Association of diffusion weighted imaging abnormalities and recurrence in transient global amnesia

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.

Sensitivity of diffusion-weighted magnetic resonance imaging in transient global amnesia as a function of time from symptom onset

BACKGROUND

The objective was to systematically evaluate the sensitivity of diffusion-weighted magnetic resonance imaging (DW-MRI) for transient global amnesia (TGA) across various time frames compared to the reference-standard clinical criteria.

METHODS

All indexed publications related to TGA and MRI through June 2020 were retrieved by a medical librarian. Two independent reviewers identified original research studies of adults with a clinical diagnosis of TGA using Caplan and Hodges and Warlow criteria (reference standard) who were evaluated with DW-MRI. Pooled estimates and its 95% confidence intervals (CI) for the proportion of acute TGA patients with positive DW-MRI (i.e., sensitivity) were obtained using random-effects meta-analysis for various time frames. Quality assessment was performed using the revised Quality of Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool.

RESULTS

After screening 665 reports, we identified 81 potentially relevant studies. Twenty-three studies representing 1688 patients met eligibility criteria, but not all studies had data available for meta-analysis. The pooled sensitivity (also described as positivity rate) of DW-MRI was 15.6% (95% CI = 2.6%-35.0%) between 0 and 12 h from symptom onset, 23.1% (95% CI = 6.1%-45.7%) at 0-24 h, 72.8% (95% CI = 40.8%-96.3) at 12-24 h, 68.8% (95% CI = 44.8%-88.8%) at 24-36 h, 72.4% (95% CI = 59.8%-83.5%) at 36-48 h, 82.8% (95% CI = 54.7%-99.6%) at 48-60 h, 66.9% (95% CI = 47.5%-83.9%) at 60-72 h, and 72.0% (95% CI = 30.1%-100.0%) at 72-96 h. There was significant concern for risk of bias in the QUADAS-2 domains of patient selection and index test, yielding a low level of certainty in the pooled estimates.

CONCLUSION

DW-MRI lesions are uncommon in patients with TGA early after symptom onset, but the sensitivity (i.e., positivity rate) of DW-MRI increases with time. Despite the limited quality of existing evidence, obtaining an early DW-MRI in patients with clinical diagnosis of TGA in the acute setting is likely a low-yield test.

Brain networks in patients with isolated or recurrent transient global amnesia

OBJECTIVES

The aim of this study was to investigate differences in cerebral blood flow (CBF) and functional networks between transient global amnesia (TGA) patients with a single event and those with recurrent events using arterial spin labeling (ASL) MRI.

METHODS

We enrolled patients with TGA and classified them into two groups according to the number of TGA events: TGA patients with a single event and those with recurrent events. MRI scans were performed within 24 h after TGA ictal onset in all patients. We quantified CBF and analyzed the functional network based on CBF using graph theory, and determined the differences in CBF and functional networks between the groups.

RESULTS

We enrolled 44 patients with TGA. Among them, 6 patients had recurrent TGA events, whereas 38 patients had a single TGA event. No regions had significantly different CBFs between TGA patients with recurrent events and those with a single event. The global functional network analysis found that the eccentricity was significantly higher in TGA patients with recurrent events than in those with a single event (5.829 vs. 4.657, p = .001). The local functional network analysis showed that several regions had significantly different betweenness centrality and eccentricity measures between TGA patients with recurrent events and those with a single event.

CONCLUSIONS

We demonstrated the differences in the functional network based on CBF using graph theory according to recurrence in patients with TGA. These findings suggest that TGA is a network disease, and functional network alterations in TGA are related to clinical symptoms.

Diagnostic Yield of Diffusion-Weighted Brain Magnetic Resonance Imaging in Patients with Transient Global Amnesia: A Systematic Review and Meta-Analysis

OBJECTIVE

To investigate the diagnostic yield of diffusion-weighted imaging (DWI) in patients with transient global amnesia (TGA) and identify significant parameters affecting diagnostic yield.

