Stroke: An underappreciated complication of chickenpox that we should never see

The vaccines that I most commonly write about are the measles-mumps-rubella (MMR) vaccine, the HPV vaccine, and the flu vaccine, although I have to a lesser extent written about the pertussis vaccine. The reason, I suspect, is that these are the vaccines that provoke the most attacks from the antivaccine movement, the MMR, of course, because it is the vaccine that Andrew Wakefield falsely implicated as a cause of autism, the HPV vaccine because it prevents a sexually transmitted disease and is often the subject of pseudoscientific attacks based on its aluminum adjuvant or false claims that it causes premature ovarian failure or female infertility—or even death; and the influenza and pertussis vaccines because they are imperfect vaccines. One vaccine, however, that I haven’t written about much (if at all) is the varicella zoster vaccine; i.e., the vaccine against chickenpox. Yes, I have written about the shingles vaccine, but not so much about the standard varicella vaccine that children receive to prevent chickenpox.

If there’s one vaccine that’s often derided as “unnecessary” by antivaxers, it’s the varicella vaccine. As they do with measles, antivaxers like to misrepresent the chickenpox as a harmless childhood disease that children get, get over, and then have lifelong “natural” immunity to the disease. For instance, here, über-quack Dr. Joe Mercola dismisses chickenpox as a “relatively benign childhood illness” and the vaccine as providing “only TEMPORARY immunity, and that immunity is not the same kind of superior, longer lasting immunity you get when you recover naturally from chickenpox” while implying that sunlight exposure will inactivate the virus, as though that would work once there’s an active case of chickenpox.

Antivaccine pseudoscience aside, prior to the vaccine:

Prior to the availability of varicella vaccine there were approximately 4 million cases of varicella a year in the U.S. Though usually a mild disease in healthy children, an estimated 150,000 to 200,000 people developed complications, about 11,000 people required hospitalization and 100 people died each year from varicella. Varicella tends to be more severe in adolescents and adults than in young children. The most common complications from varicella include bacterial superinfection of skin lesions, pneumonia, central nervous system involvement, and thrombocytopenia.

There’s also another potential complication: Stroke. A story from last week reports:

In a recent study published in The Journal of Pediatrics, it was documented that an 11-month-old boy suffered a stroke as a result of exposure to the chickenpox a few months prior.

The baby’s mother took him to the doctor after she noticed that he had weakness in his right arm and leg after he woke up from his normal afternoon nap. Tests were conducted on the baby which revealed that he had suffered a stroke, the study said.

Doctors believe that the baby’s stroke was caused by a complication relating to the chickenpox, which they think he must have contracted from a sibling. The boy, along with his two older siblings who were not vaccinated for the virus, contracted the chickenpox two to three months before he woke up with weakness on his right side.

This was also reported last month by NBC News, but somehow I missed it. I’m now rectifying this situation. First, I’ll look at the case report and how this child presented:

A previously healthy, unimmunized 11-month-old boy presented with acute right-sided weakness. On the day of presentation, his mother noted that his right arm and leg seemed to be weak when she woke him from his usual afternoon nap. Evaluation at an urgent care center confirmed right-sided facial weakness, decreased strength and movement of his right upper and lower extremities, and a lack of right-sided support in a sitting position. Computed tomography of the head without contrast was normal. He was transferred to a regional care center where head magnetic resonance imaging and magnetic resonance angiography demonstrated a left middle cerebral artery stroke and irregularities in the middle cerebral artery concerning for thrombus and vasculopathy (Figure, A and B). History revealed that the patient, as well as his older siblings, had primary chickenpox infection 2-3 months previously. The patient had a mild case of varicella, with a few scattered vesicular lesions which resolved without obvious sequelae. Owing to concern about varicella zoster virus (VZV) vasculopathy, he was started on high-dose intravenous acyclovir. A lumbar puncture performed 2 days after admission revealed a cerebrospinal fluid VZV DNA level of 880 copies/mL. Serum was positive for VZV IgG and negative for IgM. He received 10 days of intravenous acyclovir and was discharged home on oral valacyclovir 20 mg/kg 3 times daily.

Of course, this child was only 11 months old, which means he was too young to receive the first dose of of his varicella vaccine. That meant that he needed to rely on community immunity (formerly known as herd immunity) to protect him for another month. Unfortunately, having two unvaccinated older siblings in the house guaranteed that, if one sibling got the disease, they all would get the disease. Apparently that’s what happened.

To be honest, I didn’t know that stroke was a potential complication of varicella infection. I should have, I guess, but I didn’t. I knew about complications like meningoencephalitis, acute disseminated encephalomyelitis, Guillain-Barré syndrome, Ramsay-Hunt syndrome, cerebellar ataxia, myelitis, and vasculopathy, but for some reason stroke didn’t click in my mind associated with vasculopathy. The authors of the case report cite a 2014 study listing the neurologic complications of varicella zoster infection, which taught me that varicella-associated stroke generally occurs from 2-26 weeks after rash onset and that such strokes have a characteristic appearance on neuroimaging. I also noted that, in this series, at discharge from the hospital severe neurologic deficits were present in 40% and neurologic deficits persisted at least a year in 1/3 of the children who suffered stroke.

Overall, there is a four-fold increased risk of stroke in the six months after chickenpox, with no increased risk after vaccination against varicella found in a retrospective cohort study of over 3 million children. Last year, deVeber et al reported a decreased incidence of post-varicella arteriopathy after the widespread availability of vaccination in Canada.

Because the disease is less common than it was, thanks to the vaccine, parents are increasingly unaware of its potential complications:

As chickenpox cases became increasingly rare, fewer people remembered how dangerous they could be, said Dr. Tina Tan, a professor of pediatrics at Northwestern University’s Feinberg School of Medicine and a pediatric infectious disease specialist at the Robert H. Lurie Children’s Hospital.

“Everyone thinks it’s a minor illness,” said Tan, who is also chairwoman of the section on infectious diseases for the American Academy of Pediatrics. “There are a number of serious complications.”

Though relatively rare, stroke is one of them, Tan said. “Basically, the chickenpox virus infects the large blood vessels in the brain and causes inflammation in them,” she explained. “The blood vessels can scar and that can decrease blood supply to the brain, which can lead to stroke.”

As is the case in adults, the specific neurological deficits depend upon which blood vessels are involved, how extensively, and which ones clot or occlude enough to cut off the blood supply to parts of the brain. Like adults, children can be left with permanent neurologic deficits, although, depending upon how young they are, they are more likely to recover more function than an adult:

While some people recover with rehab, others live with permanent disabilities, Tan said. “They can have paralysis or seizure disorders,” she explained. “It all depends on which blood vessels are involved.”

In the case of the boy in the report, prospects looked grim. “My read on this is that he will have some type of permanent neurologic sequelae (consequences) from his disease,” Tan said. “And it is possible that he might have another stroke if his arterial disease continues to worsen.”

There is a high likelihood that this child’s stroke could have been avoided if his parents had just vaccinated their older children, but they didn’t and now they have a child who might well be left with permanent neurological deficits.

This is an incredibly sad story, the more so because it was highly preventable. It’s also not just the small risk of serious complications that vaccination against varicella zoster provides as a benefit. It’s just plain humane. I remember getting chickenpox when I was around seven years old. It’s one of the few things I remember vividly from that age, and it’s because the pox made me so very, very miserable. There’s great value in preventing that suffering as well, which is something that we sometimes forget.