Beyond Shingles: The Hidden Effects of Varicella-Zoster Virus on the Central Nervous System

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Discover how varicella-zoster virus affects the central nervous system beyond shingles. Learn about meningitis, encephalitis, stroke risk, and the link to dementia.

Introduction

When most people hear "varicella-zoster virus" (VZV), they think of chickenpox and shingles. The itchy rash of childhood. The painful, blistering skin condition that afflicts older adults. But these skin manifestations are just the tip of the iceberg.

VZV is a "neurotropic virus" it has a natural affinity for nerve tissue . After the primary infection (chickenpox) resolves, the virus does not leave the body. Instead, it travels along nerve pathways to establish lifelong latency in the "cranial nerve and dorsal root ganglia"clusters of nerve cells along the spinal cord and brainstem .

When the virus reactivates—often decades later—it can travel back to the skin to cause shingles. But it can also travel in the opposite direction, moving **retrograde along nerve pathways to invade the central nervous system (CNS)** . The result? A spectrum of potentially devastating neurological complications that extend far beyond the familiar skin rash.

This article explores the hidden effects of varicella-zoster virus on the central nervous system. You will learn about meningitis, encephalitis, stroke risk, cranial nerve palsies, and the emerging link between VZV reactivation and dementia. Understanding these complications could save lives—because when VZV affects the brain, early diagnosis and treatment are critical.

Understanding Varicella-Zoster Virus and Its Neurotropism

The Virus That Never Leaves

Varicella-zoster virus (VZV), also known as human herpesvirus-3 (HHV-3), is a double-stranded DNA virus that belongs to the Alphaherpesvirinae subfamily . It is an "exclusively human pathogen"that causes two distinct clinical diseases:

Primary infection results in varicella (chickenpox)

Reactivation = of latent virus results in herpes zoster (shingles)

After the primary infection resolves, the virus does not leave the body. It establishes "lifelong latency "in the neurons of cranial nerve ganglia and dorsal root ganglia along the entire neuraxis . The virus "hides" inside these nerve cells, evading the immune system.

Reactivation: More Than Just a Skin Rash

With a decline in VZV-specific cell-mediated immunity—often due to aging, immunosuppression, stress, or other factors—the virus can reactivate . From its latent position in the ganglia, VZV can travel:

| Direction | Result |

|-----------|--------|

| **Anterograde** (to the skin) | Herpes zoster (shingles) with characteristic rash |

| **Retrograde** (to the CNS) | Neurological complications including meningitis, encephalitis, myelitis, and stroke |

Crucially, neurological complications can occur without any accompanying skin rash . This phenomenon, known as zoster sine herpete makes diagnosis particularly challenging . Up to one-third of patients with CNS VZV infection present without a typical shingles rash .

The Spectrum of Central Nervous System Complications

VZV can affect virtually any part of the central and peripheral nervous system. The manifestations are diverse and can be life-threatening.

VZV Meningitis

VZV meningitis is inflammation of the meninges—the protective membranes covering the brain and spinal cord. A retrospective study from a tertiary hospital in Greece analyzed 14 patients with confirmed VZV CNS infection .

Key findings:

| Feature | Percentage of Patients |

|---------|----------------------|

| Headache | 71.4% |

| Rash | 57.1% |

| Fever | 35.7% |

| Nausea/vomiting | 35.7% |

| Disorientation | 35.7% |

| Nuchal rigidity | 28.6% |

| Focal neurological signs | 28.6% |

All patients showed **lymphocytic pleocytosis** (elevated lymphocytes) in their cerebrospinal fluid (CSF), a hallmark of viral CNS infection . The median age was 49 years, and 35.7% were male.

**Notably, patients without a rash were younger and had a lower comorbidity burden** compared to those with a rash . This suggests that VZV CNS infection can affect otherwise healthy individuals—not just those who are elderly or immunocompromised.

An Australian study of 48 VZV meningitis cases found a **median age of 34 years** (range 21-86 years), confirming that younger adults are also at risk . Most patients received intravenous acyclovir, and outcomes were generally favorable.

VZV Encephalitis

Encephalitis—inflammation of the brain tissue itself—is a more severe complication. VZV encephalitis can present with altered consciousness, behavioral changes, seizures, and focal neurological deficits .

A case report described a 25-year-old patient with VZV encephalitis who presented with "ear pain, multiple cranial nerve palsies, difficulty swallowing, and gait imbalance" all without any skin rash . The patient had been vaccinated against VZV, yet still developed the infection.

