Transient global amnesia: clinical features and prognostic factors suggesting recurrence / Amnesia global transitoria: características clínicas y factores pronósticos sugestivos de recurrencia

ABSTRACT The risk of recurrence of new amnesia events in patients having previously experienced transient global amnesia (TGA) ranges between 2.9-23.8%. Objective: 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.

RESUMEN El riesgo de recurrencia de nuevos eventos de amnesia en pacientes que han experimentado previamente Amnesia Global Transitoria (AGT) oscila entre el 2.9-23.8%. Objetivo: Nuestro objetivo fue buscar predictores de recurrencia en pacientes con AGT. Métodos: Análisis retrospectivo de una cohorte de 203 pacientes con AGT de un único centro en Buenos Aires, Argentina, diagnosticados entre enero-2011 y marzo-2017 Se analizaron las características clínicas y los estudios complementarios (laboratorio, Doppler de vena yugular y RM encéfalo). Se comparó el grupo de AGT recurrente versus episodio único, aplicando un modelo de regresión logística multivariada. Resultados: la edad promedio de presentación fue de 65 años (20-84); 52% mujeres. La mediana del tiempo transcurrido entre el inicio de los síntomas y la visita a la sala de emergencia fue de 2 horas, con una duración promedio del episodio de 4 horas. El seguimiento medio fue de 22 meses. 66% de los pacientes tuvieron un desencadenante identificable. El reflujo yugular estuvo presente en el 66% de los pacientes y el 22% mostró imágenes restrictivas en DWI a nivel hipocampal. 8% de los pacientes presentaron recurrencia. Los pacientes con AGT recurrente tuvieron un historial de migraña más frecuente (37.5% vs. 14%; p=0.03). Ninguna de las otras características clínicas y estudios complementarios fueron predictores de mayor riesgo de recurrencia. Conclusiones: los pacientes con migraña pueden tener un mayor riesgo de recurrencia de AGT. Ninguna de las otras características clínicas evaluadas nos permitió predecir un mayor riesgo de recurrencia. Aunque los estudios complementarios nos permitieron orientar el diagnóstico, no pareció tener un impacto significativo en la predicción del riesgo de recurrencia.

Amnésia global transitória: epidemiologia, fisiopatologia, clínica e terapêutica / Global transient amnesia: epidemiology, pathophysiology, clinical features and therapeutics

A amnésia global transitória (AGT) é um quadro súbito de amnésia global, não acompanhada de outros déficits neurológicos, com duração de duas a 24 horas e cuja recuperação se dá espontaneamente. A incidência na população geral está estimada em 5-10 casos/100.000 pessoas/ano. Diferentes mecanismos fisiopatológicos, como fatores vasculares ou epiléticos, têm sido propostos para explicar a AGT, sendo consensual que haja acometimento transitório de regiões do hipocampo e do giro para-hipocampal. Além da amnésia anterógrada acompanhada por amnésia retrógrada, o paciente apresenta desorientação (tempo/espaço), estando preservadas outras habilidades cognitivas, como memória semântica e capacidades visuo-construtivas. Esses déficits tendem a remitir após 24h, sendo o prognóstico favorável na maioria dos casos. O diagnóstico diferencial de AGT é amplo e diversas condições clínicas, como eventos cérebro-vasculares, epilepsias, infecções e intoxicações podem mimetizá-lo, de modo que uma investigação clínica cuidadosa é imperativa. As recorrências não são frequentes nos quadros típicos. A AGT não requer tratamento específico, mas devem ser tratados fatores de risco cardiovascular eventualmente identificados durante a propedêutica de AGT. O clínico deve esclarecer o paciente a respeito do caráter benigno da AGT. Estudos com seguimento longitudinal dos pacientes são necessários para maior compreensão dos mecanismos fisiopatológicos da AGT e para melhor compreensão clínica e neuro- biológica dos déficits cognitivos apresentados por esses pacientes.

