In pain management, neurontin works specifically on pain due to disorders of the parasympathetic nervous system, the neurons closer to the surface and radiate pain, such as with fibromylgia. It is usually not used for CNS-caused problems so you might check with your doc as to why he prescribed it, ask if he ran all the relevant tests re: degenerative disorder or trauma due to accident.
If indeed, you do have a spinal cord problem, it's unlikely that neurontin would help, nor would topomax. If the tests provide evidence, suggest seeing a neurologist and/or pain management specialist.
anna22