The one-and-a-half syndrome-A unilateral disorder of the pontine tegmentum

A study of 20 cases and review of the literature

Wall, Michael MD
Wray, Shirley H. MD, PhD, FRCP

Unit for Neuro-Visual Disorders, Department of Neurology, Massachusetts General Hospital, Boston.

Address correspondence and reprint requests to Dr. Wray, Director, Unit for Neuro-Visual Disorders, Massachusetts General Hospital, Ambulatory Care Center, Level 7, 15 Parkman Street, Boston, MA 02114.

Accepted for publication December 3, 1982.

Neurology 33(8):p 971-980, August 1983.

Article abstract

The one-and-a-half syndrome is a clinical disorder of extraocular movements characterized by a conjugate horizontal gaze palsy in one direction plus an internuclear ophthalmoplegia in the other. The syndrome is usually due to a single unilateral lesion of the paramedian pontine reticular formation or the abducens nucleus on one side (causing the conjugate gaze palsy), with interruption of internuclear fibers of the ipsilateral medial longitudinal fasciculus after it has crossed the midline from its site of origin in the contralateral abducens nucleus (causing failure of adduction of the ipsilateral eye). Twenty cases are reported 14 had multiple sclerosis.