Alexia without agraphia

Key Points at a Glance

Highlights of This Condition

• Alexia without agraphia (pure alexia) is an acquired reading disorder in which only reading ability is lost while writing, speech, and auditory comprehension are preserved.
• Stroke due to left posterior cerebral artery (PCA) occlusion is the most common cause, presenting as a symptom of cerebrovascular emergency.
• A characteristic pattern is “letter-by-letter reading,” where the patient reads words by naming each letter sequentially.
• Right homonymous hemianopia and right upper quadrantanopia frequently accompany pure alexia, but isolated pure alexia without visual field defects also exists.
• It develops as a “disconnection syndrome” due to damage to the visual word form area (VWFA) in the left occipital lobe or the splenium of the corpus callosum.
• It occurs in less than 1% of stroke patients, and isolated pure alexia is an even rarer condition.
• There is no curative treatment, but rehabilitation can lead to some recovery. In many patients, mild alexia persists.

1. What is alexia without agraphia?

Alexia without agraphia is an acquired reading disorder in which writing ability is preserved. It is also called “word blindness,” “letter-by-letter reading,” or “pure alexia.”

This disease concept was first reported by Déjerine in 1892 and elaborated by Geschwind in 1965. “Alexia” is a term formed by adding the negative prefix “a-” to the Greek word “lexis” (speech).

The reading system has three independent subsystems: orthographic, semantic, and phonological. In pure alexia, only orthographic processing is selectively impaired. It is a classic disconnection syndrome that occurs when access to the orthographic network of the language-dominant hemisphere is blocked after receiving visual text input.

In severe cases, global alexia occurs, and even single letters cannot be recognized. Meanwhile, it is reported to occur in less than 1% of stroke patients, and isolated pure alexia is extremely rare. ²⁾

Q How rare is alexia without agraphia?

A

It occurs in less than 1% of all stroke patients, and isolated pure alexia without any visual field defects, aphasia, or agraphia is even rarer. ²⁾ Because the symptoms are isolated and subtle, there is a risk that it may go unnoticed as a symptom of stroke.

2. Main Symptoms and Clinical Findings

Subjective Symptoms

The main complaint is a sudden loss of reading ability in a person who previously could read and write.

• Sudden loss of reading ability: Individual letters can be recognized, but words and sentences cannot be read. Many patients characteristically report, “I can see the letters, but I cannot read the text.” ²⁾
• Inability to reread what one has written: A few seconds after writing, the person cannot reread their own writing.
• Preserved speech and auditory comprehension: The ability to speak and understand spoken language is not impaired.
• Preserved writing ability: The patient can write dictated sentences. ²⁾

Clinical Findings

• Letter-by-letter reading: A characteristic reading pattern where the patient names each letter one by one before attempting to read the word aloud. Reading speed is markedly reduced, and comprehension is often absent. ²⁾
• Right homonymous hemianopia: Frequently occurs with lesions of the left occipital cortex.
• Right upper quadrantanopia (“pie in the sky”): Observed when Meyer’s loop in the temporal lobe is damaged. ¹⁾
• Color naming disorder and hemiachromatopsia: May be observed in cases without complete homonymous hemianopia.
• Preserved visual acuity: Corrected visual acuity is maintained (typically 20/20). ¹⁾
• Normal pupillary light reflex and eye movements: Because objective ophthalmological findings are scarce, this condition is easily overlooked. ¹⁾
• Preserved recognition of faces, objects, and places: Recognition impairment is limited to letters and words.

Preventing oversight during ophthalmological consultation

Distance visual acuity tests cannot detect reading impairment. It may only be discovered through near visual acuity tests (those requiring reading of text), so attention should be paid to a decrease in near visual acuity that is disproportionate to the patient’s complaints. ¹⁾

Q Why can I read letters but not sentences?

A

In pure alexia, visual recognition of individual letters is possible, but the pathway for instantly recognizing a string of letters as a word (via the visual word form area, VWFA, in the left fusiform gyrus) is disrupted. Therefore, the patient attempts to read partially by naming each letter sequentially, but cannot grasp the whole word.

3. Causes and Risk Factors

Main Causes

• Left posterior cerebral artery (PCA) occlusion: Thrombotic or thromboembolic occlusion is the most common cause. It causes infarction of the left occipital cortex and the splenium of the corpus callosum.
• Cardiogenic cerebral embolism due to atrial fibrillation: An important source of cardiogenic embolism causing left PCA infarction. Cases with newly diagnosed atrial fibrillation have been reported. ²⁾
• Left occipital lobe tumor: When it extends anteriorly and damages the splenium of the corpus callosum, it causes alexia.
• Others: Multiple sclerosis, migraine, acute encephalopathy, post-surgery for left occipital vascular malformation, epileptic focus, and occipital lobe tumors (e.g., glioblastoma) can be causes.

