Transient epileptic and global amnesia: Real-life differential diagnosis

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.

Transient global amnesia after the right temporal epilepsy surgery: A case report

Transient global amnesia (TGA) is characterized by sudden and temporary memory impairment, while transient epileptic amnesia (TEA) represents amnestic attacks as the main manifestation of focal epilepsy with presumed temporal origin. We present a 48-year-old patient who experienced transient amnesia 10 weeks after right selective amygdalo-hippocampectomy for right temporal lobe epilepsy. Despite TEA being a plausible explanation for amnesia in patients with temporal lobe epilepsy, no epileptiform discharges were found during the amnestic episode and key features indicative of TGA, including long duration, isolated occurrence, and dense anterograde amnesia of the episode, argued against a diagnosis of TEA in this case. Notably, the patient has remained seizure-free (now 4,5 years) and stopped taking antiseizure medication 32 months after surgery. Although TGA clinical criteria formally exclude patients with recent active epilepsy, neurologists should be aware that TGA can occur after epilepsy surgery in the temporal lobe. Therefore, we consider it of high clinical relevance to establish a careful differential diagnosis between TGA and epileptic amnestic attacks after epilepsy surgery to avoid unnecessary reintroduction or continuation of antiseizure medication. Additionally, this case presents the first comparison of detailed neuropsychological test results before and after a presumed TGA episode, revealing a complete recovery of anterograde memory functions within 1 day. PLAIN LANGUAGE SUMMARY: A 48-year-old patient experienced an episode of transient amnesia 10 weeks after epilepsy surgery. Given the patient's history, an epileptic origin of the episode initially seemed likely. However, tests revealed no seizure activity during the episode and the characteristics matched a condition called transient global amnesia. This case highlights the importance of correctly diagnosing memory impairments after epilepsy surgery to prevent unnecessary treatment.

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.

Clinical differences between transient epileptic amnesia (TEA) and recurrent transient global amnesia (r-TGA)

Both transient epileptic amnesia (TEA) and transient global amnesia (TGA) are clinically characterized by temporary amnesic symptoms. TEA involves recurring amnesic episodes, while TGA typically manifests as a singular occurrence. TGA rarely occurs repeatedly, known as recurrent TGA (r-TGA), which complicates differentiation, and raises the possibility of overlap between two disorders. Given the effectiveness of suitable antiseizure medications (ASMs) in treating TEA, accurate diagnosis of the initial event is crucial. In this study, We retrospectively analyzed cases of sudden-onset amnesia at Juntendo University Hospital over the past 14 years. Our investigation identified a total of 17 patients with TEA who met the criteria established by Zeman, along with a total of 9 patients with r-TGA meeting Hodges' criteria. Compared to r-TGA, TEA exhibited a higher recurrent rate, shorter symptoms, more additional symptoms, and increased structural abnormalities on head magnetic resonance imaging (MRI), and more abnormalities electroencephalography (EEG). Moreover, individual amnestic episode duration varied in both TEA and r-TGA. Our study reveals that TGA retains key features in recurrent cases and demonstrates distinctions from TEA. Nevertheless, distinguishing between the two conditions based solely on initial episodes remains challenging.

Vertebral artery hypoplasia and hemodynamic impairment in transient global amnesia: a case control study

Introduction

The aetiology of transient global amnesia (TGA) is still a matter of debate. Besides ischemia of the mesial temporal lobe including the hippocampus, migraine-like mechanisms, epileptic seizures affecting mnestic structures, or venous congestion in the (para) hippocampal area due to jugular vein insufficiency have been discussed. We assessed the diameters of the intracranial arteries of TGA patients compared to controls to identify differences that support the hypothesis of reduced hippocampal perfusion as a pivotal factor in the pathophysiology of TGA.

Methods

We reviewed magnetic resonance imaging time of flight angiographies (TOF-MRA) that were acquired during in-patient treatment of 206 patients with acute TGA.

Results

The diameters of the vertebral artery (VA) in the V4 segment, the proximal basilar artery, and the internal carotid arteries were measured manually. We compared the findings with TOF-MRA images of an age and sex matched control group of neurological patients without known cerebrovascular pathology. In TGA patients the diameter of the right VA was significantly (p < 0.01) smaller compared to controls (2.09 mm vs. 2.35 mm). There were no significant differences in the diameters of the other vessels. Only the fetal variant of the posterior cerebral artery was slightly more common in TGA.

