Sensory Processing Research & Studies 

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 Neurolmage Clinical 

Pratik Mukherjee, MD, PhD

‘Out of Sync’ Kids
Sensory processing disorders affect 5 to 16 percent of school-aged children.

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.

Elysa Marco, MD

“Most people don’t know how to support these kids because they don’t fall into a traditional clinical group,” said Elysa Marco, MD, who led the study along with postdoctoral fellow Julia Owen, PhD. Marco is a cognitive and behavioral child neurologist at UCSF Benioff Children’s Hospital, ranked among the nation's best and one of California's top-ranked centers for neurology and other specialties, according to the 2013-2014 U.S. News & World Report Best Children's Hospitals survey. 

“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.

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.

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.

Researchers at UC San Francisco have found that children with sensory processing disorders have decreased structural brain connections in specific sensory regions different than those in autism, further establishing SPD as a clinically important neurodevelopmental disorder.

The research, published in the journal PLOS ONE, is the first study to compare structural connectivity in the brains of children with an autism diagnosis versus those with an SPD diagnosis, and with a group of typically developing boys. This new research follows UCSF’s groundbreaking study published in 2013 that was the first to find that boys affected with SPD have quantifiable regional differences in brain structure when compared to typically developing boys. This work showed a biological basis for the disease but prompted the question of how these differences compared with other neurodevelopmental disorders. 

“With more than 1 percent of children in the U.S. diagnosed with an autism spectrum disorder, and reports of 5 to 16 percent of children having sensory processing difficulties, it’s essential we define the neural underpinnings of these conditions, and identify the areas they overlap and where they are very distinct,” said senior author Pratik Mukherjee, MD, PhD, a professor of radiology and biomedical imaging and bioengineering at UCSF.

SPD Gains Recognition as Distinct Condition

SPD can be hard to pinpoint, as more than 90 percent of children with autism also are reported to have atypical sensory behaviors, and SPD has not been listed in the Diagnostic and Statistical Manual used by psychiatrists and psychologists.

“One of the most striking new findings is that the children with SPD show even greater brain disconnection than the kids with a full autism diagnosis in some sensory-based tracts,” said Elysa Marco, MD, cognitive and behavioral child neurologist at UCSF Benioff Children’s Hospital San Francisco and the study’s corresponding author. “However, the children with autism, but not those with SPD, showed impairment in brain connections essential to the processing of facial emotion and memory.”

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 emotional regulation. Furthermore, a sound that is an irritant one day can be tolerated the next. The disease can be baffling for parents and has been a source of much controversy for clinicians who debate whether it constitutes its own disorder, according to the researchers.

“These kids, however, often don’t get supportive services at school or in the community because SPD is not yet a recognized condition,” said Marco. “We are starting to catch up with what parents already knew; sensory challenges are real and can be measured both in the lab and the real world. Our next challenge is to find the reason why children have SPD and move these findings from the lab to the clinic.”

The first row (in blue) shows areas of the brain where children with SPD have less white matter than typically developing children. This is especially evident in the back of the brain, the primary site for transmitting sensory information. Rows two and three (in orange) show parts of the brain where children with SPD have more white matter – although the “structural integrity” is impaired. Image courtesy of Yi-Shin Chang/UCSF

The study enrolled 40 right-handed boys and girls with SPD and 41 right-handed typically developing children, and examined the pathways for connectivity of specific white matter tracts in their brain using diffusion tensor imaging (DTI). The SPD and control subjects’ behaviors were first characterized using a parent report measure of sensory behavior called the Sensory Profile. They also were given the Acoustic Index of the Differential Screening Test and a portion of the Sensory Integration Praxis Tests to directly measure auditory and tactile processing, respectively.

“By comparing the white matter in the brain of kids with SPD and typically developing kids, we were able to relate them to direct measurements of auditory and tactile function and find strong correlations between the white matter and sensory functioning,” said senior author Pratik Mukherjee, MD, PhD, a professor of radiology and biomedical imaging and bioengineering at UCSF. “The children with SPD and the typically developing kids form a continuum, with the children with SPD at one extreme and sensory-typical at the other. This builds on the idea that SPD is a spectrum disorder and for the first time we have direct measurements, rather than solely relying on parent reports.”

The researchers used DTI to measure the structural connectivity of the kids in both groups. The advanced form of imaging measures the microscopic movement of water molecules within the brain and shows the direction of the white matter fibers and their integrity, thereby mapping the structural connections between brain regions. The microstructure of the white matter correlates with sensory functioning, especially in the back of the brain where tracts are responsible for relaying sensory information.

The imaging detected abnormal white matter tracts in the SPD subjects 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. 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.

The results of the DTI had a stronger correlation with the direct measurements of tactile and auditory processing taken during the neurological testing than in the parent report survey, which the researchers say is likely due to the direct measurements being more objective.

“Knowing that the neurological testing is a strong predictor of what we’ll see on the DTI means we can use it more confidently to calculate sensory challenges, and tailor our treatments to best help our patients,” said Elysa Marco, MD, who led the study along with postdoctoral fellow Julia Owen, PhD, and Yi-Shin Chang, MS, in the department of radiology and biomedical imaging. “This ties directly into precision medicine – not relying on one size fits all for clinical diagnoses – but objectively assessing patients using quantifiable biomarkers to then personalize their treatment.”

Clockwise from top left: Pratik Mukherjee, MD, PhD; Elysa Marco, MD; Julia Owen, PhD; and Yi-Shin Chang, MS.