Transient Global Amnesia

Transient global amnesia (TGA) is a clinical syndrome characterized by anterograde amnesia, mild retrograde amnesia, and confusion up to 24 hours. Most commonly seen in patients older than 50 years, TGA results from the temporary impairment of short-term memory formation. Clinically, patients have time disorientation and often ask repeated questions regarding the day's events. Vomiting, headache, blurry vision, dizziness, and nausea may be present. A physically or psychologically stressful precipitating event, such as emotional stress, significant physical exertion, exposure to extreme temperatures, high-altitude conditions, Valsalva maneuver, acute illness, or sexual intercourse, is often the cause. The pathophysiology of TGA is not well understood but may be related to impaired venous drainage of the hippocampus. The diagnosis is primarily clinical, but recent studies suggest that magnetic resonance imaging may be helpful. TGA is self-limited and resolves within 24 hours. There is no established treatment for episodes. The lifetime recurrence rate is 2.9% to 23.8%. Recent evidence suggests an association between TGA and migraine headaches as well as takotsubo cardiomyopathy. No apparent increased risk of cerebrovascular events occurs in patients who have had an episode of TGA. There is conflicting evidence as to whether an episode of TGA predisposes to future seizures or dementia.

Enhanced cortisol secretion in acute transient global amnesia

INTRODUCTION

Stress-related transient inhibition of memory formation in the hippocampus has been hypothesized as one of the underlying pathomechanisms of transient global amnesia (TGA). TGA episodes, during which patients cannot encode and recall new information (anterograde amnesia affecting episodic long-term memory), are frequently preceded by a psychologically or physically stressful event.

METHODS

We measured salivary cortisol during acute TGA in 14 patients, as well as cortisol day-profiles and the effect of experimental exposure to stress (using the socially evaluated cold pressor test) on cortisol levels during the subacute phase. We assessed psychiatric comorbidity as well as depression, trait anxiety and chronic stress. These findings were compared with data of 20 healthy controls.

FINDINGS

Nine patients reported a precipitating stressor and all 14 developed typical hippocampal lesions on follow-up MRI. During TGA, salivary cortisol levels were more than 3-fold higher compared to time-matched day levels. While there was no difference in mean cortisol levels of the diurnal rhythm, we found a significant interaction between groups during experimental stress exposure (p = 0.049) with the TGA group revealing a higher cortisol increase. The TGA group reported higher levels of depressive symptomatology (CES-D) and higher scores of chronic stress (TICS) compared with the control group and there was a significant correlation between cortisol increase during TGA and the results of self-rating according to the CES-D (r = 0.615; p = 0.004), as well as to the STAI (r = 0.702; p = 0.001).

CONCLUSION

Our findings of enhanced secretion of cortisol in acute TGA patients correlating with symptoms of depression and anxiety and a persisting hyperreactivity to experimental stress in the subacute phase support the hypothesis that stress might be significant for the pathogenesis of TGA.

Comprehensive Ultrasound Assessment of the Craniocervical Circulation in Transient Global Amnesia

OBJECTIVES

Structural changes and metabolic stress have been reported on diffusion-weighted magnetic resonance imaging in the cornu ammonis 1 area of the hippocampus in patients with transient global amnesia (TGA), but a consensus on pathogenesis is still lacking. The aim of our study was to perform a comprehensive ultrasound analysis of the cerebrovascular circulation in our population of patients with TGA.

METHODS

One hundred patients with TGA and 50 age- and sex-matched control participants underwent ultrasound examinations of the cervicocranial circulation.

RESULTS

The most significant risk factor for TGA was arterial hypertension (P < .01). There were no significant atherosclerotic lesions on the large arteries of the neck (mean internal carotid artery stenosis ± SD, 28.7% ± 11.7%) or on the large intracerebral arteries (good structural and hemodynamic status; P > .05). Rarely detected microembolic signals or a right-left cardiopulmonary shunt excluded an emboligenic mechanism of TGA (P > .05). The internal jugular vein valves were incompetent in 54% of patients with TGA, and this condition was associated with an increased risk of TGA (odds ratio, 4.16; 95% confidence interval, 1.91-9.04). The mean values of the breath holding index and pulsatility index, as parameters of small-vessel function, were within normal ranges and without differences between the TGA and control groups (P > .05).

