Isolated vagus nerve palsy and vagal mononeuritis.

It is useful to consider vagus nerve palsy as a form of cranial mononeuritis. In contrast with other forms of mononeuritis, the clinicoanatomical features and other aspects of vagal mononeuritis are not well defined. A series of 25 patients with isolated vagal mononeuritis were assessed by clinical and laryngoscopic examination, and laryngeal electromyography was done in all cases. Unilateral recurrent laryngeal nerve palsy was almost twice as common as unilateral superior and recurrent laryngeal nerve palsy and it appeared to have a better prognosis. The majority were on an idiopathic basis, and associated diabetes in two patients raised the possibility of diabetic mononeuritis. Three patients had bilateral palsies; bilateral vagal mononeuritis may represent a separate entity in that it occurs in younger subjects and is associated with upper respiratory tract illness. Partial or complete recovery occurred in about half of the patients.