Researchers studied four children and young adults who developed acute flaccid myelitis (AFM), a rare condition that causes sudden weakness or paralysis, after the COVID-19 pandemic began. They found that these cases looked different from typical AFM cases—some patients were older than usual, some didn’t have the typical warning signs, and all had low vitamin D levels. The study suggests that the pandemic may have changed how this rare illness appears in patients. Doctors also discovered that how long patients stayed in the hospital and certain test results were better at predicting recovery than brain imaging.

The Quick Take

  • What they studied: How acute flaccid myelitis (a rare polio-like illness causing sudden weakness) has changed since the COVID-19 pandemic started, and what signs might predict whether patients will recover well.
  • Who participated: Four patients (ranging from children to young adults) who were officially diagnosed with acute flaccid myelitis after the COVID-19 pandemic began. Two were identified with enterovirus D68, a virus linked to this condition.
  • Key finding: These four AFM cases showed unusual features compared to typical cases: some patients were older than expected, most didn’t have the typical viral warning signs beforehand, and all had low vitamin D levels. Shorter hospital stays were linked to better recovery outcomes.
  • What it means for you: If you or a loved one experiences sudden weakness or paralysis, doctors should consider AFM even if symptoms don’t match the typical pattern. Vitamin D levels and how quickly patients receive hospital care may be important for recovery. However, this is based on only four cases, so more research is needed before making major changes to treatment.

The Research Details

This study looked back at the medical records of four patients who were officially diagnosed with acute flaccid myelitis (AFM) after the COVID-19 pandemic started. The researchers carefully reviewed everything documented about each patient—when symptoms started, what tests were done, what treatments they received, and how well they recovered. They compared what they found in these four cases to what doctors typically see with AFM. This type of study, called a case series, is useful for spotting new patterns or unusual features in rare diseases, but it involves a small number of patients so the findings need to be tested in larger groups.

AFM is extremely rare, so it’s hard to study many patients at once. By carefully examining these four cases in detail, researchers can spot new patterns that might help doctors recognize and treat the illness better. The fact that these cases showed different features than typical AFM suggests that the pandemic may have changed something about how this illness develops or appears—possibly through changes in our environment, how viruses spread, or how our immune systems respond.

This study has important limitations to understand: it only includes four patients, so findings may not apply to all AFM cases. The researchers looked back at medical records rather than following patients forward in time, which can miss information. There’s no comparison group of typical AFM cases studied the same way. However, the study does use official CDC diagnostic criteria, meaning these are confirmed cases of AFM, not suspected ones. The detailed examination of each case provides valuable information for doctors treating similar patients.

What the Results Show

All four patients showed unusual features that don’t match the typical AFM pattern. Two patients were outside the normal age range for AFM (which usually affects children). Three patients didn’t have the typical viral warning signs (like fever or respiratory symptoms) that usually come before AFM. One patient had symmetric weakness (affecting both sides of the body equally) rather than the typical asymmetric pattern (affecting one side more than the other). All four patients experienced bowel and bladder dysfunction, and in two cases these problems persisted even after other symptoms improved.

When doctors performed spinal cord imaging (MRI), all four patients showed damage to the gray matter (the inner part of the spinal cord where nerve cell bodies live). However, the amount of damage seen on imaging didn’t match how severe the patient’s symptoms were—some patients with large areas of damage recovered well, while others with smaller areas had worse outcomes.

All patients tested had low vitamin D levels, which is interesting because vitamin D plays a role in immune system function. Two patients were identified with enterovirus D68, a virus known to cause AFM, and notably, both of these patients had better recoveries than the others. Patients who spent less time in the hospital tended to have better functional outcomes, suggesting that early recognition and treatment may be important.

Three of the four patients had normal or near-normal white blood cell counts in their cerebrospinal fluid (the fluid surrounding the spinal cord), which is unusual because AFM typically causes elevated white blood cell counts in this fluid. This finding suggests that post-pandemic AFM may involve different inflammatory patterns than classic AFM. Electrodiagnostic studies (electrical tests of nerve and muscle function) performed on two patients showed severe motor neuron injury, confirming that the problem was in the nerve cells controlling movement. These electrical tests appeared more helpful than MRI imaging for understanding disease severity.

