#96673: Sensory Integration and Processing Problems: Impact on Care

The visual processing system consists of the eyes gathering information from the environment. This sense assists with balance and is useful for activities of daily living, socializing, and sports. A person who has a faulty visual system might have difficulty following directions involving visual discrimination (e.g., distinguishing one medication from another), interpreting body language (leading to decreased social skills), or following written directions for a home plan. Bright lights and bright colors can be agitating to patients with visual issues, and moving about in an unfamiliar office may cause anxiety.

The olfactory system is one of the first sensory systems to develop in utero [9]. Many patients with sensory processing disorder have issues with the olfactory system. This can affect eating behaviors, as food often has an offensive smell to them. It can also affect patients socially because they may avoid going anywhere with an offensive or intense smell or interacting with individuals with a strong smell (e.g., cologne, perfume). Most clinics, dental facilities, and hospitals have smells that can be a problem for patients with olfactory processing problems.

The gustatory sense provides information about the taste of foods and liquids. A disrupted gustatory system may cause severe feeding issues. Many patients with sensory processing dysfunction are "picky" eaters for a number of reasons, one of which might be a gustatory system disruption. When gustatory issues are worked on, feeding issues often improve.

The auditory system processes and interprets information that is heard. This includes the skill of auditory discrimination—trying to determine if the sound is closer to the right or left ear, loud or soft, and the quality of the sound. In addition, one part of the cochlea is associated with the vestibular system [9]. A patient with auditory dysfunction might not have impaired hearing, but the quality of the sound could be such that the speaker sounds as if he or she is mumbling or speaking nonsense sounds. This can lead to difficulty understanding instructions or requests.

Hyperacusis occurs when a patient's auditory system is too sensitive, causing pain when a louder noise is noted (e.g., a fire truck goes by on the street). In the clinic, louder medical instruments may bother a person with a sensitive auditory system. It can be helpful to discuss the device before it is used and/or to provide a quieter area or noise-canceling headphones to address these issues during health care.

A significant problem associated with auditory discrimination is difficulty following verbal directions. This occurs due to confusion over similar-sounding words (e.g., book and look). The patient might also have a difficult time focusing when background noises are present or become overstimulated when there is too much background noise [10]. This difficulty with communication can lead to frustration for both the clinician and the patient.

Disruptions in the tactile system are common in people with sensory processing challenges. The tactile system uses information gathered from the largest sensory organ—the skin—to establish a perception of one's environment. The skin is a constant source of information, and it helps determine the quality of objects in the external environment [3]. The skin receives information about pressure, texture, temperature, and pain. There are two subsystems of the tactile system: the protective system and the discriminatory system.

According to the American Occupational Therapy Association, Qigong sensory treatment, a massage protocol, is associated with significant to improvements in self-regulatory behaviors, tactile abnormalities, autism symptoms, and parenting stress in children with sensory integration difficulties.

(https://ajot.aota.org/article.aspx?articleid=2666720 Last Accessed: April 18, 2023)

Level of Evidence: Expert Opinion/Consensus Statement

The protective system facilitates a response if a stimulus is perceived as harmful. In patients with sensory processing dysfunction, nonharmful things such as coarse fabric, clothing tags, and sock seams can trigger a protective reaction; this is called tactile defensiveness. Pain can feel unusually intense [3]. In the healthcare setting, this can translate to a patient having difficulty wearing and remaining comfortable in medical gowns, defensiveness with oral work, or anxiety with blood pressure cuffs. When this sensitivity is to items being introduced into the mouth, it is called oral defensiveness.

The second subsystem is the discriminatory system, which helps people determine the quality of the object they are touching. This system helps categorize things as hard or soft or smooth or rough. Dysfunction in this area can cause difficulties with such daily fine motor activities as buttoning a coat and handwriting. These persons might avoid certain textures of food, clothing, and surfaces [10]. Poor tactile discrimination is often a focus for sensory therapy.

Difficulty with social situations can also arise with tactile issues. People with tactile defensiveness may be too sensitive or not sensitive enough to touch. This can translate to shying away from a gentle touch or hug or not knowing when a push is too hard. In the healthcare setting, these patients may appear uncomfortable or shy away from the touch involved in a routine exam. This might offend or confuse some clinicians if they are not aware of the patient's sensory issues. Patients who are under-responsive to touch may not be aware that the clinician is palpating for pain, which can result in skewed results due to lack of patient report.