CONCLUSIONS

Our ultrasound examination did not detect significant structural atherosclerotic changes of cervicocranial arteries, and an emboligenic mechanism was excluded. Only a significant rise of blood pressure in TGA and significant valvular insufficiency of the internal jugular vein were established. New research should clarify whether these simultaneous functional circulatory changes have relevance for metabolic stress in the cornu ammonis of the hippocampus.

Vascular Risk Factors and Internal Jugular Venous Flow in Transient Global Amnesia: A Study of 165 Japanese Patients

BACKGROUND

The etiology of transient global amnesia (TGA) remains unclear. We studied the pathophysiology of TGA in 165 Japanese patients.

SUBJECTS AND METHODS

TGA was diagnosed in hospitalized patients from 2004 to 2015. We analyzed clinical characteristics, magnetic resonance imaging findings, and maximum intima-media thickness of the common carotid artery, and the reflux of internal jugular venous (IJV) flow by ultrasonography, and statistically compared patients with TGA with age-matched and sex-matched patients who have had a transient ischemic attack (TIA), small-vessel occlusion (SVO), and normal controls (each group, N = 165).

RESULTS

Patients with TGA showed lower prevalence of vascular risk factors than patients with TIA and SVO did. Eleven patients (6.7%) had 2 episodes of TAG, but specific clinical variables could not be recognized in these patients. The maximum intima-media thickness was significantly thinner in TGA (1.1 ± .7 mm) than in SVO (1.6 ± .9 mm; P = .001). The percentages of cases whose IJV flow reflux was increased by Valsalva maneuver showed no difference (P = .573) between TGA (26.0 %) and SVO (29.4%). MR diffusion-weighted imaging yielded small hyperintense signals in the hippocampus in 64 of 90 (71.1%) patients between 24 and 72 hours. Potential precipitating specific factors or events before the attacks could be recognized in 40 cases (24.2%) of 165 patients.

CONCLUSION

Arterial ischemia and IJV flow reflux might not contribute to TGA pathophysiology. The vulnerability of the hippocampus to physical or emotional stress might be suspected as an underlying mechanism in some patients with TGA.

Transient global amnesia: emergency department evaluation and management [digest]

Transient global amnesia is a clinically distinct syndrome characterized by the acute inability to form new memories. It can last up to 24 hours. The diagnosis is dependent on eliminating other more serious etiologies including toxic ingestions, acute strokes, complex partial seizures, and central nervous system infections. Transient global amnesia confers no known long-term risks; however, when abnormal signs or symptoms are present, they take precedence and guide the formulation of a differential diagnosis and investigation. In witnessed transient global amnesia with classic features, a minimalist approach is reasonable, avoiding overtesting, inappropriate medication, and medical interventions in favor of observation, ensuring patient safety, and reassuring patients and their families. This review provides a detailed framework for distinguishing transient global amnesia from its dangerous mimics and managing its course in the emergency department. [Points & Pearls is a digest of Emergency Medicine Practice].

Diagnosis of Transverse Sinus Hypoplasia in Magnetic Resonance Venography: New Insights Based on Magnetic Resonance Imaging in Combined Dataset of Venous Outflow Impairment Case-Control Studies: Post Hoc Case-Control Study

In previous studies of transverse sinus (TS) hypoplasia, discrepancies between TS diameter measured by magnetic resonance venography (MRV) and contrast T1-weighted magnetic resonance (contrast T1) were observed. To investigate these discrepancies, and considering that TS hypoplasia is associated with neurological disorders, we performed a post hoc analysis of prospectively collected data from 3 case-control studies on transient global amnesia (TGA), transient monocular blindness (TMB), and panic disorders while retaining the original inclusion and exclusion criteria. Magnetic resonance (MR) imaging of 131 subjects was reviewed to evaluate TS diameter and the location and degree of venous flow stenosis and obstruction.MRV without contrast revealed that TS hypoplasia was observed in 69 subjects, whom we classified into 2 subgroups according to the concordance with contrast T1 observations: concordance indicated anatomically small TS (30 subjects), and discrepancy indicated that the MRV diagnosis is in fact flow-related and that TS is not anatomically small (39 subjects). The latter subgroup was associated with at least 1 site of venous compression/stenosis in the internal jugular vein (IJV) or the left brachiocephalic vein (BCV) (P < 0.001), which was significantly larger in patients than controls. Compensatory dilatation of contralateral TS diameter was only observed with MRV, not with contrast T1 imaging.The clinical implication of these results is that using MRV only, IJV/BCV compression/stenosis may be misdiagnosed as TS hypoplasia. And contralateral TS have no compensatory dilatation in its diameter in contrast T1 imaging, just compensatory increased flow volume.