Discussion

The smaller diameter (hypoplasia) of the right VA supports the hypothesis of a contribution of hemodynamic factors to the pathophysiology of TGA. The fact that hypoplasia represents a congenital condition might be the explanation why previous studies failed to find an increased rate of the classical (acquired) vascular risk factors.

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.

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.

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 epileptic amnesia: a retrospective cohort study of 127 cases, including CSF amyloid and tau features

BACKGROUND

Transient epileptic amnesia (TEA) is a late-onset epilepsy syndrome encompassing transient iterative amnesias and interictal cognitive impairment, two features that overlap with incipient neurodegenerative dementias. We, therefore, examined the yield of CSF amyloid and tau biomarkers in TEA.

METHODS

In this retrospective study, 127 TEA patients with unremarkable imaging findings were divided into 2 groups, namely, CSF (n = 71) and no-CSF (n = 56). Both were compared for demographics; medical history; baseline neurological, cognitive, and behavioral features; baseline mesial temporal lobe atrophy; and cognitive follow-up at a median of 13 months. CSF samples were examined for amyloid β-42 peptide as well as phospho-tau and total-tau levels.

RESULTS

At baseline, the CSF-TEA group had significantly (p < 0.01) more frequent mild parkinsonism (42.9% vs. 20%) and cognitive concerns (31% vs. 10.7%), a more blunted sense of smell (34.3% vs. 9.4%), a lower baseline MMSE score (27 vs. 28.9), a more frequent amnestic mild cognitive impairment profile (69% vs. 42.6%), and more atrophic hippocampal changes. At follow-up, the CSF-TEA group had significantly (p < 0.01) lower MMSE scores (27.8 vs. 28.9). CSF analyses revealed amyloid and/or tau changes in 27 patients (38%), including an Alzheimer's disease (AD) profile in 17 (24%).

CONCLUSIONS

This study shows a good diagnostic value of CSF sampling in a specific population of TEA with characteristics suggestive of incipient degenerative diseases (i.e., red flags). It argues for TEA being the inaugurating feature in some cases of AD. More broadly, our results suggest an etiological heterogeneity in TEA.

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.

[Transient epileptic amnesia-A rare phenomenon in temporal lobe epilepsies]

BACKGROUND

Transient epileptic amnesia (TEA) is a rare phenomenon in temporal lobe epilepsy that is often unrecognized or misdiagnosed as transient global amnesia (TGA). It is postulated that TEA is due to both ictal and postictal disturbances. Response to antiseizure medication underlines its epileptic nature. In view of the increasing incidence of new-onset epilepsies in old age, an increase in TEA can be expected in the future.

OBJECTIVE

Analysis of TEA features in a monocentric case series.

MATERIAL AND METHODS

A search in our electronic patient data base yielded 10 patients with TEA out of 7899 patients over a period of 8 years. Clinical and paraclinical features as well as findings of additional examinations were retrospectively collected. Data are given as mean ± SD.

RESULTS

All 10 patients were diagnosed with temporal lobe epilepsy. The mean age at manifestation of TEA was 59.1 ± 6.7 years, the diagnosis was made with a delay of 21.9 ± 26.3 months. The TEA lasted on average 56 ± 37 min, and 16 ± 9.9 TEA episodes per year were reported by the patients; out of the 10 patients 6 reported that TEA usually occurred upon awakening. In 9 of 10 patients, there was evidence of typical seizure symptoms or other semiological elements during TEA. Interictal neuropsychological disturbances of temporal functions were seen in 8 of 10 patients and evidence of depressive disorder in 6 of 10 patients. Video EEG recordings revealed epileptiform activity during sleep in 4 patients over the left and in 2 patients over both temporal regions. In 3 patients, magnetic resonance imaging displayed typical alterations of the temporomesial structures (in 2 patients on the left and in 1 the right side). Antiseizure medication improved seizure control in 7 of 10 patients (seizure freedom in 6 patients), 3 patients were lost to follow-up.

