Syndromes of transient amnesia: towards a classification. A study of 153 cases

Cognitive deficits and course of recovery in transient global amnesia: a systematic review

OBJECTIVE

Published evidence suggests that cognitive impairment during a TGA (transient global amnesia) spell may not be confined to episodic memory. We undertook a systematic review to determine the pattern of cognitive deficits during a TGA episode. As a secondary objective, we aimed to delineate the course of cognitive recovery.

METHODS

MEDLINE, EMBASE, CENTRAL, and Google scholar were systematically searched up to October 2023. Observational controlled studies including 10 or more TGA patients (Hodges and Warlow criteria) were retrieved. Data from case-control, cross-sectional, and cohort studies were reviewed and qualitatively synthesized.

RESULTS

Literature search yielded 1302 articles. After the screening of titles and abstracts, 115 full texts were retrieved and 17 of them were included in the present systematic review. During the acute phase, spatiotemporal disorientation, dense anterograde and variable retrograde amnesia, semantic memory retrieval difficulties, and working memory deficits comprised the neuropsychological profile of patients with TGA. Visuospatial abilities, attention and psychomotor speed, semantic memory, confrontation naming, and other measures of executive function (apart from semantic fluency and working memory) were consistently found normal. In the course of recovery, after the resolution of repetitive questioning, the restoration of spatiotemporal orientation follows, working memory and semantic memory retrieval ensue, while episodic memory impairment persists for longer. Meticulous evaluations may reveal subtle residual memory (especially recognition) deficits even after 24 h.

CONCLUSIONS

Μemory impairment, spatiotemporal disorientation, and working memory deficits constitute the pattern of cognitive impairment during a TGA spell. Residual memory deficits may persist even after 24 h.

A Case With Bilateral Hippocampal Infarction Resembling Transient Global Amnesia

Transient global amnesia (TGA) is a benign and transient condition with a sudden short-term amnesia. One of the conditions resembling TGA is hippocampal infarction, which requires relapse prevention treatments. In this report, we present a case with bilateral hippocampal infarction in whom distinguishing these two conditions was difficult for up to 1 week from the onset. A 60-year-old female visited our hospital with sudden onset retrograde and anterograde amnesia. Thin-slice magnetic resonance imaging (MRI) with 2-mm thickness revealed hyperintense signals on diffusion-weighted imaging (DWI) with signal loss on apparent diffusion coefficient (ADC) on both sides of the hippocampus. MRI with 5-mm thickness on day 7 revealed persistent restricted diffusion on both sides, one of which was still with decreased ADC values. Based on this finding, the diagnosis of bilateral hippocampal infarction was reached, and the relapse-preventive antiplatelet was continued. This case implied the potential difficulty of distinguishing cases with TGA and those with hippocampal infarction based on MRI findings within the first several days after onset. Thin-slice brain MRI, careful search of potential cardiovascular risks, and follow-up MRI ≥ 7 days after onset will be helpful to reach a correct diagnosis in cases with sudden amnesia.

Increased risk of epilepsy after transient global amnesia: A population-based study in South Korea

PURPOSE

This study aimed to investigate the risk of epilepsy after transient global amnesia (TGA).

METHODS

Study population was recruited using the International Classification of Diseases codes from the Korean National Health Insurance Service database between 2002 and 2020. The incidence of epilepsy was compared between the TGA (n=12,390) and non-TGA (n=33,868) groups, determined using 1:3 propensity score matching. Using Cox proportional hazard regression model, we obtained adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for incident epilepsy in the TGA compared with non-TGA group. Logistic regression was performed to examine the independent variables determining incident epilepsy in the TGA group, and adjusted odds ratios (aORs) and 95% CIs were calculated.

RESULTS

The TGA group had a significantly higher cumulative incidence of epilepsy than controls (p <0.001, log-rank test). TGA was significantly associated with incident epilepsy in the Cox model (adjusted HR 1.46, 95% CI 1.36-1.56). The adjusted logistic regression showed that age (per 1 year, aOR 1.02, 95% CI 1.01-1.02), female sex (aOR 0.68, 95% CI 0.60-0.77), hypertension (aOR 1.14, 95% CI 1.00-1.30), diabetes (aOR 1.26, 95% CI 1.10-1.44), stroke (aOR 1.22, 95% CI 1.06-1.40), depression (aOR 1.44, 95% CI 1.22-1.69), anxiety (aOR 1.31, 95% CI 1.14-1.51), alcohol-related disease (aOR 1.96, 95% CI 1.38-2.78), low income (aOR 1.18, 95% CI 1.02-1.36) and rural residence (aOR 1.20, 95% CI 1.02-1.42) were associated with incident epilepsy.

CONCLUSIONS

Our results suggest a longitudinal association of TGA with incident epilepsy.

Transient global amnesia and hippocampal diffusion restriction: an overlooked radiological finding

Transient global amnesia (TGA) is characterized by isolated sudden anterograde amnesia. Diffusion restriction can be observed in the hippocampus on DWI-MRI at varying rates in TGA patients. This study analyzes the prevalence and characteristics of the hippocampal diffusion restriction (HDR), its relationship with vascular risk factors, and the prevalence of lesions overlooked in routine reports. 91 patients diagnosed with TGA at a tertiary hospital between 2011 and 2022 were evaluated retrospectively. The mean age was 64.8 ± 7.3 years, and 63.7% of patients were female. 75.8% of the patients had at least one vascular risk factor. Focal diffusion restriction was detected in 17 patients (18.5%) on DWI-MRI, with only one being extra-hippocampal. 81.2% of HDR was detected when DWI-MRI scan was performed between 12 and 96 h after the onset of symptoms. HDR was detected most when the imaging was performed in 24 to 48 h (p = 0.03). There was no correlation between the duration of symptoms and the detection rates of HDR (p = 0.55). In 9 patients (53% of 17) diffusion restriction was not specified in routine radiology reports. Although focal ischemia, venous flow abnormalities, migraine and epileptic phenomena have been suggested in its etiology, TGA is a clinical condition of which pathophysiology has not been determined clearly. Signal changes observed in DWI-MRI has led to discussions that cerebrovascular etiology may play a role, yet more comprehensive studies are required to prevent and manage TGA. HDRs can be overlooked in routine reports. Therefore, the DWI-MRI images of patients with TGA should be examined vigilantly.

[Transient global amnesia - benign memory blackout]

Transient global amnesia (TGA) is a typical clinical syndrome characterized by acute, predominantly anterograde amnesia. New epidemiological data assume a significantly higher annual incidence than previously assumed, namely around 15 cases per 100,000 people. Those affected, usually over the age of 50, cannot remember new memory content for longer than 30-180 seconds and therefore ask repetitive questions about current events. All other cognitive functions are unimpaired, and everything previously learnt, e.g. driving or cooking, can be carried out. The episodes are self-limiting and by definition subside within 24 hours. At least 10% of those affected will experience 1-5 recurrences in the future. The punctate lesions in the hippocampus, which are found on MRI in at least 50% of patients after 24-72 hours, are distributed 2/3 unilaterally and 1/3 bilaterally. Using 7 Tesla MRI the frequency of detected lesions increases to 90% compared to 50% with 1.5 or 3 Tesla. Beyond the punctiform hippocampal lesions, other memory-related network disorders, including the default network, are also suggested to be involved in the pathomechanism of TGA. TGA etiology and pathophysiology are not known in detail. Vascular, migraine-like, epilepsy-like, and psychogenic mechanisms are discussed. Triggers of the episodes are often physical exertion with a Valsalva character. Management is aimed at identifying the syndrome based on the typical clinical presentation and ruling out possible differential diagnoses with similar symptoms. During the TGA, the usually anxious relatives should be reassured of the benign and inconsequential nature of the episode.