Diagnostic clues

- CSF analysis typically shows **lymphocytic pleocytosis and elevated protein**

- VZV DNA detection in CSF by PCR has "sensitivity of 94-98% and specificity of 98-100%"

- Brain MRI may be normal in some cases, making CSF testing essential

Mortality and outcomes

- VZV encephalitis mortality is approximately **12-15%** in immunocompetent individuals and can approach 100% in untreated immunocompromised patients

- The Australian study of 13 VZV encephalitis cases found a **median age of 73 years** (range 22-94 years), with two deaths

- **Early treatment with intravenous acyclovir is critical** for favorable outcomes

Acute Limbic Encephalitis

A particularly concerning manifestation is **acute limbic encephalitis** (ALE). A Japanese study of 15 patients with herpes zoster CNS complications identified five cases of ALE .

Key features:

- Patients typically present with **fever, skin rash in the trigeminal nerve area**, and **altered consciousness**

- MRI reveals **medial temporal lobe lesions**

- The incidence of herpes zoster is increasing worldwide, and clinicians should be aware of ALE

### VZV Vasculopathy and Stroke

VZV can infect cerebral arteries, causing **vasculitis**—inflammation of blood vessel walls—that leads to stroke. This is one of the most serious hidden effects of the virus .

**Mechanism:**

VZV spreads transaxonally to innervated arteries, where it disseminates transmurally, infecting all layers of the cerebral vessel wall . This process results in:

- **Disruption of the internal elastic lamina**

- **Progressive thickening of the intima**

- **Decrease in smooth muscle cells within the media**

- **Granulomatous arteritis**

**Epidemiology:**

- In the Vascular Effects of Infection in Pediatric Stroke II study, nearly **10% of pediatric arterial ischemic stroke patients** had serological evidence of recent VZV infection

- Adults with ophthalmic-distribution zoster have a notably **higher stroke risk** compared to healthy controls

- The temporal relationship between primary infection and stroke can range from **less than 1 month to 9 months**

**Case study:** An 8-year-old boy developed **hemichorea** (involuntary movements of the right side) six months after uncomplicated chickenpox. CSF testing detected VZV DNA, and MRI revealed ischemic lesions in the basal ganglia—areas critical for movement control. He was not vaccinated against VZV. After treatment with acyclovir, prednisone, and antiplatelet therapy, he made a complete recovery .

### Cranial Nerve Palsies

VZV can affect multiple cranial nerves, causing diverse neurological symptoms.

**Facial nerve (VII):** Ramsay Hunt syndrome—facial palsy with ear rash—is well-recognized. However, other cranial nerves can also be affected.

**Glossopharyngeal (IX) and Vagus (X) nerves:** A rare case report described a 33-year-old man who developed difficulty swallowing, speech disorders, and ear pain following VZV reactivation . He had:

- Pseudobulbar syndrome with dysarthria and dysphagia

- Left vocal cord paresis

- Vesicular rash in the left external auditory canal

- CSF showing lymphocytic pleocytosis and positive VZV DNA

**Bilateral facial palsy:** Even rarer, a 2025 case report described **bilateral facial nerve paralysis** in a young adult following recent chickenpox infection . This highlights that VZV can cause "atypical" neurological presentations that may be overlooked.

### Autonomic Nervous System Involvement

VZV can also affect the autonomic nervous system—the part of the nervous system that controls involuntary functions like bladder and bowel function.

A 2026 case report described a 66-year-old immunocompetent man who developed **VZV meningoencephalitis with sacral shingles, urinary retention, and bowel dysmotility** . He required ICU admission. CSF analysis showed lymphocytic pleocytosis and markedly elevated protein, and VZV DNA was detected by PCR.

**Key takeaway:** Clinicians should be aware that **urinary retention and bowel dysmotility may represent clinically significant autonomic manifestations** of VZV reactivation, particularly with sacral dermatomal involvement .

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## Diagnosis: The Challenge of "Rash-Free" Cases

### Why Diagnosis Is Difficult

The most significant diagnostic challenge is that **neurological complications can occur without the typical shingles rash** .

Up to **one-third of patients with CNS VZV infection present without a rash** . In such cases, the diagnosis relies entirely on laboratory testing.

**Zoster sine herpete**—pain in a dermatomal distribution without rash—is a recognized variant . When accompanied by neurological symptoms, it can mimic other conditions like stroke, brain tumor, or autoimmune disease.

