Diagnostic approach to diplopia.

OBJECTIVE

This article offers a pragmatic roadmap to the practicing neurologist on how to approach the patient with double vision. Strategies of history taking and examination techniques are reviewed, followed by a broad overview of the causes of diplopia organized by neuroanatomic localization. Diplopia may be the first symptom of serious vision or life-threatening neurologic disease, and its correct localization and diagnosis are therefore essential. The systems responsible for ocular movement and alignment in the vertical and horizontal plane include complex supranuclear circuitry, brainstem nuclei, cranial nerves III, IV, and VI, and their respective neuromuscular junctions and target muscles. Disruption at any point within this system or within the vestibular afferents that govern eye movement in response to head movements may therefore produce diplopia, leading to a broad differential diagnosis for the patient with diplopia. With a careful history and examination, the neurologist should be able to observe the patterns of diplopia that reveal the site of dysfunction, thus generating a shorter localization-specific list of possible etiologies. Examination of ocular motility including smooth pursuit and saccadic function, followed, if necessary, by testing designed to uncover misalignments of the eyes, including cover and Maddox rod testing, are primary components of the efferent neurologic examination. Further testing designed to detect myasthenia (eg, lid testing and fatigable upgaze) and orbital disease (eg, measuring proptosis, testing for resistance to retropulsion) may be necessary.

RESULTS

Recent advances in the diagnosis of diplopia include the observation that vertical diplopia from skew deviation is more likely to improve with supine positioning than that caused by trochlear nerve palsies. Advances in the field of ocular myasthenia include the observation of decreased conversion to the generalized form with treatment with either steroids or thymectomy, although these conclusions need to be confirmed by prospective, randomized trials. Rarely, pure ocular myasthenia may be associated with the muscle-specific tyrosine kinase (MuSK) antibody.

CONCLUSIONS

With proper skills, the neurologist can elucidate the localization of diplopia, even in cases of complex ocular misalignment, and generate a management plan that can address the underlying disease, and, in many cases, ameliorate or cure the diplopia.