A Dive Into Oblivion: A Case of Transient Global Amnesia

Transient global amnesia (TGA) is an uncommon neurologic disorder that consists of a sudden and temporary loss of memory, both present and past. Its causes and risk factors are not well known. We describe a case of a 58-year-old woman who was brought to the emergency department (ED) with sudden onset loss of memory and disorientation after a dive in the ocean. She presented memory deficits with incapacity to retain new memories and amnesia for the previous 24 hours. All exams ordered were normal, including computed tomography of the brain and laboratory analysis. After six hours of close monitoring in the ED, she gradually started to retain short-term memories and was discharged after 48 hours with no memory or other deficits. The diagnosis of TGA was made based on the clinical presentation and the patient's rapid improvement. Follow-up neurology consultation and further testing did not demonstrate any evidence to exclude this diagnosis. Further research is needed on this topic to allow the identification of risk factors and causes to prevent it.

Ventral Anterior Cingulate Atrophy as a Predisposing Factor for Transient Global Amnesia

Background and Purpose

This study aimed to evaluate the brain magnetic resonance imaging (MRI) of patients with acute transient global amnesia (TGA) using volumetric analysis to verify whether the brains of TGA patients have pre-existing structural abnormalities.

Methods

We evaluated the brain MRI data from 87 TGA patients and 20 age- and sex-matched control subjects. We included brain MRIs obtained from TGA patients within 72 hours of symptom onset to verify the pre-existence of structural change. For voxel-based morphometric analyses, statistical parametric mapping was employed to analyze the structural differences between patients with TGA and control subjects.

Results

TGA patients exhibited significant volume reductions in the bilateral ventral anterior cingulate cortices (corrected p<0.05).

Conclusions

TGA patients might have pre-existing structural changes in bilateral ventral anterior cingulate cortices prior to TGA attacks.

Altered cerebellar volumes and intrinsic cerebellar networks in patients with transient global amnesia

This study aimed to investigate the differences in cerebellar volumes and intrinsic cerebellar networks between patients with transient global amnesia (TGA) and healthy controls. We retrospectively enrolled patients with TGA and age- and sex-matched healthy controls. We used three-dimensional T1-weighted imaging at the time of TGA diagnosis to obtain cerebellar volumes, and the intrinsic cerebellar network was calculated by applying graph theory based on cerebellar volumes. The nodes were defined as individual cerebellar volumes, and edges as partial correlations, controlling for the effects of age and sex. The cerebellar volumes and intrinsic cerebellar networks were compared between the two groups. We enrolled 44 patients with TGA and 47 healthy controls. The volume of the left cerebellar white matter in patients with TGA was significantly lower than that in healthy controls (1.0328 vs. 1.0753%, p = 0.0094). In addition, there were significant differences in intrinsic cerebellar networks between the two groups. The small-worldness index in patients with TGA was higher than that in the healthy controls (0.951 vs. 0.880, p = 0.038). In the correlation analysis, the volumes of the right cerebellar cortex and lobules VIIIB were significantly correlated with age in patients with TGA (r = -0.323, p = 0.033; r = -0.313, p = 0.038, respectively). Patients with TGA exhibit alterations in cerebellar volumes and intrinsic cerebellar networks compared with healthy controls. These findings may contribute to a better understanding of the pathophysiology of the TGA.

Changes in heart rate variability over time from symptom onset of transient global amnesia

Transient global amnesia (TGA) often involves precipitating events associated with changes in autonomic nervous system (ANS), and heart rate variability (HRV) reflects the ANS state. This study aimed to investigate HRV changes after TGA. A retrospective analysis of HRV included patients diagnosed with TGA between January 2015 and May 2020. The time and frequency domains of HRV were compared among three groups: early (< 1 week after TGA, n = 19), late (1-4 weeks after TGA, n = 38), and healthy control (HC, n = 19). The Pearson's correlation between time and time-domain HRV was also examined. The standard deviation of NN intervals (SDNN) (early, 47.2; late, 35.5; HC, 41.5; p = 0.033) and root mean square of successive RR interval differences (RMSSD) (early, 38.5; late, 21.3; HC, 31.0; p = 0.006) differed significantly among the three groups. Post-hoc analysis showed statistically significant differences only in the early and late groups in both SDNN (p = 0.032) and RMSSD (p = 0.006) values. However, the frequency domain with total power, low-frequency and high-frequency powers, and low-frequency/high-frequency ratio did not differ. SDNN (Pearson correlation coefficient =- 0.396, p = 0.002) and RMSSD (Pearson correlation coefficient =- 0.406, p = 0.002) were negatively correlated with time after TGA. Changes in HRV occurred over time after the onset of TGA, with the pattern showing an increase in the first week and then a decrease within 4 weeks.

A Rare Case of Exercise-Induced Transient Global Amnesia as an Exclusive Presenting Symptom of Hippocampus Infarct

Transient global amnesia (TGA) is a rare condition characterized by a temporary loss of the ability to form new memories. Retrograde episodic memory loss may also occur but to a lesser extent. Although TGA is generally benign, its sudden onset and similarity to more dangerous conditions like transient ischemic attack (TIA) or cerebral vascular accident (CVA) can be concerning. We present the case of a 70-year-old female who experienced confusion and general memory loss after a vigorous workout on her stationary exercise bike. After displaying considerable amnestic symptoms, she was admitted to the hospital for further medical attention and underwent a magnetic resonance imaging (MRI) that concluded a TGA diagnosis. This case report aims to investigate the prognosis associated with risk factors and refine the diagnostic criteria of TGA. We explore whether TGA caused by exercise, leading to unilateral or bilateral hippocampal lesions, is linked to cognitive decline. It is not yet clear if the development of TGA with unilateral infarct or bilateral hippocampal lesions results in different clinical presentations or varying prognoses. Further research is needed to determine the long-term risks of cognitive decline associated with resulting infarcts and clinical presentations.

Increased Risk of Dementia after Transient Global Amnesia: A Nationwide Population-Based, Longitudinal Follow-Up Study in South Korea

INTRODUCTION

The long-term cognitive outcomes after transient global amnesia (TGA) have been contradictory in the literature. Our study aimed to longitudinally investigate the association between TGA and incident dementia using long-term data from a nationwide population-based cohort in South Korea.

METHODS

The study population was recruited between 2002 and 2020 using the International Classification of Diseases (Tenth Revision; ICD-10) codes from the Korean National Health Insurance Service database. The cumulative incidence curve was plotted to compare the incidence of dementia between the TGA (ICD-10 code G45.4; n = 10,276) and non-TGA (n = 27,389) groups, determined using 1:3 propensity score matching. Using Cox proportional hazard regression models, we obtained crude and adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for the incident dementia in patients with TGA compared to non-TGA controls. To examine independent variables determining dementia in the TGA group, logistic regression analysis was performed, and adjusted odds ratios (aORs) and 95% CIs were calculated.

RESULTS

The TGA group had a significantly higher cumulative incidence of dementia than the non-TGA group (p < 0.001, log-rank test). TGA was significantly associated with incident dementia in the univariate and multivariate Cox models (HR 1.34, 95% CI 1.28-1.39 and aHR 1.40, 95% CI 1.34-1.46, respectively). The adjusted logistic regression for incident dementia in the TGA group showed that age (per 1 year, aOR 1.09, 95% CI 1.09-1.10), female sex (aOR 1.31, 95% CI 1.18-1.45), diabetes (aOR 1.21, 95% CI 1.08-1.35), stroke (aOR 1.30, 95% CI 1.16-1.46), depression (aOR 1.53, 95% CI 1.33-1.76), anxiety (aOR 1.24, 95% CI 1.01-1.39), and rural residence (aOR 1.24, 95% CI 1.10-1.41) were independently associated with incident dementia.

