Sixth cranial nerve palsy and ipsilateral trigeminal neuralgia caused by vertebrobasilar dolichoectasia

Abstract

Purpose: To report an unusual case of vertebrobasilar dolichoectasia causing both trigeminal neuralgia and ipsilateral sixth cranial nerve palsy. Observations: A patient had undergone surgical decompression of trigeminal neuralgia caused by dolichoectatic vertebral and basilar arteries years before presenting with ipsilateral sixth nerve palsy. Brain MRI showed deviant vertebrobasilar arteries that presumably now compressed the sixth cranial nerve. The unaffected left sixth cranial nerve was visible on MRI, but the affected right sixth cranial nerve was not. The central spinal fluid space in Dorello's canal on the affected side was relatively ample, suggesting atrophy of the affected sixth cranial nerve. On follow-up examination one year after presentation, the patient's diplopia was palliated with spectacle prism. Conclusions and importance: This is the tenth reported case of dolichoectasia causing sixth cranial nerve palsy, but only the second to occur with dolichoectatic trigeminal neuralgia. It provides more detailed imaging that previously reported cases. Review of reported cases of dolichoectatic compression of cranial nerves indicates that vascular decompression may be effective for trigeminal neuralgia, but is not indicated for dolichoectatic sixth nerve palsy, which will resolve spontaneously or can be effectively managed with prism or eye muscle surgery. Keywords: Dolichoectasia, Sixth nerve palsy, Diplopia, Trigeminal neuralgia