NF1_cognitive_learning

Cognitive & learning problems in NF1

Based upon Hyman, SL., Shores E.A., & North, K.N. (2005).
The Nature and Frequency of Cognitive Deficits in Children with
Neurofibromatosis Type 1. Neurology, 65, 1037-1044.

Mental retardation is present in 6-7% of children with NF1. While this rate
is approximately three times the rate of the general population, it is still
relatively low compared to other genetic disorders affecting the central
nervous system such as Fragile-X and Turners Syndrome. General
intellectual functioning is significantly lower in children with NF1
compared to both the normal population and their siblings. IQ is however
still within the lower end of the average range.

An important and unexpected finding in the study was that males with NF1
were more likely to have significantly weaker verbal than nonverbal skills
compared to females (with nonverbal skills in the average range and
verbal skills in low average range).

Children with NF1 have significantly lower reading, spelling, and
mathematical ability than their siblings. When using an IQ-achievement
discrepancy for defining specific learning disabilities (SLD), SLD was
present in 20% of children with NF1 compared to 8% of controls (2.5
times more common in NF1). One of the most intriguing findings of the
current study is the strong gender effects for SLD: 37% of males had an
SLD compared to only 5% of females. This places males at a much
greater risk for SLD in the NF1 population, and suggests that females are
at no greater risk of SLD than their unaffected siblings. These gender
effects are related to the high frequency of weaker verbal reasoning skills
in males, and it appears that males with these significantly weaker verbal
skills are at higher risk for specific learning disabilities.

Children with NF1 had a shortened attention span, as well as difficulties
with sustained and switching attention when compared to their siblings.
Interestingly they did not differ from their siblings on tasks of selective or
divided attention. Although children with NF1 have a reduced attention
span when compared to their siblings, they were able to mentally
manipulate the information that they could encode within their working
memory at the same level as their siblings. Approximately 63% of NF1
children have problems sustaining their attention.

There is a high comorbidity of NF1 with ADHD, with over 38% of the NF1
children fulfilling the diagnostic criteria for one of the ADHD subtypes.
Compared to their siblings, ADHD was three times more common in the
NF1 children. ADHD had similar frequencies in both NF1 males and
females, unlike the general population in which there appears to be a
predominance of males of approximately 3:1. The majority of NF1
children had the combined subtype (24.7%), which was double the
prevalence of the inattentive subtype (12.3%). Hyperactivity alone was very
rare (only 1/81). Interestingly, one study found that stimulant medication
lead to an improvement in attention, anxiety-depression and social
competence of children with co-morbid NF1 and ADHD.

Of those children with NF1 and SLD, approximately 45% have co-morbid
ADHD. Of those with ADHD, approximately 26% have co-morbid SLD.
Thus, there is a slightly increased risk of developing an SLD if ADHD is
present (26% compared to 20%). NF1 children with an SLD are again
slightly more likely to have ADHD than those without an SLD (45%
compared to 37%). These co-morbidity figures are somewhat lower than
those reported in the general population with some estimates as high as
70%.

Children with NF1 had deficits in both planning and abstract concept
formation when compared to controls. However, they were not
significantly impaired on a task of verbal fluency. The co-morbidity of
ADHD and these executive deficits was examined, and there was no
increase in frequency of executive deficits in those children with
NF1/ADHD.

Visuospatial deficits are one of the most commonly and consistently
reported neuropsychological deficits in NF1. Children with NF1 performed
well below their siblings on a test of visuospatial ability. Performance on a
perceptual task involving matching shapes and mental rotation was also
significantly poorer in NF1 children than their unaffected siblings.

One of the most unusual findings of the present study was that children
with NF1 did not differ from either the normal population or their siblings
on memory tasks. Spared functioning was found for immediate memory,
delayed memory and recognition memory in both the visual and verbal
modalities. Interestingly, memory scores were actually much higher than
IQ scores for the children with NF1.

The study demonstrates broad deficits in both receptive and expressive
language skills in NF1 children. Children with NF1 had greater difficulties
defining words, comprehending simple passages, and describing
pictures. They also had difficulties with higher level verbal reasoning
skills. Although studies have suggested that language deficits are just as
common as visuospatial deficits in children with NF1, this study suggests
that the language deficits are not of the same magnitude. Although
language skills were not spared, they were no more deficient than IQ
would predict, whereas visuospatial deficits were more common, more
severe, and lower than IQ would predict.

Both fine motor skills and motor speed were reduced in NF1 children
when compared to their siblings. Fine motor coordination deficits were
present in approximately 20% of NF1 children. Slowing of motor speed
was found in 30% of NF1 children.