CONCLUSION

Our results suggest a longitudinal association of TGA with incident dementia.

Incidental Petrous Apex Cephalocele Presenting With Transient Global Amnesia: A Case Report and Rapid Literature Review

Transient global amnesia (TGA) constitutes a rare clinical entity that manifests with temporary memory without any other neurological manifestation. Several pathogenetic mechanisms have been implicated, including temporal hypoperfusion, venous congestion, and cortical spreading potentials. Accordingly, the only relevant imaging findings are hippocampal CA1 areas of restricted diffusion on diffusion-weighted images. In the current case report, we present the rare case of a patient with TGA associated with bilateral petrous apex cephalocele (PAC). A 63-year-old female presented with a single episode of transient memory. The brain MRI showed a bilateral PAC and an empty sella. The patient was neurologically intact upon examination and was conservatively managed. There was no symptom recurrence during the six months of follow-up. We hypothesize that the presence of the meningocele could be associated with the pathogenesis of TGA. To the best of our knowledge, this is the first case of a petrous apex meningocele presenting with TGA. Most previously reported patients were females in their fourth decade of life, usually presenting with headaches or incidentally. Almost half of the cases were bilateral, with an empty sella. Surgical treatment was reserved for symptomatic patients with cerebrospinal fluid leaks and excruciating trigeminal neuralgia. Patients with TGA may be associated with temporal lesions, including PAC. Likewise, PAC is an extremely rare clinical entity that could occasionally present with TGA.

Automated CT perfusion analysis reveals medial temporal perfusion abnormalities during transient global amnesia

INTRODUCTION

The underlying pathophysiology of Transient global amnesia (TGA) remains elusive. Reports of perfusion abnormalities in TGA were inconsistent, but semi-automated analysis of perfusion CT (CTP) may improve reliability and precision of perfusion deficit detection.

METHODS

Per institutional protocol, all TGA patients undergo multiphasic contrast-CT with arch to vertex CT angiography, intracranial CT venography, MRI, and EEG upon admission. During the study period consecutive patients diagnosed with TGA underwent CTP during the early acute amnestic phase. We retrospectively reviewed the clinical and radiological findings.

RESULTS

Five patients (3 female. median age 71, range 47-74) fulfilled entry criteria. Automated CTP analysis revealed the absence of an ischemic core (defined by CBF < 30%) or conventionally defined clinically relevant hypoperfusion area (defined by Time-to-maximum (Tmax) >6 s) in any of the patients. However, four of the five patients demonstrated territories of benign oligemia defined as Tmax>4 s in areas supplied by the Posterior Cerebral Artery. Three of these four patients had clear involvement of the bilateral medial temporal lobes. None of the patients had epileptic activity on their EEG. Both CTA and MRI were normal apart for small foci of restricted diffusion in the hippocampus of four patients.

DISCUSSION

Deficits in perfusion were found in the hippocampi of 60% of patients in the acute phase of TGA using automated image analysis software. This method may provide a quick and simple method to detect these abnormalities. These perfusion abnormalities could help solidify the diagnosis at an early stage and may advance our understanding of this elusive syndrome.

Involvement of the default mode network in patients with transient global amnesia: multilayer network

INTRODUCTION

We aimed to investigate the alterations in the multilayer network in patients with transient global amnesia (TGA).

METHODS

We enrolled 124 patients with TGA and 80 healthy controls. Both patients with TGA and healthy controls underwent a three-teslar brain magnetic resonance imaging (MRI). A gray matter layer matrix was created using a morphometric similarity network derived from the T1-weighted imaging, and a white matter layer matrix was constructed using structural connectivity based on the diffusion tensor imaging. A multilayer network analysis was performed by applying graph theoretical analysis.

RESULTS

There were no significant differences in global network measures between the groups. However, several regions, related to the default mode network, showed significant differences in nodal network measures between the groups. Multi-richness in the left pars opercularis, multi-rich-club degree in the right posterior cingulate gyrus, and weighted multiplex participation in the right posterior cingulate gyrus were higher in patients with TGA compared with healthy controls (15.47 vs. 12.26, p = 0.0005; 41.68 vs. 37.16, p = 0.0005; 0.90 vs. 0.80, p = 0.0005; respectively). The multiplex core-periphery in the left precuneus was higher (0.96 vs. 0.84, p = 0.0005), whereas that in the transverse temporal gyrus was lower in patients with TGA compared with healthy controls (0.00 vs. 0.02, p = 0.0005).

CONCLUSION

We newly find the alterations in the multilayer network in patients with TGA compared with healthy controls, which shows the involvement of the default mode network. These changes may be related to the pathophysiology of TGA.

Clinical Course and Recurrence in Transient Global Amnesia: A Study From the TEMPiS Telestroke Network

BACKGROUND AND PURPOSE

While the clinical hallmarks of transient global amnesia (TGA) are well defined, its pathophysiological causes are poorly understood. Specifically, risk factors for recurrences are yet to be determined.

METHODS

This retrospective study analyzed TGA cases diagnosed and treated within the TEMPiS telestroke network and a university stroke center in Germany. Demographic and clinical data were assessed and characteristics of TGA episodes were recorded, such as season of occurrence, trigger factors, duration, and concomitant symptoms. Follow-up of the potential recurrence of TGA was performed using a standardized questionnaire.

RESULTS

Overall 109 patients were included (age 64±8 years [mean±SD], 59.6% female). The most common vascular risk factor was arterial hypertension (60.6%), and other concomitant conditions included migraine (11.9%), hypothyroidism (22.9%), and atrial fibrillation (4.6%). The most frequent concomitant clinical feature accompanying the TGA episode at admission was elevated blood pressure (48.6%). Nineteen patients experienced at least one recurrent TGA episode. Migraine and hypothyroidism were only observed in subjects with a single TGA episode without recurrence (migraine: 14.4% without recurrence vs. none in the recurrence group, p=0.02; hypothyroidism: 27.8% without recurrence vs. none in the recurrence group, p=0.009). In contrast, atrial fibrillation was more common in subjects with TGA recurrence (p<0.001).

CONCLUSIONS

Arterial hypertension is prevalent in TGA patients, with elevated blood pressure being the most-frequent concomitant condition. In our cohort, recurrence of TGA occurred in approximately one-fifth of patients. Concomitant conditions such as migraine, hypothyroidism, and atrial fibrillation occurred at different frequencies in the two groups.

Prolonged Transient Global Amnesia: Part of the Clinical Spectrum or a Separate Disease Entity?

Background

Transient global amnesia (TGA) is the prototypical neurologic disease for acute-onset reversible amnesia. It is currently defined by resolution of symptoms within 24-hours. In this case report we describe an atypical case of prolonged TGA, emphasizing our current lack of knowledge surrounding this disease entity and its pathophysiology.

Results

A 66-year old female presented acutely with profound anterograde amnesia and variable retrograde amnesia with no inciting event. A thorough workup to exclude alternative causes of amnesia (including computed tomography angiogram and electroencephalogram) was normal. Her magnetic resonance imaging was consistent with TGA, with punctate diffusion restriction changes bilaterally in the hippocampi. She was also mildly hypoxemic with no discernible cause. She was ultimately diagnosed with TGA although her diagnosis remains controversial as her symptoms persisted for 72-hours.

