Cortical Visual Loss
Vivek Lal in A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
This is a reduction in reading proficiency that cannot be attributed to more elementary visual, ocular motor, attentional or language problems. Writing is said to be spared, but patients with pure alexia may show difficulty writing words with irregular spelling (e.g., colonel, isle), which cannot be written from their sound alone using spelling rules, and require access to an internal dictionary (268, 269). The severity of their alexia can range from an inability to read even single letters, a “global alexia” (270) that may also affect the ability to read numbers and other abstract symbols such as numbers (271), musical notation and map symbols (272, 273), to a milder version in which reading is slow and contains errors, “spelling dyslexia” or “letter-by-letter reading” (267). A key diagnostic feature is an increased word-length effect: the more letters in the word, the longer it takes for the patient to read it (274, 275). The number of letters in a word is a perceptual variable, in that it indexes the amount of perceptual work involved, as opposed to linguistic characteristics such as the frequency of a word in a language or the part of speech. While the word length effect in normal readers is only about 10–20 msec per letter, in alexic subjects it can range from a few hundred msec to a few seconds per letter (276).
Rehabilitation and management of visual dysfunction following traumatic brain injury
Mark J. Ashley, David A. Hovda in Traumatic Brain Injury, 2017
An important part of text recognition is the decoding of visual percepts into language. Interruption of visual pathways at the left angular gyrus172 or splenium173 prevent this decoding process from occurring, resulting in acquired alexia or inability to read. Most case reports of this dysfunction show some residual reading function. Treatment of alexia using integration strategies and based on the patient’s residual reading skills has been successful. Often, a letter-by-letter reading strategy can be employed by these patients, although it severely slows reading. Motor rehearsal, in terms of copying or tracing letters and words, as well as flash card techniques pairing the written with the spoken word have been applied with some success.
Optic radiations
Fiona Rowe in Visual Fields via the Visual Pathway, 2016
Alexia is the loss of reading ability in previously literate persons (Rowe et al. 2011). Pure alexia patients can write. Global alexia includes an inability to read numbers, letters, symbols and words. In less severe alexia patients can read but with occasional errors and with reduced speed. They use letter-by-letter reading. Almost all lesions are in the left hemisphere and most are in the medial and inferior occipito-temporal region. Secondary alexia is impaired reading ability due to physical factors, for example hemi-field slide, unable to read with hemianopic field defect. Bilateral frontal or parietal lesions can impair reading severely due to saccadic dysfunction. Alexia combined with agraphia has been described (Kawahata and Nagata 1988).
Diagnosing and managing post-stroke aphasia
Published in Expert Review of Neurotherapeutics, 2021
Shannon M. Sheppard, Rajani Sebastian
In addition to broad language comprehension and production deficits, stroke can also cause reading and writing deficits. Alexia refers to reading deficits and agraphia refers to writing deficits. In cases of pure alexia, patients demonstrate reading impairments in the absence of any other deficits [34,35]. Pure alexia is associated with simultaneous damage to 1) left occipital cortex, which causes right homonymous hemianopsia where visual information is initially processed in the right occipital cortex, and 2) splenium of the corpus callosum, which then prevents visual information in the right hemisphere from crossing over to the left hemisphere, where language is processed [36]. Pure agraphia refers to cases where writing impairments are present in the absence of other difficulties [35]. Spelling deficits are associated with damage to left inferior parietal cortex and left occipitotemporal cortex [37].
Attention Process Training-3 to improve reading comprehension in mild aphasia: A single-case experimental design study
Published in Neuropsychological Rehabilitation, 2020
Jaime B. Lee, McKay Moore Sohlberg, Beth Harn, Robert Horner, Leora R. Cherney
An alternative approach to treating alexia is to directly address the cognitive deficits that underlie the reading process. Direct attention training (DAT) has been administered as an aphasia intervention in a handful of studies (e.g., Coelho, 2005; Helm-Estabrooks, Connor, & Albert, 2000; Murray, Keeton, & Karcher, 2006). DAT is based on the notion that attentional abilities can be improved by activating and stimulating the impaired attention system through repetitive drills, which promotes recovery of damaged neural circuits and improves attentional processing (Sohlberg & Mateer, 2001). While labelled “attention training,” intervention programmes that have been evaluated in the neurogenic literature target a broad range of attention, working memory and executive control processes (Butler et al., 2008; Duval, Coyette, & Seron, 2008; Sohlberg, 2000). Preliminary evidence indicates that DAT can improve attentional processing in individuals with aphasia (Barker-Collo et al., 2009; Sturm & Willmes, 1991; Sturm, Willmes, Orgass, & Hartje, 1997).
Multi-step treatment for acquired alexia and agraphia (Part I): efficacy, generalisation, and identification of beneficial treatment steps
Published in Neuropsychological Rehabilitation, 2019
Jeffrey P. Johnson, Katrina Ross, Swathi Kiran
We administered a comprehensive, multi-step treatment for reading or writing to eight patients with chronic acquired alexia and agraphia. As a function of treatment, the group significantly increased their accurate productions of trained words in their trained modality, with generalisation to untrained words and the untrained modality. Treatment effects and generalisation were most likely due to strengthened representations at the semantic and lexical levels, improved access to and retrieval of representations in the lexicon, more effective sublexical conversion and working memory (buffer) processes, and the spread of semantic and orthographic information from trained to related items. These mechanisms appear to have been driven primarily by a subset of treatment steps involving tasks that targeted lexical, sublexical, and buffer processes, thereby validating a comprehensive approach to treatment.
Related Knowledge Centers
- Developmental Language Disorder
- Dyscalculia
- Traumatic Brain Injury
- Attention Deficit Hyperactivity Disorder
- Stroke
- Learning Disability
- Subvocalization
- Learning
- Gene–Environment Interaction
- Genetics