Arthritis: "Inflammation of a joint, usually accompanied by pain, swelling, and stiffness, and resulting from infection, trauma, degenerative changes, metabolic disturbances, or other causes. It occurs in various forms, such as bacterial arthritis, osteoarthritis, or rheumatoid arthritis."
Neuropathy: "Neuropathy, strictly speaking, is any disease that affects the nervous system. In common usage, however, neuropathy is short for peripheral neuropathy, meaning a disease of the peripheral nervous system.
Aside from diabetes (see Diabetic neuropathy), the common causes of neuropathy are herpes zoster infection, HIV-AIDS, toxins, alcoholism, chronic trauma (such as repetitive motion disorders) or acute trauma (including surgery), various neurotoxins and autoimmune conditions such as celiac disease, which can account for approximately 16% of small fiber neuropathy cases. Neuropathic pain is common in cancer as a direct result of the cancer on peripheral nerves (e.g., compression by a tumor), as a side effect of many chemotherapy drugs, and as a result of electrical injury. In many cases no apparent causes can be found, in this case the neuropathy is "idiopathic" meaning no cause is found."
Neuritis: "Inflammation of one or several nerves. The cause may be mechanical, vascular, allergic, toxic, metabolic, or viral. Symptoms — tingling, burning, or stabbing pains with sensory nerves and anything from muscle weakness to paralysis with motor nerves — are usually confined to the part of the body served by the inflamed nerve. In Bell palsy, facial nerve inflammation causes a characteristic facial muscle distortion. Analgesics can relieve the pain. Once the underlying cause is treated, recovery is usually rapid but may be incomplete in severe cases, with residual motor and sensory disturbances."
These three words don't work very well together to form a diagnosis. The brain has no joints, so cannot have arthritis.
"Anti-seizure drugs. Although the reason is unclear, some anti-seizure drugs, such as divalproex sodium (Depakote), valproic acid (Depakene) and topiramate (Topamax), which are used to treat epilepsy and bipolar disease, seem to prevent migraines. Gabapentin (Neurontin), another anti-seizure medication, is considered a second-line treatment agent. Taken in high doses, however, these anti-seizure drugs, depending on which one you take, may cause side effects such as nausea and vomiting, diarrhea, cramps, hair loss and dizziness."
The prescription, along with your killer headache, makes it sound like your diagnosis is migraine headaches. Did the Clinic put your diagnosis in writing? What with all the ~itises and ~othapies and so on, it's easier to mangle one than to get it right.