The vestibular system senses the position of the head in space (i.e., spatial orientation), including direction and speed of head movement. This system involves the structures of the inner ear in conjunction with vision and the auditory system. Difficulty in the vestibular system results in low muscle tone, poor balance, poor coordination, and improper reactions to movements [3,10]. There is an anatomical association between the vestibular and auditory systems, and it is often found that a specific type of vestibular stimulation combined with auditory input results in an improved ability to communicate [9].

The vestibular system can be disrupted in several ways [9]. Gravitational insecurity causes a person to become very uncomfortable with changes in movement. They can become fearful of movements like climbing, jumping, leaning back, riding in a car, and falling. Over-responsiveness to movement can result in nausea and dizziness during or after movement. Disruption of the vestibular system can cause discriminative issues due to an inability to orient one's position in space. On the other end of the spectrum is an under-responsive system. This becomes apparent when a person is unaware of movements (e.g., rocking). Disturbances can also manifest as a need for more than the usual amount of movement. These patients may excessively run, fidget, spin, and continually re-adjust in order to satisfy their system. Vestibular issues are often very apparent in children with sensory processing dysfunction because much of play relies on an intact vestibular system [9].

The proprioceptive system is a very large system that orients an individual to the position of his or her body parts by detecting changes in the length of muscles and the position of joints. Most proprioception is done without conscious awareness. Difficulty in this area can cause problems in many daily activities, such as handwriting, fine motor and gross motor activities, and sports. Poor body awareness can result in clumsiness, difficulties with posture, and using too much or too little pressure for a task [10]. It may also result in sensory-seeking behaviors, such as crashing or excessive roughness [10].

Neural systems around the internal organs form the interoceptive system. These nerves detect and transmit information about internal regulation responses, such as thirst, waste elimination, and fullness. In a very young child, difficulty with interoception can lead to delayed toilet training success. Issues with interoception may result in a person reporting headache, stomachache, or other pain in confusion with other sensations, which could result in confused diagnosis [9].

As discussed, the sensory system relies on a continuous feedback loop of information from various senses to regulate and process sensory information in order to function. All individuals have different levels of sensory organization and tolerance [10].

After the senses receive information from the environment, this information must be processed in order for the body to react appropriately. This is the stage at which problems arise for patients with sensory processing issues. Often, the messages received by receptors in the sensing areas are misinterpreted by the brain. This misinterpretation results in the wrong messages being relayed/interpreted, and everyday routines and activities can become challenging. Some messages that are usually ignored by the brain (e.g., a shirt tag resting on the skin) suddenly become "high alert" messages of pain and discomfort that cannot be ignored. The patient's system must interpret messages from the senses based on this overload/deficit of information. Information from all of the senses is combined, which is difficult. An automatic response is then made based on missing or incomplete information, and impulses are sent to muscles and limbs to carry out the response. Functioning proprioception is required to know what the limbs are doing even before the new order to respond is put out by the system. If a patient's senses perceive misinformation, he or she must interpret and respond to that misinformation and then rely on body parts that are not responding correctly to carry out a response in the best way possible [11]. Because those with sensory processing dysfunction gather and process information differently than people with intact sensory systems, clinician-patient communication can be difficult [11].

Patients with sensory processing issues often experience disruption of many senses, though not all disruptions manifest in the same way. There may be two systems that are over-responsive and two systems that are under-responsive. A common combination is an over-responsivity to touch and sound (e.g., difficulty having ears checked, sensitive to the noise of dental equipment) but a craving for movement and proprioception (e.g., uses too much force when brushing teeth) [9]. The patient can easily feel off balance if put in new positions (e.g., tilted dental chairs), be clumsy with new movements (e.g., learning to use an inhaler), and be unable to distinguish normal body reactions from illness (e.g., stomach pain from worry).

SMD is characterized by a difficulty regulating sensory stimuli. Patients may be over-responsive, meaning they have the tendency to respond too much, too soon, or for too long to sensory stimuli most people find tolerable [14]. They often have a "fight-or-flight" response to sensation (e.g., being touched unexpectedly), which is sometimes called "sensory defensiveness" [14]. These patients are bothered by usually tolerable stimuli (e.g., the seams in a shirt).

Sensory under-responsiveness involves a delay or muted response to environmental cues. Patients may appear withdrawn, difficult to engage, or slow to process/respond because they do not detect the sensory input in their environment. These patients seem to require more stimuli to feel their environment [14]. This can also manifest as an unawareness of internal cues, such as fatigue or illness. Sensory-craving patients crave and constantly seek sensory stimulation, and the stimuli may not register correctly when it does occur. These patients may appear hyperactive (e.g., continuously jumping while waiting for an appointment) or may talk very loudly to create auditory stimulation.

