A stroke occurs when blood flow to the brain is interrupted, either by a blockage in a blood vessel (ischemic stroke) or by bleeding in the brain (hemorrhagic stroke). Brain cells begin to die within minutes without the necessary oxygen and nutrients from the blood. While strokes can strike at any moment, those that happen during sleep, often called “wake-up strokes,” present distinct challenges for both recognition and treatment.
Recognizing Symptoms Upon Waking
Individuals experiencing a stroke during sleep typically wake up with new symptoms. These can include sudden weakness or numbness, often affecting one side of the face, arm, or leg. People may notice facial drooping or find an arm too weak to lift. Speech difficulties, such as slurred words or trouble understanding others, are also common.
Vision changes, like blurred or double vision, dizziness, or a sudden, severe headache, can also indicate a stroke. The concept of “last known well” is particularly relevant, referring to the last time the person was observed without stroke symptoms, which for a sleep stroke is typically when they went to bed.
Why Strokes Occur During Sleep
Strokes can happen during sleep due to physiological changes overnight. Fluctuations in blood pressure and heart rate may increase susceptibility. Some individuals might experience abnormally high blood pressure at night, even if their daytime readings are normal.
Underlying health conditions also play a role. Obstructive sleep apnea (OSA), a condition where breathing repeatedly stops or slows during sleep, is a significant risk factor. OSA can lead to reduced oxygen levels in the blood, which may contribute to stroke. Atrial fibrillation, an irregular heart rhythm, can also increase stroke risk by allowing blood to pool and form clots.
Challenges in Diagnosing Sleep Strokes
Diagnosing a stroke that occurs during sleep poses unique difficulties because the time of symptom onset is unknown. This “last known well” time is crucial for determining eligibility for time-sensitive treatments. Since the person was asleep, the exact moment the stroke began cannot be pinpointed, making it harder to fit within narrow treatment windows.
Diagnostic tools like computed tomography (CT) scans and magnetic resonance imaging (MRI) assess the brain. A CT scan can quickly rule out bleeding. An MRI, particularly diffusion-weighted imaging (DWI), can detect new strokes and help estimate the age of the stroke. The presence of a “perfusion-diffusion mismatch” on MRI, indicating salvageable brain tissue, can also guide treatment decisions.
Immediate Actions and Medical Care
If a stroke is suspected upon waking, immediate action is necessary. Call emergency services without delay, as rapid medical evaluation can significantly improve outcomes. Do not attempt to drive to the hospital; an ambulance allows medical personnel to begin assessment and treatment en route.
Upon arrival, medical teams will conduct an assessment, including neurologic examinations and imaging tests, to determine the type of stroke and guide treatment. For ischemic strokes, clot-busting medications such as alteplase (recombinant tissue plasminogen activator or rt-PA) may be administered, ideally within 4.5 hours of symptom onset. Mechanical thrombectomy, a procedure to physically remove a clot, may also be an option for certain large vessel blockages, typically within a 6 to 24-hour window from the last known well time.