Conclusion

Our patients clinical and imaging features (apart from her protracted time-course and hypoxemia) were in keeping with a diagnosis of TGA. The association of hypoxemia, COVID-19, obstructive sleep apnea, and the development of TGA remains to be elucidated. Although the underlying pathophysiology for TGA is unknown several mechanisms have been postulated including cortical spreading depression and reversible hypoxic-ischemic injury. The time course for symptom resolution, could be an important clue in discerning the pathophysiology of TGA on an individual basis. Importantly, a clinician should not be deterred by amnestic symptoms lasting >24-hours, if the patients clinical/radiologic presentation is consistent with TGA.

Evaluating safety risks of whole-body cryotherapy/cryostimulation (WBC): a scoping review from an international consortium

Over the two last decades, whole-body cryotherapy/cryostimulation (WBC) has emerged as an exciting non-pharmacological treatment influencing inflammatory events at a cellular and physiological level, which can result in improved sleep quality, faster neuromuscular recovery after high-intensity exercise, and chronic pain relief for patients suffering different types of diseases (fibromyalgia, rheumatism, arthritis). Some evidence even suggests that WBC has benefits on mental health (depression, anxiety disorders) and cognitive functions in both adults and older adults, due to increased circulating BDNF levels. Recently, some safety concerns have been expressed by influential public health authorities (e.g., FDA, INSERM) based on reports from patients who developed adverse events upon or following WBC treatment. However, part of the data used to support these claims involved individuals whose entire body (except head) was exposed to extreme cold vaporized liquid nitrogen while standing in a narrow bathtub. Such a procedure is known as partial-body cryotherapy (PBC), and is often erroneously mistaken to be whole-body cryotherapy. Although having similarities in terms of naming and pursued aims, these two approaches are fundamentally different. The present article reviews the available literature on the main safety concerns associated with the use of true whole-body cryotherapy. English- and French-language reports of empirical studies including case reports, case series, and randomized controlled trials (RCTs) were identified through searches of PubMed, Scopus, Cochrane, and Web of Science electronic databases. Five case reports and two RCTs were included for a total of 16 documented adverse events (AEs). A critical in-depth evaluation of these AEs (type, severity, context of onset, participant's medical background, follow-up) is proposed and used to illustrate that WBC-related safety risks are within acceptable limits and can be proactively prevented by adhering to existing recommendations, contraindications, and commonsense guidelines.

Case of transient global amnesia-like syndrome after recreational cold-water swimming

We document a case of a transient global amnesia (TGA)-like syndrome following open water swimming. This case was atypical for TGA, in that symptoms were prolonged and ischaemic infarct was considered within the differential. MRI did not demonstrate any changes associated with acute ischaemia although did show a mild degree of small vessel change. With amnesia taking greater than 24 hours to resolve, we have labelled this case to be a TGA-like syndrome, provoked by the commonly reported TGA precipitant of cold water immersion. The possibility of a tiny, strategic infarct causing these symptoms was considered and antiplatelet therapy commenced.

Classification of transient epileptic amnesia attacks: Two types of amnestic seizures, the pure amnesia type and partial amnesia type

Aim

Transient epileptic amnesia (TEA) is a type of mesial temporal lobe epilepsy characterized by recurrent amnesia attacks. In 1998, Zeman et al. proposed the following diagnostic criteria for TEA: (1) recurrent, witnessed episodes of amnesia (TEA attacks); (2) other cognitive functions remain intact during attacks; and (3) evidence of epilepsy. It was also reported that patients with TEA often demonstrate two other types of memory symptoms: accelerated long-term forgetting (ALF) and autobiographical amnesia (AbA). Both ALF and AbA are persistent memory disorders, but transient epileptic seizures are not.

Methods

We encountered two cases of TEA associated with two types of amnesia attacks. Therefore, we reviewed TEA cases in the literature to clarify the type of TEA attacks that occurred.

Results

Based on the extracted TEA cases, including our two cases, we found that there are two main types of TEA attacks, and we discussed their clinical features.

Conclusion

We propose two main types of TEA attacks; that is, pure amnesia-type and partial amnesia-type seizures. Furthermore, we also propose that topographical amnesia mainly manifests as a type of amnesia attack, rather than as a chronic memory disturbance, such as ALF or AbA.

Guideline "Transient Global Amnesia (TGA)" of the German Society of Neurology (Deutsche Gesellschaft für Neurologie): S1-guideline

INTRODUCTION

In 2022 the DGN (Deutsche Gesellschaft für Neurologie) published an updated Transient Global Amnesia (TGA) guideline. TGA is characterized by a sudden onset of retrograde and anterograde amnesia for a period of one to a maximum of 24 h (with an average of 6 to 8 h). The incidence is estimated between 3 and 8 per 100,000 population/year. TGA is a disorder that occurs predominantly between 50 and 70 years.

RECOMMENDATIONS

The diagnosis of TGA should be made clinically. In case of an atypical clinical presentation or suspicion of a possible differential diagnosis, further diagnostics should be performed immediately. The detection of typical unilateral or bilateral punctate DWI/T2 lesions in the hippocampus (especially the CA1 region) in a proportion of patients proves TGA. The sensitivity of MRI is considered higher when performed between 24 and 72 h after onset. If additional DWI changes occur outside the hippocampus, a vascular etiology should be considered, and prompt sonographic and cardiac diagnostics should be performed EEG may help to differentiate TGA from rare amnestic epileptic attacks, especially in recurrent amnestic attacks. TGA in patients < 50 years of age is a rarity, therefore it is mandatory to rapidly search for other causes in particular in younger patients. The cause of TGA is still unknown. Numerous findings in recent years point to a multifactorial genesis. Because the pathomechanism of TGA is not yet clearly known, no evidence-based therapeutic or prophylactic recommendations can be made.

CONCLUSIONS

There is no evidence for chronic sequelae of TGA with respect to cerebral ischemia, chronic memory impairment, or the onset of dementia-related syndromes.

Transient global amnesia - hippocampal lesions in magnetic resonance imaging

BACKGROUND

Transient global amnesia is a benign syndrome characterized by a sudden onset loss of anterograde amnesia with full recovery. Magnetic resonance of the brain including diffusion-weighted imaging of patients with transient global amnesia revealed the presence of punctate hyperintense signal abnormalities in the hippocampus.

OBJECTIVE

Analysis of the presence of hippocampal lesions in brain magnetic resonance imaging in patients with transient global amnesia and the possible influence of additional factors on their appearance.

METHODS

In this retrospective, an observational study we assessed brain magnetic resonance imaging in 38 consecutive patients with transient global amnesia. The incidence of brain magnetic resonance imaging lesions was analyzed for the coexisting cardiovascular risk factors and precipitating events.

RESULTS

Hippocampal brain magnetic resonance imaging lesions were detected in 47% of patients with transient global amnesia. Of those, 65% had unilateral lesions, 82% were left-sided, and 28% were right-sided. Most lesions were located in the CA1 subfield. The incidence of hypertension in patients with transient global amnesia was higher than in the general population. Stress and exercise preceded the onset of transient global amnesia only in 13% and 16% of patients, respectively. There was no higher incidence of migraine in transient global amnesia patients (13%).

CONCLUSIONS

We found that nearly 50% of patients with transient global amnesia had hyperintense hippocampal brain magnetic resonance imaging lesions. In addition to hypertension, individuals with transient global amnesia had similar cardiovascular risk factors as the general population. We did not identify any precipitating events prior to the onset of transient global amnesia.

