The 10 Types of Dyslexia
Dyslexia is a persistent and specific literacy disorder that occurs in people without any concomitant physical, mental, or sociocultural difficulties. Its origin seems to be derived from a neurodevelopmental disorder, but a lot of research is still required to find a specific cause that’s applicable in all cases. Do you know that there are many types of dyslexia?
Although this condition seems isolated and anecdotal, sources that we’ll explore below estimate that 7% of the world population suffers from dyslexia, regardless of their ethnicity, their sex (although there seems to be a certain proclivity in men), and their sociocultural environment. Here, we’ll tell you what dyslexia consists of in general features and how it’s classified according to its etiology. Keep reading!
What is dyslexia?
The Mayo Clinic defines dyslexia as a learning disorder that involves difficulty reading as a result of problems identifying speech sounds and understanding how these are related to letters and words. The degree of affection varies between each patient and its causality is found in both genetic and environmental factors.
It’s estimated that 3 to 7% of the world’s population suffers from dyslexia. Especially in children, this condition is closely related to attention deficit hyperactivity disorder (ADHD). Although the global incidence figures aren’t excessive, it should be noted that up to 20% of the general population has symptoms of dyslexia (although they don’t develop the complete picture).
Some of the general symptoms of this condition are as follows:
- Their reading level is very low compared to what’s expected for their age (at school).
- Difficulty in processing and understanding while listening.
- Avoidance of activities that involve reading.
- Slow and difficult reading and writing.
- Difficulty spelling.
- Difficulty memorizing, solving math problems, learning a foreign language, or telling stories.
The general symptoms derived from dyslexia are very different depending on the life stage in which the patient is and their social environment. In any case, most diagnoses are made between the ages of 5 and 7 (when children are starting to read at school).
A maximum of 7% of the population suffers from dyslexia, but up to 20% have symptoms similar to this disorder.
What are the existing types of dyslexia?
Patients with dyslexia are neurotypical people whose difficulty is only limited to tasks related to reading and writing. Those children with difficulties derived from genetic conditions (trisomy 21 or Down syndrome, fragile X syndrome, and more), developmental disorders or not attending school aren’t considered dyslexic per se. This condition is isolated and doesn’t affect more terrain.
Dyslexia can be classified according to its origin and other parameters, both symptomatic and etiological. Let’s see what they are below.
1. Types of dyslexia according to their origin
The cerebellum is substantially active during the early stages of development and the learning process. As indicated by the Statpearls medical portal, people with dyslexia seem to have certain imbalances in the aforementioned area compared to those who don’t have the condition. For example, they show a reduced amount of gray matter in the right lobe of one of their segments.
However, it should be noted that the disruptions in the cerebellum area that cause dyslexia aren’t the same as those detected in autism spectrum disorders or ADHD. For this reason, it’s suggested that the different maladjustments in groups of brain circuits cause specific conditions. Let’s see what the types of dyslexia are according to their etiology.
Dyslexia always involves the brain, but the mismatch that causes it can take place in the genes, in the embryonic environment, or during adult life.
1.1 Primary dyslexia
This is the most common type of dyslexia by far. It’s a presumably inherited condition that’s present from the infant’s birth. For this reason, it’s believed that newborns with dyslexic parents (or more distant relatives) are more likely to manifest this condition throughout their cognitive development.
Many genes have been associated with the likelihood of dyslexia at birth. The best known are DCDC2 (located on chromosome 6), KIAA0319 (chromosome 6), and DYX1C1 (chromosome 15). Proteins encoded in the DNA of some of these genes could be involved in neuronal migration processes, thus explaining their link with dyslexia.
The heritability pattern for dyslexia is estimated to be 50-70%. A child with dyslexic parents is very prone to present the condition.
1.2 Secondary dyslexia
This condition also occurs from the birth of the baby, but differs from the previous one by a clear factor: Neuronal failure isn’t encoded by genes but derives from problems in brain development during pregnancy. In other words, the cause is external to the genome of the individual, although it’s gestated before birth.
As indicated by information sources, this variant can be triggered by very subtle changes in the fetus, such as a micro-stroke, maternal stress, or a vertical viral contagion (mother-child through the placenta). Another explanation could be the variable prenatal fluctuation of testosterone, something that would explain why more men have secondary dyslexia than women.
Maternal addictions to alcohol, tobacco, or other drugs can also hinder the neurological development of the fetus.
1.3 Acquired dyslexia
While the types of dyslexia mentioned exist from birth and manifest in childhood, the acquired variant occurs for a specific reason at any time in the patient’s life. Some of the more common triggers are the following:
- Head trauma: A physical injury of mechanical origin (car accidents, falls, and more) produced on the brain tissue that alters its function temporarily or permanently, depending on the area that’s affected.
- Stroke or cerebrovascular accident (CVA): These events can be ischemic or hemorrhagic. In any case, in both cases, the brain tissue ends up dying due to a lack of irrigation or waterlogging (due to the rupture of a capillary). Dyslexia can derive from this condition if it affects the areas that control reading.
- Tumors: Brain cancer creates a mass in the brain that can press on and damage adjacent structures. Although it’s very rare, this possible trigger should be cited.
2. Other types of dyslexia
Besides its origin, there are various types of dyslexia categorized according to the symptoms they cause. We’ll present them to you in the following paragraphs.
