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- Published on: 26 February 2019
- Published on: 12 February 2019
- Published on: 26 February 2019Reply to: Benign positional "vertical opsoclonus", or "upbeat nystagmus"?
We thank Drs. Robert and Vidal for their comments. After carefully reading their original series of 5 patients and observing their videos [1], our impression was that both series could definitely refer to the same unique phenomenon.
As stated before [2], a drawback of our series was the inability to acquire eye movement recordings for any of our patients due to technical obstacles and parental refusal. We found Robert and Vidal’s ability to do so in one of their patients very important to the understanding and definition of the phenomenon [1]. Clearly their recordings demonstrate an upbeating nystagmus that would be expected in patients with tonic downgaze, assuming the eyes drift down while saccadic correcting movements are upward towards primary gaze. Hopefully, additional supporting recordings will be added to the literature in the future, allowing us to conclude that this is a representing finding for all of these patients.
This condition was apparently described under different titles over the years owing to scarce descriptions in the literature and difficulty providing convincing support for one definition over the other. This is an important step in that direction. We agree that with their addition of data, the term should include “upbeat nystagmus” and therefore suggest the term “benign infantile positional tonic downgaze with upbeat nystagmus”.1. Robert MP, Michel S, Adjadj E, Boddaert N, Desguerre I, Vidal PP. Benign intermittent upbeat nystag...
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None declared. - Published on: 12 February 2019Benign positional "vertical opsoclonus", or "upbeat nystagmus"?
Dear Editor,
We read with great interest the nice series from Sternfeld et al. about so-called “benign positional vertical opsoclonus in infants”. [1] As stated by the authors, the very specific condition they describe is not uncommon in the population, yet still poorly described in the scientific literature. Additionally, it is called differently by different authors, one reason for it being the difficulty to assess through the naked eye the very nature of the high frequency eye movements, as shown in video n°1.
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The condition combines a positional tonic downgaze and abnormal vertical eye movements. Oculomotor recordings of infants presenting with this clinical picture do actually confirm that these movements comprise downbeating slow phases and upbeating saccades 2, as clinically seen in video n°2, and are therefore a vertical kind of nystagmus. We therefore proposed to refer to them as benign intermittent upbeat nystagmus in infancy. [2] As stated by the authors, the association of a tonic downgaze and an upbeat nystagmus is logical and has been related to posterior semicircular canal predominance. [3]
In addition to the evidence of slow phases in this condition and to the fact that, to the best of our knowledge, no pulse of purely vertical saccades has ever been recorded, the very possibility for the oculomotor system to produce such movements is questionable. Opsoclonus, by definition, designates a succession of multidirectional saccades. We therefo...Conflict of Interest:
None declared.