What can cause episodic expressive aphasia?

Causes of Episodic Expressive Aphasia

Episodic expressive aphasia is most commonly caused by transient ischemic attacks (TIAs) or ischemic strokes affecting the left hemisphere language areas, particularly in the distribution of the left internal carotid or middle cerebral artery. 1

Vascular Causes (Most Common)

Transient Ischemic Attack (TIA)

• TIA affecting the left internal carotid artery or middle cerebral artery distribution causes aphasia as a cardinal symptom, with typical symptom duration of 15 minutes, though the conventional definition allows up to 24 hours. 1
• Aphasia from left hemisphere ischemia may occur with or without accompanying right-sided weakness, right-sided sensory loss, or monocular blindness affecting the left eye. 1
• In ambidextrous or left-handed individuals, aphasia can result from right internal carotid artery ischemia. 1
• Carotid stenosis remains the main determinant of disease severity and risk for subsequent TIA and stroke. 1

Ischemic Stroke

• Acute ischemic stroke presents with neurological deficits persisting longer than 24 hours, with aphasia being a common manifestation. 1
• Isolated aphasia as the sole stroke presentation is uncommon (only 3% of stroke presentations), and when it occurs without motor or sensory deficits, stroke mimics are more likely than actual ischemia. 2
• However, true isolated aphasia from stroke can occur, particularly in patients with prior history of stroke or TIA. 2, 3
• Cardioembolic sources, particularly patent foramen ovale, are important causes of isolated aphasic strokes in younger patients. 3

Autoimmune/Inflammatory Causes

Autoimmune Encephalitis

• Dysphasia, hesitant speech, and deterioration in handwriting are prominent features that can progress to expressive and receptive aphasia in autoimmune encephalitis. 1
• Autoimmune encephalitis typically presents acutely or subacutely over less than 3 months. 1
• Speech and autonomic dysfunction occur in NMDAR-antibody encephalitis as part of a polysyndromic presentation. 1
• Hyperacute presentations are atypical for autoimmune encephalitis and should prompt consideration of vascular etiology. 1
• A preceding viral infection, fever, or viral-like prodrome is common, and autoimmune encephalitis may be triggered by herpes simplex virus encephalitis or immune-modulating therapies. 1

Treatment-Related Causes

CAR T-Cell Therapy Complications

• Immune effector cell-associated neurotoxicity syndrome (ICANS) from CAR T-cell therapy causes dysphasia, hesitant speech, and deterioration in handwriting that can progress to expressive and receptive aphasia. 1
• Symptoms typically include tremor, confusion, agitation, and seizures alongside the language disturbances. 1
• High fever (38.9°C) and hemodynamic instability within 36 hours of CAR-T infusion predicts severe ICANS with high sensitivity. 1

Steroid-Induced Aphasia

• Steroid use, particularly dexamethasone, can cause reversible purely expressive aphasia—a previously undescribed but important cause. 4
• Recognition is critical given increased steroid utilization since the COVID-19 pandemic. 4

Neurodegenerative Causes

Primary Progressive Aphasia

• Progressive aphasic syndromes present with speech and language impairments as the primary feature, typically in a chronic rather than episodic pattern. 1
• Logopenic variant primary progressive aphasia (usually due to Alzheimer's disease) presents with word-finding difficulty, impaired repetition, and relatively preserved comprehension. 1
• Non-fluent variant primary progressive aphasia (usually due to FTLD-tau) features hesitant, effortful speech with agrammatism and speech sound errors. 1
• While typically progressive, focal cortical degeneration can present with transcortical expressive aphasia evolving over years. 5

Metabolic/Toxic Causes

• Toxic/metabolic disturbances are the most common stroke mimics (39%) presenting as isolated "aphasia" in the emergency department. 2
• These include electrolyte abnormalities, hypoglycemia, drug intoxication, and other systemic metabolic derangements. 2

Critical Diagnostic Approach

When evaluating episodic expressive aphasia:

• Obtain immediate NIH Stroke Scale assessment focusing on item #9 (Best Language) and urgent brain imaging (CT or MRI) within hours to rule out acute stroke. 6
• Document precise time of symptom onset to determine thrombolytic therapy eligibility. 6
• In patients with isolated aphasia and no motor/sensory deficits, stroke mimics are more likely than ischemia, but prior history of stroke/TIA increases likelihood of vascular etiology. 2
• Consider autoimmune encephalitis if subacute presentation with polysyndromic features, preceding viral illness, or known autoimmune history. 1
• Evaluate for recent CAR T-cell therapy or steroid use as reversible iatrogenic causes. 1, 4
• MRI is superior to CT for detecting vascular lesions and subtle pathology. 6

Common Pitfalls to Avoid

• Do not attribute episodic aphasia to "normal aging" without thorough evaluation—this represents pathology requiring investigation. 6
• Do not delay imaging while pursuing extensive cognitive testing if acute stroke is possible. 6
• Do not assume isolated aphasia is always stroke—metabolic causes are more common in this presentation. 2
• Do not overlook cardioembolic sources, particularly patent foramen ovale in younger patients with cryptogenic isolated aphasia. 3