During an occupational therapy appointment in Chicago, a therapist packed colorful wrist and ankle weights on a four year old girl with pigtails. The patient had been diagnosed with Attention Deficit/Hyperactivity Disorder (ADHD) as well as Sensory Processing Disorder (SPD). The weight bands helped her get a better sense of her body as she worked on coordination tasks.
SPD is an umbrella term used to describe a person’s difficulty in processing sensory information. For some people, SPD can mean they have trouble sensing the size of a room or if other people are too close. For others with SPD, the lights, sounds, or touches can be painfully overwhelming. Some estimates suggest that as much as 15 percent of the population has some form of SPD.
SPD is currently a controversial condition, and the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) does not recognize it. But some practitioners argue that the SPD exists and deserves official recognition.
For people with SPD, their brain forms an inappropriate response to sensory messages. Often the person experiences an increased response that makes a ceiling light sound like a spotlight or a phone sound like a blaring horn.
There are three types of behavior associated with SDP. A person with the first type, sensory modulation disorder, has difficulty responding appropriately to sensory messages. Many have an increased response, although researchers have identified that some people feel the opposite and have a muted reaction.
The second type, sensory motor disorder, affects the way a person moves or plans their movements. The patient with the pigtails, for example, had trouble grasping objects with her hand, which meant she tired easily when writing or coloring.
With the third type, sensory discrimination disorder, a person has trouble seeing variation in their sensory inputs. There are eight subtypes related to visual, auditory, tactile sensations, taste, smell, movement and balance, body positioning, and internal bodily sensations.
Researchers began to study SPD in the 1960s, and considered it a theory of how the brain processes sensory messages and then regulates behavior. Health practitioners continue to debate SPD, and the divide is disciplinary. On the one hand, occupational therapists say they see it in their patients. On the other hand, some pediatricians say that SPD is not a real disorder.
Different diagnostic manuals reflect the division on the SPD. Although the SPD is included in major diagnostic manuals such as The diagnostic classification of mental health and developmental disorders in infancy and early childhood, a leading pediatric group is not convinced.
In 2012, the American Academy of Pediatrics issued a strong statement against the SPD. In a policy statement in the review Pediatrics, the group cautioned against SPD diagnoses that were not linked to other conditions such as ADHD or autism. They called SPD a theory and said research has yet to prove whether SPD results from a neural pathway disorder or if the deficits are indicative of another condition.
The following year, the DSM-5 did not recognize SPD in its updated edition and said more peer-reviewed studies were needed. Since then, researchers have learned more about the conditions commonly associated with SPD. They also learn more about the brains of people with SPD and how they might function differently.
Visualization of the SPD
In 2013, a published study in NeuroImage: clinic used diffusion tensor imaging (DTI), a type of magnetic resonance imaging (MRI) to examine the brains of 16 boys, ages eight to 11, who were diagnosed with SPD. They compared the boys’ images with boys without SPD, who were the same age and IQ level.
DTI revealed that boys with SPD had abnormal posterior white matter microstructure compared to boys without SPD. Because posterior cerebral white matter microstructure is linked to sensory behavior, the authors concluded that they could use it as a biomarker in the future to diagnose SPD.
A follow-up study in the journal Neurology compared white matter connectivity between boys with SPD, autism, and a control group. The researchers found that boys with SPD and autism had similar abnormal connectivity in their sensory processing pathways, but only autistic boys showed abnormal connectivity in pathways associated with social and emotional processing. The results supported claims that it is possible to have SPD, but not autism, and experts should not automatically associate the two conditions.
Currently, no less than 90% of people with autism also have SPD, and it is present in no less than 60% of ADHD cases. Further brain imaging research could help scientists prove to leaders in the medical community that SPD is a distinct condition worthy of its own diagnostic criteria.