Turner syndrome (TS) is associated with a characteristic neurocognitive
profile which includes average to low full scale intelligence quotient (FSIQ)
with a significant discrepancy between verbal IQ (VIQ) and performance IQ
(PIQ) [1].They have average verbal skills but weaker non verbal skills
like visuospatial, perceptual, processing speed and executive functioning
leading to problems in academics, especially mathematics [2]. Mental
retardation associated with a ring chromosome karyotype is rare (2-4%).
We assessed an adolescent girl with Turner syndrome in
our learning disability clinic, referred for difficulties in
comprehension, written expression and mathematics. Her scores on Wechsler
Intelligence Scale for Children were VIQ-103, PIQ-99 with a Full Scale
IQ-101 i.e normal intelligence capacity (90-109). The verbal
subtests implicated she had average abilities in verbal reasoning, a good
working memory but possible deficits in abstract thinking. She had a good
number sense but struggled with numerical sequencing and reasoning. Her
performance subtests implied she was poor in areas of spatial
visualization, visual perception and visuomotor coordination. In tests of
Visuo Motor Integration, she was below average for speed and dexterity and
tests of Visual Perception confirmed her poor visual working memory.
On the Woodcock Johnson–Revised Psychoeducational
Battery, her scaled scores of broad reading, broad mathematics and broad
written language were below average causing a significant potential -
achievement discrepancy, the essential criteria for diagnosis of specific
learning disabilities in areas of reading, writing and mathematics. In
mathematics, there was difficulty with reasoning and applied problems
skills. There was a slowed response on all timed tests i.e. reading,
writing and mathematics fluency suggesting processing speed deficits. In
lieu of above findings a diagnosis of generalized learning disability (LD)
in areas of reading, writing and mathematics with Turner syndrome was
made.
The etiology of impaired cognition in TS is
multifactorial. Imaging studies have shown that the parietooccipital
cortex involved in visual-spatial processing is smaller in Turner
syndrome. Estrogen deficiency influences memory, processing speed and
motor skills which improves on supplementation but deficits in visual
perceptual and spatial skills persist lifelong. Genetic studies have
mapped the visuospatial deficits to the PAR 1 of Xp22.3 [3].
Research on neurocognitive profile has lead to specific
instructional recommendations for school aged girls to improve
visuospatial, organizational skills to compensate for non verbal learning
disabilities (NVLD). A full psychoeducational evaluation along with
occupational therapy and physiotherapy is recommended. It is imperative to
screen for dyslexia, present in our case; as it may be overlooked since TS
association with NVLD is more known [2,5]. On detection of LD, remediation
remains the cornerstone [5]. Academic provisions give the child an
opportunity to continue in mainstream and be able to perform and compete
with peers in schools.
References
1. Hong D, Kent J, Kesler S. Cognitive profile of
turner syndrome. Developmental Disabil Res Rev. 2009;15:270-8.
2. Mazzocco M. The cognitive phenotype of Turner
syndrome: Specific learning disabilities. Int Congr Ser. 2006;1298:83-92.
3. Tartaglia N, Hansen R, Hagerman R. Advances in
Genetics. In: Odom SL, Horner RH, Snell ME, (eds) Handbook of
Developmental Disabilities, New York: Guilford Publications. 2009; p.
98-128.
4. Murphy M , Mazzocco M. Mathematics learning
disability in girls with Fragile X or Turner syndrome during late
elementary school. J Learn Disabil. 2008;41:29-46.
5. Rovet J. The psychoeducational characteristics of
children with Turner syndrome. J Learn Disabil. 1993;26:333-41.