Recurrent Episodes of Transient Global Amnesia: A Rare Clinical Entity

Transient global amnesia (TGA) is a syndrome characterized by anterograde amnesia with otherwise intact cognitive function, resolving within 24 h of onset, occurring in the absence of neurological changes. Recurrent episodes remain rare. We report an interesting case of recurrent episodes of TGA in a 63-year-old woman presenting with altered mental status. She had no memory of antecedent events and demonstrated repetitive questioning but retained awareness of self. Physical examination and laboratory diagnostics were unremarkable. Brain magnetic resonance imaging revealed scattered foci of increased FLAIR signal within the bilateral periventricular and subcortical white matter. She was notably diagnosed with TGA a few months prior when she had presented with similar symptoms. During the current hospitalization, she remained alert and fully oriented, with resolution of perseveration. This case emphasizes the recognition of TGA as an important neurological diagnosis, uniquely describes not only the recurrence, but the short interval between recurrent episodes.

Network localization of transient global amnesia beyond the hippocampus

BACKGROUND

Transient global amnesia is common in the older adult, but the cause and mechanism remain unclear. Focal brain lesions allow for causal links between the lesion location and resulting symptoms, and we based on the reported TGA-causing lesions and used lesion network mapping to explore the causal neuroanatomical substrate of TGA.

METHODS

Fifty-one cases of transient global amnesias with DWI lesions from the literature were identified, and clinical data were extracted and analyzed. Next, we mapped each lesion volume onto a reference brain and computed the network of regions functionally connected to each lesion location using a large normative connectome dataset.

RESULTS

Lesions primarily occurred in the hippocampus, and in addition to the hippocampus, there are also other locations of TGA-causing lesions such as the cingulate gyrus, anterior thalamic nucleus (ATN), putamen, caudate nucleus, corpus callosum, fornix. More than 90% of TGA-causing lesions inside the hippocampus were functionally connected with the default mode network (DMN).

CONCLUSION

Structural abnormality in the hippocampus was the most consistently reported in TGA, and besides the hippocampus, lesions occurring at several other brain locations also could cause TGA. The DMN may also be involved in the pathophysiology of TGA. According to the clinical and neuroimaging characteristics, TGA may be a syndrome with multiple causes and cannot be treated simply as a subtype of TIA.

The link between reversible cerebral vasoconstriction syndrome and transient global amnesia

Reversible cerebral vasoconstriction syndrome (RCVS) and transient global amnesia (TGA) are acute and self-limiting intra-cerebral conditions. Although previously studied as independent phenomena, there are increasing reports of co-occurrence of these two pathologies. We report a 55-year-old male who presented to the hospital with recurrent thunderclap headaches over the course of 1 week with sudden onset of anterograde memory loss. His medications included a selective serotonin reuptake inhibitor and intermittent use of pseudoephedrine. On examination he was amnestic to recent events and notably perseverating. Magnetic resonance imaging of the brain without contrast showed a small, punctate focus of restricted diffusion in the left hippocampus. He was diagnosed with TGA based on his clinical presentation. His headaches and amnesia resolved over the next 12 h throughout the course of his stay with acetaminophen and oral verapamil and he was discharged. Repeat computed tomography angiogram at 2 weeks revealed diffuse and segmental narrowing of the anterior and posterior intracranial circulation, which resolved on follow-up imaging at 3 months, confirming RCVS. The acute and reversible nature of these conditions and increasing reports of co-occurrence suggests a common pathophysiologic link. We review the literature highlighting similar cases and the presumed pathophysiology.

Can Artificial Intelligence Diagnose Transient Global Amnesia Using Electroencephalography Data?

BACKGROUND AND PURPOSE

This study aimed to determine the ability of deep learning using convolutional neural networks (CNNs) to diagnose transient global amnesia (TGA) based on electroencephalography (EEG) data, and to differentiate between patients with recurrent TGA events and those with a single TGA event.

METHODS

We retrospectively enrolled newly diagnosed patients with TGA and healthy controls. All patients with TGA and the healthy controls underwent EEG. The EEG signals were converted into images using time-frequency analysis with short-time Fourier transforms. We employed two CNN models (AlexNet and VGG19) to classify the patients with TGA and the healthy controls, and for further classification of patients with recurrent TGA events and those with a single TGA event.

RESULTS

We enrolled 171 patients with TGA and 68 healthy controls. The accuracy and area under the curve (AUC) of the AlexNet and VGG19 models in classifying patients with TGA and healthy controls were 70.4% and 71.8%, and 0.718 and 0.743, respectively. In addition, the accuracy and AUC of the AlexNet and VGG19 models in classifying patients with recurrent TGA events and those with a single TGA event were 71.1% and 88.4%, and 0.773 and 0.873, respectively.

CONCLUSIONS

We have successfully demonstrated the feasibility of deep learning in diagnosing TGA based on EEG data, and used two different CNN models to distinguish between patients with recurrent TGA events and those with a single TGA event.

Disruption in normal correlational patterns of metabolic networks in the limbic circuit during transient global amnesia

Transient global amnesia is characterized by the sudden apparition of severe episodic amnesia, mainly anterograde, associated with emotional changes. Even though the symptoms are stereotyped, cerebral mechanism underlying transient global amnesia remains unexplained and previous studies using positron emission tomography do not show any clear results or consensus on cerebral regions impacted during transient global amnesia. This study included a group of 10 transient global amnesic patients who underwent ¹⁸F-fluorodeoxyglucose positron emission tomography during the acute or recovery phase of the episode and 10 paired healthy controls. Episodic memory was evaluated with the encoding-storage-retrieval paradigm and a story recall test of the Wechsler's memory scale and anxiety was assessed with the Spielberger scale. We used statistical parametric mapping to identify modifications of whole-brain metabolism. Regarding hypometabolism, there was no brain region systematically affected in all transient global amnesic patients and the comparison between amnesic patients and controls did not show any significant differences. To better understand the specific implication of the limbic circuit in the pathophysiology of transient global amnesia, we then conducted a correlational analysis that included regions of this network. Our findings showed that in healthy controls, regions of the limbic circuit seem to operate in a synchronized way with all regions being highly correlated to each other. On the opposite, in transient global amnesic patients, we observed a clear disruption of this normal correlational patterns between regions with the medial temporal lobe (the hippocampus, parahippocampal gyrus and amygdala) included in one cluster and the orbitofrontal cortex, anterior and posterior cingulate gyrus and thalamus gathered in the other one. Given the individual variability in the time course of transient global amnesia, the direct comparison between a group of patients and controls does not seem to favour the identification of subtle and transient alterations in regional metabolism. The involvement of an extended network, such as the limbic circuit, seems more likely to explain the symptoms of patients. Indeed, the synchronization of regions within the limbic circuit seems to be altered during transient global amnesia, which could explain the amnesia and anxiety observed in transient global amnesic patients. The present study thus deepens our understanding of the mechanisms underlying not only amnesia but also the emotional component of transient global amnesia by considering it as a disruption in the normal correlational patterns within the limbic circuit.

Neuroimaging for differential diagnosis of transient neurological attacks

BACKGROUND

Rapid yet comprehensive neuroimaging protocols are required for patients with suspected acute stroke. However, stroke mimics can account for approximately one in five clinically diagnosed acute ischemic strokes and the rate of thrombolyzed mimics can be as high as 17%. Therefore, to accurately determine the diagnosis and differentiate mimics from true transient ischemic attacks, acute ischemic stroke is a challenge to every clinician.