A 2017 study explored subtypes of sensory processing disorder using data from the Sensory Processing 3-Dimension Inventory of 252 children. Three distinct cluster groups emerged [30]:

The authors recommend SP-3D as a tool for better identification of sensory dysfunction that can lead to more precise intervention [30].

Patients with SDD have difficulty interpreting subtle qualities of objects, places, people, or the environment. For example: Do I see a "P" or a "Q"? Do I hear "cat" or "cap"? Do I feel a quarter or a dime in my pocket? This can affect any of the senses alone or in combination (i.e., auditory DD, visual DD, gustatory DD, olfactory DD, tactile DD, vestibular DD, proprioceptive DD, or interoceptive DD), making SDD the most difficult category to identify [13,14]. For the patient with SDD, interpreting ordinary demands and responding appropriately may require enormous effort and extra time [15].

Individuals with SBMD can regulate sensory input but have difficulty with balance, motor coordination, and the performance of skilled, not-habitual, and/or habitual motor tasks. SBMD is sometimes co-exhibited with SMD [16]. There are two subtypes of SBMD: postural disorder and dyspraxia [14,16].

With postural disorder, patients have difficulty maintaining the optimal posture. Posture is important because it is the base from which all of our upper and lower limbs anchor their movements away from the body. Poor or weak postural muscles result in difficulty with scapular stabilization, which leads to difficulty with such milestones as handwriting and strength movements involving the legs. A weak core can have many implications for individuals with SBMD as they age.

The tactile and proprioceptive sensory systems are most affected by postural disorder. The patient may move slowly and cautiously, if at all; sedentary activities may be preferred. Moving on uneven (bumpy) surfaces is challenging and maintaining stability while performing simple actions, such as stepping on or off a curb, requires an enormous amount of effort. This decreased stability and poor muscle control causes the patient to compensate by increasing his or her "base of support" (e.g., standing with legs shoulder width apart). The patient with postural disorder fatigues quickly and may lean against furniture or slouch frequently. Being bumped by another person may trigger a "fight, flight, or freeze" reaction if the patient is forced to move; more often, however, the individual chooses not to move. Patients with postural disorder often feel unstable, insecure, and unsafe, and they often exhibit poor self-esteem and self-confidence [17].

Dyspraxia involves difficulty thinking of or generating new ideas, planning, and/or executing skilled movements, especially novel movement patterns [16]. These individuals are often seen as clumsy and awkward, as they have problems with gross and fine motor activities (e.g., climbing, playing ball games, handwriting, tying shoes, timing movements, dressing) [16]. They may prefer sedentary activities or try to hide their motor planning problem with verbalization or with fantasy play [14]. Early physical and occupational therapy can help immensely.

Although the cause of sensory processing dysfunction has not been identified, studies have shown that children with sensory processing issues have different neurophysiologic responses to sensory stimuli compared to typically developing controls [18,19,20]. For example, children with sensory processing challenges demonstrate less sensory gating (filtering out redundant, unnecessary stimuli) and more within-group variability than controls, and while sensory gating improves with age in typically developing children, the developmental trajectory in children with sensory processing dysfunction is significantly different [21,22]. A 2013 study found that boys with sensory processing issues have decreased white matter connectivity, particularly in the parietal regions of the brain, that distinguishes them from typically developing boys [1,2]. This established a biologic cause for sensory integration difficulties.

A later study, the largest imaging study of sensory processing dysfunction, compared typically developing boys and girls with those with sensory processing issues [31]. Researchers found abnormal white matter tracts in the connections between auditory, visual, and tactile systems and abnormal connections between the left and right hemispheres in children with sensory processing dysfunction. It is believed these abnormalities most likely affect the timing of sensory transmission across multiple senses input, thus leading to difficulty, if not failure, in processing. In addition, less white matter was found in the back of the brain, the primary area for transmission of sensory motor information. This research supports the theory that SPD is a spectrum disorder and, with advanced imaging techniques, direct measurements may be used to diagnose the disorder and individualize treatment [31].

Children with sensory processing dysfunction also have different physiologic (electrodermal) responses to sensory stimuli compared to controls and children with autism spectrum disorders, suggesting that SPD and autism should be distinct diagnoses [23].

Several risk factors for sensory processing dysfunction have been suggested and are being investigated, including [24,25,26,27,28]: