Dyslexia

Article Author:
Kailey Remien
Article Editor:
Raman Marwaha
Updated:
5/22/2020 10:15:57 AM
PubMed Link:
Dyslexia

Introduction

Reading is a skill unique to humans and is crucial for living in the world today.[1] Learning to read is one of the first teaching points of elementary school. Children are many times cast into expected long-term education success tiers based on their ability to learn to read. Dyslexia (developmental dyslexia) is when children have a difficult time learning to decode words. Decoding is the accuracy or fluency one develops when reading aloud.[2] These children struggle with sounding out words and recognizing “sight words.” They have poor reading fluency and a difficult time with spelling.[2] These children typically do not struggle with oral or nonverbal abilities.[1] It is important to note that the reading disability cannot be accounted for by decreased educational opportunities or low intellectual capacity.[3]

Etiology

Dyslexia is hereditary; however, home literacy and the teaching quality strongly impact the child’s reading ability. Twin studies have shown that reading difficulties are highly heritable, and recent genetic studies have found several small genes that affect reading development.[2] These genes affect neuron migration, cortical morphogenesis, the outgrowth of neurites, and the structure and function of cilia.[1]

Epidemiology

Reading ability is very diverse in the population and varies vastly with education level. The diagnosis of dyslexia can be difficult, but a common criterion is a reading accuracy 1.5 standard deviations below the mean. Approximately 7% of the population has dyslexia.[2]

Pathophysiology

The cerebellum is substantially active during the initial stages of the learning process. Structural and functional imaging has found differences in the cerebellum of those with dyslexia. These individuals were found to have reduced grey matter in the right lobule of VI. It was also found that this lobule has abnormal activity in patients with dyslexia when asked to name objects rapidly. It is important to note that the cerebellar disruptions in dyslexia are different than those found in autism spectrum disorder and attention deficit hyperactivity disorder (ADHD), suggesting that specific circuits lead to various symptoms.[3]

Postmortem imaging has showed decreased asymmetry of the left and right sides of the planum temporale, left perisylvian architectonic dysplasias, and neuronal ectopias.[1] Magnetic resonance imaging (MRI) scanning is used for in vivo studies. Functional MRI (fMRI) is currently being used to study the brain areas involved in performing certain tasks. fMRI testing has found that those with dyslexia have altered activations in the left temporoparietal regions and bilaterally in the frontal and occipital regions.[1]

History and Physical

Children with reading difficulties present differently depending on their age. Early intervention is essential to improving their outcome seeing as most children with reading issues still present in the third grade continue to struggle throughout their formal education. Diagnosis is not typically made until formal reading education has been attempted, usually in the first grade.

At-risk preschoolers may present with:[4]

  • Rhyming difficulty
  • Confusing words that sound similar
  • Trouble learning the names of letters

At-risk kindergarten and first graders may present with:

  • Inability to learn letters[5] 
    • Strong predictor for reading ability[6]
  • Unable to read words and difficulty spelling by the end of first grade[5] 

Second grade and beyond may present with:[7]

  • Poor school performance
  • Dislike of school
  • Somatic dysfunctions when heading to school or before work is due

Children with reading disabilities will avoid reading; this will expose them to fewer words and increase their reading deficiency. The physical exam for patients with dyslexia should be standard. The physical is a time to look for signs of other neurological, medical, or genetic causes of their impairment.

Evaluation

Due to the ability to diagnose dyslexia as early as preschool, early intervention is possible. One study found that if there is a familial risk, but the child develops the early ability to letter-name, then the risk of having dyslexia dramatically decreases.[2] Children who have poor letter-naming skills at 4.5 to 5.5 years of age but have good phonological awareness are also at a reduced risk of having dyslexia.[2] Dyslexia is complicated, and the outcome of many factors. Those with language difficulties at the end of preschool are at high risk, and this is when screening is most effective.[2]

These children should first be screened for hearing and vision impairment. Laboratory or imaging testing is not typically necessary for these children unless there are other factors influencing this decision that was found in their history and physical examination. fMRI is used for research purposes and not for a diagnosis.

Children suspected of dyslexia should be referred for evaluation by the school system. Their reading ability, executive function, and intelligence quotient (IQ) will be tested. This testing, in the United States, is free and is typically required before services can be rendered.