Risk Factors

Cardiovascular risk factors are the main underlying cause.

• Hypertension (especially poorly controlled cases) ²⁾
• Type 2 diabetes ²⁾
• Atrial fibrillation (cardioembolic source) ²⁾
• History of transient ischemic attack (TIA) ²⁾

Prevention and daily care

Since the main cause of this disease is stroke, managing hypertension, diabetes, and arrhythmias is the most important preventive measure. Sudden reading difficulty may be an emergency sign of stroke. If symptoms appear, seek medical attention immediately.

Q Why can I write but not read?

A

This is due to the mechanism of disconnection syndrome. The pathway to the angular gyrus and language centers required for writing is preserved, so writing is possible. On the other hand, the pathway that transfers visual information to language areas (VWFA → left hemisphere language areas) is blocked, so the patient cannot read back what they have written.

4. Diagnosis and Examination Methods

Clinical Evaluation

• Near visual acuity test: Distance visual acuity is normal, but near visual acuity test (requiring reading) reveals reading impairment. This often becomes the starting point for diagnosis. ¹⁾
• Assessment of non-visual language functions: It is essential to confirm that oral language, auditory comprehension, and writing ability are preserved. In pure alexia, all are normal. ¹⁾
• Visual field test: Standard 30-2 automated perimetry detects right homonymous hemianopia or right upper homonymous quadrantanopia. ¹⁾

Neuroimaging

• Head CT (non-contrast/contrast): Confirms low-density area in the left occipitotemporal region. Useful for differentiating stroke from tumor and abscess. In the acute phase, it supports the diagnosis of cerebral infarction. ¹⁾²⁾
• CT angiography (CTA): Can confirm partial thrombotic occlusion of the distal left PCA. ²⁾
• Head MRI (diffusion-weighted imaging): Most useful for diagnosing hyperacute cerebral infarction; can detect high signal in the left occipital lobe even within 1–3 hours of onset. Typical findings show a lesion consistent with the PCA vascular territory extending to the splenium of the corpus callosum. In the acute phase, sensitivity is highest in DWI, followed by FLAIR, T2, and T1.
• Electrocardiogram (ECG): Detects arrhythmias such as atrial fibrillation and evaluates cardioembolic sources. ²⁾

Differential Diagnosis

It is clinically important to distinguish between the three conditions.

Condition	Homonymous Hemianopia	Nature of Reading Difficulty
Pure alexia (this disease)	Often accompanied by right homonymous hemianopia	Inability to visually recognize whole words
Hemianopic alexia	Right homonymous hemianopia present	Inability to read the right side of words due to right visual field defect
Left hemialexia	No homonymous hemianopia	Inability to read the left side of words with isolated splenium lesion

5. Standard treatment

Treatment of Underlying Disease

Acute stroke management is the highest priority.

• Antiplatelet therapy: Dual antiplatelet therapy for PCA infarction is prescribed at discharge. ¹⁾
• Secondary prevention: If atrial fibrillation is identified, anticoagulation therapy is initiated to prevent recurrence of cardioembolism. ²⁾
• Thrombolytic therapy: It is contraindicated if the recommended treatment window from the time last known well has passed. ¹⁾
• Risk factor management: For patients with PCA infarction, evaluation and management of treatable risk factors such as hypertension, diabetes, and atrial fibrillation are recommended.

Visual rehabilitation

There is no curative treatment; the goal is to learn compensatory strategies and achieve partial recovery of reading function.

Sequential Reading Training

Sequential (letter-by-letter) reading improvement training: Improves the skill of recognizing words by naming each letter one by one.

Oral re-reading method: May contribute to improved accuracy and reading speed.

Orthographic vocabulary access training: Presents words and non-words on a computer and performs lexical decision tasks.

Sensory and Motor Training

Tactile therapy: The examiner traces letters on the patient’s skin, and the patient names them.

Kinesthetic therapy: The patient writes letters with their finger and then names them.

Combination training: Tracing letters on one’s own skin to supplement letter recognition using sensory pathways other than vision.

• Use of auditory communication: The use of auditory communication and audiobooks plays an important role in maintaining and recovering daily life. ¹⁾
• Surgery: Depends on the etiology (occipital lobe tumor, hemorrhage, arteriovenous malformation, etc.).

Prognosis

Many patients have residual mild alexia. Cases have been reported where alexia persisted at discharge; partial recovery of reading ability can be expected, but complete recovery is not guaranteed. ¹⁾

Q Can alexia be cured?

A

There is currently no curative treatment. Rehabilitation (sequential reading training, oral reading repetition method, tactile-kinesthetic technique) can lead to some improvement, and cases of gradual improvement through letter-by-letter decoding as a compensatory strategy have been reported. ²⁾ However, mild alexia persists in many patients. ¹⁾

6. Pathophysiology and detailed pathogenesis

Pure alexia is understood as a disconnection syndrome in which the pathway from visual input to the language system is interrupted at two sites.