2.1 Phonological dyslexia
As indicated by professional portals, phonological dyslexia causes problems when dissecting words into syllables and sound subunits known as phonemes. The main manifestation is the inability to recognize the dependence between the phonic and orthographic structure of words.
People with phonological dyslexia have serious problems reading little-known or unreal words (pseudowords), as these complex constructs require analyzing and synthesizing the constitutive phonic elements. The patient has difficulties in linking sounds with symbols (words) and encoding them.
In this case, the affected child or adult uses the visual route (which allows us to read globally without dividing the word into parts) to understand messages. Some of the symptoms of people with phonological dyslexia are the following:
- Little ability to analyze the sequence of sounds and syllables in words
- Poor ability to remember individual sounds or sound sequences
- Difficulty mixing individual sounds into words
- Difficulty hearing words and omitting one sound and replacing it with another
- Trouble remembering the sounds that individual letters represent (and phonetically regular or irregular letter combinations)
- Guessing unfamiliar words instead of employing word analysis skills
- Strange letters and syllables are omitted when spelling
There are many more signs that indicate phonological dyslexia in a patient, but these are among the most important. It should be noted that it’s considered a type of acquired dyslexia that usually results from a stroke, brain damage, or progressive disease. It affects reading skills already obtained in previous moments of development.
Phonological dyslexia is usually associated with pictures acquired by diseases that affect the brain.
2.2 Superficial or developmental dyslexia
Superficial dyslexia is characterized by a malfunction of the visual, lexical, or direct path. Due to the deficit in this mechanism, the patient chooses to use the phonological route, reading words using grapheme-phoneme conversion (identifying letters and transforming them into sounds).
This type of dyslexia refers to children or adults who have trouble reading because they don’t “recognize” letters with their eyes. This problem becomes even more evident when it comes to interpreting words that are pronounced the same or in a very similar way (hello and jello).
Some of the signs of superficial dyslexia include the following:
- Confusion when identifying similar letters that differ in orientation (bd, pq).
- Difficulty identifying words that are written the same, but reversed (es, se).
- Slowness in recognizing words in a text. Very few are instantly recognized and have to be interpreted individually, just as if they were being seen for the first time.
- Omission of words because they haven’t been “noticed” in the text.
- Difficulty remembering the way a letter is written.
- Insertions, omissions, and substitutions if the meaning of the passage guides the reading.
This is the typical and most common type of dyslexia in children.
2.3 Deep dyslexia
The deep variant is a combination of the 2 types of dyslexia mentioned above. The patient has problems understanding texts at a semantic level, but also visually (phonological and visual routes). Again, this variant is often associated with severe brain damage due to trauma or life-long illness. It’s the most disabling of all.
2.4 Rapid-naming dyslexia
This type of dyslexia involves a clear difficulty when assigning the names corresponding to numbers, letters, and colors when the patient needs to do it quickly. For example, when you see a 9, it’ll be difficult for you to say “nine” with the expected readiness for your mental condition or “red” when you see a red tone on a paper.
These people can assign the proper names to things that are presented to them, but they take much longer to do so than someone without dyslexia.
2.5 Letter position dyslexia (LPD)
In this case, the patient is able to identify the letters in the correct way (they don’t confuse a b with a d or a p with a q), but they have many problems when it comes to “placing” each letter in its proper position. For example, it’s common to read could instead of cloud and to make other similar minor mistakes. It’s also common to omit a letter without realizing it (from beach to bach, for example).
2.6 Attentional dyslexia
This variant is characterized by the migration of letters between neighboring words. For example, a patient with attentional dyslexia may read “fig free” instead of “fig tree.” The problem isn’t in identifying the letters as their own entities, but in mixing them in close segments of the text.
2.7 Neglect dyslexia
This special type of dyslexia is derived from neurological damage. In this case, the patient can’t perceive part of their visual field due to previous damage to the brain, so they omit the beginning or the end of the words. It’s a very specific case and can be left-field (to the left) or right-field (to the right).
The types of dyslexia and their clinical importance
Although there are 10 types of dyslexia (and even more, since we’ve left out a specific variant), it’s important to note that the vast majority of young patients are categorized into the primary or secondary group and the superficial type. These labels represent the typical scene of a child with reading problems during the school year.
Despite the fact that dyslexia is conceived as a genetic condition that’s present from birth, you may have noticed that many people develop this disorder after an accident that involves certain areas of the brain. Be that as it may, the difficulty with reading and understanding texts is a common point in all the variants.It might interest you...
- Dislexia, MayoClinic. Recogido a 19 de noviembre en https://www.mayoclinic.org/es-es/diseases-conditions/dyslexia/symptoms-causes/syc-20353552
- Remien, K., & Marwaha, R. (2021). Dyslexia. StatPearls [Internet].
- DYSLEXIA MAY BEGIN IN THE PRENATAL BRAIN, Chicago Tribune. Recogido a 19 de noviembre en https://www.chicagotribune.com/news/ct-xpm-1987-02-22-8701150266-story.html
- 12 types of dyslexia, EDUBLOX ONLINE TUTOR. Recogido a 19 de noviembre en https://www.edubloxtutor.com/dyslexia-types/