Is there a likely correlation between glossopharegial neuralgia and trigeminal neuragia?

Aberrant vessels: Both trigeminal neuralgia and glossopharygeal neuralgia are related in that they are usually caused by a prominent or tortuous vessel coming off the vertebro-basilar artery system. These vessels are more prominent and "dig" into these nerves thus leading to a pain syndrome. Treatment for both is often with neurosurgical microvascular decompression--that is, padding the nerves from the vessel.

Neuralgia: There are two different diseases involving two different cranial nerves. In my years of practice I have not seen a patient with both. While it could happen it would be a very rare occurrence.