion is common. Cord edema with mild cord expansion over several vertebral segments, disproportionate to lesion size, is usually seen in spinal metastasis.

Spinal PNET -  common site are filum terminale and cauda equine with diffuse heterogeneous enhancement . CSF seeding of tumor  shows  leptomeningeal enhancement.

Ganglioglioma-  rarely involves conus medullaris, seen predominantly in children and young adults with mixed signal intensity on T1 weighted images with patchy enhancement. Calcification are common.

Less common hypervascular tumors are hemangioblastomas & paragangliomas with intense enhancement & serpentine vascular flow voids in the vicinity.

Lymphoma of the spinal cord accounts for fewer than 1% of all lymphomas in the body & patients commonly present with ambulatory difficulties and muscle weakness. Lymphomas of the spinal cord shown high signal intensity on T2-weighted images with irregular enhancement.

Benign tumors –

Filum terminale lipomas – usually incidental & very common  (upto 5% in general population).

Dermoid cyst  - 20% are located in the cauda equina seen younger than 20 years of age & usually contain fatty elements with no enhancement or mild rim enhancement.

Epidermoid cyst similar intensity to CSF on T1 and T2 weighted images & are non-enhancing, however, a thin rim of contrast enhancement may be seen & show diffusion restriction.