Trigeminal neuralgia pain caused by a lesion, such as a tumor, is referred to as secondary trigeminal neuralgia. A tumor that severely compresses or distorts the trigeminal nerve may cause facial numbness, weakness of chewing muscles, and/or constant aching pain. Medications usually help control secondary TN pain when first tried, although often become. Surgically removing the tumor usually alleviates pain and trigeminal function may return. At the time of surgery, after the removal of the tumor, the trigeminal nerve may be found to also be compressed by an artery or vein that causes the typical features of TN. This vessel must then be moved away from the nerve by microvascular decompression techniques to cure TN.