Teaching Case

Degradation of health condition with hepatic metastasis of unknowned neoplasia. Apparition of bilateral sciatalgia.

A 39 year-old woman presented a rapid degradation of health condition. Initial work up disclosed hepatic metastasis of neuro-endocrine type at histology. The primary tumor was not found. A bilateral sciatalgia conducted to perform a MRI of the spine. MRI showed a main subarachnoid nodule at the L4 level associated with multiple subarachnoidal nodules located in the thecal sac along the nerve roots.

Leptomeningeal metastasis are the most frequently secondar to primary intracranial neoplasms like the medulloblastoma (48%) and the glioblastoma (14%). Systemic tumors can also spread to the cerebral spine fluid, by different mechanisms, including direct extension into the surachnoid space, peripheral lymphatic invasion, hematogenous dissemination, or seeding via the choroid. Carcinoma of the breast is the most common primitive tumor, followed by carcinoma of the lung, malignant melanoma, carcinoma of the genitourinary tract and carcinoma of the head and neck or colon. Clinically the lesions may manifest by many signs, related to their locations : Cranial nerve palsies, spinal cord dysfonction, meningismus, radiculopathy, conus medullaris syndrome or cauda equina syndrome. The diagnosis may remain difficult even after CSF examination (lumbar tap), as abnormal cells may not be found. At MR imaging, the lesions may manifest by a fine layer of enhancement overlying all the structures, or by multiple nodules in the subarachnoid space as in our observation. The roots of the cauda equina may be thickened and may look clustered.