There is no single test that confirms Havana Syndrome. Because no consistent biomarker or brain imaging signature has been identified, testing involves a broad battery of clinical evaluations designed to document symptoms and rule out other conditions. The process typically spans auditory, vestibular, visual, neuropsychological, and blood-based assessments, often coordinated through specialized centers like the National Institutes of Health or Walter Reed National Military Medical Center.
Why There Is No Definitive Test
A large NIH study comparing 81 people who reported anomalous health incidents (AHIs) with 48 matched controls found no significant differences on MRI brain scans, blood biomarkers, or most clinical measures after adjusting for statistical rigor. The researchers concluded that if the symptoms were caused by some external phenomenon, they left no persistent or detectable physiological changes with current methods. That does not mean symptoms aren’t real. People reporting AHIs consistently describe severe problems with hearing, balance, cognition, and vision. But the lack of a measurable “fingerprint” means diagnosis relies on documenting those symptoms through a series of tests while excluding other explanations.
Neuroimaging
Brain MRI is one of the first evaluations performed, and it serves mainly to rule out tumors, strokes, or structural abnormalities that could explain symptoms. In the NIH imaging study published in JAMA, researchers used standard MRI, diffusion MRI (which tracks the structure of nerve fiber bundles), and functional MRI (which measures how different brain regions communicate). After correcting for multiple comparisons, none of these scans showed statistically significant differences between AHI participants and controls.
Some suggestive findings appeared before statistical correction: the corpus callosum, the large fiber bundle connecting the brain’s two hemispheres, was about 7% larger in the AHI group and showed subtle changes in fiber organization. Small differences also appeared in brain networks involved in attention and awareness. But these were not reliable enough to distinguish an individual case from a healthy person, which is why imaging alone cannot confirm a diagnosis.
Vestibular and Balance Testing
Balance problems and dizziness are among the most common complaints, so vestibular testing is a core part of the evaluation. The tests used in this context are the same ones used broadly in ear and balance medicine:
- Videonystagmography (VNG): Tracks eye movements in response to visual cues and head positions. Abnormal eye movements can reveal problems in the inner ear or the brain’s balance circuits.
- Caloric testing: Warm and cold water or air is introduced into the ear canal to stimulate the inner ear. The resulting eye movements help determine whether one or both ears are functioning normally.
- Rotational chair testing: You sit in a motorized chair that rotates at varying speeds while your eye movements are recorded. This evaluates how well the inner ear and eyes coordinate during motion.
- Video head impulse test (vHIT): Your head is quickly turned while you focus on a fixed target. The test measures whether your eyes can stay locked on that target, which reflects inner ear function.
- Posturography: You stand on a platform that can tilt or shift while sensors measure how well you maintain balance using vision, sensation from your feet, and inner ear input.
About 71% of the U.S. diplomats initially evaluated after the Cuba incidents showed impairment of the reflex that stabilizes vision during head movement, a finding consistent with inner ear or brainstem involvement.
Vision and Eye Movement Testing
Many people with suspected Havana Syndrome report blurred vision, difficulty reading, and light sensitivity. Eye movement testing checks for specific patterns that overlap with concussion-like injuries. In the initial group of diplomats evaluated, 52% had convergence insufficiency (difficulty focusing both eyes on a nearby object), 52% had abnormal smooth pursuit (trouble tracking a moving target), and 47% had problems with saccades, the quick eye jumps you make when shifting your gaze between two points. These are assessed by an eye movement specialist using infrared cameras that track the eyes precisely during a series of visual tasks.
Hearing Tests
Since many affected individuals describe a sudden onset of unusual sounds, pressure, or hearing loss, a full audiological workup is standard. This includes measuring hearing thresholds across different frequencies, testing uncomfortable loudness levels to map the ear’s dynamic range, and speech recognition testing to see how well the brain processes spoken language. Some evaluations also include speech-in-noise tests, which measure your ability to understand words against background babble, a task that’s especially sensitive to subtle auditory processing problems.
Neuropsychological Evaluation
Cognitive testing covers a broad set of mental functions. Evaluators typically measure executive function (planning, decision-making, mental flexibility), mood and behavior scales covering depression, anxiety, panic, anger, and apathy, and standardized questionnaires for post-traumatic stress. Tools like the Beck Depression Inventory, the Beck Anxiety Inventory, and the PTSD Checklist are commonly used alongside the Frontal Systems Behavior Scale, which specifically assesses whether the brain’s frontal lobe circuits are working normally. These tests help document cognitive complaints and also help identify conditions like depression or PTSD that can produce overlapping symptoms.
Blood Biomarkers
The NIH study tested for two proteins in the blood that rise after brain injury: glial fibrillary acidic protein, which is released when support cells in the brain are damaged, and neurofilament light chain, which leaks out of damaged nerve fibers. Neither marker showed significant differences between AHI participants and controls, even among those whose blood was drawn shortly after symptom onset (median of 76 days after the incident). These biomarkers are useful for ruling out active brain injury but cannot confirm or deny Havana Syndrome specifically.
What the Evaluation Actually Looks Like
If you’re a U.S. government employee or family member, the process typically starts with reporting through your agency. The Department of Labor treats AHIs as traumatic injuries, meaning you file a Form CA-1 (Notice of Traumatic Injury). If you were diagnosed with a traumatic brain injury, a fully detailed medical opinion on cause isn’t required to start the claims process. For other conditions, a physician’s statement is needed, though employees stationed overseas in remote areas can initially submit reports from a nurse or physician’s assistant, which are then reviewed by a stateside physician or a district medical advisor.
The comprehensive medical evaluation itself can take days. Expect separate appointments for hearing, balance, vision, cognitive testing, blood draws, and brain imaging. Many patients end up working with rehabilitation specialists in multiple areas, particularly for eye movement and balance retraining, as symptoms often persist for weeks or months. The majority of initially evaluated diplomats required intervention from multiple rehabilitation experts before their symptoms improved.
Ruling Out Other Conditions
Because there is no unique marker for Havana Syndrome, a significant part of testing is differential diagnosis: systematically eliminating other conditions that could explain the symptoms. The symptom profile overlaps with concussion, vestibular migraine, inner ear disorders like Meniere’s disease, anxiety and stress-related conditions, and autoimmune disorders affecting the nervous system. Brain imaging rules out structural causes. Blood work can screen for inflammation or metabolic problems. Vestibular and hearing tests can identify specific inner ear diseases. Neuropsychological testing helps distinguish cognitive symptoms caused by mood disorders from those with other origins.
Ultimately, a diagnosis of a suspected anomalous health incident is made when the pattern of symptoms matches the known profile, the onset corresponds to a reported incident, and other medical explanations have been excluded. It remains a diagnosis built on clinical judgment rather than a single confirmatory test.