Speech, language, social communication, and communication assessments in Rett syndrome: A systematic review

Rett syndrome (RTT) is a rare genetic condition associated with profound impacts on communication. While difficulties with speech, language, and social communication have been described previously, no review has comprehensively brought together evidence across these domains. This systematic review examined 59 studies to characterize communication abilities in RTT, and identify the assessment approaches most commonly used in research. Across studies, communication impairments were consistently reported in both classic and atypical forms of RTT, although severity and presentation varied between individuals. Spoken language was the most affected domain, with many individuals experiencing a loss of previously acquired speech following regression. However, communicative ability was not absent. Many individuals continued to express themselves through non-verbal means, including eye gaze, gesture, body movement, facial expression, and vocalisation. Importantly, the ability to understand language often appeared stronger than the ability to express thoughts verbally. Many individuals also demonstrated continued social interest and engagement, despite differences in how social communication was expressed. Outcomes varied according to factors such as age, clinical severity, and genetic variant. Most studies relied on caregiver report, reflecting the challenges of assessing communication in individuals with significant motor and speech impairments. These findings highlight the importance of recognizing non-verbal forms of communication, and avoiding assumptions that limited speech reflects limited understanding.