MATERIALS AND METHODS

A systematic literature search of the MEDLINE and EMBASE databases was conducted to identify studies that assessed the diagnostic yield of DWI in patients with TGA. The pooled diagnostic yield of DWI in patients with TGA was calculated using the DerSimonian-Laird random-effects model. Subgroup analyses were also performed of slice thickness, magnetic field strength, and interval between symptom onset and DWI.

RESULTS

Twenty-two original articles (1732 patients) were included. The pooled incidence of right, left, and bilateral hippocampal lesions was 37% (95% confidence interval [CI], 30-44%), 42% (95% CI, 39-46%), and 25% (95% CI, 20-30%) of all lesions, respectively. The pooled diagnostic yield of DWI in patients with TGA was 39% (95% CI, 27-52%). The Higgins I² statistic showed significant heterogeneity (I² = 95%). DWI with a slice thickness ≤ 3 mm showed a higher diagnostic yield than DWI with a slice thickness > 3 mm (pooled diagnostic yield: 63% [95% CI, 53-72%] vs. 26% [95% CI, 16-40%], p < 0.01). DWI performed at an interval between 24 and 96 hours after symptom onset showed a higher diagnostic yield (68% [95% CI, 57-78%], p < 0.01) than DWI performed within 24 hours (16% [95% CI, 7-34%]) or later than 96 hours (15% [95% CI, 8-26%]). There was no difference in the diagnostic yield between DWI performed using 3T vs. 1.5T (pooled diagnostic yield, 31% [95% CI, 25-38%] vs. 24% [95% CI, 14-37%], p = 0.31).

CONCLUSION

The pooled diagnostic yield of DWI in TGA patients was 39%. DWI obtained with a slice thickness ≤ 3 mm or an interval between symptom onset and DWI of > 24 to 96 hours could increase the diagnostic yield.

Factors Associated With Risk of Recurrent Transient Global Amnesia

Importance

Transient global amnesia (TGA) is usually considered a benign event with a low recurrence rate. However, recurrence rates vary considerably among studies and there are no known risk factors for TGA.

Objective

To examine risk factors for the recurrence of TGA.

Design, Setting, and Participants

This retrospective cohort study involved medical record review of patients with isolated or recurrent TGA presenting to the Mayo Clinic in Rochester, Minnesota, between August 1, 1992, and February 28, 2018. A total of 1491 cases were reviewed and 1044 met diagnostic inclusion criteria for TGA, with the remainder excluded owing to indeterminate or alternate diagnoses or limited information available in the medical record.

Exposures

Single vs recurrent episodes of TGA.

Main Outcomes and Measures

Demographics, precipitating factors, migraine history, imaging and electrodiagnostic findings, and family history of TGA were collected. The main outcome measure was TGA recurrence.

Results

Of 1044 included patients, 575 (55.1%) were male, and the mean (SD) age at inclusion was 75.0 (11.5) years. A total of 901 patients (86.3%) had a single episode of TGA and 143 (13.7%) had recurrent episodes of TGA. The 2 groups were similar in age at inclusion, sex, identifiable triggers, and duration of anterograde amnesia. The number of recurrences ranged from 1 to 9, with 137 individuals (95.8%) having 3 or fewer recurrences. The mean (SD) age at first episode of TGA was 65.2 (10.0) years for individuals with a single episode vs 58.8 (10.3) years for those with recurrent episodes (P < .001). There was a personal history of migraine in 180 individuals (20.0%) with a single episode of TGA and 52 individuals (36.4%) with recurrent episodes of TGA (P < .001), and a family history of migraine in 167 individuals (18.5%) with a single episode of TGA and 44 individuals (30.8%) with recurrent episodes of TGA (P = .001). There were no electroencephalographic findings associated with increased risk of TGA recurrence. Acute and subacute temporal lobe abnormalities on results of magnetic resonance imaging were seen rarely and did not require intervention. A family history of TGA was identified in 12 individuals (1.3%) with a single episode of TGA and 4 individuals (2.8%) with recurrent episodes of TGA.