DISCUSSION

TEA is rare, occurs in older adults and is correctly diagnosed after about 2 years. Thorough assessment of additional symptoms and circumstances, the recurrent occurrence as well as typical EEG and imaging findings of temporal lobe epilepsy enables the distinction between TEA and TGA.

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.

Development of Mechanistic Neural Mass (mNM) Models that Link Physiology to Mean-Field Dynamics

Brain rhythms emerge from the mean-field activity of networks of neurons. There have been many efforts to build mathematical and computational embodiments in the form of discrete cell-group activities-termed neural masses-to understand in particular the origins of evoked potentials, intrinsic patterns of activities such as theta, regulation of sleep, Parkinson's disease related dynamics, and mimic seizure dynamics. As originally utilized, standard neural masses convert input through a sigmoidal function to a firing rate, and firing rate through a synaptic alpha function to other masses. Here we define a process to build mechanistic neural masses (mNMs) as mean-field models of microscopic membrane-type (Hodgkin Huxley type) models of different neuron types that duplicate the stability, firing rate, and associated bifurcations as function of relevant slow variables - such as extracellular potassium - and synaptic current; and whose output is both firing rate and impact on the slow variables - such as transmembrane potassium flux. Small networks composed of just excitatory and inhibitory mNMs demonstrate expected dynamical states including firing, runaway excitation and depolarization block, and these transitions change in biologically observed ways with changes in extracellular potassium and excitatory-inhibitory balance.

Clinical outcomes in Transient Epileptic Amnesia: a 10-year follow-up cohort study of 47 cases

Objective

Transient epileptic amnesia (TEA) is a form of adult‐onset epilepsy where presenting features are well described, but little is known regarding prognosis. This study aimed to elucidate the long‐term prognosis of TEA regarding seizure control, memory, medical comorbidities, and life expectancy.

Methods

Up‐to‐date clinical information was collected for 47 people diagnosed with TEA who had joined the The Impairment of Memory in Epilepsy (TIME) study 10 years earlier. At entry to the study, information about comorbid conditions was systematically collected. Details regarding subsequent diagnoses, seizure activity, changes to treatment, or reports of cognitive impairment were obtained through the family doctor. The variables of interest were compared with UK population data.

Results

Mortality in the cohort was 21 of 47 (45%), with an average age at death of 82.5 years. Seizures remained well controlled for the majority but medications required adjustments in dose and type for some (28%). A small number (three cases) remained seizure‐free without medication. History of cardiovascular disorders was frequent (78.7%), typically involving hypertension (55.3%). Autoimmune disorders (25.5%), cancer (23.4%), and depression (21.3%) were also commonly reported. Although persisting memory problems were often noted, dementia was diagnosed in seven cases (14.9%). Life expectancy and comorbidities in TEA did not differ from available population norms.

Significance

Results suggest that life expectancy is not reduced in TEA. Although TEA does not appear to be a self‐limiting form of epilepsy, seizures are typically well controlled via medication. Because adjustments to medication may be required, even after long periods of stability, ongoing medical monitoring is recommended. Comorbid vascular disorders are frequent but appear similar to general population estimates. Monitoring mood may be important, given that people with chronic conditions are often vulnerable to depression. Because of persisting memory difficulties, the development of effective memory interventions for people with TEA is warranted.

Transient epileptic amnesia is significantly associated with discrete CA1-located hippocampal calcifications but not with atrophic changes on brain imaging

BACKGROUND

The exact etiology of transient epileptic amnesia (TEA) is currently unknown. In older individuals, common neurodegenerative dementias and small-vessel diseases (SVDs) could be major contributors. We examined these hypotheses on the basis of imaging analysis.

METHODS

In total, 36 TEA patients were compared with 25 healthy controls for (1) cortical atrophic changes (in the mesial temporal, frontal, anterior temporal, and parietal regions) using four established MRI-based visual rating scales, and for (2) SVD evidence using two MRI-based visual rating scales (Fazekas and MARS scores). In 24 TEAs cases, there were also brain CT scans available that were compared with 57 controls for the presence of hippocampal calcifications (HCs).