DISCUSSION

Medical history and neurological examination, noncontract head computed tomography, and routine magnetic resonance imaging play important roles in the assessment and management of patients with transient neurological attacks in the emergency department. This review attempts to summarize how neuroimaging can be utilized to help differentiate the most common mimics from transient ischemic attack and acute ischemic stroke.

CONCLUSION

Although imaging can help direct critical triage decisions for intravenous thrombolysis or endovascular therapy, more detailed medical history and neurological examination are crucial for making a prompt and accurate diagnosis for transient neurological attack patients.

EPIAMNE: A New Scoring System for Differentiating Transient EPIleptic AMNEsia from Transient Global Amnesia

Transient epileptic amnesia (TEA) is a rare cause of acute amnestic syndromes (AAS), often misdiagnosed as transient global amnesia (TGA). We proposed a scoring system—the EPIlepsy AMNEsia (EPIAMNE) score—using quantitative EEG (qEEG) analysis to obtain a tool for differentiating TEA from TGA. We retrospectively reviewed clinical information and standard EEGs (stEEG) of 19 patients with TEA and 21 with TGA. We computed and compared Power Spectral Density, demonstrating an increased relative theta power in TGA. We subsequently incorporated qEEG features in EPIAMNE score, together with clinical and stEEG features. ROC curve models and pairwise ROC curve comparison were used to evaluate and compare the diagnostic accuracy for TEA detection of EPIAMNE score, presence of symptoms atypical for TGA (pSymAT) and identification of anomalies (interictal epileptiform or temporal focal spiky transients) at stEEG (PosEEG). Area Under the Curve (AUC) of EPIAMNE score revealed to be higher than PosEEG and pSymAT (AUCEPIAMNE = 0.95, AUCpSymAT = 0.85, AUCPosEEG = 0.67) and this superiority proved to be statistically significant (p-valueEPIAMNE-PosEEG and p-valueEPIAMNE-pSymAT < 0.05). In conclusion, EPIAMNE score classified TEA with higher accuracy than PosEEG and pSymAT. This approach could become a promising tool for the differential diagnosis of AAS, especially for early TEA detection.

A Case of Transient Global Amnesia Triggered by Sexual Intercourse

Transient global amnesia (TGA) is described as a sudden onset of anterograde and retrograde amnesia. In this case report, we present a case of a 52-year-old man who came to our hospital experiencing sudden-onset confusion and memory loss an hour after engaging in sexual activity with his wife. Before this, the patient had no previous medical history. Four hours following the event, a non-contrast computed tomography (CT) scan was performed and showed no signs of any intracranial pathology. In addition, T1-weighted and T2-weighted magnetic resonance imaging (MRI) was performed 13 hours following the incident and demonstrated punctate focus of restricted diffusion in the medial right temporal lobe in the region of the hippocampus. A diagnosis of transient global amnesia was made after other causes were ruled out. We present this rare case of transient global amnesia (TGA), highlighting sexual intercourse as a probable triggering component of the disease and demonstrating how crucial it is to rule out other severely morbid conditions before managing TGA.

Transient global amnesia with unexpected clinical and radiological findings: A case series and systematic review

BACKGROUND

Transient global amnesia (TGA) represents a benign neurological syndrome of unknown pathophysiology, often accompanied by vanishing hippocampal punctate diffusion-weighted imaging lesions (HPDL). The literature suggests that TGA may present with unusual features. This study analyses atypical clinical and radiological manifestations of patients with TGA and/or HPDL.

METHODS

We retrospectively reviewed patients with atypical clinical or radiological presentations of TGA and/or HPDL in three neurology centers. We also performed a systematic review of literature using predefined search terms. Results were classified as: A) Atypical clinical manifestations of TGA (such as amnesia with additional manifestations, or only non-amnesic manifestations); B) Atypical radiological manifestations of clinically typical TGA.

RESULTS

We identified 83 patients: 18 in our centres (median age 63.5 years, 39% female) and 65 in the literature. In group A, 43 patients presented atypical clinical manifestations such as TGA with added transitory cognitive or sensory-motor deficits, seizures, headaches, but also non-amnesic presentations associated with HPDL and incidental HPDL without symptoms. In group B, 40 patients with typical clinical TGA showed extra-hippocampal punctate diffusion lesions (E-HPDL) which disappeared on follow-up imaging. Using clinical and radiological manifestations, we classified these patients into different categories describing a "TGA-PDL spectrum".

CONCLUSIONS

TGA may have atypical clinical manifestations despite typical neuroimaging and patients with typical TGA may show vanishing extra-hippocampal punctate diffusion lesions. TGA, related clinical manifestations, and vanishing punctate diffusion lesions should be considered part of a larger "TGA-PDL spectrum", allowing for better diagnosis of typical and atypical cases and stimulating further studies.

Transient Global Amnesia (TGA): Sex-Specific Differences in Blood Pressure and Cerebral Microangiopathy in Patients with TGA

Transient global amnesia (TGA) is defined by an acute memory disturbance of unclear aetiology for a period of less than 24 h. Observed psychological, neuroanatomical and hormonal differences between the sexes in episodic memory suggest sex-specific differences in memory disorders such as TGA. The aim of this study was to determine sex-specific differences in cardiovascular risk profiles, recurrences and magnetic resonance imaging (MRI). In total, 372 hospitalised TGA patients between 01/2011 and 10/2021 were retrospectively analysed. Comparisons were made between female and male TGA patients and compared to 216 patients with acute stroke. In our sample, women were overrepresented (61.8%), especially compared to the general population in the 65−74 age category (χ2 = 10.6, p < 0.02). On admission, female TGA patients had significantly higher systolic blood pressure values and a higher degree of cerebral microangiopathy compared to male TGA patients, whereas acute stroke patients did not. No sex-specific differences were observed with respect to recurrences or hippocampal DWI lesions. Our data demonstrate sex-specific differences in TGA. The higher blood pressure on admission and different degree of cerebral microangiopathy in female TGA patients supports the theory of blood pressure dysregulation as a disease trigger. Distinct precipitating events in female and male patients could lead to differences in the severity and duration of blood pressure abnormalities, possibly explaining the higher incidence in female patients.

Transient Global Amnesia Masquerading as Transient Ischemic Attack

Transient global amnesia (TGA) is a rare self-limited syndrome characterized primarily by anterograde amnesia. It shares multiple characteristics with a transient ischemic attack and ischemic stroke, which carry a more ominous outlook. There is a debate with respect to what is sufficient for ruling out more serious pathologies. Additionally, there is data that challenge the historical view that TGA is a benign condition requiring no long-term management. Here, we present the case of a 70-year-old female who was admitted to a free-standing emergency room with confusion, memory loss, and hypertensive crisis that was diagnosed as TGA. The patient was evaluated by a neurologist and transferred to the hospital. The patient was discharged after more serious pathologies were excluded after an extensive workup. This scenario showcases how physicians have to balance the risk of serious diseases with the need for further testing. Future research should focus on how to accurately identify or rule out serious diseases leading to a reduction in adverse events and patient costs. It is also not clear if TGA is truly benign or has an association with stroke.

Diagnostic yield of diffusion-weighted brain MR imaging in patients with cognitive impairment: Large cohort study with 3,298 patients

Objective

There is a paucity of large cohort-based evidence regarding the need and added value of diffusion-weighted imaging (DWI) in patients attending outpatient clinic for cognitive impairment. We aimed to evaluate the diagnostic yield of DWI in patients attending outpatient clinic for cognitive impairment.

