Stroke & Aphasia
Cerebrovascular
Side view
Midline view
Stroke occurs when blood supply to part of the brain is interrupted; when it damages language centres, it can cause aphasia - difficulty producing or understanding language.
Common Signs & Symptoms
- Sudden weakness or numbness, often on one side of the body
- Sudden confusion or trouble speaking or understanding speech
- Sudden vision problems in one or both eyes
- Sudden severe headache with no known cause
- Loss of balance or coordination
Why These Symptoms Happen
Each symptom can be traced, at least in part, to the job a particular part of the brain normally does. These links are simplified: real symptoms usually come from several connected regions.
| Symptom | Brain region | Why it happens |
|---|---|---|
| Weakness of the face, arm, or leg on one side | Frontal Lobe | The motor cortex at the back of the frontal lobe controls movement on the opposite side of the body, so a stroke there - or in the fibres leaving it - weakens the other side. |
| Slow, effortful, broken speech (Broca's aphasia) | Frontal Lobe | Broca's area in the left frontal lobe helps plan and assemble speech. Damage leaves comprehension relatively intact but makes producing fluent sentences very hard. |
| Fluent speech that makes little sense, and poor understanding (Wernicke's aphasia) | Temporal Lobe | Wernicke's area in the left temporal lobe links sounds to meaning. Damage disrupts understanding, and the person often doesn't realise their own speech has gone wrong. |
| Numbness or ignoring one side of space | Parietal Lobe | The parietal lobe processes touch and builds our map of the space around us. Right-sided parietal strokes can cause "neglect", where the person stops noticing the left side of the world. |
| Losing part of the field of vision | Occipital Lobe | Each occipital lobe processes the opposite half of what both eyes see, so a stroke on one side can wipe out the same half of vision in both eyes. |
Overview
A stroke occurs when blood flow to part of the brain is interrupted, either by a blockage (ischaemic stroke, the most common type) or bleeding (haemorrhagic stroke), depriving brain tissue of oxygen. Because different brain regions handle different functions, the effects of a stroke depend heavily on exactly where it occurs. A stroke is a medical emergency - recognising symptoms quickly and seeking immediate treatment significantly improves outcomes, since "time is brain": brain tissue is lost rapidly the longer blood flow remains disrupted.
A simple way to remember the main warning signs is FAST: Face drooping on one side, Arm weakness, Speech that is slurred or confused, and Time to call emergency services immediately.
Affected Brain Regions
Stroke affecting the frontal lobe's Broca's area or the temporal lobe's Wernicke's area can cause aphasia - Broca's aphasia, marked by slow, effortful, fragmented speech with relatively preserved comprehension, or Wernicke's aphasia, marked by fluent but often meaningless speech and impaired comprehension. Stroke in the parietal lobe can cause spatial and sensory deficits, including hemispatial neglect, while stroke affecting the occipital lobe typically causes vision loss in part of the visual field.
How It's Studied
In hospital, a CT scan is usually done first, because it quickly shows whether a stroke is caused by bleeding - which changes the treatment completely. MRI is more sensitive to the early signs of a blockage and shows exactly which tissue is affected. For aphasia, speech and language therapists use structured tests of naming, repetition, comprehension, reading, and writing to work out which parts of language are affected.
Stroke has also taught us much of what we know about the brain. In the 1860s, Paul Broca linked speech loss to the left frontal lobe by examining the brains of his patients after death. In 2007, researchers scanned those same preserved brains with modern MRI and found the damage extended deeper than the area now named after Broca - a reminder that language depends on networks, not single spots.
Common Myths
"Strokes only happen to older people."
Risk rises with age, but strokes can happen at any age, including in children and young adults. The warning signs are the same, and they always need urgent attention.
"If the symptoms go away, there's no need to see a doctor."
Symptoms that come and go may be a transient ischaemic attack (TIA, or "mini-stroke"), which is a strong warning that a full stroke may follow. It needs urgent medical assessment even if the person feels fine again.
"People with aphasia have lost their intelligence."
Aphasia affects language, not intelligence. Many people with aphasia know exactly what they want to say but can't get the words out, or can't decode what they hear.
Current Research Directions
Acute stroke treatment has advanced substantially, with clot-dissolving medication and mechanical clot-retrieval procedures now able to reverse or limit damage if given quickly enough after symptom onset. For aphasia and other lasting deficits, speech-language therapy remains the mainstay of recovery, and research into how the brain reorganises itself after injury (neuroplasticity) is informing newer rehabilitation approaches, including techniques that pair therapy with non-invasive brain stimulation.
Key Terms
Related Brain Regions
Explore the regions involved in stroke & aphasia in more depth:
This article is for general education and isn't a substitute for professional medical advice or diagnosis. If you suspect someone is having a stroke, seek emergency medical care immediately.
Sources & Further Reading
- Stroke Overview - National Institute of Neurological Disorders and Stroke
- Aphasia - National Institute on Deafness and Other Communication Disorders
- Stroke: Symptoms - NHS
- Paul Broca's historic cases: high resolution MR imaging of the brains of Leborgne and Lelong - Dronkers et al. (2007), Brain