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| The image shows areas of the brain that can be affected by sensory processing disorders. Using an advanced form of MRI, researchers at UCSF have identified abnormalities in the brain structure of children with SPD primarily in the back of the brain. |
Sensory processing disorders (SPD) are more prevalent in children
than autism and as common as attention deficit hyperactivity disorder,
yet the condition receives far less attention partly because it’s never
been recognized as a distinct disease.
In a groundbreaking new study from UC San Francisco, researchers have
found that children affected with SPD have quantifiable differences in
brain structure, for the first time showing a biological basis for the
disease that sets it apart from other neurodevelopmental disorders.
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| Pratik Mukherjee, MD, PhD |
One of the reasons SPD has been overlooked until now is that it often
occurs in children who also have ADHD or autism, and the disorders have
not been listed in the Diagnostic and Statistical Manual used by
psychiatrists and psychologists.
“Until now, SPD hasn’t had a known biological underpinning,” said senior author Pratik Mukherjee,
MD, PhD, a professor of radiology and biomedical imaging and
bioengineering at UCSF. “Our findings point the way to establishing a
biological basis for the disease that can be easily measured and used as
a diagnostic tool,” Mukherjee said.
The work is published in the open access online journal Neuro Image: Clinical.
‘Out of Sync’ Kids
Sensory processing disorders affect 5 to 16 percent of school-aged children.
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| Elysa Marco, MD |
Children with SPD struggle with how to process stimulation, which can
cause a wide range of symptoms including hypersensitivity to sound,
sight and touch, poor fine motor skills and easy distractibility. Some
SPD children cannot tolerate the sound of a vacuum, while others can’t
hold a pencil or struggle with social interaction. Furthermore, a sound
that one day is an irritant can the next day be sought out. The disease
can be baffling for parents and has been a source of much controversy
for clinicians, according to the researchers.
“Sometimes they are called the ‘out of sync’ kids. Their language is good, but they seem to have trouble with just about everything else, especially emotional regulation and distraction. In the real world, they’re just less able to process information efficiently, and they get left out and bullied,” said Marco, who treats affected children in her cognitive and behavioral neurology clinic.
“If we can better understand these kids who are falling through the cracks, we will not only help a whole lot of families, but we will better understand sensory processing in general. This work is laying the foundation for expanding our research and clinical evaluation of children with a wide range of neurodevelopmental challenges – stretching beyond autism and ADHD,” she said.
Imaging the Brain’s White Matter
In the study, researchers used an advanced form of MRI called diffusion tensor imaging (DTI), which measures the microscopic movement
of water molecules within the brain in order to give information about
the brain’s white matter tracts. DTI shows the direction of the white
matter fibers and the integrity of the white matter. The brain’s white
matter is essential for perceiving, thinking and learning.
The study examined 16 boys, between the ages of eight and 11, with
SPD but without a diagnosis of autism or prematurity, and compared the
results with 24 typically developing boys who were matched for age,
gender, right- or left-handedness and IQ. The patients’ and control
subjects’ behaviors were first characterized using a parent report
measure of sensory behavior called the Sensory Profile.
The imaging detected abnormal white matter tracts in the SPD
subjects, primarily involving areas in the back of the brain, that serve
as connections for the auditory, visual and somatosensory (tactile)
systems involved in sensory processing, including their connections
between the left and right halves of the brain.
“These are tracts that are emblematic of someone with problems with
sensory processing,” said Mukherjee. “More frontal anterior white matter
tracts are typically involved in children with only ADHD or autistic
spectrum disorders. The abnormalities we found are focused in a
different region of the brain, indicating SPD may be neuroanatomically
distinct.”
The researchers found a strong correlation between the
micro-structural abnormalities in the white matter of the posterior
cerebral tracts focused on sensory processing and the auditory,
multisensory and inattention scores reported by parents in the Sensory
Profile. The strongest correlation was for auditory processing, with
other correlations observed for multi-sensory integration, vision,
tactile and inattention.
The abnormal microstructure of sensory white matter tracts shown by
DTI in kids with SPD likely alters the timing of sensory transmission so
that processing of sensory stimuli and integrating information across
multiple senses becomes difficult or impossible.
“We are just at the beginning, because people didn’t believe this
existed,” said Marco. “This is absolutely the first structural imaging
comparison of kids with research diagnosed sensory processing disorder
and typically developing kids. It shows it is a brain-based disorder and
gives us a way to evaluate them in clinic.”
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| These brain images, taken with DTI, show water diffusion within the white matter of children with sensory processing disorders. Row FA: The blue areas show white matter where water diffusion was less directional than in typical children, indicating impaired white matter microstructure. Row MD: The red areas show white matter where the overall rate of water diffusion was higher than in typical children, also indicating abnormal white matter. Row RD: The red areas show white matter where SPD children have higher rates of water diffusion perpendicular to the axonal fibers, indicating a loss of integrity of the fiber bundles comprising the white matter tracts. |
Future studies need to be done, she said, to research the many
children affected by sensory processing differences who have a known
genetic disorder or brain injury related to prematurity.
The study’s co-authors are Shivani Desai, BS, Emily Fourie, BS, Julia
Harris, BS, and Susanna Hill, BS, all of UCSF, and Anne Arnett, MA, of
the University of Denver.
The research was supported by the Wallace Research Foundation. The
authors have reported that they have no conflicts of interest relevant
to the contents of this paper to disclose.
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children and their families find compassionate care at the forefront of
scientific discovery, with more than 150 experts in 50 medical
specialties serving patients throughout Northern California and beyond.
The hospital admits about 5,000 children each year, including 2,000
babies born in the hospital. For more information, visit www.ucsfbenioffchildrens.org.
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