Materials and methods

This retrospective, observational, single-institution study included 3,298 consecutive patients (mean age ± SD, 71 years ± 10; 1,976 women) attending outpatient clinic for cognitive impairment with clinical dementia rating ≥ 0.5 who underwent brain MRI with DWI from January 2010 to February 2020. Diagnostic yield was defined as the proportion of patients in whom DWI supported the diagnosis that underlies cognitive impairment among all patients. Subgroup analyses were performed by age group and sex, and the Chi-square test was performed to compare the diagnostic yields between groups.

Results

The overall diagnostic yield of DWI in patients with cognitive impairment was 3.2% (106/3,298; 95% CI, 2.6–3.9%). The diagnostic yield was 2.5% (83/3,298) for acute or subacute infarct, which included recent small subcortical infarct for which the diagnostic yield was 1.6% (54/3,298). The diagnostic yield was 0.33% (11/3,298) for Creutzfeldt-Jakob disease (CJD), 0.15% (5/3,298) for transient global amnesia (TGA), 0.12% (4/3,298) for encephalitis and 0.09% (3/3,298) for lymphoma. There was a trend towards a higher diagnostic yield in the older age group with age ≥ 70 years old (3.6% vs 2.6%, P = .12). There was an incremental increase in the diagnostic yield from the age group 60–69 years (2.6%; 20/773) to 90–99 years (8.0%; 2/25).

Conclusion

Despite its low overall diagnostic yield, DWI supported the diagnosis of acute or subacute infarct, CJD, TGA, encephalitis and lymphoma that underlie cognitive impairment, and there was a trend towards a higher diagnostic yield in the older age group.

Acute neurological disease as a trigger or co-occurrence of transient global amnesia: a case series and systematic review

BACKGROUND

Transient global amnesia (TGA) represents a benign neurological syndrome of unknown pathophysiology, often accompanied by vanishing hippocampal punctate lesions on diffusion-weighted imaging (hippocampal punctate diffusion lesion, HPDL). The recent literature suggests that TGA may be triggered by acute neurological conditions.

OBJECTIVE

To study patients with TGA triggered by an acute neurological disease.

METHODS

We retrospectively reviewed patients from two neurology centres with TGA (with or without HPDL) in whom an acute neurological condition could be identified as trigger. We also performed a systematic review of the literature of this situation using predefined search terms.

RESULTS

We identified 38 patients (median age 62 years, 55.3% female): 6 from our centres and 32 from the literature. Acute neurovascular diseases that preceded or were associated with TGA included ischemic and haemorrhagic strokes, convexity subarachnoid haemorrhage, and reversible cerebral vasoconstriction syndrome. As non-vascular acute neurological diseases, we identified migraine and peripheral-origin vertigo. The clinical manifestation of the neurological trigger showed a variable temporal relation with TGA onset; in some cases preceding and in others co-occurring with TGA manifestation. In some cases, presumed neurological triggers were asymptomatic and diagnosed from the neuroimaging done for the TGA.

CONCLUSIONS

Acute vascular and non-vascular neurological events may trigger TGAs or may occur simultaneously. In the first case, such an acute neurological disease may activate direct pathways within the nervous systems leading to TGA, or alternatively elicit a bodily sympathetic overactivity cascade. In the second case, both neurological events may be the result of a common external stressor.

Limbic covariance network alterations in patients with transient global amnesia

BACKGROUND

We compared limbic structure volumes and graph theory parameters of the limbic covariance network between patients with transient global amnesia (TGA) and healthy controls, and between patients with single and recurrent TGA events.

METHODS

We retrospectively enrolled 122 patients with TGA (single event, n = 107; recurrent events, n = 15) and 50 healthy controls who underwent three-dimensional T1-weighted MRI imaging of the brain. Volumetric analysis of the subcortical limbic structures, including the hippocampus, amygdala, thalamus, mammillary body, hypothalamus, basal forebrain, septal nuclei, fornix, and nucleus accumbens, was performed. We examined the limbic covariance network using a graph theory.

RESULTS

Limbic structure volumes did not differ between patients with TGA and healthy controls, and between patients with a single event and those with recurrent events. However, the radius of the limbic covariance network was significantly greater in patients with TGA than in healthy controls (6.595 vs. 4.564, p = 0.040). Furthermore, the radius, diameter, eccentricity, and characteristics path length were greater (4.066 vs. 2.000, p = 0.009; 7.062 vs. 3.645, p = 0.029; 5.633 vs. 2.774, p = 0.013; 3.373 vs. 1.688, p = 0.004; respectively), whereas the average strength, global efficiency, local efficiency, mean clustering coefficient, transitivity, and small-worldness index were lower (5.595 vs. 10.831, p = 0.004; 0.350 vs. 0.642, p = 0.002; 0.531 vs. 1.724, p = 0.004; 0.304 vs. 0.624, p = 0.006; 0.456 vs. 0.935, p = 0.003; 0.913 vs. 0.993, p = 0.017; respectively), in patients with recurrent events than in those with a single event.

CONCLUSION

The limbic covariance network shows significant alterations in patients with TGA, as well as differences between patients with recurrent events and those with a single event. These findings suggest that changes in the limbic covariance network could be related to the pathogenesis of TGA.

Forgetting the Unforgettable: Transient Global Amnesia Part II: A Clinical Road Map

Transient global amnesia (TGA) is a clinical syndrome characterized by the sudden onset of a temporary memory disorder with profound anterograde amnesia and a variable impairment of the past memory. Usually, the attacks are preceded by a precipitating event, last up to 24 h and are not associated with other neurological deficits. Diagnosis can be challenging because the identification of TGA requires the exclusion of some acute amnestic syndromes that occur in emergency situations and share structural or functional alterations of memory circuits. Magnetic Resonance Imaging (MRI) studies performed 24–96 h after symptom onset can help to confirm the diagnosis by identifying lesions in the CA1 field of the hippocampal cornu ammonis, but their practical utility in changing the management of patients is a matter of discussion. In this review, we aim to provide a practical approach to early recognition of this condition in daily practice, highlighting both the lights and the shadows of the diagnostic criteria. For this purpose, we summarize current knowledge about the clinical presentation, diagnostic pathways, differential diagnosis, and the expected long-term outcome of TGA.

Transient global amnesia: 7 Tesla MRI reveals more hippocampal lesions with diffusion restriction compared to 1.5 and 3 Tesla MRI

PURPOSE

To assess the ability of 7 T MRI to detect hippocampal DWI lesions in the acute phase of TGA compared to 1.5 T/3 T MRI.

METHODS

Patients with a clinical diagnosis consistent with TGA and a 1.5/3 T MRI underwent an additional 7 T MRI when the 7 T system was available for clinical use, thus serving as their own controls.

RESULTS

Thirteen TGA patients with a median age of 68.5 years (range 46-77 years) were included and imaged at 1.5/3 T (median 17 h after onset of symptoms, range 3-23 h) and 7 T (median 23 h after onset, range 15-46 h). The 7 T MRIs were performed a median of 15 h after the 1.5/3 T MRIs (range 1-28 h). At 1.5/3 T, six patients (46%) were found to have at least one hippocampal DWI-lesions supporting the TGA diagnosis, which increased to 11 patients (85%) when examined at 7 T (p = 0.03). At 1.5/3 T, nine hippocampal DWI lesions were detected, which increased to 19 at 7 T, giving an increased detection rate of 111% (p = 0.002). Both neuroradiologists found the hippocampal DWI lesions at 7 T to have higher conspicuity and be easier to categorize as true findings compared to 1.5/3 T.

