Convergence spasm and voluntary nystagmus

While convergence spasm can occur in isolation (e.g., in lateral gaze, which can mimic unilateral or bilateral 6th nerve palsies), oftentimes it occurs with simultaneous voluntary (flutter-like) nystagmus. This does not represent actual nystagmus or even ocular flutter, and when seen with convergence spasm and features of the near triad (convergence, miosis), the examiner can be reassured of a benign, non-physiologic etiology. Although convergence spasm is almost always functional in origin, rare exceptions exist, so neurologic and ocular motor abnormalities should be sought, especially those referable to the midbrain.