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.

Transient global amnesia

Transient global amnesia (TGA) is a clinical syndrome characterized by the sudden onset of anterograde amnesia (the inability to encode new memories), accompanied by repetitive questioning, sometimes with a retrograde component, lasting up to 24 hours, without compromise of other neurologic functions. Herein, we review current knowledge on the epidemiology, pathophysiology, clinical diagnosis, and prognosis of TGA. For this review, we conducted a literature search of PubMed, with no date limitations, using the following search terms (or combinations of them): transient global amnesia, etiology, pathophysiology, venous hypertension, migraine, magnetic resonance imaging, computed tomography, electroencephalography, prognosis, and outcome. We also reviewed the bibliography cited in the retrieved articles. Transient global amnesia is a clinical diagnosis, and recognition of its characteristic features can avoid unnecessary testing. Several pathophysiologic mechanisms have been proposed (venous insufficiency, arterial ischemia, and migrainous or epileptic phenomena), but none of them has been proved to consistently explain cases of TGA. Brain imaging may be considered and electroencephalography is recommended when episodes are brief and recurrent, but otherwise no investigations are necessary in most cases. Data on long-term prognosis are limited, but available information suggests that the relapse rate is low, the risk of stroke and seizures is not considerably increased, and cognitive outcome is generally good.

Transient global amnesia

Transient Global Amnesia (TGA) is a clinical syndrome characterized by temporary inability to form new memories described as anterograde amnesia. It is associated with retrograde amnesia and repetitive questioning. During the attack patients remain conscious and communicative and personal identity is preserved. Focal neurological symptoms and epileptic features are absent and general conditions appear intact. The ability to store new memories gradually recovers and subjects return to normal conditions except for a substantial amnestic gap for the duration of the attack. TGA has an incidence of 3-8 per 100 000 people per year. It usually affects patients between the ages of 50 and 70 years, at an average age of 61 years; occurrence in patients younger than 40 years of age is rare. The rate of recurrence is between 6% and 10% per years. No gender prevalence has been recorded. The patients with definite TGA have a very good prognosis; their rate of subsequent major vascular events is less than 1% per year.

Transient epileptic amnesia: clinical report of a cohort of patients

Transient epileptic amnesia is a seizure disorder, usually with onset in the middle-elderly and good response to low dosages of antiepileptic drugs. We describe the clinical, electroencephalography (EEG), and neuroimaging features of 11 patients with a temporal lobe epilepsy characterized by amnesic seizures as the sole or the main symptom. We outline the relevance of a detailed clinical history to recognize amnesic seizures and to avoid the more frequent misdiagnoses. Moreover, the response to monotherapy was usually good, although the epileptic disorder was symptomatic of acquired lesions in the majority of patients.

Transient global amnesia

Transient global amnesia (TGA) is a sudden and severe anterograde memory disturbance accompanied by various degrees of retrograde amnesia and sometimes executive dysfunction. TGA affects elderly individuals and men and women equally. During the episode, patients cannot recall novel episodic information and therefore repeatedly ask the same questions. They are not fully oriented to space and time. Diagnostic criteria first established in 1985, and elaborated in 1990, demand that there is no clouding of consciousness, other impairments of cognition, or a history of epilepsy or head trauma. An episode of TGA resolves within 24 h leaving a memory gap for the length of the attack. While in rare cases TGA might happen repeatedly, it mostly occurs as a single attack. TGA is considered a benign disorder as memory deficits resolve completely and do not lead to long-term sequelae. In up to 90% of reported TGA cases, a precipitating event - mainly described as physical or emotional stress - is present. The cause of TGA has been a matter of long-standing debate among researchers. In search of an answer, several possible causes (ischemia, migraine, epileptic seizures, or, more recently, a disturbance of venous hemodynamics) have been hypothesized. However, to date there is no scientific proof of any of these mechanisms. By using diffusion-weighted MRI 24-48 h after a TGA episode, small dot-like lesions have been detected in the hippocampus. This has led to the implication that the selective vulnerability of CA1 neurons to metabolic stress might play a role in the pathophysiology of TGA.

[Usefulness of electroencephalograms in evaluating transient global amnesia]

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.

