Trigeminal neuralgia (TN) causes sudden, usually unilateral, severe, brief stabbing recurrent pains in the distribution of one or more branches of the trigeminal nerve. Radiological examination is not required, however, patient interview and physical examination are necessary for diagnosis alone. When a patient is diagnosed with TN, an MRI is recommended to exclude tumor, cyst or multiple sclerosis, irrespective of the patient's age. From the etiological viewpoint, TN is classified into primary or idiopathic TN and secondary or symptomatic TN. From the symptomatic viewpoint, TN is classified into typical TN and atypical TN. Atypical TN, trigeminal neuropathy, pretrigeminal neuralgia, and short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) are also described.

Neurovascular compression at the root entry zone accounts for more than 80% of trigeminal neuralgia (TN) cases, but not all patients with TN have neurovascular compression. Many non-TN subjects have neurovascular contact at the root entry zone. TN is reported to occur in 0.9% to 4.5% of patients with multiple sclerosis (MS). In patients with TN, 1.7% to 15% of patients suffer from MS. The reported range for patients with TN due to tumors is from 0.8% to 11.6%. Because carbamazepine may relieve pain temporarily, relief of pain with carbamazepine does not exclude the diagnosis of a tumor or cyst. There are the peripheral cause theory, central cause theory, peripheral origin central pathogenesis theory, and multiple factors theory in the pathology of TN. Dental pain and/or treatment may trigger TN. Alveolar cavitational osteonecrosis may also cause TN.

The right side was affected in 61% of reported cases and the left side was affected in 39% of approximately 30,000 patients with trigeminal neuralgia (TN) affected on only one side. Side-to-side asymmetry of neurovascular compression in healthy persons cannot account for side-to-side asymmetry in TN. Size asymmetry and shape asymmetry of the rotundum and ovale foramens may account for the higher incidence of TN on the right side. This paper proposes a multiple factors theory: the summation of multiple factors reaches a critical level at which TN occurs. It is rational that entrapment of the maxillary and mandibular nerves when they cross the ovale and rotundum foramens is one of the factors which cause TN. The multiple factors theory can account for a TN patient without neurovascular compression and a healthy person with neurovascular compression.

Trigeminal neuralgia (TN) causes sudden, usually unilateral, severe, brief stabbing recurrent pains in the distribution of one or more branches of the trigeminal nerve. Radiological examination is not required, however, patient interview and physical examination are necessary for diagnosis alone. When a patient is diagnosed with TN, an MRI is recommended to exclude tumor, cyst or multiple sclerosis, irrespective of the patient's age. From the etiological viewpoint, TN is classified into primary or idiopathic TN and secondary or symptomatic TN. From the symptomatic viewpoint, TN is classified into typical TN and atypical TN. Atypical TN, trigeminal neuropathy, pretrigeminal neuralgia, and short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) are also described.

The right side was affected in 61% of reported cases and the left side was affected in 39% of approximately 30,000 patients with trigeminal neuralgia (TN) affected on only one side. Side-to-side asymmetry of neurovascular compression in healthy persons cannot account for side-to-side asymmetry in TN. Size asymmetry and shape asymmetry of the rotundum and ovale foramens may account for the higher incidence of TN on the right side. This paper proposes a multiple factors theory: the summation of multiple factors reaches a critical level at which TN occurs. It is rational that entrapment of the maxillary and mandibular nerves when they cross the ovale and rotundum foramens is one of the factors which cause TN. The multiple factors theory can account for a TN patient without neurovascular compression and a healthy person with neurovascular compression.