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Skip Navigation Links > Competency 2: Identification of FASD and Diagnosis of FAS > 5c. Central Nervous System Defects

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Competency 2: Identification of FASD and Diagnosis of FAS

FAS Diagnostic Criteria, Continued

Diagnostic References: Central Nervous System Defects

The brain and spinal cord make up the CNS. The CNS can be damaged at any time during pregnancy. It is one of the first systems to form after conception and continues developing after birth. Prenatal exposure to alcohol can result in an array of structural, functional, neurological problems, or a combination of these, as well as abnormalities of the CNS.1

The CNS may be affected in many complex ways. CNS damage can cause learning and behavior problems. For example, children with an FASD may have acute sensitivity to sound, light, touch, and temperature; irritability; attention problems; and jitteriness.4,5 Neurotransmitters are chemical messengers that allow communication to occur among nerve cells in the brain. This occurs thousands of times a day and is responsible for brain function. Prenatal exposure to alcohol significantly disrupts many neurotransmitter systems.

For example, prenatal alcohol exposure may contribute to reduced serotonin levels.6 Serotonin plays a role in regulating mood, aggression, sexual activity, sleep, and sensitivity to pain. Fetal alcohol exposure has also been linked to attention and hyperactivity problems caused by dopamine abnormalities.7 Dopamine regulates motor function, pleasure and reward, and attention.

Studies of prenatal alcohol exposure have consistently found impaired motor control. Motor control is a complex function influenced by the CNS. It also involves the peripheral nervous system, which provides sensory feedback to the CNS. The vestibular system plays a role as well. It is located in the inner ear and is involved in a person's sense of balance. Defects in any of these systems can affect motor control.6

To meet the FAS diagnostic criteria for CNS abnormality, structural, neurological, or functional deficits, or a combination thereof, must be documented. It is also possible for an individual to present with more than one CNS structural, neurological, functional deficit or abnormality. Examples of these CNS abnormalities follow:2

  • Structural. Documented small or diminished overall head circumference (at or below the 10th percentile) adjusted for age and gender; clinically significant brain abnormalities observable through imaging techniques (e.g., reduction in size or change in shape of the corpus callosum, cerebellum, or basal ganglia).
  • Neurological. Documented evidence of neurological damage to the CNS, such as seizures or other soft neurological signs outside normal limits (e.g., coordination problems, visual motor difficulties, difficulty with motor control).
  • Functional. Assessment findings that indicate deficits, problems, or abnormalities in functional skills of the CNS. Problems may include decreased IQ or significant developmental delay in children too young for an IQ assessment or deficits in at least three functional domains. Several specific domains need to be assessed. Domains most often cited as areas of concern for individuals with FAS include:
    • Cognitive deficits, such as slow information processing and visual-spatial deficits
    • Executive functioning deficits, such as poor organization, lack of inhibition, and difficulty grasping cause and effect
    • Motor functioning delays or deficits, such as delayed walking, difficulty with writing or drawing, clumsiness, and balance problems
    • Attention and hyperactivity problems
    • Social skills problems, such as lack of stranger fear, gullibility, and inappropriate choice of friends
    • Sensory problems, pragmatic language problems, memory deficits, and difficulty responding appropriately to common parenting practices (e.g., not understanding cause-and-effect discipline)

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