Monkeypox linked to encephalitis, confusion, seizures

Key takeaways

• In a review of 19 studies dating back to 2003, researchers identified seizures (2.7%), confusion (2.4%) and encephalitis (2%) in patients with monkeypox.
• Other reported symptoms included headaches, anxiety, depression, myalgia and fatigue, though their prevalence could not be calculated due to high heterogeneity.

Preliminary evidence suggests there is an association between monkeypox and neuropsychiatric complications, including encephalitis, confusion and seizures, a study published in EClinicalMedicine found.

According to researchers, previous studies have linked adverse neurological events to related Orthopoxviruses. However, less is known about the neurological presentations of monkeypox.

“Analogous data from smallpox infection and vaccination with vaccinia indicate that neurological and psychiatric features may be significant,” James B. Badenoch, a researcher in the Preventive Neurology Unit at Queen Mary University of London, and colleagues wrote in EClinicalMedicine. “Encephalopathy is a common feature of the clinical presentation of smallpox and, whilst rare, cases of encephalitis, seizures and stroke have been described following both smallpox infection and vaccination.”

Badenoch and colleagues analyzed 19 eligible studies published between 2003 to 2022 that were comprised of 1,512 participants with suspected monkeypox. Among them, 68.2% had tested positive through the CDC or PCR testing.

The median age of participants based on eight studies was 24.2 years, and 45.1% were women. In the 12 studies that reported on monkeypox treatment, 77.9% of participants were hospitalized.

Results showed a 2.7% pooled prevalence for seizures (95% CI, 0.7-10.2), a 2.4% pooled prevalence for confusion (95% CI, 1.1-2.5), and a 2% pooled prevalence for encephalitis (95% CI, 0.5-8.2).

Researchers were unable to calculate the prevalence of several common symptoms due to high heterogeneity.

“The prevalence of other neuropsychiatric symptoms including myalgia, fatigue, headache, anxiety and depression are less clear, but several studies found at least half of individuals experiencing some of these outcomes,” Badenoch and colleagues wrote.

However, they noted that since these symptoms are common in both viral infections and patients who are hospitalized, their occurrences are more likely a “reaction to systematic illness,” rather than a neurological injury.

“Additionally, a paucity of follow-up and lack of evaluation of symptom severity and timing makes it hard to ascertain whether these symptoms are potentially highly disabling or milder and/or transient,” they wrote.

The researchers said their analysis was limited due to small sample sizes, as the pooled prevalence of seizures was based on two studies comprising of 74 patients. Furthermore, no studies reviewed clinical diagnosis methods for encephalitis or confusion in infected patients, leaving clinical implications unknown.

Because of the uncertainty of the long-term effects of encephalitis, in addition to it resulting “in considerable neurological and neuropsychiatric morbidity” in infectious or autoimmune causations, Badenoch and colleagues concluded more research on health outcomes of patients with the complication should be a key research objective.

References:

• Badenoch J, et al. EClinicalMedicine. 2022;doi:10.1016/j.eclinm.2022.101644
• Monkeypox linked to encephalitis or confusion in some patients. https://www.eurekalert.org/news-releases/964057. Published Sept. 8, 2022. Accessed Sept. 12, 2022.