Various locations were proposed for the primary lesion during the nineteenth century, including nerve roots , ganglia , trunks and branches, as well as the brain and spinal cord. In 1828, JC Warren  and TJ Graham  placed the cause in the trunk or branch of the nerve innervating the perceived site of the pain, though Graham also attributed neuralgia to "morbid sensibility of the nervous system" due to "great disorder of the general health". Teale in 1830  and many after him argued that it may be located in the spinal cord or nerve root. Later in the century some proposed it may be an affliction of organs such as the uterus or liver, while others classed certain headaches as neuralgias, and proposed that emotional distress may promote the condition. 
The differential diagnosis includes temporomandibular disorder .  Since triggering may be caused by movements of the tongue or facial muscles, TN must be differentiated from masticatory pain that has the clinical characteristics of deep somatic rather than neuropathic pain. Masticatory pain will not be arrested by a conventional mandibular local anesthetic block.  One quick test a dentist might perform is a conventional inferior dental local anaesthetic block, if the pain is in this branch, as it will not arrest masticatory pain but will TN.