Havana syndrome: Neurologic symptoms in diplomatic personnel and the challenge of uncertain etiology

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Background and case definition

Havana syndrome refers to a cluster of neurologic and systemic symptoms first reported in 2016 among United States and Canadian diplomatic personnel stationed in Havana, Cuba. Affected individuals described an acute onset of auditory phenomena, followed by persistent symptoms including headache, dizziness, cognitive difficulties, sleep disturbance, and imbalance. Subsequent reports emerged from diplomatic postings in other countries.

No universally accepted diagnostic criteria exist. The term “anomalous health incidents” has been adopted in some government reports to avoid the presumption of a mechanism. From a neurologic perspective, most described cases resemble a mild traumatic brain injury-like syndrome without documented head trauma.

Reported clinical features

Across published case series, common features include:

• Sudden onset of:
• Loud or unusual auditory sensations
• Pressure or vibration sensations
• Subacute to chronic symptoms:
• Headache
• Dizziness and imbalance
• Cognitive complaints (attention, processing speed, memory)
• Sleep disturbance
• Visual discomfort
• Tinnitus

In an early cohort evaluated at the University of Pennsylvania, clinicians described a constellation of vestibular and cognitive symptoms similar to concussion. Objective findings included abnormalities on neuropsychological testing and vestibular measures in some patients, although conventional structural neuroimaging was largely unrevealing.

Neuroimaging findings

Advanced imaging studies have yielded mixed results. A diffusion tensor imaging study reported group-level white matter differences compared with matched controls. However, findings were subtle, not clearly localized to a single pathway, and did not establish causation.

Other investigations have failed to demonstrate consistent structural injury. Importantly, group-level statistical differences do not necessarily translate into diagnostic biomarkers for individual patients. No reproducible imaging signature has been validated.

Proposed mechanisms

Several hypotheses have been advanced:

1. Directed energy exposure. Speculation has centered on microwave radiation or other directed energy sources, based in part on historical research into radiofrequency effects on the auditory system. The so-called “microwave auditory effect” has been described experimentally but typically requires specific exposure conditions.
2. Toxin exposure. Organophosphate exposure was proposed by some investigators, particularly in the context of anti-mosquito fumigation in Cuba. However, objective toxicologic confirmation has been inconsistent.
3. Functional or psychogenic mechanisms. Some analyses have emphasized the role of expectation, stress, and social contagion in symptom amplification. Reviews in neurology and psychiatry journals have raised the possibility of mass psychogenic illness or functional neurologic symptom disorder in at least a subset of cases.
4. Environmental or acoustic sources. Another analysis suggested that recorded sounds attributed to “sonic attacks” were consistent with insect calls, challenging early assumptions of an acoustic weapon.

Recent United States intelligence community assessments have concluded that a foreign adversary-operated energy weapon is unlikely to explain most cases, though uncertainty remains in a minority of reports.

Differential diagnosis and clinical approach

For practicing neurologists, Havana syndrome is less a discrete disease than a diagnostic framework for evaluating unexplained neurologic symptoms in high-profile occupational settings. The differential diagnosis should include:

• Mild traumatic brain injury
• Vestibular migraine
• Functional neurologic symptom disorder
• Anxiety-related somatic symptoms
• Toxic or metabolic exposures
• Primary sleep disorders

A structured evaluation may include:

• Detailed temporal history of symptom onset
• Comprehensive neurologic examination
• Neuropsychological assessment
• Vestibular testing
• Standard structural magnetic resonance imaging
• Targeted laboratory testing guided by exposure history

Clinicians should avoid premature attribution to a specific mechanism in the absence of objective evidence. At the same time, symptoms should be taken seriously and managed using established approaches for post-concussive and vestibular syndromes.

Implications for neurology

Havana syndrome highlights several broader issues relevant to neurologists:

• The limits of current neuroimaging in detecting subtle injury
• The risk of conflating hypothesis with diagnosis in politically charged contexts
• The overlap between functional neurologic symptom disorder and environmentally attributed illness
• The need for careful communication with patients when etiology is uncertain

The episode underscores that clusters of neurologic symptoms can arise in complex psychosocial and geopolitical environments. For clinicians, the central task remains unchanged: provide a systematic evaluation, apply evidence-based management, and maintain diagnostic neutrality when pathophysiology is unclear.

As additional data emerge, the condition may ultimately be parsed into heterogeneous subgroups rather than a single unified entity. Until then, Havana syndrome remains a reminder of the intersection between neurology, public health, and international affairs.

Further reading

Bartholomew RE, Baloh RW. "Havana Syndrome": A post mortem. Int J Soc Psychiatry 2024;70(2):402-5. PMID 38146090

Muth CC, Lewis SL. Neurological symptoms among US diplomats in Cuba. JAMA 2018;319(11):1098-100. PMID 29450490

Swanson RL, Hampton S, Green-McKenzie J, et al. Neurological manifestations among US government personnel reporting directional audible and sensory phenomena in Havana, Cuba. JAMA 2018;319(11):1125-33. PMID 29450484

Verma R, Swanson RL, Parker D, et al. Neuroimaging findings in US government personnel with possible exposure to directional phenomena in Havana, Cuba. JAMA 2019;322(4):336-47. PMID 31334794

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