Square Wave Jerks

    • Horizontal oscillating back-to-back saccades that interrupt fixation
    • Can be physiologic if the saccades are of low amplitude and infrequent
    • Sign of brainstem dysfunction if the saccades are frequent
    • No visual symptoms unless the saccades are frequent enough to reduce foveation time
    • Common causes: progressive supranuclear palsy (PSP), cerebellar degenerations, brainstem trauma, multiple sclerosis
    • Uncommon causes: Parkinson disease, Huntington disease, schizophrenia
    • Core clinical features
      • Horizontal nonrhythmic saccades that carry both eyes in one direction away from fixation and then, after a pause (“intersaccadic interval”), bring them back to fixation
      • May be physiologic if the saccadic amplitude is less than 5º and saccades are infrequent
    • Possible accompanying clinical features
      • Saccadic pursuit, hypometric saccades, and other neurologic deficits
    • Saccades of inattention or thinking
    • Infantile nystagmus syndrome
    • Acquired pendular nystagmus
    • Ocular dysmetria
    • Ocular flutter
    • Volitional flutter
    • Dismiss this eye movement abnormality as physiologic only if the saccades are of low amplitude, infrequent, and unaccompanied by other neurologic abnormalities
    • Consider the imitators, especially saccades of inattention or thinking, ocular flutter, volitional flutter, and ocular dysmetria
    • Square wave jerks persist
    • Trap: they are often mistaken for nystagmus, causing fear and fruitless evaluation

    Nystagmus-like Oscillations

    Overview Video Convergence Retraction Superior Oblique Myokymia Square Wave Jerks Saccades of Inattention Ocular Flutter and Opsoclonus Volitional Flutter Ocular Dysmetria Ocular Bobbing Ping Pong Gaze Oscillations of Internuclear Ophthalmoplegia Epileptic Oscillations