Imagine being spun around on a merry-go-round or being in the middle of a frantic ride on the Tilt-a-Whirl. How long before you get dizzy? Thirty seconds? Five minutes? When an occupational therapist wanted to see how long it would take Nancy Hemenway's daughter to become dizzy, it took an hour and a half. In fact, Hemenway says, her daughter would hold her head in such a way to enhance the sensation of being spun.

Hemenway of Arlington, Va., knew her daughter had a number of serious emotional and physical problems when she was adopted in China. She has an aversion to water and for a long time refused to drink. She is orally evasive and won't put a spoon in her mouth or have her teeth brushed. "My first thought was 'do kids this young have sensory processing disorder?'" says Hemenway, whose professional background is in mental health. After doing some research, she discovered that yes, very young children can have sensory processing disorder (SPD).

What Is SPD?

Sensory processing is the ability to recognize and interpret all five senses in a meaningful way. Although everyone has some discomfort with some sort of sensory processing (fingernails on a chalkboard, accidentally biting down on a piece of aluminum foil, the tightness around the neck from a turtleneck sweater), most of us are able to process various tastes, smells and noises naturally.

SPD is a disorder of the brain that misinterprets ordinary sensory information. It also can affect body movement. SPD can be evident during infancy, but it can also occur after an illness or an injury. The inability to properly interpret sensory information can create emotional, mental and physical distress. Between five and 10 percent of children have SPD, but it can be difficult to diagnose, because it is very similar to other disorders.

"Many children can't process the world around them," says Victoria Nackley, assistant professor of occupational therapy at Utica College. "For the child with SPD, the floor isn't flat."

According to Christine Achenbach, fieldwork coordinator for Elizabethtown College Occupational Therapy Department, there are four types of SPD:

• Sensory Modulation Disorders This is when the nervous system cannot monitor or regulate itself. This is often seen in children with autism, and is one reason why children with SPD are assumed to be autistic. (Please note many children with autism are diagnosed with SPD, but one diagnosis does not automatically mean the child has the other.)
• Sensory Perception and Discrimination Here, the brain's ability to interpret sensory information is short-circuited. These are children who are often diagnosed with learning disabilities.
• Vestibular Disorders This affects balance, movement and gravity. Children with vestibular disorders often have trouble with equilibrium, muscle tone and distinguishing between left and right.
• Dyspraxia This is also known as "clumsy child syndrome." Children struggle with coordination and poor motor skills. They are unable to conceptualize, plan and execute many motor skills. Older children have poor handwriting skills.

These types show themselves in different ways. Some children are sensory cravers or seekers and need a lot of stimulation. These are the children who will touch a hot stove even after they are warned it is hot, because they have a high threshold of pain. Or they are children who will climb too high in trees or turn the television on at the highest levels.

Children who are sensory avoiders are the opposite. They are extremely sensitive to noise, fear taking any type of risk and cry out in pain with the slightest touch. Children who are sensory avoiders can be difficult to groom because brushing the hair or being cleaned with a washcloth is painful and traumatic.

Signs and Symptoms

Because SPD shows itself in so many ways, each child will show symptoms unique to him or her. However, there are some behaviors that should raise red flags for parents, Nackley says. "Symptoms can surface as early as infancy," she says. "Babies who don't like to cuddle, don't want a bottle, aren't calmed by typical means or are unable to console themselves may have SPD."

As children get older, what are symptoms of SPD may be mistaken for bad behavior, like a child who acts out because the bright fluorescent lights at the grocery store are too bright and cause pain, or the child who plays too rough and hurts other children.