RESULTS

We did not find significant differences in cortical atrophy between TEAs and controls, nor did we observe a different SVD brain load on MRI. However, TEAs were significantly associated (p < 0.01) with uni- or bilateral CA1-located HCs in half of the patients compared with the controls (less than 20 %).

CONCLUSIONS

This study argues in favor of a hippocampal-restricted SVD (as indicated by HCs) as one of the major etiologies of TEA, while neurodegenerative dementias are probably minor causes. It furthermore highlights the pivotal role of the CA1 hippocampal subfield in the pathophysiology of this syndrome.

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.

Seizure Diaries and Forecasting With Wearables: Epilepsy Monitoring Outside the Clinic

It is a major challenge in clinical epilepsy to diagnose and treat a disease characterized by infrequent seizures based on patient or caregiver reports and limited duration clinical testing. The poor reliability of self-reported seizure diaries for many people with epilepsy is well-established, but these records remain necessary in clinical care and therapeutic studies. A number of wearable devices have emerged, which may be capable of detecting seizures, recording seizure data, and alerting caregivers. Developments in non-invasive wearable sensors to measure accelerometry, photoplethysmography (PPG), electrodermal activity (EDA), electromyography (EMG), and other signals outside of the traditional clinical environment may be able to identify seizure-related changes. Non-invasive scalp electroencephalography (EEG) and minimally invasive subscalp EEG may allow direct measurement of seizure activity. However, significant network and computational infrastructure is needed for continuous, secure transmission of data. The large volume of data acquired by these devices necessitates computer-assisted review and detection to reduce the burden on human reviewers. Furthermore, user acceptability of such devices must be a paramount consideration to ensure adherence with long-term device use. Such devices can identify tonic–clonic seizures, but identification of other seizure semiologies with non-EEG wearables is an ongoing challenge. Identification of electrographic seizures with subscalp EEG systems has recently been demonstrated over long (>6 month) durations, and this shows promise for accurate, objective seizure records. While the ability to detect and forecast seizures from ambulatory intracranial EEG is established, invasive devices may not be acceptable for many individuals with epilepsy. Recent studies show promising results for probabilistic forecasts of seizure risk from long-term wearable devices and electronic diaries of self-reported seizures. There may also be predictive value in individuals' symptoms, mood, and cognitive performance. However, seizure forecasting requires perpetual use of a device for monitoring, increasing the importance of the system's acceptability to users. Furthermore, long-term studies with concurrent EEG confirmation are lacking currently. This review describes the current evidence and challenges in the use of minimally and non-invasive devices for long-term epilepsy monitoring, the essential components in remote monitoring systems, and explores the feasibility to detect and forecast impending seizures via long-term use of these systems.

The syndrome of transient epileptic amnesia: a combined series of 115 cases and literature review

The term transient epileptic amnesia was coined in 1990 to describe a form of epilepsy causing predominantly amnestic seizures which could be confused with episodes of Transient Global Amnesia. Subsequent descriptions have highlighted its association with ‘atypical’ forms of memory disturbance including accelerated long-term forgetting, disproportionate autobiographical amnesia and topographical amnesia. However, this highly treatment-responsive condition remains under-recognized and undertreated. We describe the clinical and neuropsychological features in 65 consecutive cases of transient epileptic amnesia referred to our study, comparing these to our previous cohort of 50 patients and to those reported in 102 literature cases described since our 2008 review. Findings in our two cohorts are substantially consistent: The onset of transient epileptic amnesia occurs at an average age of 62 years, giving rise to amnestic episodes at a frequency of around 1/month, typically lasting 15–30 min and often occurring on waking. Amnesia is the only manifestation of epilepsy in 24% of patients; olfactory hallucinations occur in 43%, motor automatisms in 41%, brief unresponsiveness in 39%. The majority of patients describe at least one of the atypical forms of memory disturbance mentioned above; easily provoked tearfulness is a common accompanying feature. There is a male predominance (85:30). Epileptiform changes were present in 35% of cases, while suspected causative magnetic resonance imaging abnormalities were detected in only 5%. Seizures ceased with anticonvulsant treatment in 93% of cases. Some clinical features were detected more commonly in the second series than the first, probably as a result of heightened awareness. Neuropsychological testing and comparison to two age and IQ-matched control groups (n = 24 and 22) revealed consistent findings across the two cohorts, namely elevated mean IQ, preserved executive function, mild impairment at the group level on standard measures of memory, with additional evidence for accelerated long-term forgetting and autobiographical amnesia, particularly affecting episodic recollection. Review of the literature cases revealed broadly consistent features except that topographical amnesia, olfactory hallucinations and emotionality have been reported rarely to date by other researchers. We conclude that transient epileptic amnesia is a distinctive syndrome of late-onset limbic epilepsy of unknown cause, typically occurring in late middle age. It is an important, treatable cause of memory loss in older people, often mistaken for dementia, cerebrovascular disease and functional amnesia. Its aetiology, the monthly occurrence of seizures in some patients and the mechanisms and interrelationships of the interictal features—amnestic and affective—all warrant further study.