Global transient amnesia (GTA) is a clinical syndrome characterized by the sudden onset of anterograde and retrograde amnesia, without permanent neurological deficits, and which presents complete remission spontaneously within 2 to 24 hours. The incidence of GTA in the general population ranges from 5 to 10 cases per 100.000 individuals/ year. Different pathophysiological mechanisms have been proposed for GTA, such as vascular or epileptic factors, and it is consensual that there is transitory involvement of hippocampal and parahippocampal gyri in this condition. In addition to anterograde and retrograde amnesia, GTA patients typically present time-space disorientation, with the preservation of other cognitive abilities, such as semantic memory and visuoconstructive capacities. The differential diagnosis includes stroke, epilepsy, infections and intoxication, and a careful clinical investigation is essential to establish the GTA diagnosis. Recurrence is uncommon in typical cases and, in general, no specific treatment is required. However, clinical investigation of GTA may eventually disclose cardiovascular risk factors; these factors should be treated when identified. GTA is considered a benign condition, with good clinical and cognitive prognostics in most of the cases. More studies are needed to advance the current knowledge on the pathophysiology and on the neural basis of the transitory cognitive impairment observed in GTA.

Longitudinal Cerebral Perfusion Change in Transient Global Amnesia Related to Left Posterior Medial Network Disruption.

BACKGROUND: The pathophysiology of transient global amnesia (TGA) is not fully understood. Previous studies using single photon emission computed tomography (SPECT) have reported inconclusive results regarding cerebral perfusion. This study was conducted to identify the patterns of regional cerebral blood flow (rCBF) in TGA patients via longitudinal SPECT analysis. An association between the observed SPECT patterns and a pathophysiological mechanism was considered. METHODS: Based on the TGA registry database of Seoul National University Bundang Hospital, 22 TGA patients were retrospectively identified. The subjects underwent initial Tc-99m-ethyl cysteinate dimer (ECD) SPECT within 4 days of an amnestic event and underwent follow-up scans approximately 6 months later. The difference in ECD uptake between the two scans was measured via voxel-based whole brain analysis, and the quantified ECD uptake was tested using a paired t-test. RESULTS: The TGA patients had significantly decreased cerebral perfusion at the left precuneus (P<0.001, uncorrected) and at the left superior parietal and inferior temporal gyrus according to the voxel-based whole brain analysis (P<0.005, uncorrected). A difference in the quantified ECD uptake between the 2 scans was also found at the left precuneus among the 62 cortical volumes of interest (P = 0.018, Cohen's d = -0.25). CONCLUSION: We identified left hemispheric lateralized hypoperfusion that may be related to posterior medial network disruption. These findings may be a contributing factor to the pathophysiology of TGA.

[Usefulness of electroencephalograms in evaluating transient global amnesia]. / Utilidad de la electroencefalografia en la valoracion de la amnesia global transitoria.

INTRODUCTION: Transient global amnesia (TGA) is a perfectly well defined clinical picture, but nevertheless even today its aetiology remains unknown. The three most widely accepted theories suggest it has a vascular origin, it is related with the pathophysiology of migraine or it is of an epileptiform nature. AIM: To analyse whether there is an electroencephalographic pattern that is consistently repeated in a series of electro-encephalograms (EEG) carried out on patients with TGA. PATIENTS AND METHODS: The study consists in a retrospective analysis of a sample of 345 patients referred to have an EEG after an episode of TGA. RESULTS: In almost 20% of the EEGs something that could be considered abnormal was found, although most of these findings (64%) were of little pathological significance. Of the remaining 26%, attention should be drawn to the cases of two patients with subclinical rhythmic electroencephalogram discharges of adults (a pattern with a meaning that is not altogether clear and which has previously been associated with TGA). CONCLUSIONS: A considerable percentage of patients have TGA and EEG alterations, although most of them are of scarce pathological significance or can be attributed to some other underlying condition. We have not succeeded in identifying any pattern that is consistently repeated. Our results suggest that the EEG is a test with low diagnostic effectiveness in this pathology and it is necessary to reconsider the need to systematically perform such tests in suspected cases of TGA.

[Transient global amnesia after general anaesthesia]. / Amnesia global transitoria en el contexto de una anestesia general.

Transient global amnesia is a neurological syndrome in which there is a sudden and brief inability to form new memories, as well as an intense retrograde amnesia. However, awareness, personal identity and attention remain intact. It is an uncommon condition seen after an anaesthetic procedure. There are several aetiopathogenic hypotheses (epileptic, migrainous or ischaemic origin) and triggering factors (pain, anxiety, temperature changes, exercise, Valsalva manoeuvres, diagnostic tests or certain drugs). We describe the case of a patient with a high level of pre-operative anxiety who suffered an episode of transient global amnesia after undergoing otolaryngology surgery. With an acute and continued amnesia after general anaesthesia, the first thing that must be done is to establish a suitable differencial diagnosis, which should include transient global amnesia, as this is mainly an exclusion diagnosis. Preoperative anxiety may be a triggering factor to take into account in this condition, with anxiolytic treatment prior to the surgery being important.

