Alexia

Alexia is a total disorder of the reading skill, accompanied by the inability of visual perception and understanding of the text. With this violation, a person cannot learn to read or loses the ability to recognize letters and combine them into words. Alexia can develop in isolation or combined with aphasia, agraphy. The disorder is diagnosed using neuropsychological and speech therapy testing, neuroimaging methods (CT, MRI, PET of the brain). Correctional work is aimed at the development of visual-spatial functions, memory, attention, analytical and synthetic processes.

ICD 10

R48.0 Dyslexia and alexia

General information

Alexia is also called “verbal blindness” or “visual aphasia” because of the inability to read what is written. Close attention to the problem began to be paid more than a hundred years ago due to the increased interest in neuroanatomy and psychology. The “pioneer” in the study of pathology was the French neurologist J. Dezherin, who in 1892 for the first time described “pure Alexia” with preserved speech and localized concomitant lesions in the brain. In modern speech therapy, there is a distinction between partial unformed reading – dyslexia and complete absence / disintegration of the skill – alexia.

Causes

Any reading disorders have a neurological basis and are associated with damage to the areas of the brain involved in this process. Isolated acquired alexia in most cases develops as a result of impaired blood supply in the basin of the posterior cerebral artery, which feeds blood to the posterior parts of the brain, including the visual cortex and the sulcus of the corpus callosum.

In addition, Alexia can enter into the structure of various types of aphasia (motor, sensory) and occur as a result of damage to the corresponding brain departments. Etiofactors of local disorders of cerebral blood flow can be:

• ischemic stroke;
• traumatic brain injury;
• neurosurgical operation;
• neuroinfections;
• brain tumors;
• demyelinating diseases of the central nervous system;
• intoxication with neurotropic poisons.

In children, the inability to learn to read is most often associated with adverse perinatal factors: hypoxic brain damage, intrauterine infections, birth head injuries. Also, the cause of Alexia in childhood may be a lack of speech contacts, autism, severe intellectual disabilities.

Pathogenesis

Reading, as a process, consists of two components: technical and semantic. The technical side consists of recognizing the visual image of the letter – grapheme, correlating it with the articuleme and phoneme, folding graphemes into lexemes. The semantic side is to understand what you read. The psychophysiological mechanisms of reading are ensured by the safety and clear interaction of the visual (occipital cortex), acoustic (temporal cortex), speech motor (lower parietal, posterior frontal divisions) analyzers.

Alexia develops when any links of this chain are affected. In various types of aphasia, the primary defect may be articulatory or oral-articulatory apraxia, auditory agnosia, as a result of which the phoneme-articuleme-grapheme relationship breaks down. This leads to a secondary disruption of the reading process.

The central mechanism of pure forms of alexia are defects of visual or visual-spatial gnosis, visual mnesis. In these cases, the perception of the graphic symbol of the letter, its spatial location is disrupted, memory for letters suffers. The result of letter agnosia and amnesia is the inability of patients to correctly read and differentiate graphemes, words.

Classification

Depending on the structure of reading disorders , there are 2 groups of disorders:

1. Speech. They occur within the framework of the corresponding motor and sensory forms of aphasia. They are represented by afferent and efferent motor, acoustic-gnostic and acoustic-mnestic alexia and agraphy.
2. Non-verbal (Gnostic). They proceed without an oral speech disorder. They are based on visual and visual-spatial agnosia. These forms include optical, opto-spatial and opto-mnestic alexia. Optical, in turn, is divided into:

• literal – patients do not recognize letters;
• verbal – patients recognize and name individual letters, but cannot merge them into syllables and words.

Symptoms of alexia

Isolated reading disorders (Alexia without aphasia and agraphy) occur against the background of normal oral speech and its auditory perception. The function of writing is also preserved, but after a while the patient cannot read what he previously wrote. The recognition of words by ear is not impaired, the difficulty is caused only by the recognition of written text. The patient perceives letters as drawings, not understanding their meaning, mixes graphemes similar in spelling.

The main symptom is slow letter-by-letter reading. Patients first try to identify each letter individually, and then put them into a word. The “word length effect” is characteristic, in which long words are read more slowly and are less likely to be read correctly than short words. Recognition of numbers and other symbols (punctuation marks, mathematical signs) is also disrupted, anomie often occurs. Isolated alexia is often accompanied by loss of visual fields (right-sided hemianopia), color perception disorder.