Two mechanisms of blockage:

1. Damage to the left occipital lobe: Loss of visual input from the right visual field (processed by the left occipital lobe).
2. Damage to the splenium of the corpus callosum: Visual information normally processed by the right occipital lobe cannot be transferred to the language areas of the left hemisphere.

As a result, written information from both visual fields cannot reach the language system, making reading impossible.

Role of the Visual Word Form Area (VWFA): The VWFA, located in the left fusiform gyrus, is a region specialized for visual recognition of letter strings. Damage to this area or its surroundings is key to pure alexia. ²⁾ Left PCA occlusion can cause alexia even without involving the angular gyrus, as input to the angular gyrus is interrupted, while the angular gyrus itself is preserved, maintaining writing ability.

Reason for preserved writing: Damage to structures anterior to the splenium of the corpus callosum also causes agraphia. Conversely, in this disorder, the anterior writing pathway is spared, allowing writing. Damage to the left angular gyrus results in Gerstmann syndrome (finger agnosia, acalculia, left-right disorientation).

Disconnection Alexia

Lesion location: Splenium of the corpus callosum, periventricular white matter (posterior)

Mechanism: Blockade of the fiber bundle from the right visual cortex to the left angular gyrus. The right visual cortex itself is not damaged.

Features: Writing and language functions are fully preserved.

Cortical Alexia

Lesion site: Occipitotemporal cortex / VWFA (anterior)

Mechanism: Direct damage to the VWFA makes visual recognition of letter strings impossible.

Features: May be accompanied by more severe recognition impairment.

Anatomical background of the visual pathway: The left posterior cerebral artery perfuses the calcarine sulcus (V1: primary visual cortex) on the medial surface of the occipital lobe and the ventral temporal lobe. The lateral geniculate body receives dual blood supply from the anterior choroidal artery (AchoA: branch of the internal carotid artery) and the lateral posterior choroidal artery (LPchoA: branch of the posterior cerebral artery). 90% of optic tract fibers enter the lateral geniculate body, while the remaining 10% enter the pretectal area and superior colliculus of the midbrain, participating in the pupillary light reflex. Therefore, in pure alexia, the pupillary reflex is usually preserved.

Relationship between language-dominant hemisphere and handedness: 96% of right-handed individuals have left hemisphere dominance, and alexia develops with left hemisphere lesions. Even among strong left-handers, 73% are left hemisphere dominant (Knecht et al.).

---

7. Latest Research and Future Prospects (Research Stage Reports)

For Patients: Please Read

The following information is currently in the research stage or under clinical trials and is not standard treatment available at general hospitals. It is reference information for professionals regarding future medical developments.

Insights from Case Reports

Romano et al. (2024) reported a case of pure alexia in a 40-year-old man. It was accompanied by right upper homonymous quadrantanopia (“pie in the sky”) due to left PCA occlusion, and reading impairment was discovered during near vision testing. The mechanism of quadrantanopia was attributed to an infarction in the PCA perfusion area of the Meyer loop. Dual antiplatelet therapy was initiated at discharge, but mild alexia persisted. The role of ophthalmologists in detecting cerebrovascular emergencies is emphasized. ¹⁾

Gnieber et al. (2025) reported a case of isolated pure alexia in a 66-year-old woman. It was caused by a left PCA infarction, and newly diagnosed atrial fibrillation was identified as the cardioembolic source. There were no motor or sensory deficits; isolated reading impairment was the only symptom. Gradual improvement was achieved through a compensatory strategy of letter-by-letter decoding, and the patient was referred to community rehabilitation. ²⁾

New Developments in Classification

Lopez et al. have proposed a new classification of pure alexia based on anatomical lesion sites, dividing it into “disconnection alexia” (lesions of the splenium of the corpus callosum and periventricular white matter) and “cortical alexia” (damage to the occipitotemporal cortex and VWFA). This classification may be applied to individualize rehabilitation strategies.

---

8. References

1. Romano J, Silva S, Oliveira N, et al. Beyond words: a case of pure alexia following posterior cerebral artery occlusion. Cureus. 2024;16(1):e52734. DOI: 10.7759/cureus.52734

2. Gnieber KO, Barakat AA, Khan A, et al. ‘I can see letters but cannot read sentences’: a case of pure alexia without agraphia due to left posterior cerebral artery infarction. Cureus. 2025;17(8):e89974. DOI: 10.7759/cureus.89974

3. Bhat DI, Santosh Kumar SA, Pai SS, Chandramouli BA. Alexia Without Agraphia: Can Write But Not Read!. Neurol India. 2022;70(5):2231-2242. PMID: 36352656.