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Sensory Modulation Disorder: Definition & Symptoms

Instructor: Justine Fritzel

Justine has been a Registered Nurse for 10 years and has a Bachelor's of Science in Nursing degree.

Sensory modulation disorder impacts how your brain processes input from the body's senses. In this lesson, we will learn more about this disorder and the symptoms associated with it.

Sensory Modulation Disorder

We all learned about the five senses early in school: sight, hearing, taste, smell, and touch. We also have senses about the position of our body, temperature, and even pain. Senses are involved in virtually every aspect of our life. Can you imagine what life would be like without these senses? We probably don't think about them much, but they truly impact every memory, situation, and perception we have.

But if your senses are processed in such a way that it actually impairs your ability to perform your daily activities and routines, this becomes a problem. Sensory modulation disorder (SMD) is simply defined as difficulty responding to sensory stimulus appropriately. A person with SMD may over react or under react to sensory stimulus.

There are three types of sensory modulation disorder: over-responsivity, under-responsivity, and sensory-seeking. We will look at examples of each one of these to better understand them.

Over-responsivity SMD

Billy's mom recalls that Billy was fussy as a baby. He would startle easily and didn't even seem to like to be touched. He was generally behind in his motor development at his check-ups with the doctor. As a toddler, he was a picky eater, and really, just picky about everything. He didn't like certain fabrics of clothing and hated the tags on clothes. He remained fussy and moody with frequent melt-downs over small things. He didn't even like bathing, which most toddlers seem to enjoy.

Billy was later diagnosed with sensory modulation disorder. Looking back, his mom was identifying characteristics that were associated with this over-responsivity. Over-responsivity SMD is the nervous system overreacting to a stimulus, an exaggerated response to a minor sensory stimulus.

Other behaviors associated with this type of SMD include getting overwhelmed with noisy environments and not liking messy play such as finger paints. Billy will likely enjoy spending time alone and avoiding busy situations. He may be irritable and moody and easily irritated by noises that other people can tune out.

Under-responsivity SMD

Paisley just turned five-years-old. For some time, her pediatrician has suspected Paisley has a type of sensory modulation disorder. Paisley's mom finds this hard to believe since she was always such an easy child, even as a baby.

As a baby, Paisley was delayed in her motor development, and she was slow to respond to stimulus like sounds or sights. Even now, things don't seem to bother her. She doesn't seem to notice things like if she is messy or if her pants are twisted up. Her mom just thinks she's very laid back.

Paisley demonstrates under-responsivity SMD, which is a lack of response to sensory stimuli. Other types of behaviors seen in this type of SMD is frequent daydreaming or lack of focus. Children with under-responsivity SMD may ask 'what' a lot.

They have an increased pain tolerance due to their lack of response to stimulus, and they often have decreased muscle tone and may be overweight. They will often have poor fine motor control, have an awkward gait, and tend to be clumsy.

Sensory-seeking SMD

Jimmy is a rambunctious six-year-old boy! He seems to never stop moving and loves to wrestle and rough house. He thrives on busy environments like birthday parties. Sounds like a typical boy, right?

Jimmy actually has sensory-seeking SMD. In this disorder, the nervous system needs an intense level of sensory input for the brain to register the sensation. Therefore, the brain craves these intense sensations.

Although the behaviors we looked at with Jimmy seem normal, there are more behaviors that are connected to his SMD. He exhausts his mother because he is in constant motion. He even crashes into things on purpose. This makes sense when you think that his brain needs extreme stimulus to process it.

He loves spicy, salty, chewy, and crunchy foods - all of which provide heightened stimulus. He has to touch everything. It's hard to take him anywhere, and it's difficult to allow him to play with other kids because he plays very rough. He has a poor attention span, and everywhere he goes, he is either running, jumping, or skipping - but you will rarely see him just walking.

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