One time (per cycle) between Day 15 and Day 21 of Cycles 2, 4, 6, 8, 10, 12, 14, 16, and 18, a sample (about 2 teaspoon each time) of CSF will be collected from your spine through a spinal tap, and from your brain through an Ommaya Reservoir tap. This will be done in order to look for cancer cells. You will also have an MRI of the brain and spine.