The long-term prognosis of Transient Global Amnesia: a systematic review

Transient Global Amnesia (TGA) constitutes an enigmatic amnestic condition. In view of the admittedly limited knowledge regarding the nature of TGA, we decided to systematically review existing evidence for the generally regarded benign course of the disease. MEDLINE, EMBASE, CENTRAL and PsycINFO were searched for relevant articles. Observational (case-control, cross-sectional and cohort) controlled studies were retrieved. TGA diagnosis was made according to the diagnostic criteria of Caplan, validated by Hodges and Warlow. The TGA group was compared with either healthy controls (HC) or/and individuals with transient ischaemic attacks (TIA). The long-term risks of dementia, epilepsy, psychological-emotional disturbances, as well as long-term vascular and (vascular or nonvascular) mortality risks, were evaluated. Quality assessment was based on the Newcastle-Ottawa Scale. Literature search provided 12 eligible articles. Retrospective, prospective or mixed cohort designs were implemented in every study. Five articles registered a high quality, five registered a moderate quality, while two articles were assessed as part of the grey literature (conference abstract, abstract in English-article in Spanish). Overall, retrieved evidence was suggestive of similar vascular and mortality risks in TGA patients and HC, while TIA individuals exhibited elevated risks. Moreover, psychological disturbances were comparable between TGA and healthy individuals. On the other hand, studies for dementia and epilepsy obtained contradictory results, indicating both a similar and an increased risk in the TGA group compared to the HC group. Therefore, additional high-quality studies are warranted for the acquisition of more determining conclusions regarding the long-term risk of dementia and epilepsy in TGA.

Prevalence of Mimics and Severe Comorbidity in Patients with Clinically Suspected Transient Global Amnesia

BACKGROUND

Transient global amnesia (TGA) is a syndrome featuring acute anterograde amnesia as the most striking clinical symptom. Its etiology is still a matter of debate. Most neurological guidelines allow the diagnosis on the basis of clinical criteria only; a more extensive evaluation is recommended only for patients with "red flags" like severe headache, nausea or vomiting, or metabolic abnormalities. The aim of our study was to assess the frequency of a severe underlying disease or alternative diagnoses (mimics) in patients fulfilling the clinical criteria.

METHODS

We evaluated the medical records and the imaging data of an unselected consecutive cohort of patients with suspected TGA over a 7-year period. All patients were hospitalized and received a neurological workup including brain imaging, color-coded duplex sonography of the brain supplying arteries, electroencephalography, and laboratory studies of blood and (in selected cases) cerebrospinal fluid.

RESULTS

163 patients with 166 episodes of suspected TGA were hospitalized (3 patients twice). After the workup, the diagnosis of TGA was confirmed in 148/166 (89.2%) episodes ("simple TGA"). Eighteen patients (10.8%) either had an alternative diagnosis or a severe comorbidity that was assumed to have had an impact on the occurrence of the amnestic episode ("complicated TGA/mimic"). The most important differential diagnosis was stroke (11 patients, 6.6% of all TGA suspects and 61.1% of the complicated TGA/mimic group). Other mimics were transient epileptic amnesia (2 patients) and steroid-induced delirium (1 patient). Important comorbidities that had not been obvious at the time of presentation were severe sleep apnea (2 patients), triptan overuse (1 patient), and an involuntary amlodipine intoxication during TGA.

