Outcome measures in children with Angelman syndrome

Angelman syndrome (AS) is a rare genetic disorder resulting in severe
intellectual disability/developmental delay, speech impairment, and problems
with movement or balance. Children with AS often have epilepsy, psychiatric
symptoms (short attention span, anxiety, autistic features), sleeping, and
feeding problems. Since 2010, 125 AS patients are seen for prospective,
structural and multidisciplinary follow-up at our ENCORE Expertise Center for
Genetic Neurodevelopmental Disorders, resulting in a large set of natural
history data (non-WMO protocol VOLG ENCORE MEC-2015-203).

Knowledge on the feasibility of sensitive outcome measures for children with AS
is lacking. Standard outcome measures are often less suitable for AS patients.
Characteristics of AS such as speech impairment, inattention, behavioural
problems (motivation and anxiety), tiredness due to sleep problems, and
epilepsy can bias the outcome of such tests. This lowers the test's validity
and reliability. It can also result in a floor effect, lack of variance between
individuals, and therefore the inability to detect change in treatment studies.
Current treatment studies often use outcome measures that are less suitable for
children with AS, thus raising questions about the reliability and validity of
such studies.

Current therapeutic strategies for AS are symptomatic. However, treatment
studies for etiologic (targeted) therapy are anticipated. An antisense
oligonucleotide treatment has been developed, and promising results in
preclinical mice studies foresee treatment studies in patients in the near
future. No one knows what such a treatment will mean for AS patients. It is
unclear in which domains they may show improvement with treatment, what the
size of the effect will be, what the lag time between administration of the
treatment and clinical improvement will be, or what the influence of age of the
patient will be on the potential effect. For the design of future treatment
studies, it is of vital importance to identify feasible outcome measures that
will likely be sensitive to relevant treatment effect. These measures are
currently lacking.

Furthermore, new insights and hypotheses based on recent literature and
clinical experience have led to new interests regarding natural history
variables, for example concerning metabolic, endocrine, and autonomic
(dis)function in AS. These variables cannot yet be included into our ENCORE
clinical follow-up, but are of major importance to gain further insight into
the AS phenotype.

The primary objective of this study is to investigate the feasibility of
several promising outcome measures in children with AS, which may later serve
as potential outcome measures for treatment studies and other research.

The study*s secondary objective is to further unravel the phenotype of Angelman
syndrome, i.e., deep phenotyping.

For the secondary objective, we will:
1. Collect additional measures to complement our existing natural history
database.
2. Relate the variables of our primary objective to a) each other; b) the
variables of our secondary objectives, and; c) the variables of our existing
natural history study.
3. Relate the genotype to several of the primary and secondary outcome
variables.

This is an observational cross-sectional study.

The study design is as follows:

1) Telephone call with the parent(s)/caregiver(s): explaining the study and
answering questions, eligibility interview (20 min total).

2) 'Home assessments', to be carried out by the parent/caregiver (total
duration 130 minutes). The home assessments do not have to be completed all at
once, but completion can be spread over multiple moments of the
parent/caregiver*s own choosing. The questionnaires are on the behaviour and
medical history of the child. Additionally, there is a food diary for the child
(3 days).

The assessments ential:
• Temperature measurements of the child (3x).
• Urine collection of the child (1x).
• Fluid balance for the child (1 day).
• Look up GGD growth data of the child.

3) Visit 1 will take place in our mobile research lab (the Sophia Research Bus)
at a location of the participant*s choosing. This minimizes the burden of
travelling for the study visit. The total task time during this visit is 80
minutes, we will have 1 or multiple breaks in consultation with the parent and
child.

Tasks during this visit:
• While the child watches pictures and videos, we simultaneously conduct
eye-tracking and fNIRS measurements.
• Short physical examination.
• Gait assessment (m-POMA-G). The child is asked to walk a few meters (with
their own walking aid if needed).
• We cut a few hairs from the head in order to measure cortisol.
• Venipucture.
• If genotype is incomplete, we take an additional tube of blood for exact
genotyping (only when the participant's legal representative has given consent
for this on the informed consent form).
• We conduct a short interview with the parent/caregiver (CGI-S-AS).

4) 'Home assessments', to be carried out by the parent/caregiver (total
duration 120 minutes). The home assessments do not have to be completed all at
once, but completion can be spread over multiple moments of the
parent/caregiver*s own choosing. The questionnaires are about sleep of the
child. Additionally, parents are asked to fill in a sleep diary for the child
and for themselves (2 weeks).

