Havana syndrome: a scoping review of the existing literature

Introduction

Since 2016, numerous American and Canadian diplomats and secret (intelligence) agents in Cuba, China, and other places in the world have experienced an abrupt onset of unusual clinical symptoms including, tinnitus, vertigo, visual problems, and cognitive difficulties, after they encountered strange sounds or sensations; this has been called “Havana syndrome” (HS) [1], [2], [3]. Multiple hypotheses and potential mechanisms have been proposed, but none had been proven and the surrounding circumstances remain unclear [1], [2], [3]. For the very same reason, the optimal preventive or management strategy for HS is not clear yet. This syndrome should be considered, studied, and managed as a health concern, and not as a political issue; the scientific community has the moral obligation of addressing the questions surrounding this issue [1].

The aim of the current review is to make a comprehensive search of the literature to depict a clear picture of what we know about this mysterious syndrome. This may pave the road to tackle the mysteries and questions around this topic by designing future steps. The main questions to be answered in the current manuscript are: 1. What are the symptoms of HS? 2. What is the etiology of HS? 3. How should we prevent HS from happening (how to protect the people)? 4. How to treat HS?

Methods

While this study was not considered to be a typical systematic review due to scarcity of the publications and data, the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement were followed to increase the reliability of the data collection process [4, 5] (Figure 1). MEDLINE (accessed from PubMed) [6], Scopus [7], and Ovid [8] databases from 2016 until 24 September 2021 were systematically searched for the related published manuscripts. The following search strategy was implemented in all the electronic databases and these key words were used: “Havana syndrome” OR “Neurological Symptoms and US Diplomats” (all fields). To ensure the literature search saturation, Google Scholar [9] was also searched with the key word “Havana syndrome” for the most relevant hints.

Figure 1:

PRISMA flow diagram for the study.

All articles were included (no exclusions). Finally, the reference lists of the included studies or other reviews were scanned to add any other relevant manuscripts.

The full articles for all the titles that appeared relevant or where there was any uncertainty were acquired. The following data were extracted from the included manuscripts: study authors, year of publication, the country, and also the study design, main results, and limitations. The methodological quality of the included studies was assessed. The class of evidence was defined following the Levels of Evidence – Wiley Online Library (Appendix 1) [10].

Data availability statement

Research data sharing is not applicable to this endeavor.

Results

The primary search yielded 120 publications. After an extensive search of all the sources (see the methods), only five original studies (Table 1) and 18 non-original articles (Appendix 2) were considered to be relevant and were included in the current review [1], [2], [3, 11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30] (Figure 1). There were three clinical original studies [15, 19, 30]. While these studies provided a constellation of signs and symptoms for HS, none provided a good level of evidence and all had significant limitations (Table 1). There were two original imaging studies [16, 23]. None of the imaging studies were sufficient to serve as a basis for a case definition or for the management of HS [22].

Discussion

Since 2016, numerous American and Canadian diplomats and secret (intelligence) agents in Cuba, China, and other places in the world have experienced an abrupt onset of unusual clinical symptoms called “Havana syndrome” (HS). The documented number of these people is 134 persons (61 people in the follow-up studies) [15, 16, 19, 23, 30]. The current review, in spite of all the skepticism in the literature [12, 17, 20, 21, 24, 28], suggests that HS is a nonspecific neurological illness with an unidentified causative factor(s), an acute phase of specific auditory-vestibular symptoms and signs, and a chronic phase of nonspecific neurobehavioral symptoms and signs. While the cause of this illness is not clear yet, a combination of factors (e.g., pulsed RF energy source, neurotoxins, psychological issues, etc.) may interact to affect an individual. For the very same reason, there is no proven treatment or preventive options for this illness yet.

The scientific community has the obligation of investigating and addressing the questions surrounding this illness. Other stakeholders should facilitate the work that needs to be done by the scientific community. For the first step, holding an international scientific meeting to discuss the various aspects of the illness by different stakeholders (e.g., physicians, scientists, politicians, patient advocacy groups, etc.) is a very reasonable approach. On February 10, 2022 (after the initial submission of the current paper and during the review process), UT Southwestern hosted a comprehensive symposium on Havana Syndrome from a medical and scientific perspective on a national level [32]. While this meeting was a valuable endeavor, considering the various aspects of this condition, it is probably more reasonable to hold an international scientific meeting to discuss this issue more comprehensively and by different stakeholders. In the second step, a core group of experts, including physicians (e.g., neurologists, ear specialists, psychiatrists, radiologists), toxicologists, rehabilitation therapists, psychologists, neuroscientists, physicists, and others should address various aspects of this illness (e.g., definition, terminology, diagnosis, treatment, and prevention).

While at the moment no solid recommendations could be provided, the following suggestions may pave the road for the next steps in tackling this issue [22, 32]:

1. Have baseline neurocognitive, auditory, and vestibular assessments in all personnel at risk, before their deployment.

2. The at risk personnel should be trained and equipped with the capability to measure and characterize their exposure to RF energy in real time, should the need arise in the future.

3. A systematic approach should be developed for neuro-otologic, motor, cognitive, neuroimaging, and toxicological assessments, should the need arise in the future.

4. A database system should be developed to collect all the information in a prospective manner.

Conclusions

Havana syndrome is a nonspecific neurological illness with a yet unidentified etiology, a clear acute phase of auditory-vestibular symptoms, and a chronic phase of neurobehavioral symptoms. This syndrome should be considered and investigated as a health concern, and not as a political issue.