Medicine:Sensory Integration Dysfunction

Sensory integration dysfunction refers to difficulties in emotional and behavioral regulation, attention, perceptual-motor functions, and learning related to atypical processing and integration of sensory information, particularly from the proximal senses (vestibular, proprioceptive and tactile systems). Sensory integrative disorder is not recognized as a standalone medical diagnosis in DSM or ICD classifications. The DSM-5, however, lists sensory hypo- and hyperreactivity among the criteria of autism spectrum disorder (ASD). It was coined by the occupational therapist and psychologist Dr Anna Jean Ayres based on her research with children with learning disorders. Therapies claiming to treat sensory integration disfunction are considered "ineffective," the theoretical underpinnings and assessment practices of sensory integration therapy are "unvalidated," exist "outside the bounds of established evidence-based practice," and are "quite possibly a misuse of limited resources."

Terminology

An alternative term used for sensory integration dysfunction is "sensory processing disorder" (SPD). The proposal to replace the term "sensory integration dysfunction" with SPD has not been uniquely accepted. One of the reasons may be that the importance of integrating sensory information has been highlighted by recent research - particularly in the context of autism. The importance of the integration of sensory input is further validated by a branch of research in the neurosciences, multisensory integration (MSI), that examines sensory integration on a cellular level (e.g. Stein, Meredith, Wallace). Thus, many authors, scholars, and practitioners use both terms – sensory integrative dysfunction and sensory processing disorder – interchangeably.

Types of sensory integration dysfunction

Current understanding of sensory integrative dysfunction has evolved from over 50 years of research tradition. Circa 1960, Ayres started examining the contribution of the body senses to learning disorders. She carefully analyzed patterns of sensory integrative dysfunction. Between 1967 and 1989, she conducted numerous factor and cluster analytic studies (Ayres, 1965, 1966a, 1966b, 1969, 1972b, 1977, 1989). Based on Ayres' original empirical findings and recent replications of her findings[23], the current types of sensory integrative dysfunction are:

1. Vestibular-proprioceptive bilateral integration and sequencing disorder

2. Tactile and visual discrimination disorder

3. Tactile defensiveness and attention deficit

4. Visuo- and somatodyspraxia.

Other researchers who developed their own tools for evaluation of sensory functions such as Dr Winnie Dunn (Sensory Profile; Dunn 1999 respectively the Sensory Profile 2, Dunn, 2014), categorize sensory dysfunctions in different ways based on their data. Dunn describes four types of responders to sensory input: sensory seeker, sensory avoider, sensor, and sensory bystander. It must be noted, however, that the Sensory Profile is a parent questionnaire and as such an indirect and "noisy" measure of function compared to a direct psychometric measure of function.

Miller et al. proposed a novel categorization (nosology) of sensory integrative dysfunction, differentiating three types of SPD: sensory modulation disorder, sensory discrimination disorder, and sensory-based motor disorder. The proposed nosology has not been generally accepted and is criticized for not being derived from empirical research.

The common grounds of these differing views and models are the understanding that underlying atypical processing and integration of sensory information contribute to atypical visible behavior and problems in occupational performance and participation.

Identification of sensory integrative dysfunctions

The identification of sensory integrative dysfunctions is usually done by occupational therapists with a specialized postgraduate training in sensory integration. The starting point of the evaluation process are the client's problems in daily occupations. Analysis of the activities that are difficult for the client from a sensory integrative perspective leads the therapist to formulate initial hypotheses about the potential contribution of sensory integration deficits. The gold standard of the evaluation is a combination of direct and indirect assessments that yields qualitative and quantitative data of the client's reactivity and sensory integrative functions.

The key instrument for the assessment of sensory integration dysfunction is the Sensory Integration and Praxis Tests (SIPT; Ayres 1989), a norm-referenced standardized test battery for children 4;0 to 9;0 years of age. This test provides information of the client's performance on tactile, kinesthetic, and visual perception, vestibular processing and integration, some measures of sensorimotor coordination (e.g., visuo-motor coordination, bilateral integration and sequencing), and diverse aspects of praxis (e.g., imitation of body positions, movement sequences, 2 and 3-dimensional construction, translating verbal commands into action). This information is completed by a series of clinical observations of sensory integration that Ayres adapted from adult neurology exams. These observations were edited and semi-standardized by Blanche. They include assessments of neurological soft signs such as diadochokinesis or Schilder's arm extension test. Attempts have been undertaken to standardize and quantify these observations (e.g., Clinical Observations of Motor and Postural Skills (COMPS). Additionally, questionnaires such as the Sensory Processing Measure or the Sensory Profile 2 provide information on how the client responds to sensory stimulation in natural environments. These standardized and norm-referenced questionnaires are completed by parents or the client themselves (if they are an adolescent or adult).

There are some guidelines for the interpretation of results of such an evaluation:

1. Sensory integration dysfunction is considered after exclusion of more severe organic causes for the observed problems, such as neuromotor problems based on (minimal) brain damage or primary sensory loss because of dysfunctions of the sensory receptor. These possible causes as well as disorders of the peripheral nervous system have to be excluded by a physician before sensory integrative dysfunction can be considered.

2. Only clusters of observations are interpreted. A trained therapist will not call a single behavior that is typical of SI dysfunction a sensory integration disorder.

3. The evaluator has to consider alternative explanations.

4. The evaluator has to build a stringent and conclusive argument how atypical sensory processing and integration contribute to the problems in occupational performance and participation.