Though the risk appears small, a new review suggests that, in rare instances, monkeypox may trigger serious neurological complications, including seizures and brain inflammation.
The finding is based on a look at 19 studies conducted in the United States, the United Kingdom and across Africa.
All of the investigations worked with data collected before the recent monkeypox outbreak began in May. And the investigators cautioned it's not clear how applicable past outbreak experiences are to the current one, as viral types, medical care and patient profiles may differ considerably.
Still, the earlier research efforts collectively indicated that monkeypox patients face a 2% to 3% risk for being struck by at least one seizure, serious brain swelling (encephalitis) and/or mental confusion.
“Monkeypox is generally thought of as a skin disease,” said study author Dr. Jonathan Rogers, a researcher of neuropsychiatric disorders in the division of psychiatry at the University College London in the United Kingdom.
“But smallpox — a related viral infection — has been associated with serious neurological complications,” he added. “We wanted to find out whether there was anything similar in monkeypox.”
The answer appears to be yes, said Rogers, a conclusion that he characterized as “concerning.”
The studies collectively included just over 1,500 patients, a little more than 1,000 of whom had a confirmed monkeypox infection.
The team determined that depression and anxiety are common symptoms among monkeypox patients, as are muscle aches, fatigue and headaches.
In terms of rarer symptoms, the study authors noted that not all of the studies under review had data on all types of neurological complications. But by pooling data, the team ultimately pegged seizure risk at 2.7%, confusion risk at 2.4% and the risk for developing disabling encephalitis at 2%.
The researchers pointed out that most of the patients who experienced brain swelling had been hospitalized at the time, and therefore were already seriously ill.
Yet, Rogers noted that the review “didn't find that severe complications were restricted to very vulnerable groups.”
Nevertheless, Rogers emphasized that given “a massive gap in our understanding of this condition,” it's impossible to draw any firm conclusions about what effect such complications might have on patient health.
The report was published online Sept. 8 in the journal eClinicalMedicine.
Meanwhile, Rogers said that even if the risk for such severe complications is low, those who find themselves at risk during this latest outbreak would be wise to take advantage of the monkeypox vaccine Jynneos.
“If you're offered vaccination as part of a high-risk group, take it,” he said. “We just don't know who could become seriously unwell with monkeypox.”
That thought was seconded by Dr. Erica Johnson, chair of the American Board of Internal Medicine's Infectious Disease Board, and an assistant professor of medicine at Johns Hopkins Medicine in Baltimore.
“I think that vaccination is an important way to control the outbreak,” said Johnson. “And continuing to get the vaccination to as many people at risk as possible as quickly as possible should continue to be a major public health focus.”
Johnson also echoed Rogers' cautions that until more research is done — involving patients impacted by the latest outbreak — it remains unclear just how much the neurological risk seen in prior outbreaks still applies.
But, she added, “I think the more common clinical manifestations we are seeing in the current outbreak — mainly the pain associated with the lesions, and the long period of time that people must isolate due to risk of transmitting infection — are important reasons alone for individuals at risk to seek vaccination as soon as it is available to them.”
There's more on monkeypox at the U.S. Centers for Disease Control and Prevention.
SOURCES: Jonathan Rogers, MD, PhD-candidate, researcher, neuropsychiatric disorders, division of psychiatry, University College London, London; Erica Johnson, MD, chair, Infectious Disease Board, American Board of Internal Medicine (ABIM), and assistant professor of medicine, Johns Hopkins Medicine, Baltimore; eClinical Medicine, Sept. 8, 2022, online