Leukemia cells occasionally will circulate into the spinal column in the fluid called cerebrospinal fluid (CSF). For them to cause paralysis would be EXTREMELY RARE. See, leukemia cells are blood cells and don't form a 'lump' to compress the spinal column. Solid tumors such as breast, lung, or prostate cancer can spread to the spine and cause paralysis.
Typically, if the leukemia in the spinal column isn't treated the symptoms are usually visual (blurred vision, loss of vision,etc.) or nausea/vomiting.
Treatment of the spinal column usually involves having a special catheter put in place (Omaya reservoir) so chemotherapy (methotrexate or cytarbine) can be injected directly into the CSF.
This is usually done in addition to treating the leukemia throughout the body with systemic chemotherapy.
I am a Board Certified Oncology Pharmacist practicing somewhere in the midwest