A case of indirect cauda equina syndrome from metastatic prostate cancer.

We report the case of a patient with metastatic hormone refractory prostate cancer in whom "indirect" cauda equina syndrome developed concurrent with multilevel spinal cord compression (SCC). Three months after his first positive bone scan, a 65-year-old otherwise healthy man presented with severe back pain, bilateral lower extremity paresthesias, leg weakness and urinary retention. Magnetic resonance imaging (MRI) showed a dural-based mass causing SCC at the T9, T10 and T11 vertebrae, with a normal cauda equina. He received corticosteroids and palliative external beam radiotherapy, resulting in good pain control and gradual improvement in his neurological symptoms. He did well for 8 months, at which time his residual bilateral leg weakness abruptly worsened and he experienced numbness, paresthesias, urinary incontinence and constipation. Repeat MRI showed progression of epidural metastatic disease compressing the spinal cord or thecal sac at 7 thoracic vertebral levels. The cauda equina was also distorted and flattened without evidence of direct solid tumour impingement. We hypothesized that the etiology was increased intrathecal pressure due to disrupted cerebrospinal fluid flow resulting from multiple levels of upstream thecal sac compression. It is essential to image the entire spinal cord and cauda equina when patients with metastatic bone disease present with neurological symptoms to institute correct treatment and preserve function and mobility.