The GDS rates dystonia in 14 body areas. The GDS is a Likert type scale with ratings from 0 to 10 (0 is no dystonia, 1 minimal, 5 moderate and 10 severe dystonia). A higher score represents more severe dystonia.

The Patient Reported Outcomes Measurement Information System (PROMIS) Fatigue Parent Proxy evaluates a range of self-reported symptoms, from mild subjective feelings of tiredness to an overwhelming, debilitating, and sustained sense of exhaustion that likely decreases one's ability to execute daily activities and function normally in family or social roles. Fatigue is divided into the experience of fatigue (frequency, duration, and intensity) and the impact of fatigue on physical, mental, and social activities. Scores range from 0 to 40 with a higher score indicating higher fatigue impact.

The Patient Reported Outcomes Measurement Information System (PROMIS) Pain Interference Parent Proxy measures the self-reported consequences of pain on relevant aspects of one's life. This includes the extent to which pain hinders engagement with social, cognitive, emotional, physical, and recreational activities. It assesses pain interference over the past seven days. Scores range from 0 to 40 with a higher score indicating higher pain interference.

The Patient Reported Outcomes Measurement Information System (PROMIS) Peer Relations Parent Proxy assesses the quality of relationships with friends and other acquaintances. Scores range from 0 to 28. A higher score indicates better peer relations.

The Patient Reported Outcomes Measurement Information System (PROMIS) Physical Functional Mobility Parent Proxy measures self-reported capability rather than actual performance of physical activities. This includes the functioning of one's upper extremities (dexterity), lower extremities (walking or mobility), and central regions (neck, back), as well as instrumental activities of daily living, such as running errands. Each form assesses current function rather than function over a specified time period. Scores range from 0 to 32 with a lower score indicating lower mobility.

The Patient Reported Outcomes Measurement Information System (PROMIS) Physical Function Upper Extremity Parent Proxy measures self-reported capability rather than actual performance of physical activities. This includes the functioning of one's upper extremities (dexterity), lower extremities (walking or mobility), and central regions (neck, back), as well as instrumental activities of daily living, such as running errands. Each form assesses current function rather than function over a specified time period. Scores range from 0 to 32 with a lower score indicating lower mobility.

The Patient Reported Outcomes Measurement Information System (PROMIS) Anxiety Parent Proxys measures self-reported fear (fearfulness, panic), anxious misery (worry, dread), hyperarousal (tension, nervousness, restlessness), and somatic symptoms related to arousal (racing heart, dizziness). Anxiety is assessed over the past seven days. Scores range from 0 to 32 with a higher score indicating higher anxiety.

The Patient Reported Outcomes Measurement Information System (PROMIS) Anxiety Parent Proxys assessed self-reported negative mood (sadness, guilt), views of self (selfcriticism, worthlessness), and social cognition (loneliness, interpersonal alienation), as well as decreased positive affect and engagement (loss of interest, meaning, and purpose). It assesses depression over the past seven days. Scores range from 0 to 32 with higher score indicating more depressive symptoms.

The CHQ is a self administered quality of life measure of 14 physical and psychosocial concepts and assesses a child's physical, emotional, and social well-being from the perspective of a parent or guardian.

The Clinical Global Impression - Severity scale (CGI-S) is a 7-point scale that requires the clinician to rate the severity of the participant's illness at the time of assessment, relative to the clinician's past experience with participants who have the same diagnosis. Considering total clinical experience, a participant is assessed on severity of mental illness at the time of rating 1, normal, not at all ill; 2, borderline mentally ill; 3, mildly ill; 4, moderately ill; 5, markedly ill; 6, severely ill; or 7, extremely ill.

The Clinical Global Impression - Improvement scale (CGI-I) is a 7 point scale that requires the clinician to assess how much the participant's illness has improved or worsened relative to a baseline state at the beginning of the intervention. and rated as: 1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; or 7, very much worse.

The Parental Clinical Global Impression of Improvement Scale is a 7 point scale that requires the parent/guardian to assess how much the participant's illness has improved or worsened relative to a baseline state at the beginning of the intervention. and rated as: 1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; or 7, very much worse.

Parents/caregivers will rank their most concerning top three symptoms associated with their child's diagnosis of Rett syndrome. Rankings range on a line scale from best to worst.

The Clinical Severity Scale is a measure of onset or disease regression, growth, motor and communication skills, and disease behaviors. Measures are rated on a severity scale from 0 to 5. A higher score indicates more progressive disease.

The MBA is a measure of onset or disease regression, growth, motor and communication skills, and disease behaviors. Measures are rated on a severity scale from 0 to 5. A higher score indicates more progressive disease.

The RSBQ is a self-administered questionnaire completed by caregivers. The RSBQ measures frequency of disease behaviors on a scale from 0 to 2 (0 indicating a statement is not true, 1 indicating a statement is somewhat or sometimes true, and 2 indicating a statement is very true).

The Hand Apraxia Scale is a validated 10-item scale, with a score for a given task being 1 if it could be performed and 2 if it could not.

The RSGMS assesses the ability of subjects to sit, transfer to standing, stand, walk, side-step, turn, bend, step over obstacles, walk and run. Completion time for videotaping by parents is typically 30 45 minutes.

Participants will begin walking at 3 KPH. The speed will be increased each minute by a set amount (alternating between 0.3 and 0.2 KPH). The test will continue until one of three outcomes occurs: 1) the participant indicates they would like to stop, 2) the predicted maximum heart rate (90) is reached, or the principal investigator or therapist determines the subject should no longer continue. In each possible outcome, the maximum speed achieved during the final full-minute stage will be recorded. The participant will rest, and the test will be repeated, with the goal to achieve one speed interval (0.3 or 0.2 KPH) higher than the previous test. The maximal heart rate will be recorded as the heart rate at the end of the first and second walk.

Participants will begin walking at 3 KPH. The speed will be increased each minute by a set amount (alternating between 0.3 and 0.2 KPH). The test will continue until one of three outcomes occurs: 1) the participant indicates they would like to stop, 2) the predicted maximum heart rate (90) is reached, or the principal investigator or therapist determines the subject should no longer continue. In each possible outcome, the maximum speed achieved during the final full-minute stage will be recorded.

EEG monitoring will be performed for 24 hours with a standard 21 electrode international 10-20 protocol. Frequency of EEG activity will be measured by manual spike counting and frequency of clinical and subclinical electrographic seizures.

Photoplethysmographic heart rate will be measured using the Empatica E4 watch which has a built-in algorithm for seizure prediction.

Accelerometry will be measured using the Empatica E4 watch which has a built-in algorithm for measuring step count.

Electrodermal Activity (EDA) will be measured using the Empatica E4 watch which has a built-in algorithm for seizure prediction.

Skin Temperature will be measured using the Empatica E4 watch which has a built-in algorithm for seizure prediction.