Acute onset concomitant esotropia: when is it a sign of serious neurological disease?

The onset of concomitant strabismus in most cases occurs during early infancy or childhood.' The two major categories of early onset concomitant esotropia are accommodative and congenital (infantile). While some disagreement exists as to the appropriate treatment of these strabismic disorders, there is general consensus that these are not usually causally related to any serious underlying neurological pathology. In contrast, the patient who presents with the acute onset of esotropia and diplopia should prompt a careful consideration of whether or not the strabismus is a sign of serious central nervous system pathology. First and foremost, one needs to establish if the deviation is concomitant or inconcomitant. An acute onset esotropia with inconcomitance must be considered to be the result of paresis of the lateral rectus muscle (abducens nerve) until proved otherwise. There is no doubt that the vast majority of neuropathic or myopathic causes of strabismus present as an inconcomitant deviation. On the other hand, does concomitancy in an acute onset esotropia assure one of the benign underlying nature of the strabismus? Until recently most authorities would probably have agreed that acute onset esotropia that is concomitant without divergence insufficiency is benign in nature with no risk that it might be associated with intracranial pathology.2 Regrettably, it is now apparent that this simple algorithmic way ofviewing acute onset esotropia, while valid in the vast majority of cases, is not appropriate in any single case since too many exceptions exist. Concomitancy in acute onset esotropia does not rule out the possibility of an underlying serious neurological condition.3 How, then, is the clinician to evaluate the patient with acute onset concomitant esotropia? Does every patient with this form of strabismus deserve a neuroradiological and/or neurological evaluation? If not, what features or findings in a case of acute onset concomitant esotropia would indicate that this patient is at particular risk? In order to answer these questions an overview of the types of acute onset concomitant esotropia is necessary.