Transient amnesia in a patient with left temporal tumor: symptomatic transient global amnesia or an epileptic amnesia?

BACKGROUND: An isolated prolonged episode of transient amnesia can be a major manifestation of transient global amnesia (TGA) and transient epileptic amnesia (TEA). We report a case of transient amnesia associated with a left temporal tumor and try to elucidate the possible mechanism of the amnesia. CASE REPORT: A 67-year-old right-handed man with the past history of migraine developed a transient declarative amnesia with a permanent memory gap for 5 hours. During the attack, he drove for 100 km flawlessly, but was not aware of his memory deficit. Selective retrograde amnesia during the episode was also observed. Investigations revealed an impaired verbal memory on neuropsychological tests, a possible metastatic tumor in the left temporal lobe by cerebral MRI, isolated wicket temporal spikes in the left mesial temporal area by sphenoidal electroencephalogram (EEG), and an additional brief phase of confusion. No recurrence of a similar attack occurred by 17 months after treatment with radiotherapy and chemotherapy. DISCUSSION: This case serves to emphasize that transient dense anterograde amnesia resembling TGA might possibly occur as a manifestation of TEA and that there is a risk of subsequent epileptic features. The amnesia in this case also supports the hypothesis of spreading depression in patients with TGA and migraine and could support the epileptic hypothesis for the pathogenesis of TGA.

High-field, T2 reversed MRI of the hippocampus in transient global amnesia.

OBJECTIVE: To investigate the fine structural integrity of the hippocampus in patients with transient global amnesia (TGA) using high-resolution T2 reversed (T2R) MRI. METHODS: The authors performed detailed structural analysis of the hippocampus in 15 patients who had recovered from an episode of TGA and 150 randomly recruited normal volunteers across the adult age spectrum using high-resolution T2R MRI obtained on a 3.0-T system. An additional 100 subjects, with stroke or tumor, were similarly studied and served as disease controls. RESULTS: The overall incidence of hippocampal cavities detected in normal volunteers increased with age but never exceeded 40%, whereas the incidence in disease control group was 31%. They were always unilateral. In contrast, cavities were found in all 15 patients with TGA (100%), an incidence higher than in normal or disease controls (p < 0.05; Ryan's multiple comparison test), and were bilateral in eight patients (53%). The cavities in all but one of the normal volunteers (99%) and all disease controls (100%) were crescent shaped and < or =2 mm in width. The cavities in 14 of 15 patients with TGA (93%) were considerably larger (>3 mm in width), and five of the patients had giant cavities (>5 mm in width). Most of the cavities in patients with TGA had a rounded shape and resembled pathologic cavities described in specimens of hypoxia-related CA1 necrosis. CONCLUSION: The data indicate that transient global amnesia may not be a benign entity. Delayed neuronal loss within CA1 area of Lorente de No may represent its important sequel.

Evolution of temporal lobe hypoperfusion in transient global amnesia: a serial single photon emission computed tomography study.

Previous functional neuroimaging studies performed during transient global amnesia (TGA) have not answered the central question regarding the etiology of TGA, namely: whether the observed hypoperfusion in the mesial temporal lobe structures reflects a primarily ischemic process or whether it represents a secondary phenomenon resulting from locally decreased metabolism. The authors performed Tc 99-m-bicisate brain single photon-emission computed tomography (SPECT) scanning in a 66-year-old man during an episode of TGA, 24 hours after the episode and 3 months after the episode. To the authors' knowledge, this is the only reported study in which a follow-up SPECT scan was performed within 24 hours. The initial study showed bilateral mesial temporal lobe hypoperfusion that partially resolved after 24 hours and returned to normal at 3 months. Resolution of the SPECT scan abnormalities correlated well with resolution of the memory loss. These findings agree with previously reported SPECT, positron-emission tomography (PET), and diffusion magnetic resonance imaging (MRI) studies that indicate the mesial temporal lobe structures as the major site of pathology in TGA. The authors suggest that a process causing decreased local metabolism, such as cortical spreading depression, constitutes the primary pathophysiologic mechanism in this case.

Transient amnesia triggered by acute marijuana intoxication.

We report an unusual case of sudden isolated transient amnesia triggered by acute marijuana use. The memory disorder, apart from the long duration, had the characteristics of a transient global amnesia-like episode. Acute marijuana intoxication can affect memory more globally and severely than previously reported.