Conclusions and Relevance

This study suggests that, in this large cohort of patients with TGA, recurrent TGA was associated with earlier age at the time of first TGA episode and higher prevalence of both personal and family history of migraine compared with isolated cases. These results can be used to counsel patients about risks of recurrence and may have implications for the understanding of TGA pathophysiology.

Transient global amnesia: clinical features and prognostic factors suggesting recurrence

OBJECTIVE

The risk of recurrence of new amnesia events in patients having previously experienced transient global amnesia (TGA) ranges between 2.9-23.8%. Our objective was to search for recurrence predictors in TGA patients.

METHODS

Retrospective analysis to identify recurrence predictors in a cohort of 203 TGA patients from a single center in Buenos Aires, Argentina, diagnosed between January 2011 and March 2017 Clinical features and complementary studies (laboratory results, jugular vein Doppler ultrasound and brain MRI) were analyzed. Comparison between patients with recurrent versus single episode TGA was performed, applying a multivariate logistic regression model.

RESULTS

Mean age at presentation was 65 years (20-84); 52% were female. Median time elapsed between symptom onset and ER visit was two hours, with the average episode duration lasting four hours. Mean follow-up was 22 months. Sixty-six percent of patients referred to an identifiable trigger. Jugular reflux was present in 66% of patients; and 22% showed images with hippocampus restriction on diffusion-weighted MRI. Eight percent of patients had TGA recurrence. Patients with recurrent TGA had a more frequent history of migraine than patients without recurrence (37.5% vs. 14%; p = 0.03). None of the other clinical characteristics and complementary studies were predictors of increased risk of recurrence.

CONCLUSIONS

Patients with migraine may have a higher risk of recurrent TGA. None of the other clinical characteristics evaluated allowed us to predict an increased risk of recurrence. Although the complementary studies allowed us to guide the diagnosis, they did not appear to have a significant impact on the prediction of recurrence risk.

[A case of recurrent transient global amnesia showing different symptom duration and MRI findings]

A 66-year-old man was admitted to our department with anterograde amnesia. He was diagnosed with transient global amnesia (TGA) because of the symptom lasting for several hours and no abnormal findings on MRI and EEG. About a year after the episode, he recurred amnesia lasting only for 20 minutes. MRI diffusion weighted image (DWI) revealed a small hyperintense signal in the right hippocampus, while there was no abnormality on EEG. We diagnosed him with recurrent TGA. This case may be interesting in that symptom duration and MRI-DWI finding are much different between two attacks of TGA.

Prevalence of obstructive sleep apnea syndrome in a population of patients with transient global amnesia

OBJECTIVE

The etiology of transient global amnesia (TGA) is largely undetermined. The aim of this study was to investigate whether the prevalence of obstructive sleep apnea syndrome (OSAS), a condition associated with subtle changes in brain structures involved in memory processes, increases in subjects who have previously experienced a TGA episode.

METHODS

Twenty-nine patients who had had a TGA episode were included. A case-control model was used, matching cases with controls by sex, age, and body mass index category. Diagnosis of OSAS was based on the results of the Berlin Questionnaire, which was later confirmed by means of an all-night polysomnography recording.

RESULTS

The prevalence of OSAS among TGA patients was significantly higher with respect to that in controls (44.8% vs 13.8%, p = 0.020, χ² test). At logistic regression model, subjects with TGA had an odds ratio of 8.409 (95% confidence interval = 1.674-42.243; p = 0.010) of having OSAS when compared with controls.

CONCLUSIONS

According to our findings, an accurate investigation of sleep disturbances could be considered for a complete assessment of patients with TGA. The subtle cerebral anatomo-functional damage induced by the repeated nocturnal apneic episodes may be a pathophysiologic link between OSAS and TGA.

