The painful rash known as shingles, or herpes zoster, is caused by the reactivation of the varicella-zoster virus (VZV). After an initial infection, VZV remains dormant in the body’s nerve cells and can re-emerge years later, typically as a localized rash. While primarily known for causing skin lesions and nerve pain, VZV reactivation has been linked to other serious health complications, including an increased risk of stroke.
The Link Between VZV and Arterial Inflammation
The connection between a skin rash and a stroke lies in the virus’s ability to directly infect and inflame blood vessels in the brain, a condition termed VZV vasculopathy. VZV is a neurotropic and vasculotropic virus, meaning it targets both nerve tissue and the walls of blood vessels. When the virus reactivates, it can travel along the nerve pathways, specifically from the cranial nerves like the trigeminal ganglion, to the cerebral arteries they innervate.
This transaxonal spread allows the virus to invade the adventitia, the outer layer of the artery wall. From there, the virus spreads transmurally, moving through the layers of the vessel wall to cause an inflammatory response. This direct infection triggers a type of inflammation called vasculitis.
The inflammation and direct viral damage lead to changes within the artery, including intimal thickening. This remodeling causes the blood vessel to narrow, a process known as stenosis. The compromised and narrowed artery becomes a site where blood clots are more likely to form, a condition called thrombosis, which ultimately blocks blood flow and results in an ischemic stroke.
Identifying the Highest Risk Window and Populations
The risk of experiencing a stroke is highly concentrated in a specific short-term window following a shingles outbreak. Studies show that the risk of acute ischemic stroke increases immediately after the onset of symptoms. The highest risk period is within the first two weeks following the appearance of the rash.
This elevated risk gradually diminishes but can remain statistically significant for up to six months after the initial outbreak. For example, some data indicates the stroke rate can be up to 61% higher in the first 14 days after shingles compared to the baseline risk.
Certain populations and clinical presentations are associated with a greater likelihood of this complication. Older adults, generally those aged 50 and above, are the most susceptible group due to age-related decline in immune function that allows VZV to reactivate. A particularly high-risk presentation is Herpes Zoster Ophthalmicus (HZO), which involves a shingles rash affecting the eye or forehead area supplied by the ophthalmic division of the trigeminal nerve. Individuals with HZO face up to a three-fold increase in stroke risk for a short period, as the virus has a direct path to the cerebral arteries.
Mitigation Through Vaccination and Acute Care
The most effective strategy for preventing VZV-associated stroke is primary prevention through vaccination. The current recombinant zoster vaccine is highly effective at preventing shingles, thereby eliminating the associated risk of VZV vasculopathy and subsequent stroke. Research suggests that vaccination is associated with a reduction in the risk of cardiovascular events, including stroke, by approximately 16% to 18% in adults 50 years and older.
In the event of an active shingles outbreak, acute antiviral treatment is recommended to reduce the severity and duration of the infection. Medications such as acyclovir or valacyclovir, when started within 72 hours of the rash onset, can limit viral replication and spread. While the primary benefit is treating the rash and pain, prompt antiviral therapy may also help lower the subsequent stroke risk, although the evidence remains mixed.
Regardless of antiviral treatment, anyone experiencing a shingles outbreak must be aware of potential stroke symptoms, especially during the first few weeks. Sudden onset of neurological deficits, such as facial drooping, arm weakness, or difficulty with speech, requires an immediate medical evaluation. Recognizing and treating stroke symptoms quickly remains the most important action to limit long-term disability should a stroke occur.