Individuals grow physically, mentally and emotionally through a number of developmental landmarks.  For example, most children say their first words between 10 and 14 months of age. Most walk between 12 and 18 months of age.

These milestone events are examples of developmental landmarks. A child who does not experience these landmarks at the expected age may have a developmental disability.

A developmental disability is a severe chronic disability which:

• Is caused by mental or physical impairment or a combination of these impairments
• Is evident before a person reaches age 22
• Is likely to continue throughout a person's lifetime
• Results in substantial limitations in three or more of the following areas of life activity: self care, receptive and expressive language, learning, mobility, self-direction, or ability to live with independence and economic self-sufficiency
• Reflects a person's need for services on a lifetime or extended basis.

Until recently, professionals used measures of the intelligence quotient (IQ) test score to define mental retardation. Our agency uses an IQ score of 70 or below as a criterion for eligibility.  However, the American Association on Mental Retardation has revised their definition of mental retardation as a disability characterized by a significantly substantial limitation in intellectual functioning existing concurrently with related limitations in two or more of the following areas:

• Communication;
• Self-care;
• Home living;
• Community use;
• Self-direction;
• Health and safety;
• Functional academics;
• Leisure and/or Work

Mental retardation occurs before age 22 (the use of age 22 is a departure from the AAMR definition, which recognizes age 18). The use of age 22 broadens restrictions on the definition and keeps it in line with other federal regulations which define school age and developmental disabilities. 

The use of adaptive behavior measures prevents people from being diagnosed based on IQ score alone. Some children may have poor IQ scores because their environment is not intellectually stimulating. These children may adapt well to the patterns of life in their community and are not considered below average by their families and peers.

People with autism have difficulty relating to other people and establishing normal personal relationships. They avoid or do not pay attention to people around them and often become upset by changes in their environment. Delayed language development contributes to their difficulty in communicating with others. These symptoms also make learning new behaviors a difficult process.

Autism is usually diagnosed before a child is 3 years old, and the condition may improve somewhat by adulthood. There is no medical test for this disability, so the diagnosis is made by observing a child's behavior.  

A head injury, also called a traumatic brain injury, is caused by an external blow to the head. A "closed head injury" occurs when the skull hits a stationary object and turns on its axis, causing damage. The brain may also rebound against the skull, resulting in further damage. An "open head injury" may result from a gunshot wound, an accident or an object which penetrates the skull and damages the brain. This type of injury is more likely to damage a specific area of the brain.

Impairment depends upon the extent and location of injury. Three major areas of functioning are typically affected. Following is a list of symptoms which may result from head injury:

• Somatic (headache, dizziness, poor coordination, weakness);
• Cognitive (amnesia, confusion);
• Emotional (agitation, depression);
• Psychosocial (fearfulness, impatience); and/or
• Psychological (anxiety, guilt).

Individuals with a head injury realize these difficulties, as well as the emotional trauma of a sudden change in skills, sense of self and other role changes brought about by the injury. Some individuals will retain many skills they possessed prior to injury. Others must regain a number of skills. 

The spinal cord is about 14 inches in length and runs from the neck to the lower back. Spinal cord injury affects sensory, motor and autonomic function.

Key factors which influence the outcome of spinal cord injury are the location and extent of injury. If the cord is completely severed, there will be no sensation or movement below the location of the injury. Approximately half of all injuries are incomplete, leaving some sensation and movement below the site of injury.

Generally, urinary, bowel and sexual functions are impaired to some extent for all spinal cord injuries, because these functions are controlled at the lower level of the spinal cord.

The severity of the injury is a significant factor in determining a person's ability to recover, in addition to individual physical and mental commitment to maximize the amount of ability which remains.