Neurological Symptoms in US Government Personnel in Cuba-Reply

In Reply

Our study¹ was a retrospective evaluation of data generated solely as part of clinical care. Research with this patient cohort was not originally anticipated due to secrecy and privacy concerns. However, owing to the extraordinary nature of patient reports and clinical findings, the US Department of State cleared the study as a public health matter. Although we must continue to withhold certain sensitive information and despite the preliminary nature of the data, we believe that we can address concerns raised by the letters.

Contrary to consensus findings by our evaluation team, Dr Bartholomew asserts that mass psychogenic illness is aplausible explanation. His diagnostic criteria for mass psychogenic illness include “preponderance of female participants,” “symptoms with rapid onset and recovery,” and “symptoms that are transient and benign.”² In contrast, there were 11 women in our cohort of 21 individuals, and symptoms were often disabling and persisted for many months. The reference to a more prolonged form of mass psychogenic illness describes “a slow accumulation of pent-up stress,” “dissociation,” and “shaking,” entirely different from the chronic symptoms found in our cohort. Furthermore, certain affected individuals had no interactions with others in the cohort, and at the time of our examinations, news reports focused primarily on auditory symptoms. Yet, the complex constellation of neurological symptoms was consistent across the cohort and objective deficits in the cognitive, visual, and balance systems were typically the most prevalent and troubling for affected individuals.

We agree with Dr Stone and colleagues that malingering and functional neurological disorders are not synonymous. However, it is unclear whether they are suggesting that each individual independently developed a functional neurological disorder or whether the mechanism was akin to mass psychogenic illness. Furthermore, functional neurological disorders are diagnosed when deficits are not better explained by an organic etiology. The challenge of this diagnosis was recently highlighted by posturography findings typically associated with psychogenic postural instability in patients with confirmed spinocerebellar ataxia.³ We look forward to more thorough demonstration of the inconsistency of functional neurological disorders in our patients in forthcoming publications. The provided examples of persistent postural perceptual dizziness and acoustic shock do not account for the full presentation of individuals in our cohort.⁴ It is also misleading to suggest that acoustic shock exhibits similar symptom frequencies to the cohort we described because the reference that Stone and colleagues provided lists no data on symptom prevalence nor any mention of physical examination findings.⁵

Dr Shura and colleagues raise concerns regarding our preliminary neuropsychological data. Interpretation of these results is more nuanced than a simple counting of scores lower than conventional percentile cutoffs. Within-individual deviations from an average performance are considered signs of brain dysfunction. Percentile scores in our report showed that all impaired patients had several scores that deviated by more than 1 SD from their respective means, some exceeding 2 SDs, which translates to more than 40 percentile points below their means ( below 10th percentile relative to their average performance). This meets standard criteria for neuropsychological impairment and was the justification for our clinical determination of domains of cognitive weakness.

In an attempt to be comprehensive in describing deficits, we did not have space in a single report to provide sufficient detail about each relevant clinical and research domain. For example, audiologic evaluations beyond pure tone audiometry, such as suggested by Dr Gianoli and colleagues, were conducted but omitted. Based on these unpublished findings and expertise of our colleagues in audiology and otorhinolaryngology, there were not clinical indications of unilateral or bilateral labyrinthine injury.

To further address these discussions, we are performing advanced neuroimaging studies of the patient cohort, hoping to identify structural brain changes that may underlie the neurological manifestations.