Speech forms occur with the phenomena of aphasia: afferent motor, Broca, Wernicke, acoustic-mnestic. In severe forms of the aphatic syndrome, reading breaks up completely. In less severe cases, reading becomes slow, syllabic, guessing, multiple letter substitutions are noted. Global reading is available to some patients, they can correctly decompose the captions under the pictures. With acoustic-mnestic alexia, it is not the reading technique that is violated, but the understanding of a long text.

Complications

Patients with alexia lose the ability to read fluently, and often speak and write, which negatively affects self-esteem, the possibility of learning, professional realization. This is a serious disabling factor that interferes with full-fledged social interaction. Patients often develop depressive syndrome, a feeling of hopelessness and doom. Mental experiences are often aggravated by physical infirmity: impaired motor functions, the ability to self-serve.

Diagnostics

To build a correctional program, it is important to establish the nature and mechanism of the defect, the etiology and localization of the pathological focus. A patient with a reading disorder is consulted by a neurologist, a clinical speech therapist, and a neuropsychologist. Diagnostic search uses:

• Methods of neuroimaging. In order to determine the cause of alexia and conduct topical diagnostics of the lesion, in clinical neurology, cerebral CT, MRI, and less often, PET‒CT of the brain are resorted to. To assess the parameters of cerebral hemodynamics, a duplex scan .
• Examination of oral and written speech. Speech diagnostics begins with an assessment of impressive and spontaneous speech, oral and articulatory praxis, speech automatisms, repeated speech. The ability to ideogram reading, reading printed, written letters, words, sentences, short texts, reading “to myself” (finding captions to pictures) is investigated. The skills of cheating, dictation writing, and independent writing are tested.
• Neuropsychological testing. It is important to assess the state of various types of gnosis (especially visual, alphabetic), praxis. Tests are also conducted to investigate cognitive skills: memory (including auditory-speech), perception, thinking, spatial orientation.

Correction of alexia

Medical interventions

Treatment is carried out taking into account the primary disorder and its nature (vascular, infectious, tumor pathology, trauma). It includes drug therapy, neurorehabilitation, psychocorrection, according to indications – surgical interventions:

• Pharmacotherapy. With CVA, hypotensive, vasoactive, neurotrophic, disaggregant, antioxidant therapy is prescribed. In case of head injuries, the administration of nootropics, diuretics, sedatives, analgesics is indicated. Etiotropic therapy of neuroinfections may include the use of antimicrobial or antiviral agents, interferons, immunoglobulins, glucocorticosteroids.
• Neurosurgical operations. Early neurosurgical intervention allows to minimize the area of brain damage, reduce the phenomena of alexia, accelerate recovery. During the “therapeutic window” of ischemic stroke, systemic or selective thrombolysis is indicated. With TBI, it may be necessary to remove bone fragments of depressed fractures, evacuation of intracranial hematomas. For brain tumors, chemotherapy, stereotactic removal, and surgical excision are performed.
• Neurorehabilitation and neurocorrection. After the relief of acute symptoms, physical therapy, ergotherapy, mechanotherapy, electrical stimulation of oral muscles are performed. Neuropsychological correction implies the development of optical gnosis, visual-spatial representations, concentration of attention, memory.

Speech therapy correction

Logotherapy for Alexia is built taking into account the central mechanism of speech disorders. In aphasia, it is disinhibition of oral speech, overcoming kinetic and kinesthetic apraxia, activation of auditory gnosis, expansion of auditory-speech memory, restoration of connections between the articuleme, phoneme and grapheme. At the stage of gross disorders, global reading is stimulated, and then they proceed to the sound-letter analysis of the composition of the word.

In the case of isolated Alexia, priority is given to restoring the optical image of the letters. To do this, kinesthetic, motor sensations, pronunciation, auditory actualization are connected. As visual perception is restored, they gradually move from letter-by-letter to syllabic reading, increasing the speed, retelling what they read.

Prognosis and prevention

The restoration of reading skills is a long painstaking work that requires the diligence and patience of the patient, speech therapist, relatives. Not always, even after several courses of logotherapy, it is possible to achieve a premorbid level. Elements of alexia in the form of a syllabic reading in many patients are preserved for life. Prevention consists in minimizing the risk factors for the development of causal diseases (strokes, head injuries, etc.). When Alexia occurs, it is important to start early and follow the program of rehabilitation measures accurately.