How is a diagnosis of Soto syndrome made?
At the current time there are no specialized laboratory tests that can be conducted to definitively diagnose Sotos syndrome, although the bone age of children with Sotos syndrome is generally advanced in the early years. Bone age can be determined with an x-ray of the child’s wrist. The diagnosis is typically made through the observation of a number of physical characteristics including bone age, facial features, muscle tone and developmental delays.
Below is a description of the diagnostic criteria typically used to diagnose Sotos syndrome summarized from a list compiled by Angela E. Lin, MD, G. Bradley Schaefer, MD, Rebecca Anderson, MS, JD, and Trevor Cole, MD.
Sotos Diagnostic Criteria:
- Growth: Increased length at birth. Increased height, weight, head circumference in childhood. Head size remains large, but height and weight tend to normalize. Sotos children do not become "giants".
- Appearance: Characteristic facial features including large head, elongated shape, high forehead, long chin, slightly wide-spaced eyes which tend to slant downward. Sotos kids look more like each other than their siblings.
- Development: Early development delay, especially gross motor due to hypotonia. Behaviour problems common.
- Bone Age: Advanced bone age (as determined by an X-ray).
The "strict criteria" proposed for a diagnosis of Sotos syndrome requires that the individual have at least three of the following:
- Facial appearance: large head, tall narrow skull, wide set down-slanting eyes, flat-bridged nose, high arched palate, early eruption of teeth (often by 3 months of age), thin hair, pointed chin, prominent forehead, and the appearance of a receding hairline.
- Birth length above the 90th percentile
- Bone age above the 90th percentile
- Early verbal and motor delays
Individuals who have some of these characteristics but insufficient to be classified as "typical" Sotos syndrome, are often said to be "Sotos-Like".
MRI scan of the brain:
Though not one of the 4 key criteria, additional evidence can be provided by the brain MRI scan. Children with Sotos syndrome do not have severe brain malformations. However, they usually have extra fluid on the surface of the brain, enlarged ventricles and absence or reduced size of the corpus callosum. The brain itself is normal size. The extra fluid, which fills up the space inside the skull, is not "hydrocephalus, although some people have used that term. These findings are not unique to Sotos syndrome, but they are very common.
MRI diagnosis criteria:
- Excess fluid between the brain and skull\
- Generously sized ventricles - particularly in the "trigone" region
- Small corpus callosum (particularly in the middle third)
- Midline changes (absent corpus callosum, wide / cavum septum pellucidum, mega cisterna magna)
- Small cerebellar vermis (especially lobules 6 & 7)
- Normal sized brain in larger than average skull
What is not present:
As important as what is present, remember these guidelines about what is not:
- Multiple birth defects (aside from the problems which are associated with low tone, e.g. flat feet, pronated feet, scoliosis, and facial structure, e.g. teeth crowding.)
- Metabolism problems
- Severe mental retardation.