NIH Neuroimaging Study of Anomalous Health Incidents (Havana Syndrome)

Overview

The National Institutes of Health (NIH) conducted a comprehensive five-year study evaluating U.S. government personnel and family members who experienced Anomalous Health Incidents (AHIs), commonly known as "Havana Syndrome." The research, published in JAMA on March 18, 2024, found no significant MRI-detectable brain injury or biological abnormalities despite participants reporting severe symptoms.

Study Design and Methodology

Researchers evaluated more than 80 U.S. government employees and adult family members stationed abroad who reported AHIs, comparing them to matched healthy controls with similar work assignments but no AHI reports. The control groups included volunteers from the same geographic areas who did not experience anomalous health incidents.

Clinical Assessment Battery

Participants underwent comprehensive testing including:

Clinical assessments
Auditory testing (relevant to directional sound phenomena)
Balance and vestibular evaluation (for dizziness/vertigo symptoms)
Visual system assessment
Neuropsychological testing
Blood biomarker analysis

Neuroimaging Protocol

Participants received multiple MRI scan types aimed at investigating:

Brain volume measurements
Structural integrity
Functional brain activity

MRI scans were obtained an average of 80 days following symptom onset, with some participants scanned as early as 14 days after reporting an AHI.

Key Findings

Neuroimaging Results (Pierpaoli et al., JAMA March 2024)

Using thorough and robust methodology resulting in highly reproducible MRI metrics, researchers were unable to identify a consistent set of imaging abnormalities that differentiated participants with AHIs from controls.

> "A lack of evidence for an MRI-detectable difference between individuals with AHIs and controls does not exclude that an adverse event impacting the brain occurred at the time of the AHI. It is possible that individuals with an AHI may be experiencing the results of an event that led to their symptoms, but the injury did not produce the long-term neuroimaging changes typically observed after severe trauma or stroke." — Carlo Pierpaoli, M.D., Ph.D.

Clinical and Biomarker Results (Chan et al., JAMA March 2024)

No significant differences were found between AHI participants and matched controls across most clinical measures, except for certain self-reported outcomes:

| Symptom Category | Finding |
|-----------------|---------|
| Fatigue | Significantly increased in AHI group |
| Post-traumatic stress | Significantly elevated in AHI group |
| Depression | Significantly higher in AHI group |
| Functional neurological disorders (FND) | 41% of AHI participants met criteria |

Functional Neurological Disorders and PPPD

Forty-one percent of participants with AHIs, from nearly every geographic area, met criteria for functional neurological disorders (FNDs) — common neurological movement disorders caused by abnormal brain function. Most FND cases in the AHI group also met specific criteria for:

Persistent Postural-Perceptual Dizziness (PPPD):

Dizziness and non-spinning vertigo

Fluctuating unsteadiness provoked by environmental or social stimuli

Symptoms cannot be explained by other neurologic disorders

Study Limitations and Interpretation

The researchers note several important caveats:

1. Absence of detectable injury does not rule out an event: "It is possible that individuals with an AHI may be experiencing the results of an event that led to their symptoms, but the injury did not produce long-term neuroimaging changes typically observed after severe trauma or stroke."

2. Methodological limitations: Current methodologies and sample size may limit detection of subtle physiologic markers.

3. Temporal considerations: The study captured a snapshot in time; participants with AHIs experienced symptoms that were "very real, cause significant disruption in the lives of those affected and can be quite prolonged, disabling and difficult to treat." — Leighton Chan, M.D.

4. Stress-related factors: Post-traumatic stress and mood symptoms are not surprising given ongoing concerns about health and future among participants who experienced significant life disruption.

Research Team Leadership

Leighton Chan, M.D. — Chief, Rehabilitation Medicine; Acting Chief Scientific Officer, NIH Clinical Center (lead author on clinical/biomarker paper)
Carlo Pierpaoli, M.D., Ph.D. — Senior Investigator and Chief of Laboratory on Quantitative Medical Imaging, National Institute of Biomedical Imaging and Bioengineering (NIH) (lead author on neuroimaging paper)
Louis French, Psy.D. — Neuropsychologist; Deputy Director of National Intrepid Center of Excellence at Walter Reed National Military Medical Center

Publication Details

Two papers published in JAMA:
1. Pierpaoli C, Nayak A, Hafiz R, et al. Neuroimaging Findings in United States Government Personnel and their Family Members Involved in Anomalous Health Incidents. Published online March 18, 2024.

2. Chan L, Hallett M, Zalewski C, et al. Clinical, Biomarker, and Research Tests Among United States Government Personnel and their Family Members Involved in Anomalous Health Incidents. Published online March 10, 2024.