Herpes zoster infection (shingles): Clinical sciences

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Introduction0:00–0:34

Herpes Zoster infection, also known as shingles, occurs in individuals who have had a primary infection called varicella, or chickenpox, which is caused by the Varicella Zoster Virus.
Following the primary infection, the virus remains dormant in the dorsal root ganglia of spinal nerves or the trigeminal ganglion.
In times of stress or immunosuppression, the virus can reactivate and travel down the sensory neurons, causing herpes zoster.
Now, if your patient presents with a chief concern suggesting herpes zoster infection, first you should perform an ABCDE assessment to determine if your patient is unstable or stable.

Unstable patient0:34–1:36

If the patient is unstable, stabilize their airway, breathing, and circulation. Next, obtain IV access and put your patient on continuous vital sign monitoring including heart rate, blood pressure, and pulse oximetry.
Finally, If needed, provide supplemental oxygen. Now, here’s a high-yield fact to keep in mind!
If your patient is unstable, they may have disseminated herpes zoster, which can present with associated hepatitis, encephalitis, or meningitis.
This can happen because of compromised cell-mediated immunity, or following hematopoietic stem cell transplant, in which case high viremia causes an atypical presentation.
These patients can also be unstable on presentation because of the high viral load. Okay, now let’s go back to the ABCDE assessment and take a look at stable patients.

Stable patient1:36–3:23

If your patient is stable, obtain a focused history and physical exam. History typically reveals a prior history of varicella infection, as well as a painful, itchy, or tingly rash that may have been preceded by a prodromal illness of malaise, headache, fatigue, and a low-grade fever.
Physical exam typically reveals a maculopapular or vesicular rash in the distribution of 1 to 2 adjacent dermatomes, which are areas of skin innervated by a single nerve.
Typically, the rash appears on the trunk or the face, and it doesn’t cross the midline! At this point, you can clinically diagnose Herpes Zoster infection!
Now, keep in mind that the diagnosis of zoster infection is typically made clinically. However, in those cases where clinical findings aren’t enough to make the diagnosis, you can unroof a vesicle and use a PCR swab to detect the viral DNA and confirm the diagnosis!
Other diagnostic methods include the Tzanck test or smear, which detects multinucleated giant cells in the vesicle fluid; and the detection of serum IgM antibodies against the varicella-zoster virus.Now, here’s a high-yield fact!
Some patients can present with herpes zoster ophthalmicus, which occurs when the virus reactivates in the trigeminal ganglion and travels down the ophthalmic nerve.
This can affect all parts of the eye, including the retina, and eventually cause retinal detachment and necrosis, which can compromise longstanding vision.Ok, once you have diagnosed your patient with Herpes Zoster infection, proceed with treatment.

Herpes zoster infection3:23–4:23

Ideally, within 3 days of rash onset, you should start antiviral therapy, with medications such as acyclovir, famciclovir, and valacyclovir.
Immunocompetent patients can be treated with oral antivirals, such as acyclovir, famciclovir, and valacyclovir; while immunocompromised patients should be hospitalized to get IV acyclovir.
Of note, an important side effect of IV acyclovir is crystal-induced kidney injury, so to prevent it, make sure to also administer IV isotonic saline.
Also, don’t forget to prescribe oral analgesics, since shingles can be very painful, and the pain can last for days to weeks.
Finally, consider glucocorticoids, particularly in patients over 50 years of age, because they can reduce acute pain and promote early healing.assess your patient for possible complications 90 days following Herpes Zoster infection.

Postherpetic neuralgia4:23–5:50

The most common complication is postherpetic neuralgia, or PHN for short. With PHN, the pain is often disproportionate to stimuli and your patient will usually describe it as an “electric shock-like” feeling.
Postherpetic neuralgia occurs due to viral replication in the dorsal root ganglia that eventually leads to necrosis of nerve cell bodies.
Risk factors that increase the likelihood of postherpetic neuralgia include older age, ophthalmic involvement, immunosuppression, and the severity of prodromal or rash symptoms.
Also, keep in mind that the initial use of antivirals or glucocorticoids in treating Herpes Zoster infections doesn’t decrease the risk of this complication.
Once you diagnose postherpetic neuralgia, start the treatment with topical lidocaine or capsaicin. In severe cases, consider systemic medications targeting nerve pain, such as gabapentin, pregabalin, or tricyclic antidepressants.Now, here’s a clinical pearl to keep in mind!
Patients with Herpes Zoster Ophthalmicus can also experience postherpetic neuralgia, however, for them, topical analgesics are contraindicated due to corneal toxicity!Now let’s go back and take a look at a patient that has no dermatomal pain for 90 days following Herpes Zoster infection.

Dormant herpes zoster5:50–6:36

This means that the virus is dormant in the ganglia, so your patient requires no further intervention, but you can follow up clinically if needed.
And here’s one final clinical pearl! Herpes Zoster infection and postherpetic neuralgia are both vaccine-preventable.
Individuals older than 50 years of age are eligible to receive two immunizations with an adjuvant recombinant VZV vaccine administered 2 to 6 months apart.
The vaccine has been shown to reduce the incidence of Herpes Zoster infection in the majority of patients who receive it.
Alright, as a quick recap… Herpes Zoster infection, also known as shingles, occurs when a latent infection of the Varicella-Zoster-Virus, or VZV for short, reactivates and causes a painful rash along 1-2 adjacent dermatomes.

Review6:36–7:34

Once you diagnose Herpes Zoster infection, proceed with oral or IV antiviral medication and oral analgesics. In individuals over 50 years of age, you can consider glucocorticoids as well.
Next, wait 90 days and assess your patient for possible complications. If the dermatomal pain persists 90 days following the infection, diagnose postherpetic neuralgia and start your patient on topical analgesics or systemic medications that target nerve pain.
On the flip side, if your patient has no complications after 90 days, no further intervention is needed, but you can follow up clinically.
on the flip side If your patient has no complications after 90 days no further intervention is needed but you