The Ultimate Guide to Sensory Processing Disorder

Did you know that there are actually 8 sensory systems in your body, not just 5?

Our bodies take information in through sensory systems:

1. Auditory - sound/hearing
2. Visual - sight
3. Olfactory - smell
4. Gustatory - taste
5. Tactile - touch
6. Vestibular- movement
7. Proprioception - input from muscles and joints
8. Interoception - internal sensors indicating physiological conditions

Sensory Integration is the process your central nervous system goes through when it takes information in from your body’s 8 senses, processes that information, and then responds accordingly.

What is Sensory Processing Disorder (SPD)?

When one’s central nervous system has difficulty processing any of this sensory information, the body’s responses are atypical and can be observed in motor, language, or behavioral skill difficulties. Occupational therapists diagnose these atypicalities as Sensory Processing Disorder or SPD.

When we talk about Sensory Processing Dysfunction (SPD), occupational therapists diagnose 3 subtypes of SPD:

• Sensory Modulation Disorder
• Sensory-Based Motor Disorder
• Sensory Discrimination Disorder

It is likely that people with sensory processing dysfunction demonstrate a combination of symptoms from the subtypes, however, a trained OT will know how to address the different deficit areas in Sensory Integration Therapy.

If you’re a parent struggling to understand how your child’s sensory system works, what it all means for your everyday life, and how to help, we’ve tried to outline some of the basics to help you make “sense” of it all! And, since OTs often use visuals to help with SPD kids, we’ve put together a visual of SPD just for you!

1) Sensory Modulation Disorder (SMD)

The STAR Institute defines Sensory Modulation Disorder as “difficulty regulating responses to sensory stimuli.” The magnitude of these sensory processing difficulties affects key areas of daily functioning and, for many children, it affects their ability to purposefully interact and engage because their arousal level and level of alertness is affected! 

Sensory Modulation Disorder is further split into 3 categories or types based on those atypical responses: Over-Responsive, Under-Responsive, and Craving/Seeking.

SMD Over-Responsive Type - (SMD-SOR)

Child has a low threshold for sensory stimuli - meaning, it doesn’t take much for them to be overwhelmed, overstimulated, irritated, or avoidant. This child is very sensitive to sensory stimuli. Play, exploration, safety, and comfort are all affected because of this over-responsivity to sensory input. Sensory defensiveness is seen in any or all sensory systems. Child avoids or becomes irritated by sensations (fight, fright, flight response). SMD is seen to affect social, emotional, and behavioral areas.

SMD Under-Responsive Type - (SMD-SUR)

Child has a high threshold for sensory stimuli - meaning, it takes a lot of sensory input to get him to respond as compared to the typical person Child does not attend or respond to sensory stimuli in his environment Can appear passive, quiet, or disengaged Child may appear clumsy, have difficulty with body awareness, have a high pain tolerance/no pain response, difficulty understanding temperature gradations (hot/cold) Difficulty regulating the force or volume of movements.

SMD Sensory Craver (SMD-SC)

The child often looks disorganized as they seek more sensation. Child seeks constant stimulation, an intensity of input - jumping, crashing, bouncing, touching, moving, mouthing…however he can get the sensory input he’s seeking! Unsafe, extreme sensory seeking behaviors Happiest in busy, stimulating environments.

A child with SMD-SC can be referred to as a "Sensory Seeker".

2) Sensory Discrimination Disorder (SDD)

Close your eyes, put your hand in your pocket or handbag, and feel around for your keys. Did you find them or did you touch upon that old gum wrapper? How do you know what’s what? How do you know how far and in what direction to reach, how to pull your hand out, or what material you were touching?

Better yet, how do you know what is your car key versus your house key without opening your eyes? Now put on a pair of gloves and try again.

Were you as successful in finding what you needed without using a secondary sense of vision? It’s unlikely!

You may not realize it, but every day you use a combination of discrimination senses to help you navigate your world - in this case, you just used your proprioceptive and tactile discrimination senses to help you find what you needed without your eyes!

Sensory Discrimination Disorder can happen in any of the eight sensory systems. Here are some characteristics or common observations with SDD:

Difficulty interpreting or giving meaning to the specific qualities of sensation. Trouble detecting similarities and differences among sensory stimuli. Difficulties in daily routines and activities. Difficulties with motor planning. May be awkward with gross and fine motor skills. May appear inattentive to people and objects in their environments.

3) Sensory-Based Motor Disorder (SBMD)

Sensory-Based Motor Disorders are manifested by difficulties with balance, motor coordination, and motor tasks. There are two subtypes of SBMD: postural disorder and dyspraxia.

SBMD Postural Disorder

Low muscle tone, decreased balance, decreased motor control; bilateral movements, ocular motor control, oral motor. Child’s decreased muscle strength affects postural control (sitting, standing with balance) in order to do higher-level skills with control.

SBMD Dyspraxia/Motor Planning

Child appears clumsy or awkward. Child knows the purpose of the task but cannot organize motor actions to solve the motor problem - planning, sequencing, problem-solving. Prefers familiar activities (novel activities require too much motor planning). Frustrated easily. Gross motor delays may be more evident than language or fine motor delays.

Takeaways and Tips

There’s a lot to know about the ins and outs of sensory processing. This guide is not meant to diagnose your child’s sensory processing disorder, it is intended to help you begin an informed conversation with your occupational therapist about some of the sensory behaviors that are causing you to seek professional guidance.

Be sure to reference the STAR Institute Website for more information on sensory processing and check back with Harkla for more information to advise you in Sensory Integration Therapy!

If you found this article useful, you may like our other articles about Sensory Processing Disorder:

• Sensory Processing Disorder and Sleep
• The Ultimate List of Sensory Toys
• Our 10 Favorite Sensory Seeking Activites