The distribution of the transient global amnesia in the province of Ferrara, Italy, a clue to the pathogenesis?

Chronobiology of transient global amnesia

INTRODUCTION

The etiology of transient global amnesia (TGA) is still a matter of debate. Based, among others, on the observation of a close temporal relation between certain events and subsequent TGA episodes, recent proposals discuss the relevance of stress-associated processes impacting on hippocampal functioning. Circadian, infra- and ultradian rhythmicity has been found to play a relevant role in the multifactorial pathomechanisms of various disorders but has not been thoroughly studied in TGA.

METHODS

Data of patients with a final diagnosis of TGA were collected in Mannheim, Germany (06/1999-01/2018, n = 404), and in the Kansai district, Japan (04/2006-03/2018, n = 261). Chronological patterns of TGA occurrence were determined.

RESULTS

Significant circadian rhythmicity of TGA occurrence with bimodal peaks (mid-morning, late afternoon) was found for the entire population (p = 0.002) and for either sub-cohort (Mannheim: p = 0.003, Kansai: p = 0.007). This finding was confirmed for either sex (women: p = 0.004, men: p = 0.004) and different age groups (< 65 years: p = 0.0009, ≥ 65 years: p = 0.003). There was no variation according to day of the week, month or season, but the proportion of patients with a weekday episode was significantly higher in the Mannheim cohort (p = 0.002).

DISCUSSION

We identified a robust circadian rhythm in TGA occurrence which remarkably applied to either of the two study sites located on different continents and which was independent of sex and age. In light of abundant evidence of circadian rhythmicity of both, components of the human stress response system and memory, chronobiological analyses may provide an opportunity to further uncover the mechanisms underlying TGA.

Sex-related differences in stressful events precipitating transient global amnesia - A retrospective observational study

INTRODUCTION

Physically or emotionally charged events have consistently been reported as precipitating an episode of transient global amnesia (TGA). In conjunction with evidence of hippocampal involvement from neuroimaging, this has promoted the hypothesis that TGA is a stress-related disorder.

METHODS

In this retrospective observational study, medical records of 389 patients with TGA were analysed regarding documented precipitating events, which were classified according to previously suggested criteria. Moreover, comorbidities and results of magnetic resonance imaging were collected.

FINDINGS

In our cohort of TGA patients, 231 were female (59.4%). A precipitating factor was identified in 266 patients (68.4%). Of these, 136 patients (51.1%) reported physical triggers, the most common being physical exertion (64.0%). Another 122 patients (45.9%) presented with an emotional trigger, most frequently classified as an interpersonal conflict (42.7%). In 8 cases (2.1%), TGA was preceded by a medical procedure. Emotional triggers were more often experienced by women (37.2% vs 22.8%, p = 0.003), while physical stressors were more often present in men (30.7% vs 41.1%, p = 0.035). Women had a significantly higher number of hippocampal MRI lesions than men (mean 1.13 vs 0.92; p = 0.042).

CONCLUSION

Our data suggest a female predominance in TGA occurrence and a sex-related difference in susceptibility to certain triggering events in TGA patients. In light of recent research on sex-specific differences in vulnerability to stress, these findings support the hypothesis that this might be a significant contributing factor in the pathogenesis of TGA.