The assessments entail:
• Collecting some saliva for melatonine measurements, which will be obtained
using cotton wool dots (see C1. Protocol Appendix I for a comprehensive
descriptiono this measurement). Children can chew on them for several seconds,
or parents can swipe the cavity of the child*s mouth, or parents can collect
the saliva that drips out of the child*s mouth. Since most children with
Angelman syndrome have a tendency to drool, this will be not difficult to
achieve. This will be done during one natural day, every hour from 17.00 (<12
years) or 18.00 (>12 years) to onset sleep, once during the night (only if the
child and parent are already awake due to other factors), once in the morning
after awakening, and once at noon on the next day.
• Actigraphy: a non-invasive measure of activity and heath beat. A small
actimeter device can be worn as an ankle band or be attached to the clothing if
that makes it more acceptable for the patient. The actigraph should be worn
during 14 consecutive nights and days. As participants will likely get used to
the actigraph while they wear it, we advise to not take the device off during
these days. The only task for the parent is to put on the actimeter once.
• The researcher will install an infrared video camera in the bedroom of
the child after the first study visit. The camera will automatically turn on
and off, and film only during the participant's bed time. Using the videos,
nightly physical activity can be registered and checked for the kind of
movement or activity (e.g., turning in sleep, actual awakening, or epileptic
seizures). The camera films during 4 nights, of which 3 will be used for
analyses, and 1 serves as stand-by in case of technical difficulties with the
camera - after quality control the unnecessary nights will be removed.

5) Visit 2 will be in the Erasmus MC - Sophia. The total task time during this
visit is 80 minutes, we will have 1 or multiple breaks in consultation with the
parent and child.

Tasks during this visit:
• Zeno Walkway Gait Analysis System: measuring spatiotemporal gait parameters.
• Indirect Calorimetry: measuring resting energy expenditure
• Measuring body composition in two ways, to compare which one is most feasible
and accurate in children with AS.
- BOD POD: Body-composition assessment via air-discplacement plethysmography
- Bio-impedance analysis: through electrodes, a weak electric current flows
through the body and the voltage is measured in order to calculate impedance
(resistance) of the body. The child does not feel the current.

Participation in all assessments and visits of this study is desirable, but not
mandatory for study inclusion. Participants can choose if they want to
participate in the full study, just one of the study visits and the home
assessments, or even only the home assessments.

The risks and inconveniences of this study are negligible: there are no known
risks or side effects to the measurements we use. It is possible that a
participant may experience a particular measurement as unpleasant, scary, or
stressful. If the participant shows signs of discomfort or objection (as
described in the 'Code of conduct relating to the expression of objection by
people with mental disabilities in the context of the WMO'), or if the
parent/caregivers objects, we will at all times stop the measurement.

We have undertaken additional measures to reduce the chance of possible
inconveniences for the participant. To reduce the possible inconvenience of the
venipucture, we will apply EMLA cream as topical anesthetic and distract the
participant during the venipuncture. During the BOD POD and IC measurements,
the children can watch distracting movies. Concerning the fNIRS measurement,
the tightness of the fNIRS cap (like a swimming cap) and may induce an
uncomfortable sensation in those participants that are highly sensitive to
touch. A practice fNIRS cap will be send home so that the child can practice
and acclimate to the situation before the actual study visit. The fNIRS
measurement is silent, and children can move freely because of the wireless cap
(in contrast to a more invasive fMRI measurement). Eye-tracking is
non-invasive.The parent(s)/caregiver(s) will receive individually tailored
counselling how to best prepare the participant for the above measurements
using pictures. Individually tailored behavioural support and distraction will
be offered during the measurement by the executive researcher.

The total burden of participation will be two visits of 80 minutes for the
child and the parent/caregiver. For the first study visit, we will visit
participants at a location of their choosing with the Sophia Research Bus,
minimizing the burden of travelling. The second study visit can be combined
with a regular clinical visit, if desired by the parent/caregiver. One or more
breaks can be taken during the study visits, in close consultation with the
parent and child (time for breaks is not included in the 80 minutes yet). The
additional burden of participation for the parent/caregiver will be two series
of home assessments of 130 and 120 minutes. The home assessments do not have to
be completed all at once, but completion can be spread over multiple moments of
the parent/caregiver*s own choosing. Participation in all assessments and
visits of this study is desirable, but not mandatory for study inclusion.
Participants can choose if they want to participate in the full study, just one
of the study visits and the home assessments, or even only the home
assessments. Furthermore, should a participant or parent/caregiver refuse to
participate in a specific task or questionnaire, he/she can still continue with
the rest of the study or visit.

Scientific benefit will be gained by pointing out feasible and suitable outcome
measures in children with AS. These outcome measures can be used in future
treatment studies, thereby facilitating improved assessment of treatment
efficacy. These outcome measures can additionally be used in other scientific
research, and maybe in clinical practice. Moreover, benefit will be gained by
further elucidating the AS phenotype in great detail, thus aiding knowledge on
the natural history of the syndrome, which can guide treatment studies and may
contribute to a clearer prognosis for children with Angelman syndrome.

The current study can only be performed using the current population of
children with Angelman syndrome, because the main goal is to find feasible
outcome measures for this population and clarify the natural history of this
syndrome. Feasibility of outcome measures for mentally competent individuals
would not generalize to this unique population of children with Angelman
syndrome.