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5121: Neurodevelopmental Assessments in the Longitudinal Study of Urea Cycle Disorders: Comparison of Standard (Traditional) Neuropsychological Battery and NIH Toolbox


We are doing this study to see how the results of two sets of tools used to measure developmental progress relate to one another and how acceptable completing each of these measures is to children and families of children with Urea Cycle Disorders. We are anxious to make longitudinal assessment (repeated observations over time) of cognition easier, quicker and more accessible for families of children with urea cycle disorders. In order to do so we want to understand the relationship between the 2 sets of measures.


This study is for all urea cycle disorders.

  • Arginase Deficiency
  • Argininosuccinate Lyase Deficiency
  • Argininosuccinate Synthetase Deficiency
  • Carbamyl Phosphate Synthetase Deficiency
  • Citrullinemia II
  • N-Acetylglutamate Synthase Deficiency
  • Ornithine Transcarbamylase Deficiency
  • Ornithine Translocase Deficiency


Urea cycle disorders are a group of metabolic disorders that prevent the body from effectively using protein to create energy. Enzymes needed to properly metabolize protein are weak or not functioning in those with urea cycle disorders, and ammonia, a toxic product of protein metabolism builds up in people who have a urea cycle disorder. The ammonia can build up in the brain and cause problems with thinking and movement. We are interested in the longitudinal course of these thinking difficulties, so that we can help families plan, work with schools to establish more successful programs, and can be certain when treatment(s) are developed that they protect the brain and preserve cognition. Cognition includes all forms of knowing and awareness, such as perceiving, conceiving, remembering, reasoning, judging, imagining, and problem solving.

We have been collecting cognition data for many years as part of the Longitudinal Study, but it has been hard to capture as much data as would be most helpful because the tests currently used are lengthy, and scheduling time with professionals who can administer them is sometimes difficult. We want to know if a measure administered more quickly, perhaps during regular clinic appointments, and by more available personnel will work in providing cognitive information that can be used to learn more about UCD’s impact on the brain.

About this Study

This study is observational and there is no treatment involved. Children enrolled, or planning to enroll, in the Longitudinal Study of Urea Cycle Disorders are eligible. All children will complete one testing session during which they will complete both the standard neuropsychological battery and the NIH Toolbox (NIH-T) test battery. The standard neuropsychological battery was shortened to include only the tests that we expect to be captured by the NIH-T. Children will be asked to remember, to read, to complete pegboards, and to respond quickly. Parents will complete questionnaires reporting their child’s adaptive functioning and executive functioning. Parents and children will be asked to report on the experience of scheduling and completing both sets of measures.

Target Enrollment

To be eligible to participate, you must be an individual with the following:

  • Diagnosed urea cycle disorder
  • English speaking or educated in English
  • Vision adequate to see small pictures
  • Hearing adequate for normal conversation
  • Use of your dominant hand is not impaired
  • Age between 3 years and 16 years 11 months
  • Willing to sit and complete mental activities for 90 minutes, with a break
  • Prior neuropsychological (cognitive) assessments given for the Longitudinal Study (5101) have been successfully completed (if the child has been previously tested)

How to Participate

In order to participate in a study, you must contact the study coordinator of any of the participating institutions by phone or by e-mail. Please use the information to the right to inquire about participation.