Insight into the Hydrocephalic Brain Using Diffusion Tensor Imaging
by Ashly Westrick, Research Programs Manager and Marvin Sussman, Ph.D.
HA is dedicated to providing our community with the latest updates on research in an easily understandable fashion. Sometimes the scientific and research journal articles can be daunting to those of us not in the medical and scientific fields. Ashly Westrick, M.P.H., our Research Programs Manager, and Marvin Sussman, Ph. D., an HA board member, take on this task. We received interest in understanding the paper published in February in the journal American Journal of Neuroradiology entitled, “Diffusion Tensor Imaging Properties and Neurobehavioral Outcomes in Children with Hydrocephalus.” Below is a summary of that paper.
Increased intracranial pressure due to hydrocephalus can result in damage throughout the brain, including white matter structures such as the corpus callosum, internal capsule, and fornix. This damage has been reported to be a factor in poor neurological outcomes. In the study, researchers used diffusion tensor imaging (DTI) to quantify the diffusion properties in the white matter structures for children with hydrocephalus.
What is DTI? DTI is a form of MRI that allows the non-invasive mapping of the diffusion (spreading) process of molecules, mainly water, in the tissues of a living organism. Conventional MR imaging techniques allow for detection of major structural abnormalities, but are not sensitive enough to quantify white matter abnormalities. DTI allows researchers to understand the extent of tissue damage and how parts of the brain are connected. Water molecule spreading patterns reveal microscopic details about tissue structure in the normal or diseased tissues. One such detectable change is white matter structural alterations with trauma and disease. White matter is one of the two components of the central nervous system, and is mostly glial cells. Glial cells are non-neuronal cells involved in homeostasis, myelin formation, and protection for neurons. Changes in white matter may correspond with disease progression. In conditions causing structural abnormalities or tissue degeneration, DTI measurements can quantify these changes, and can be used as a non-invasive tool to monitor disease progression or therapeutic efficacy of an intervention.
Few studies have been done using DTI in pediatric hydrocephalus; the authors attribute this to the narrow time window between diagnosis of this condition and treatment. As many of us know from experience, once we are diagnosed, treatment in the form of a shunt placement or ETV quickly follow, thereby minimizing the window for studying white matter damage due to intracranial pressure. The current paper reports initial findings from the imaging and neurobehavioral tests in children with hydrocephalus before surgical management.
The study evaluated a total of 44 children, comparing DTI images in 24 with hydrocephalus to 20 control subjects (all between birth and 51 months). Participants in this study were from an ongoing multicenter, prospective longitudinal imaging trial of pediatric hydrocephalus. The authors propose that children with hydrocephalus would demonstrate abnormal diffusion or spreading properties as evidenced by tissue changes using DTI, that may be characteristically different in the white matter structures of the corpus callosum and internal capsule. In addition, researchers hypothesized that neuropsychological outcome measures, such as child’s independence skills, communication, daily living, social and motor skills, would be abnormal and would correspond with alterations in DTI measurements. Briefly, the main findings of the paper were:
- Diffusion properties in children with hydrocephalus demonstrated altered DTI in white matter regions compared to healthy controls.
- The patterns of abnormality in DTI measurements vary in different white matter regions.
- A strong correlation was found between the DTI indices and the motor skills reported by the parents, providing initial evidence for white matter alteration and functional deficits.
The authors conclude that DTI reveals alterations in the white matter structure in children with hydrocephalus, with preliminary findings suggesting a correlation with clinical motor deficits. As more data are collected, the researchers will continue to quantify the progression of white matter changes and how these changes impact clinical outcomes to both short- and long-term surgical outcomes.
The meaning? The goal of this research is to be able to learn and quantify the damage occurring in the hydrocephalic brain. This knowledge could help provide valuable information to medical professionals and parents on how to, potentially, plan earlier interventions to help their children overcome possible challenges. These are preliminary findings and more research is needed but we are encouraged by the direction of this hydrocephalus research.