Sensory Processing Disorder (SPD)

What is sensory processing disorder (SPD)?

Sensory processing disorder is a neurological condition which affects how the brain interprets sensory information. It can affect the 8 senses, which each have their own unique functions. Through sensory integration, the information our brain receives from each sense helps create a picture of our environment and how to appropriately react. Someone with SPD experiences sensory input much differently than other people, which shapes how they interact with the world.

Indicators of SPD include inappropriate or problematic motor, behavioural, attentional, or adaptive responses following or anticipating sensory stimulation. There are three subtypes of sensory processing disorder and people can experience multiple types of them at once.

Sensory motor-based disorder

Sensory motor-based disorder (SMBD) refers to an impairment in the vestibular (controls balance), tactile and/or proprioceptive (awareness of orientation of your body) system. Someone with SMBD either has trouble with interpreting or understanding sensory messages or has an inability to move their body in the way they want. These refer to the two subtypes of SMBD: dyspraxia and postural disorder.

 


 

People with dyspraxia have trouble processing environmental stimuli and responding with a motor action. They struggle with three aspects of motor action:

  • Ideation – the ability to conceive or imagine a task
  • Sequencing – the ability to plan the steps in that task
  • Motor execution – the ability to carry out the task in sequence

For example, when we go to make a cup of tea, it may come ‘naturally’ to us, and automaticity may be at play. This refers to the ability to complete a task without much thought being put into it; the subcortical mechanisms (lower brain) have taken over. Someone with SMBD, however,  may struggle, as there can be up to 20 steps in making a cup of tea, from filling the kettle with water to boil to taking the tea bag out of the packet.

Symptoms of dyspraxia may include:

  • Difficulty putting on clothes in the right order (e.g. putting on shoes then socks) and orientation (e.g. shirt back to front, shoes on wrong feet)
  • Ineligible handwriting
  • Struggles to walk up or down stairs
  • Struggles to navigate a new environment
  • Struggles to follow a series of actions after given verbal command
  • Preference for routine as they can know what to expect and be prepared

 


 

Meanwhile, postural disorder affects one’s ability to move and operate their muscles successfully or in the way they want. People with postural disorder often prefer sedentary activity as their body fatigues quickly.

Symptoms of postural disorder may include:

  • Can appear lazy as they tire out easily (e.g. leans on furniture, slumping over with poor posture and resting head and arms on table when sitting)
  • Struggles to control both sides of body at same time (e.g. catching a ball, ride a bike)
  • Struggles to maintain balance
  • Difficulty focusing eyes
  • Dislikes and avoids sports
  • Clumsy

Sensory modulation disorder

Sensory modulation disorder (SMD) refers to the impairment in detecting, modulating, interpreting, or responding to sensory stimuli. This means someone with SMD would have trouble reacting appropriately due to their perceived intensity of the sensory input. There are three subtypes of SMD: sensory over-responsivity, sensory under-responsivity, and sensory seeking.


 

Someone who is overresponsive is hypersensitive to different sensations, like sound, touch and movement. Often, they react much quicker, more intensely and for longer to sensory input than someone with a typical responsivity.

Examples of sensory over-responsivity include:

  • Avoids group activities, disengages from social activity
  • Aggressive or impulsive when overwhelmed by sensory stimuli
  • Cautious of trying new things
  • Adverse to change

 

Someone who is under-responsive to sensory stimuli is less sensitive and aware of sensory stimuli. They often appear passive and withdrawn.

Examples of sensory under-responsivity include:

  • High pain threshold, so will not notice if they’ve been cut, scratched or hurt
  • Unaware that they need to go to the bathroom
  • Apathetic and slow to respond
  • Difficult to engage in social situations
  • Prefers sedentary activity

 

Someone who is sensory craving actively seeks out sensory sensations, often in ways that may be considered socially unacceptable.

Examples of sensory craving behaviour include:

  • Purposely running, jumping and crashing into walls or people
  • Intrusive, often touching objects and other people excessively
  • Dominant in conversation, often unable to take turns
  • Risk taker
  • Loud
  • Appears to be unable to sit still, frequently moving

Sensory discrimination disorder (SDD)

A person with sensory discrimination disorder has trouble distinguishing the characteristics of sensory stimuli, such as objects, people, places or environments, and disregarding irrelevant sensory information. As such, they do not accurately understand what they are perceiving. This can affect one of the 8 senses.

 

Examples of symptoms of sensory discrimination disorder:

  • Touch: Inability to distinguish between different textures through touch so would need to see it in order to distinguish the difference
  • Touch: Burning tongue due to inability to determine temperature of food
  • Hearing: Appears to ignore others and difficulty following instructions
  • Vestibular: Can recognise they are falling over, but does not know in what direction their body is falling, putting them at risk of hurting themselves
  • Proprioception: Plays roughly due to inability to recognise the force output of muscles when interacting with objects
  • Interoceptive: Inability to recognise when one is hungry, thirsty or needs to go to the bathroom
  • Sight: Difficulty distinguishing letters that look like one another (e.g. p and q)

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