Historically, AFM follows a biennial (every-two-years) outbreak pattern, but this pattern was disrupted by the COVID-19 pandemic. The cases described in this study show a broader range of clinical features than typically reported in AFM literature. The presence of sensory symptoms (abnormal feelings like tingling or numbness) in three patients is notable, as classic AFM primarily affects motor function (movement). The older age of some patients and the atypical cerebrospinal fluid findings suggest that post-pandemic AFM may represent an evolving disease pattern, possibly influenced by pandemic-related changes in viral circulation, population immunity, or environmental factors.

This study has several important limitations: only four patients were included, which is a very small number for drawing broad conclusions. The study is retrospective, meaning researchers looked back at medical records rather than following patients forward, which can result in missing information. There’s no control group of typical AFM cases studied the same way for comparison. Not all patients had the same tests performed (for example, only two had electrodiagnostic studies), making it hard to compare findings across all cases. The study cannot prove that the pandemic caused these changes—it only shows that the pattern appears different. Vitamin D was only measured in some patients, not all. Finally, because AFM is so rare, these four cases may not represent all post-pandemic AFM cases.

The Bottom Line

Based on this small study, doctors should consider AFM in patients with sudden weakness or paralysis even if they don’t have the typical warning signs or age profile. Checking vitamin D levels in patients with suspected AFM may be worthwhile, though more research is needed to understand why deficiency appears common. Early hospital admission and treatment appear associated with better outcomes, so seeking medical care quickly if symptoms develop is important. However, these recommendations are based on only four cases, so they should be confirmed in larger studies before becoming standard practice.

Parents and caregivers should be aware of AFM symptoms (sudden weakness, especially in the arms and legs, often after a viral illness) and seek immediate medical attention if they occur. Healthcare providers treating patients with sudden paralysis should consider AFM even in atypical presentations. Researchers studying rare neurological conditions and post-pandemic health effects should pay attention to these evolving patterns. People with vitamin D deficiency may want to discuss AFM risk with their doctors, though the connection needs more research. This study is less relevant for people without neurological symptoms or those living in areas with low AFM prevalence.

Recovery from AFM varies widely. In this study, patients who recovered well showed improvement within weeks to months of hospital admission. However, two patients had persistent bowel and bladder dysfunction even after other symptoms improved, suggesting some effects may be long-lasting. The timeline for seeing benefits from vitamin D supplementation (if deficiency is confirmed as important) would likely take weeks to months. More research is needed to establish realistic recovery timelines for post-pandemic AFM cases.

Want to Apply This Research?

  • If you have AFM or are at risk, track daily muscle strength and function using a simple scale (0-10) for arm and leg weakness, plus daily notes on bowel and bladder function. Record any new symptoms like tingling or numbness. This helps you and your doctor monitor progression and response to treatment.
  • Work with your healthcare team to ensure adequate vitamin D intake through diet, sunlight exposure, or supplementation if deficient. Keep detailed records of any viral symptoms (fever, cough, sore throat) that precede weakness, as this helps doctors identify patterns. Seek immediate medical attention if you develop sudden weakness or paralysis—don’t wait.
  • Set up a weekly check-in to assess muscle strength in arms and legs using a consistent method. Track vitamin D levels every 2-3 months if supplementing. Keep a symptom diary noting any changes in sensation, movement, or bowel/bladder function. Share this information with your neurologist at each visit to help identify trends and adjust treatment as needed.

This research describes only four cases of acute flaccid myelitis and should not be used to diagnose or treat any individual. AFM is a medical emergency requiring immediate professional evaluation. If you or someone you know experiences sudden weakness, paralysis, or loss of muscle control, seek emergency medical care immediately. Vitamin D supplementation should only be undertaken under medical supervision after proper testing. This summary is for educational purposes and does not replace professional medical advice. Always consult with qualified healthcare providers for diagnosis, treatment, and management of neurological conditions.