Defining Sensory Processing Disorders: What exactly are they?
This article is co-authored by Ms Esther Yap, a speech-language therapist of 20 years’ experience based in Kuala Lumpur, Malaysia, and Dr Noel K.H. Chia, a board certified educational therapist of also 20 years’ experience based in Singapore.
The term sensory processing disorders is a syndrome of composite neural transmission inconsistency and/or poor integration of sensory information resulting in neurological disorganisation affecting afferent and efferent neural processes resulting in one or more of three primary subtype categories: (1) sensory responsivity disorders (also known as sensory modulation disorders), which can be further divided into sensory hyper-responsivity disorder, sensory hypo-responsivity disorder, and sensory indulgence disorder; (2) sensory discrimination disorder; and (3) sensory-motor disorders, which can be further divided into postural-motor disorder and developmental motor coordination disorder, also known as dyspraxia.
Sensory responsivity disorder (SRD) concerns about the response of the nervous system to the external stimuli in terms of too much (hyper-responsivity) or too little (hypo-responsivity) reaction relative to the external stimuli. Hence, the first two secondary subtypes are sensory hyper-responsivity disorder and sensory hypo-responsivity disorder, respectively. A third secondary subtype is the sensory indulgence disorder in which the person continuously seeks and craves for an unusually or intensively high level of stimulation in obtain more sensory input to satisfy his/her sensory indulgence.
Sensory dsicrimination disorder (SDD) concerns the disability to distinguish one specific input from another and such a person often encounters the challenge of distinguishing and categorising various attributes about the physical environment (Delaney, 2008).
Sensory-motor disorders (SMD) concerns disability in processing and/or integrating movement and somatic information resulting in somatosensory-motor interference. According to Delaney (2008), there are two secondary subtypes of SMD: (1) postural-motor disorder; and (2) developmental motor coordination disorder or dyspraxia. The former subtype refers to an individual’s difficulty in maintaining appropriate somatic postures for any given motoric activity and/or sedentary activity. The individual would display poor or low muscle tone and feel fatigued easily. The latter concerns breakdown in any of the three main steps in praxis (i.e., the complex procedure of steps the brain and the body collaborate to see that some expected task is done properly and correctly): ideation, i.e., knowing what to do and how to go about doing it; perceptuo-motor planning, i.e., determining how to perform a task through constant revision and accommodation of new information; and execution, i.e., to act on the idea and the perceptuo-motor planning that the brain has processed.
Chia (2009) argued that sensory processing disorders also play an important part in causing the following related deficits: (1) deficits in auditory processing which can be either aural or otic (to hear) processing, e.g., dysphonesia, or oral (to talk) processing, e.g., dysphonia; (2) deficits in visual or opto- (to see) processing, e.g., dyseidesia; (3) deficits in gustatory processing (to taste), i.e., dysgeusia; (4) deficits in olfactory (to smell) processing, i.e., dysosmia; (5) deficits in haptic (to touch) processing, i.e., dysesthesia; and (6) deficits in taxic or kinetic (to move) processing, e.g., dystaxia and dysnemkinesia. These six subtypes of sensory processing deficits are closely associated with the sensory-motor disorders.
How to help children with sensory processing disorders? It is best to seek professional help as soon as the parents realize that their children display symptoms typical of the SPDs. Professionals such as occupational therapists, speech-language therapists, educational therapists and special needs therapists trained to deal with sensory processing issues will be best people to approach for help and advice. Accurate diagnosis and identification of the sensory processing challenges and implementation of an early intervention programme play an essential part to ensure better prognosis for such children.
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