[Memory and metamemory during transient global amnesia: a comparative study about long-term follow up]

INTRODUCTION

Diagnostic criteria of transient global amnesia (TGA) establishes that memory functioning has to be recovered in 24 hours. However, there are contradictory data about the existence of long-term sequelae. Furthermore, there is no consensus about which is the most suitable tool in order to use in the assessment of the follow up of these patients.

AIMS

To assess episodic memory of TGA patients during amnesic episode and 7, 30 and 90 days after with free recall and Mini-Mental tasks. Moreover, it has been measured patient's metamemory.

SUBJECTS AND METHODS

17 TGA patients and 17 healthy volunteers, matched by age, sex, and educational level were assessed. A longitudinal (four assessments) and factorial (patients and control group) study was carried out.

RESULTS

During TGA, free recall and Mini-Mental tasks were significantly affected. However, only free recall task showed improvement along time and impairment after three months. It has been also detected that metamemory of TGA patients is imprecise.

CONCLUSIONS

Comparing with control group, both free recall and Mini-Mental tasks have significant lower levels during TGA, but only the first one is sensitive enough to show long-term disturbance associated with this amnesia.

Subclinical rhythmic electrographic discharges of adults and transient global amnesia: a causal or casual association?

Subclinical rhythmic electrographic discharges of adults (SREDA) is an uncommon distinctive EEG rhythmic pattern with uncertain significance. We report a patient with transient global amnesia in whom an EEG recording, performed after the acute phase of the neurological event, showed SREDA. Based on this EEG finding, we discuss about a possible correlation between SREDA and transient global amnesia. The presence of SREDA in our patient with transient global amnesia seems to be incidental. When described in association with transient global amnesia, SREDA should be recognized in order to avoid misdiagnosis. Although SREDA has been fortuitously described in association with transient global amnesia, a patho-physiological correlation with mechanisms which produce it seems unlikely.

[A study of right-left shunt in transient global amnesia]

INTRODUCTION

Transient global amnesia (TGA) is a disorder of unknown aetiology. In recent studies, TGA was associated with a right to left shunt (RLS). We studied the presence of the RLS in patients with TGA and we compared this series with patients who had suffered a transient ischaemic attack (TIA).

PATIENTS AND METHODS

We included 66 consecutive TGA patients. In these patients a transcranial Doppler was performed to determine the presence of a RLS. We collected data on the TGA episode, vascular risk factors, migraine history, recurrence of TGA and neuroimaging in patients with and without RLS. We compared the prevalence of the RLS in TGA series with 59 patients with TIA.

RESULTS

The prevalence of RLS was 21.2% in patients with TGA. The RLS was associated with the migraine history (40% versus 13%; p = 0.014) and a Valsalva manoeuvre as a triggering factor (50% versus 14.5%; p = 0.022). A greater prevalence of RLS was detected in patients with TIA (55.9% versus 21.2%; p < 0.001).

CONCLUSIONS

The RLS prevalence in TGA patients is similar to the general population but significantly lower than the prevalence in TIA patients. The association with a Valsalva manoeuvre as a precipitating factor in the TGA patients with RLS could play a role in the aetiopathogenesis of the TGA.

Transient global amnesia: cerebral venous outflow impairment-insight from the abnormal flow patterns of the internal jugular vein

Cerebral venous reflux is found frequently in transient global amnesia (TGA) patients. The cerebral venous reflux mostly results from left brachiocephalic venous obstruction, and the level of reflux depends on different respiratory status. For further understanding of the role of venous outflow impairment in the pathogenesis of TGA, we used color duplex sonography to reveal the flow patterns in the internal jugular vein (IJV) and its branches (JB) under different respiratory conditions. We compared the frequency of abnormal venous flow of IJV and/or JB on color duplex sonography between 17 TGA patients and 17 age- and gender-matched normal individuals both at rest (regular breathing) and at deep inspiration. Further, these venous-flow abnormalities in IJV and JB were well described. Cranial 3-D time-of-flight magnetic resonance arteriography (MRA) were performed in all patients three to seven days after their TGA attacks and in all normal individuals to analyze the abnormal flow signals in the intracranial venous structures. In the result, abnormal flow-patterns in the left IJV and/or left JB during regular breathing were found more frequently in TGA patients than normal individuals (65% vs. 6%; p < 0.001). These abnormalities in TGA patients were (1) isolated reversed flow in the left JB, (2) segmental reversed flow in the left distal IJV and (3) continuous reversed flow in the left IJV and JB. The MRA study revealed that only the most severe reflux in the IJV causes intracranial venous reflux; six were in the group of continuous reversed flow in left IJV and one was in the group of segmental reversed flow in left distal IJV. These findings suggest that TGA might be one of the clinical manifestations of the "cerebral-type intermittent venous claudication," which stems from cerebral venous outflow impairment, insufficient venous collaterals and specific precipitating factors.

