Shingles is a painful rash caused by the reactivation of the varicella-zoster virus (VZV), the same virus responsible for chickenpox. After recovery from chickenpox, VZV remains dormant in nerve tissues. A decline in the immune system can allow the virus to reawaken as shingles. There is a clear, documented link between a shingles episode and an elevated risk of experiencing a stroke. Studies show that adults who have had shingles face an increased likelihood of developing a cardiovascular event, such as a stroke, compared to those who have not. This heightened risk is most pronounced in the weeks and months immediately following the rash.
The Direct Link How Shingles Affects Blood Vessels
The biological mechanism connecting a rash on the skin to a cerebrovascular event in the brain is known as VZV vasculopathy. This process begins when the reactivated virus travels beyond the sensory nerves that supply the skin and penetrates the walls of nearby arteries, particularly those supplying the brain. The virus productively infects the cells lining the cerebral arteries, which triggers an intense inflammatory response called arteritis or vasculitis. This inflammation leads to a thickening and disruption of the arterial wall’s structure, causing the vessel to narrow and become less flexible.
This narrowing, or stenosis, can significantly impede blood flow to parts of the brain, creating the conditions for an ischemic stroke. Furthermore, the virus-induced inflammation promotes the formation of blood clots inside the damaged vessel. Researchers have identified that the virus may also release lipid vesicles called exosomes that carry prothrombotic proteins, further encouraging clotting. In combination, these effects lead to the occlusion of the artery, cutting off the oxygen supply and causing a stroke.
The virus spreads from the nerve ganglion, where it lies dormant, along the nerve fibers directly to the outer layer of the artery wall. From this outer layer, the virus spreads inward toward the vessel’s lumen, causing chronic damage that can persist long after the visible rash has healed. This direct invasion and subsequent inflammatory remodeling of the blood vessel is a unique way a viral infection can cause stroke.
Identifying High-Risk Situations
While any case of shingles elevates the risk of stroke, certain circumstances carry a higher risk. The most important factor is the location of the rash, specifically Herpes Zoster Ophthalmicus (HZO), which involves the ophthalmic branch of the trigeminal nerve. When shingles affects the forehead, eyelid, or eye area, the virus is in close proximity to the major arteries supplying the brain. This anatomical closeness allows VZV to spread more easily to the cerebral blood vessels, leading to a stroke risk three to four times higher than a rash elsewhere on the body.
The timing of the stroke is also a strong indicator, with the highest risk occurring in the acute phase following the shingles outbreak. The incidence of stroke is most elevated in the first few weeks, particularly within the first 14 days after the rash appears. This heightened risk gradually decreases over the following months but can remain elevated for up to a year. Patients under the age of 40 also have a particularly acute increase in risk.
Urgent Warning Signs and When to Seek Help
Recognizing the signs of a stroke or transient ischemic attack (TIA) following a shingles episode requires immediate action. The established mnemonic for recognizing stroke symptoms is F.A.S.T., which helps people quickly assess the situation.
F – Face Drooping
Check if one side of the face is numb or if the smile is uneven.
A – Arm Weakness
See if the person can raise both arms and keep them there without one drifting down.
S – Speech Difficulty
Listen for slurred speech or an inability to speak coherently and repeat a simple phrase.
T – Time to Call
Call emergency services immediately if any of these signs are present. A more comprehensive assessment, sometimes called B.E. F.A.S.T., includes Balance loss and Eye/vision changes, which can also be symptoms of a stroke.
If a person has recently had a shingles rash and begins to exhibit any of these neurological symptoms, emergency medical services must be contacted without delay. Inform emergency responders about the recent history of shingles. The window for effective stroke treatment, such as clot-busting medications, is very narrow, making the immediate communication of medical history a potentially life-saving action.
Reducing the Risk Through Vaccination and Treatment
The most effective strategy for mitigating the stroke risk associated with VZV is to prevent the shingles infection. The recombinant zoster vaccine, Shingrix, is highly effective at preventing the reactivation of the virus. This vaccine is recommended for adults aged 50 and older, as well as for those 19 and older who are immunocompromised.
When a shingles rash occurs, immediate treatment with antiviral medication is necessary. These medications limit the virus’s ability to replicate and reduce the severity and duration of the painful rash. Prompt initiation of these antivirals, ideally within 72 hours of the rash onset, is the standard of care. While antivirals treat the acute infection, studies suggest they may not significantly reduce the stroke risk once the vasculopathy process has begun. Therefore, the focus remains on preventative vaccination to protect against shingles and its serious neurological complications.