MAYO CLINIC: CLICK TO READ MORE"Multiple sclerosis can be difficult to diagnose. Your doctor may base a diagnosis of MS on the following:

Medical history. Your doctor reviews your symptoms and the pattern of the symptoms.
Neurological examination. This examination systematically tests various parts of your nervous system, including your reflexes, muscle strength, muscle tone, and sensations of pain, heat, touch and vibration. Your doctor may also observe your gait, posture, coordination and balance, and ask you questions to help determine the clarity of your thinking, judgment and memory.
Magnetic resonance imaging (MRI) scan. The cylinder-shaped MRI scanner creates tissue-slice images on a computer from data generated by a powerful magnetic field and radio waves. Your doctor can view these images from any direction or plane. This imaging technique may reveal MS lesions, which are caused by myelin loss. Newer MRI techniques can provide even greater detail.
Spinal tap (lumbar puncture). In this procedure, a doctor or nurse removes a small sample of cerebrospinal fluid from within your spinal canal for laboratory analysis. This sample can show abnormalities associated with MS, such as abnormal levels of white blood cells or proteins. This procedure can also help rule out viruses and other conditions that can cause neurological symptoms.
Evoked potential test. This test measures the electrical signals sent by the brain in response to stimuli. An evoked potential test may use visual stimuli or electrical stimuli, in which short electrical impulses are applied to the legs or arms."