Tramadol is a pain reliever. It has very weak serotonin actions too, making it useful for chronic pain. It is used for this reason in Fibro patients.

Tramadol seems more effective for some with chronic pain, of nerve origin, than opiates. Some neuropathic pain does not respond to opiates in some patients. Tramadol's effects on serotonin help with CNS pain perception too.

I use tramadol infrequently only for bad times. I only use it at night here and there, so I have no tolerance issues with it.

Topamax is an anti-seizure drug, like others used for nerve pain.
Migraine, trigeminal neuralgia, RSD, neuropathies, respond to anti-seizure medications which change the conductivity of nerves. Gabapentin (Neurontin) and Lyrica are in this family of drugs. Topamax has serious side effects involving the eyes (glaucoma), metabolic acidosis, kidney stones which the others do not. So it is used less frequently if others in this group are tolerated by the patient.