### Diagnostic Tests

|------|-------------|-------------|-------|

| CSF VZV DNA PCR | 94-98% | 98-100% | Gold standard for diagnosis |

| CSF analysis | N/A | N/A | Typically shows lymphocytic pleocytosis, elevated protein |

**Important considerations:**

- **PCR sensitivity is lower in VZV vasculopathy** (as low as 28%) compared to meningitis or encephalitis

- **CSF VZV IgG testing is recommended when PCR is negative** and clinical suspicion remains high

- **Brain imaging (CT/MRI) may be normal** in some patients, particularly those with isolated meningitis or cranial nerve palsies

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## Treatment: The Critical Role of Acyclovir

### Standard Treatment

Intravenous acyclovir remains the **standard of care** for VZV CNS infections .

Dosing

- Typical regimen: **10 mg/kg intravenously three times daily** (or 5x800 mg orally in mild cases)

- Duration: **14-21 days**, depending on severity

Outcomes:

- In the Greek study, **all patients received IV acyclovir** after VZV identification in CSF, with only one death (7.1%)

- In the Australian study, **all VZV encephalitis patients** and 77.1% of meningitis patients received IV acyclovir, with two deaths in the encephalitis group

- In the case of a 25-year-old with atypical presentation, early empiric acyclovir led to **complete neurological recovery**

The Role of Corticosteroids

Corticosteroids (like dexamethasone or prednisone) are sometimes used in addition to antivirals, particularly in cases with:

VZV vasculitis

Cranial nerve involvement

Significant inflammation on imaging

The evidence base for corticosteroids is limited, but they are commonly used in clinical practice, especially for more severe cases.

Treatment Considerations

| Condition | Recommended Treatment | Notes |

|-----------|----------------------|-------|

| VZV encephalitis | IV acyclovir | All cases should receive IV treatment |

| VZV meningitis | IV acyclovir in most cases | Oral antivirals may be considered in low-risk patients |

| VZV vasculitis | IV acyclovir + corticosteroids | Early treatment critical to prevent stroke |

| Cranial nerve palsies | IV/oral acyclovir ± corticosteroids | Prompt treatment may improve recovery |

HE Dementia Connection: Emerging Evidence

A Groundbreaking Discovery

Perhaps the most alarming hidden effect of VZV is its potential link to dementia. A landmark 2025 study published in **Nature Medicine** analyzed health records from **over 100 million individuals** in the United States .

The key findings were striking:

| Finding | Impact |

|---------|--------|

| **Recurrent shingles** | Associated with **7-9% higher risk of dementia** compared to single episode |

| **Shingles vaccination (Zostavax)** | Associated with **33% lower risk of dementia** at 3 years |

| **Shingles vaccination (Shingrix, 2+ doses)** | Associated with **27% lower risk of dementia** at 3 years |

| **Multiple vs. single Shingrix doses** | **24% lower dementia risk** with multiple doses |

| **Waning vaccine protection** | Protection against dementia **waned in correlation** with waning shingles protection |

How VZV May Contribute to Dementia

The study's authors propose that **continuous VZV reactivation** is the mechanism by which shingles contributes to dementia development .

Potential mechanisms:

- VZV infection of neural cells may trigger **inflammation and gliosis**

- VZV reactivation may **cause HSV-1 reactivation** in co-infected cells, leading to dementia-like cellular changes

- Increased levels of **amyloid and amylin** have been observed in CSF from VZV-infected individuals

- The waning of vaccine protection against shingles is **highly correlated** with waning protection against dementia, supporting a causal relationship

The clinical implication: VZV reactivation appears to be a modifiable risk factor for dementia . Vaccination against shingles not only prevents the immediate pain and rash but may also offer long-term protection against cognitive decline.

Risk Factors and Prevention

Who Is at Risk?

**Age:** The most significant risk factor. VZV reactivation increases with age due to declining cell-mediated immunity.

**Immunocompromised states:**

- Active cancer (solid or hematological)

- HIV infection

- Immunosuppressive therapy

- Organ transplantation

Stress and other factors:Physical or emotional stress can trigger reactivation .

Not just the elderly: CNS VZV infection can affect immunocompetent children and young adults. In the Greek study, patients ranged from 1 to 88 years of age . A case of hemichorea from VZV vasculitis occurred in an 8-year-old boy .

Prevention Through Vaccination

Varicella vaccine (for children) Since its introduction in 1995, the live attenuated varicella vaccine has prevented an estimated 91 million cases and over 2,000 deaths .