Hippocampal modifications in transient global amnesia

Transient global amnesia (TGA) is an acute and transient syndrome with a remarkably stereotypical set of signs and symptoms. It is characterized by the abrupt onset (no forewarning) of massive episodic memory impairment, both anterograde and retrograde. Ever since it was first described, TGA has fascinated neurologists and other memory experts, and in recent years, there has been a surge of neuroimaging studies seeking to pin down the brain dysfunction responsible for it. Several pathophysiological hypotheses have been put forward, including the short-lived suggestion of an epileptic mechanism. All the available data indicate that the brain modifications are reversible, and that the mechanism behind TGA is of a functional nature. However, while diffusion-weighted imaging studies have clearly identified the hippocampus and, more specifically, the CA1 area, as the locus of brain modifications associated with TGA, researchers have yet to determine whether the origin of the mechanism is vascular or neurochemical. Spectroscopy may provide a means of settling this issue once and for all.

Anterior portion of the cingulate gyrus: A novel location for transient global amnesia?

Transient global amnesia (TGA) is characterized by abrupt transient loss of anterograde memory, lasting up to 24 hours, and no other focal neurological signs. We report the case of a right-handed 71-year-old female patient who presented temporal-spatial disorientation 5 minutes after ingestion of 1000 ml of iodinated contrast. The patient had mild temporal-spatial disorientation, with significant deficit in anterograde memory. After 12 hours under observation, the patient progressed to gradual improvement and was discharged. A reevaluation after 15 days showed normal cortical functions, score on mini-mental state exam of 30, and unaffected working and recall memory. MRI performed 48 hours after the event showed hypersignal in the diffusion sequence in the anterior portion of the cingulate gyrus, with hypointense signal in MAP/ADC, confirming a finding consistent with TGA. No previous reports in the literature have described the location affected in this patient, rendering it a novel site consistent with this diagnosis.

Transient amnesic syndromes

Transient amnesic syndromes are striking clinical phenomena that are commonly encountered by physicians in acute medical settings. Diagnosis of such syndromes can be challenging, and their causes have been debated for over 50 years. Critical clinical distinctions, such as between transient global amnesia (TGA) and transient epileptic amnesia (TEA), as well as important clues to the underlying pathophysiology, have recently been revealed. TGA is characterized by the sudden onset of a profound anterograde and retrograde amnesia that lasts for up to 24 h, with neuroimaging after an acute TGA event showing transient perturbation of specific hippocampal circuits that are involved in memory processing. Some cases of transient amnesia are attributable to focal seizure activity and are termed TEA, which has a clinical presentation similar to that of TGA, but can be distinguished from the latter by the brevity and frequency of amnesic attacks. Moreover, TEA carries a risk of persistent memory impairment that can be mistaken for dementia. Here, we summarize clinically relevant aspects of transient amnesic syndromes, giving practical recommendations for diagnosis and patient management. We describe results from imaging and epidemiological studies that have shed light on the functional anatomy and pathophysiological mechanisms underlying these conditions.

Transient global amnesia after ablation of the left lateral accessory pathway

Transient global amnesia (TGA) could be encountered in many situations even during invasive procedures. In ablation therapy for arrhythmia, there was only one reported case in the ablation of premature ventricular beats. We report a 31-year-old man having paroxysmal supraventricular tachycardia who underwent TGA at the end of ablation and recovered quickly after 8-9 hours later. Long-term follow-up showed no neurologic deficits for 8 months.

Long-term outcome in transient global amnesia patients with and without focal hyperintensities in the CA1 region of the hippocampus

Focal hippocampal diffusion-weighted imaging (DWI) lesion patterns are detected in transient global amnesia (TGA) patients in different frequency. It has been speculated that acute diffusion restrictions are associated with a worse outcome. Therefore, we evaluated the influence of acute DWI lesions on the cognitive long-term outcome in TGA patients. Seventeen otherwise healthy patients with the clinical syndrome of TGA, who had MRI investigations on admission as well as 1 day later, were investigated with a comprehensive neuropsychological test battery 2 years later. Acute hippocampal DWI lesions in TGA patients were detected in almost two thirds of the patients. Psychometric evaluation revealed no differences in cognitive performance between patients with and without DWI lesions as well as compared to healthy subjects. In addition, no relapse of the attack has been recognized in either group of TGA patients.