Treatment / Management

As a clinician, it is crucial to work with parents, schools, and caregivers to identify patients with dyslexia early. However, most treatment is provided at school and at home. Early intervention will focus on vocabulary, comprehension, and necessary skills such as phonics. As students progress through their education, the intervention will move to improve understanding of word meanings, improved comprehension, more challenging reading, and strategies to excel.[8]

Differential Diagnosis

  • Difficulty heading
  • Vision impairment
  • Educational deficits
    • Decreased exposure
    • Increased absences
    • Poor instruction
  • Cognitive impairment
  • Learning disabilities
  • Toxin exposure (lead poisoning)
  • Familial dysfunction
  • Emotional illness

Prognosis

Those with reading difficulty that is overcome during early education typically develop average reading skills. Those children who have a persistent reading deficit may become proficient in reading words in their area of interest. A longitudinal study has found that reading disabilities improve with age, but a gap may remain when compared to their peers.[9]

Deterrence and Patient Education

Working with schools and local resources to ensure that the necessary services are available is crucial. It is also essential to explain to parents the importance of obtaining early intervention and following through with treatment. Educate parents and guardians that with early steps, their child may close the reading gap between them and their peers.

High achieving and high IQ students may be overlooked early in their educational careers. They can still have dyslexia but compensate in other ways and miss their window for early intervention. This can have a drastic effect on their outlook towards schooling as reading becomes more complicated and have a lasting impact on their ability to learn.[10]

If the family is not satisfied or the clinician is still worried by the outcomes of the intervention provided by the school, referrals may be necessary. Patients may benefit from seeing developmental and behavioral pediatricians, child neurologists, psychologists, and or neuropsychologists. It is important to note that the patient’s insurance may not cover these specialists.

Enhancing Healthcare Team Outcomes

A team involving optometrists, ophthalmologists, occupational therapists, and nursing working together will lead to the best outcomes.


References

[1] Mascheretti S,De Luca A,Trezzi V,Peruzzo D,Nordio A,Marino C,Arrigoni F, Neurogenetics of developmental dyslexia: from genes to behavior through brain neuroimaging and cognitive and sensorial mechanisms. Translational psychiatry. 2017 Jan 3;     [PubMed PMID: 28045463]
[2] Hulme C,Snowling MJ, Reading disorders and dyslexia. Current opinion in pediatrics. 2016 Dec;     [PubMed PMID: 27496059]
[3] Stoodley CJ, The Cerebellum and Neurodevelopmental Disorders. Cerebellum (London, England). 2016 Feb;     [PubMed PMID: 26298473]
[4] Grizzle KL, Developmental dyslexia. Pediatric clinics of North America. 2007 Jun;     [PubMed PMID: 17543907]
[5] Shaywitz SE,Gruen JR,Shaywitz BA, Management of dyslexia, its rationale, and underlying neurobiology. Pediatric clinics of North America. 2007 Jun;     [PubMed PMID: 17543912]
[6] Thompson PA,Hulme C,Nash HM,Gooch D,Hayiou-Thomas E,Snowling MJ, Developmental dyslexia: predicting individual risk. Journal of child psychology and psychiatry, and allied disciplines. 2015 Sep;     [PubMed PMID: 25832320]
[7] Keys MP, The pediatrician's role in reading disorders. Pediatric clinics of North America. 1993 Aug;     [PubMed PMID: 8345972]
[8] Scammacca NK,Roberts G,Vaughn S,Stuebing KK, A Meta-Analysis of Interventions for Struggling Readers in Grades 4-12: 1980-2011. Journal of learning disabilities. 2015 Jul-Aug;     [PubMed PMID: 24092916]
[9] Shaywitz SE,Fletcher JM,Holahan JM,Shneider AE,Marchione KE,Stuebing KK,Francis DJ,Pugh KR,Shaywitz BA, Persistence of dyslexia: the Connecticut Longitudinal Study at adolescence. Pediatrics. 1999 Dec;     [PubMed PMID: 10585988]
[10] Cohen BH, Neurologic causes of learning disabilities. Seminars in neurology. 1991 Mar;     [PubMed PMID: 1903552]