OBJECTIVE A variant type of the primitive trigeminal artery (PTA) is a rare anomalous vessel that originates from the internal carotid artery and directly supplies the territory of the anteroinferior cerebellar artery and/or the superior cerebellar artery. We report a case of trigeminal neuralgia associated with this PTA variant, and we discuss the characteristics of this vessel. METHODS A 51-year-old woman presented with a 10-year history of left paroxysmal facial pain. Magnetic resonance angiography and cerebral angiography demonstrated that an aberrant vessel originating from the left internal carotid artery directly supplied the cerebellum, without a basilar artery anastomosis. METHODS Surgical exploration was performed via a left retrosigmoid approach. A loop of the aberrant vessel, which entered the posterior fossa through the isolated dural foramen, was compressing the trigeminal nerve. This aberrant vessel was displaced medially from the nerve with a prosthesis, with care to avoid kinking and avulsion of the perforating arteries. The patient's neuralgia resolved postoperatively. CONCLUSIONS Although the PTA variant is frequently associated with intracranial aneurysms, it is extremely rare for the variant to lead to trigeminal neuralgia. During microvascular decompression surgery, surgeons should be careful to prevent injury of the perforating arteries arising from the PTA variant.