WHAT IS INTELLECTUAL DISABILITY

Intellectual disability, until recently referred to as mental retardation, is a condition which originates during the developmental period (conception to age 18 years) and results in significantly below average intelligence and failure of development of adaptive skills (functional life skills). Developmental delay is another term that is often used to descrtibe this condition but its use should be confined to infants and young children less than 5 years old when the diagnosis is uncertain.

 

HOW COMMON IS INTELLECTUAL DISABILITY?

Intellectual disability affects about 3% of the general population. This figure is probably higher in developing countries.

 

WHAT IS INTELLIGENCE?

Intelligence may be broadly defined as the general ability to learn about, learn from, understand and intereact with one’s environment. The environment in this instance refers to one’s immediate surroundings such as home, family, school and workplace. Intelligence involves the specific abilities to reason, to think in abstract terms, to solve problems, to plan ahead and to use language.

 

CATEGORIES AND CAUSES

CATEGORIES OF INTELLECTUAL DISABILITY

  • MILD: IQ 50-70. Achieves up to grade 6 academic & vocational skills
  • MODERATE: IQ 35-50. Achieves grade 2 skills. Can perform unskilled or semi-skilled tasks, but needs supervision
  • SEVERE: IQ 20-35. May say a few words and acquires elementary self-care skills
  • PROFOUND: IQ <20. Acquires little or no self-care skills; requires constant aid

 

HOW DOES INTELLECTUAL DISABILITY USUALLY PRESENT?

  • Delay in achievement of developmental milestones (sitting, walking, speaking, understanding, self-care)
  • Poor progress at primary school (reading, writing, mathematics)
  • Incidental finding in children presenting with other types of brain dysfunction (epilepsy, cerebral palsy, behavioural disorder)

 

SOME NORMAL DEVELOPMENTAL MILESTONES

  • Sitting unsupported at 6 months
  • Walking at 12 months
  • Saying single words at 12-15 months
  • Stringing words together at 21 months
  • Asking who, what & where at 24 months
  • Asking why, how and when at 36 months
  • Describing the day’s experiences and telling stories at age 48 months

 

WHAT ARE THE LIKELY CAUSES OF INTELLECTUAL DISABILITY?

Intellectual disability may result from either abnormal development of the brain or damage to the immature brain.

Abnormal brain development may be due to a genetic defect (genes are the hereditary factors contained in the nucleus of all the cells in our body) or a chromosomal abnormality (chromosomes are the strings in the nucleus that carry the genes). Some of the genetic disorders may be inherited from one or both of our parents while others arise as as spontaneous mutations (alterations), deletions or duplications of genetic material. The commonest chromosomal disorders causing intellectual disability are Down syndrome (Trisomy 21) and Fragile-X syndrome

Damage to the immature brain may be caused by malnutrition, physical injury (accidental; non-accidental/physical abuse), toxins (e.g. lead), lack of oxygen or glucose or hormonal deficiency (e.g. thyroid hormone)

 

BRAIN DISORDERS THAT MAY ACCOMPANY INTELLECTUAL DISABILITY

  • Epilepsy
  • Cerebral palsy
  • Hearing impairment
  • Visual impairment
  • Behavioural disorder

 

HOW DO WE DIAGNOSE INTELLECTUAL DISABILITY?

  1. By taking a thorough clinical history, enquiring about prenatal and birth events, developmental milestones, school achievement; family history, visual and hearing ability, seizures and behaviour

  2. By doing a complete physical examination noting growth measurements, structural abnormalities (dysmorphisms), eye contact, social skills; speech content and behaviour

  3. By carrying out developmental screening using instruments that are completed by parent or caregiver e.g. Parents Evaluation of Developmental Status (PEDS)

  4. By performing laboratory studies that are guided by the history and findings on physical examination. These studies may include genetic and chromosomal analysis and brain imaging (CT; MRI).  Limited availability and cost of these special tests are factors that have to be taken into consideration when deciding to order them

  5. By performing assessment of IQ and adaptive skills using standardized tests

DID YOU KNOW THAT?

85% of children diagnosed as being intellectually disabled fall into the mild category

The majority of children with mild intellectual disability are normal in physical appearance and do not have any other brain disorders

IQ determined below the age of 6 years is a poor predictor of ultimate IQ

A severely disabled child who cries excessively, screams, grimaces, rocks repeatedly, takes up peculiar postures or becomes aggressive, may be experiencing pain

 

HOW IS INTELLECTUAL DISABILITY MANAGED?

The paediatrician or family doctor should:

  • make an early diagnosis so that access to early intervention can be arranged

  • arrange for placement of the child with mild to moderate intellectual disability in a special education or vocational training unit

  • refer for hearing and visual assessment if  problems in these areas are suspect or detected

  • refer to the appropriate specialty or service for management of associated problems such as epilepsy

  • give appropriate advice and treatment for other commonly associated problems such as constipation, feeding difficulty, drooling & gastro-esophageal reflux (regurgitation of stomach contents into the gullet)

  • arrange for day care/respite care of severely retarded children through family help or social services

  • monitor growth and development, provide nutritional advice, keep immunization status up to date and give anticipatory guidance

 

JOIN THE JAMAICA ASSOCIATION ON INTELLECTUAL DISABILITIES TODAY!

Tel: (876)-977-0134 or (876)-977-1118