Shingles vaccines (for adults)

Zostavax (live attenuated): ~65% efficacy against shingles, protection wanes over ~10 years

Shingrix (recombinant): >80% efficacy against shingles; two-dose series recommended

Emerging evidence suggests shingles vaccination may also reduce

- Risk of stroke

- Risk of dementia

When to See a Doctor

Red Flags for VZV CNS Infection

If you or a loved one experience any of the following symptoms—especially with recent or past chickenpox/shingles—seek medical attention promptly:

Neurological symptoms:

- Severe headache

- Confusion or disorientation

- Neck stiffness (nuchal rigidity)

- Seizures

- Focal neurological deficits (weakness, speech problems, vision changes)

Cranial nerve symptoms:

- Facial weakness or paralysis

- Double vision or vision changes

- Difficulty swallowing

- Hoarseness or voice changes

- Ear pain

Movement disorders:

- Involuntary movements (chorea, tremors)

- Gait imbalance

Autonomic symptoms:

- Urinary retention

- Constipation

**Important:** These symptoms may occur **with or without a shingles rash**. The absence of rash does not rule out VZV CNS infection .

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Conclusion

Varicella-zoster virus is far more than a childhood illness or a skin condition. It is a neurotropic pathogen that can cause a devastating array of central nervous system complications: meningitis, encephalitis, vasculitis, stroke, cranial nerve palsies, autonomic dysfunction, and potentially even dementia.

The key takeaway is that these complications can occur **even in healthy individuals** and **even without a rash**. Early recognition and prompt treatment with intravenous acyclovir are critical for favorable outcomes . For VZV vasculitis and stroke, corticosteroids may also be necessary .

Prevention through vaccination is the most powerful tool. The varicella vaccine protects children from primary infection, while the recombinant shingles vaccine (Shingrix) dramatically reduces the risk of VZV reactivation in older adults. The emerging evidence that vaccination may also reduce the risk of dementia adds another compelling reason to get vaccinated.

If you or someone you know develops unexplained neurological symptoms—particularly with a history of chickenpox or shingles—do not ignore them. VZV is a virus that can strike beyond the skin, with hidden effects that can be life-altering. But with awareness, timely diagnosis, and appropriate treatment, the prognosis is often favorable.

Frequently Asked Questions

1. Can varicella-zoster virus affect the brain without causing a rash?

Yes. Up to one-third of patients with VZV CNS infection present without the characteristic shingles rash . This is called "zoster sine herpete" and makes diagnosis challenging .

2. What neurological complications can VZV cause?

VZV can cause meningitis, encephalitis, acute limbic encephalitis, vasculitis, stroke, cranial nerve palsies (including Ramsay Hunt syndrome), Guillain-Barré syndrome, myelitis, and autonomic dysfunction .

3. Is VZV CNS infection serious?

Yes. VZV encephalitis has a mortality rate of 12-15% in immunocompetent individuals and can approach 100% in untreated immunocompromised patients . Early treatment with acyclovir is critical.

4. Does shingles increase the risk of dementia?

Yes. A landmark 2025 Nature Medicine study found that recurrent shingles is associated with a 7-9% higher risk of dementia compared to a single episode . Conversely, shingles vaccination is associated with significantly lower dementia risk .

5. How is VZV CNS infection diagnosed?

Diagnosis is typically made by detecting VZV DNA in cerebrospinal fluid using PCR (sensitivity 94-98%, specificity 98-100%) . CSF analysis typically shows lymphocytic pleocytosis and elevated protein . CSF VZV IgG testing may be useful when PCR is negative .

6. Can healthy people get VZV CNS complications?

Yes. While the elderly and immunocompromised are at higher risk, VZV CNS infection can affect healthy individuals of all ages. The Greek study included patients from 1 to 88 years of age . Case reports have described VZV encephalitis in a 25-year-old and vasculitis in an 8-year-old .

7. What is the treatment for VZV CNS infection?

Intravenous acyclovir is the standard of care . Typical duration is 14-21 days. Corticosteroids may be added in cases of vasculitis or significant inflammation .

8. Can shingles vaccination prevent neurological complications?

Yes. Shingrix has >80% efficacy against shingles. Emerging evidence suggests vaccination may also reduce the risk of stroke and dementia . The 2025 Nature Medicine study found that Zostavax was associated with 33% lower dementia risk at 3 years .

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Beyond Shingles: The Hidden Effects of Varicella-Zoster Virus on the Central Nervous System