CONCLUSION

Seven-Tesla MRI showed both a statistically significant increase in the total number of detected hippocampal DWI lesions and the proportion of patients with at least one hippocampal DWI lesion supporting the TGA diagnosis compared to 1.5/3 T. Clinical use of 7 T will increase the number of patients having their TGA diagnosis supported by MRI, which can be especially useful in patients with negative 1.5/3 T MRI and low clinical certainty.

Forgetting the Unforgettable: Transient Global Amnesia Part I: Pathophysiology and Etiology

Transient global amnesia (TGA) is a clinical syndrome characterized by the sudden onset of a temporary memory disorder with a profound anterograde amnesia and a variable impairment of the past memory. Since the first description, dating back over 60 years, several cases have beenreported in the literature. Nevertheless, TGA remains one of the most mysterious diseases in clinical neurology. The debate regarding the etiology of this disease has focused mainly on three different mechanisms: vascular (due to venous flow changes or focal arterial ischemia), epileptic, and migraine related. However, to date there is no scientific proof of any of these mechanisms. Furthermore, the demonstration by diffusion-weighted MRI of lesions in the CA1 field of the hippocampus cornu ammonis led us to hypothesize that the selective vulnerability of CA1 neurons to metabolic stress could play a role in the pathophysiology of TGA. In this review, we summarize current knowledge on the anatomy, vascularization and function of the hippocampus. Furthermore, we discuss the emerging theories on the etiology and the pathophysiological cascade leading to an impairment of hippocampal function during the attacks.

Pathophysiological insight into transient global amnesia from quantitative electroencephalography

Transient global amnesia (TGA) is recognized as a benign memory disorder, with characteristic clinical and imaging features. However, the pathophysiology of TGA remains elusive. This study aims to elucidate the pathophysiological changes underlying TGA by exploring the brain activities. In total, 215 patients with TGA (age: 61.8 ± 7.8 years; women: 146) with MRI (within 7 days) and EEG studies (within 90 days) were recruited. Quantitative EEG (QEEG) power spectra and network analysis were performed by the artificial intelligence EEG analysis platform (iSyncBrain®). Subgroup analyses were conducted for different clinical groups, based on symptom duration, EEG timing after onset, and cytotoxic lesions on the MRI. Compared with 252 age- and sex-matched subjects (age: 64.5 ± 8.3 years, women: 182), TGA patients showed a global decrease in absolute power in all band waves, a relative decrease in alpha waves, a relative increase in theta waves, and atypical compensation activity. These QEEG changes were observed regardless of having cytotoxic lesions in MRI and they were significant up to 1 week after symptom onset. Network analysis showed that TGA was more activated than normal controls in alpha1 band-waves, exhibiting a compensatory process. TGA results in prolonged and widespread alterations of brain activity and connectivity. QEEG provide insight into pathophysiology of TGA.

COVID-19 Vaccine-Associated Transient Global Amnesia: A Disproportionality Analysis of the WHO Safety Database

Coronavirus disease 2019 (COVID-19) spread rapidly, resulting in a global pandemic for which vaccines were quickly developed. As their safety continues to be monitored, cases of transient global amnesia (TGA) following mRNA vaccination with elasomeran have been reported. TGA is characterized by sudden onset of anterograde amnesia with preservation of other cognitive functions and resolution within 24 h. We aimed to investigate the potential link of TGA with COVID-19 vaccines. We queried the World Health Organization VigiBase® for all reports of "Transient global amnesia", up to 6 December 2021. Disproportionality analysis relied on the Reporting Odds Ratio (ROR) with its 95% Confidence Interval (CI) and the Information Component (IC). A positive lower end of the 95% CI of the IC (IC025) is used to statistically detect a signal. Of all TGA cases, 289 were associated with a COVID-19 vaccine, representing the most frequent association. Tozinameran was mostly represented (147, 50.8%), followed by AZD1222 (69, 23,8%), elasomeran (60, 20.8%), and JNJ-78436735 (12, 4.2%). With an IC025 > 0, COVID-19 vaccines showed a significant ROR (5.1; 95%CI 4.4-6.0). Tozinameran reached the strongest ROR (4.6; 95%CI 3.9-5.0), followed by elasomeran (4.4; 95%CI 3.4-6.0), AZD1222 (3.8; 95%CI 3.0-5.0), and JNJ-78436735 (3.7; 95%CI 2.1-6.0). Our analysis of COVID-19 vaccines-related TGA reports shows significant disproportionality. Cerebrovascular, inflammatory, or migrainous mechanisms may underlie this association. Yet, numerous confounding factors cannot be tackled with this approach, and causality cannot be ascertained. The identification of this trigger of TGA may help the clinician in his etiological research.

Transient Global Amnesia Recurrence: Prevalence and Risk Factor Meta-analysis

Background:

Transient global amnesia (TGA) is an acute amnestic disorder with unclear pathophysiology. Although considered a benign phenomenon, the possibility of a recurrence is a major concern for the patient. Our objective is to identify the prevalence and risk factors of relapse, to help clinicians counsel patients about it.

Methods:

According to PRISMA guidance, we screened 1658 studies from MEDLINE, Lilacs and Embase databases, published from 1985 to April 2021, in English or Spanish. We included 36 observational case-control and cohort studies that included patients with TGA according to Caplan’s or Hodges and Warlow’s diagnostic criteria. We performed a meta-analysis with a random effect model for proportions and calculation of odds ratio for identified risk factors. Methodological quality was assessed according to the Newcastle-Ottawa Scale.

Results:

We identified 4514 TGA and 544 recurrence events (12.73%). Follow-up had no impact on its variance. We identified a statistically significant association between recurrence and sexual activity as a trigger, past or present personal history of migraine and depression (OR 1,481 95%CI [1,0341; 2,1222] p=0,04; OR=2,0795 IC95% [1,3892; 3,1128] p=0,003; and OR=4,487195%CI [1,890; 10,651] p=0,0288, respectively).

Conclusions:

The analysis showed that about 1 out of 8 subjects may have recurrence, with an increased risk in case of past or present history of migraine, depression or sexual intercourse prior to the event. Personal history of migraine and depression are associated with two and four times risk, respectively.

Neuroimaging and Electroencephalographic Correlation in Patients with Transient Global Amnesia: Clinical Case Series

Objective. To determine if there is any correlation between the electroencephalographic and neuroimaging findings in patients with Transient Global Amnesia (TGA). Methods: We retrospectively reviewed files of the First Department of Neurology of AHEPA University Hospital, including patients with a clinical diagnosis of TGA. Only patients who had the characteristic high signal in the temporal lobes in the DWI MRI and those who underwent electroencephalographic recording (EEG) were selected. Results: Out of 28 patients, 8 were selected. We found that 6 out of 8 patients (75%) who had imaging findings in DWI, in at least one medial temporal lobe, also had had intermittent slow theta waves on the electroencephalographic recording. Of these 6 patients, 3 (50%) had bilateral EEG findings, 2 patients (33,3%) only had findings on the left hemisphere and 1 (17%) had on the right hemisphere. 3 out of 6 patients (50%) had electroencephalographic dominance on the left, while 2 out of the 6 (33%) had on the right. In 2 patients with imaging findings in DWI no anomalies were demonstrated on EEG. In 3 out of 8 patients, both MRI and EEG findings correlated on the same side, while 1 patient had opposite findings, depending on which hemisphere the EEG anomalies dominated. Conclusions: There is no absolute matching between the DWI MRI and EEG findings in patients with the clinical diagnosis of TGA. However, there is some degree of correlation, when we focus on the focal dominance of the EEG anomalies, although not statistically significant.