Subjective visual vertical/horizontal and video head impulse test in dyslexic children

Different studies have tried to establish a relationship between dyslexia and the vestibular system function. Subjective Visual Vertical/Horizontal (SVV and SVH) and Video Head Impulse Test (VHIT) are useful for studying the vestibular system and can be easily performed in children. Our aim was to evaluate the vestibular function in dyslexic children by SVV/SVH and VHIT. We enrolled 18 dyslexic children (10M/8F; mean age 10.7 +/- 2.3 years; range 7-14 years) and 18 age-matched children with typical development of learning abilities. All children performed VHIT, SVV and SVH. We found normal gain and symmetry of vestibulo-ocular-reflex both in dyslexic and typically developing children. Fifteen out of 18 dyslexic children (83.3%) showed a difference of at least one amongst SVV or SVH. The mean value of SVV was 2.3 degrees and the mean value of SVH was 2.6 degrees. Statistical analysis showed a significant difference between typically developing and dyslexic children for both SVV and SVH. We confirm a relationship between dyslexia and the alteration of SVV and SVH. Our results could be related to the pathogenetic hypothesis of a visual processing impairment related to a dysfunction of the magnocellular pathway or to a general deficit related to a multimodal cortical network.