CONCLUSION

As approximately every tenth patient with suspected TGA either had an alternative diagnosis or a severe comorbidity, which had not been obvious at the time of admission, we consider in-patient treatment of all suspected TGA cases as appropriate, preferably in the setting of a stroke unit, as ischemic stroke was the by far most important diagnosis mimicking TGA.

Power Spectral Differences between Transient Epileptic and Global Amnesia: An eLORETA Quantitative EEG Study

Transient epileptic amnesia (TEA) is a rare epileptic condition, often confused with transient global amnesia (TGA). In a real-life scenario, differential diagnosis between these two conditions can be hard. In this study we use power spectral analysis empowered by exact Low Resolution Brain Electromagnetic Tomography (eLORETA) to evidence the differences between TEA and TGA. Fifteen patients affected by TEA (64.2 ± 5.2 y.o.; 11 female/4 male; 10 left and 5 right temporal epileptic focus) and 15 patients affected by TGA (65.8 ± 7.2 y.o.; 11 females/4 males) were retrospectively identified in our clinical records. All patients recorded EEGs after symptoms offset. EEGs were analyzed with eLORETA to evidence power spectral contrast between the two conditions. We used an inverse problem solution to localize the source of spectral differences. We found a significant increase in beta band power over the affected hemisphere of TEA patients. Significant results corresponded to the uncus and para-hippocampal gyrus, respectively Brodmann’s Areas: 36, 35, 28, 34. We present original evidence of an increase in beta power in the affected hemisphere (AH) of TEA as compared to TGA. These differences involve key areas of the memory network located in the mesial temporal lobe. Spectral asymmetries could be used in the future to recognize cases of amnesia with a high risk of epilepsy.

Diffusion-weighted MRI in transient global amnesia and its diagnostic implications

OBJECTIVE

To analyze how the evidence of hippocampal diffusion-weighted imaging (DWI) lesions may support the clinical diagnosis of transient global amnesia (TGA).

METHODS

In this retrospective observational study, 390 consecutive patients with isolated TGA were analyzed, who were evaluated at our institution between July 1999 and August 2018. The size, location, and number of lesions and time-dependent lesion detectability were examined. The incidence of DWI lesions was reviewed with regard to different levels of clinical diagnostic certainty upon presentation to the emergency department.

RESULTS

Hippocampal DWI lesions were detected in 272 (70.6%) patients with TGA, with a mean of 1.05 ± 0.98 (range 0-6) and a mean lesion size of 4.01 ± 1.22 mm (range 1.7-8.6 mm). In the subgroups of lower diagnostic certainty (amnesia witnessed by layperson or self-reported amnestic gap), DWI was helpful in supporting the diagnosis of TGA in 76 (69.1%) patients. In 187 patients with information about the exact onset, DWI lesions were analyzed in relation to latency between onset and MRI. Lesions could be detected at all time points and up to 6 days after symptom onset in individual patients; the highest rate of DWI-positive MRI (93%) was in the 12-24 hours time window.

CONCLUSION

MRI findings can support the diagnosis of TGA and may be particularly valuable in situations of low clinical certainty. DWI-ideally performed with a minimum delay of 20 hours after onset-should therefore be considered a useful adjunct to the diagnosis of TGA.

Epilepsy in the elderly: Unique challenges in an increasingly prevalent population

Elderly individuals (aged at least 60 or 65 years) represent a rapidly growing segment of the population. The incidence and prevalence of epilepsy is higher in this age group than in any other. Diagnosing epilepsy in the elderly can be challenging because the causes and clinical manifestations of seizures often differ as compared with younger individuals. Particular differential diagnoses, such as syncope and amyloid spells, are commonly encountered in the elderly population. A diagnosis of epilepsy has important implications in the older adult, many of which already present a variety of concomitant complex medical problems, such as cognitive impairment, comorbid cerebrovascular disease, and frailty. The treatment of epilepsy in the elderly is complicated by a variety of factors related to aging, including physiological changes, medical comorbidities, and polypharmacy. In this narrative review, we will address the descriptive epidemiology, clinical presentation, differential diagnosis, diagnostic evaluation, treatment, and prognosis of epilepsy in the elderly individual.

[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.