Acute fourth nerve paresis.

Dr. Nelson has no financial or proprietary interest in the materials presented herein. doi: 10.3928/01913913-20121008-01 Acute fourth nerve paresis is probably the most frequent cause of acquired vertical diplopia. In this issue, Khaier et al. found that many cases of acute fourth nerve paresis have a benign etiology and clinical course. Although the most common cause of vertical diplopia related to a fourth nerve palsy has been thought to be a decompensation of a congenital condition, the authors in the current study found microvascular disease to be the most common cause. However, acute fourth nerve paresis can be an early clinical sign of a serious intracranial abnormality. The authors suggest that because they found a benign etiology and clinical course for most acute fourth nerve paresis, there is no need for hasty neuroimaging. This recommendation is predicated on a normal neurological assessment and the clinical presentation is compatible with a benign etiology. Because a normal neurological assessment in a patient with an acute fourth nerve palsy does not completely rule out a serious intracranial abnormality, neurological imaging prior to a 3-month observation period, recommended by the authors, may be a better course of action.