Subclinical Impairment of Neuromuscular Transmission in Transient Global Amnesia

OBJECTIVE

To investigate the neuromuscular transmission (NMT) of the patients with transient global amnesia (TGA) using single fiber electromyography (SFEMG).

BACKGROUND

The pathophysiology of TGA remains unknown and several elements support the hypothesis of a shared background with migraine. Recent studies showed that some migraineurs have subclinical abnormalities of NMT by using SFEMG. We aimed to test the patients with TGA using SFEMG.

METHODS

We investigated 6 patients diagnosed with TGA according to published criteria and 5 healthy volunteers with similar ages. SFEMG during voluntary contraction of the extensor digitorum communis muscle, nerve conduction studies and concentric needle electromyography were performed and 20 single fiber potential pairs were recorded from each subject and individual and mean jitter values were calculated.

RESULTS

Three patients with TGA showed pronounced NMT failure by SFEMG, whereas none of the controls disclosed this abnormality. The mean jitter value of TGA patients (35+/-33) was greater than that of the control subjects (25+/-15) (P=0.006). Seventeen of the 120 individual jitter values of the TGA group and only 3 (from 3 different volunteers) of the 100 individual jitter values of the control group exceeded upper normal limit (P=0.004).

CONCLUSIONS

These results suggest that TGA shares the same type of subclinical abnormality of NMT observed in migraine patients in recent studies.

Selective affection of hippocampal CA-1 neurons in patients with transient global amnesia without long-term sequelae

The aetiology, pathomechanisms and anatomical correlates of transient global amnesia (TGA) still remain obscure. Recently, focal MR-signal diffusion-weighted imaging (DWI) changes in the hippocampus have been described in patients with TGA, but the exact localization, long term outcome and pathophysiological nature of these lesions still remain unknown. The topography and time course of hippocampal DWI lesions in 41 TGA patients was studied using serial 3 T high-resolution MR-imaging and correlated to clinical and neuropsychometric results. Of these, 29 patients showed 36 DWI lesions with corresponding T(2) lesions in the hippocampus within a time window of 48 h after onset. Almost all lesions (94%; 34/36) were selectively found in the CA-1 sector (Sommer sector) of the hippocampal cornu ammonis. Most DWI lesions (8/10) were already detectable in the peri-acute phase <6 h after onset of symptoms. A follow-up study 4-6 months after the episode did not show evidence for residual structural sequelae of these lesions (n = 20/20). A venous MR angiography of the intracranial dural sinus showed an asymmetric venous drainage in 21/24 (88%) patients. In 11/16 (69%) patients with unilateral lesions, the asymmetry corresponded to the side of the DWI lesion. Significant episodic verbal memory deficits in the acute phase (n = 14/18) were associated with lesions of the dominant hemisphere while impairment of visuospatial memory was associated with lesions of the non-dominant hemisphere. Persistent neuropsychological sequelae were not detected 4-6 months after the episode (n = 16). This is the first prospective study combining high-resolution imaging and neuropsychometry analysing the detailed functional anatomy and outcome of hippocampal DWI/T(2) lesions in TGA supporting the view the TGA being a benign transient disorder. The TGA can be considered a model for a focal transient perturbation of memory circuits in the temporo-mesial region.

Recurrency in transient global amnesia: a retrospective study

Transient global amnesia (TGA) is a well-defined clinical syndrome of unknown etiology, which often occurs once in life. Several mechanisms have been proposed but only trigger events have been clearly associated with the attack such as physical exertion, emotional stress, sexual intercourse or immersion in cold water. According to our knowledge, this is the first study, which associates trigger events and TGA recurrency. The aim of this retrospective study was to evaluate the risk factors which contribute to TGA recurrency. TGA patients consecutively admitted, performed clinical and neurological evaluation, electroencephalogram and structural brain imaging scan. TGA-trigger events were evaluated and comorbidities were carefully recorded. The risk factor sum was calculated as the sum of the considered triggers. Eighty-five TGA patients were grouped according to the presence of single TGA (n = 73) or two episodes of TGA (n = 12). The 14.11% of patients experienced two episodes. A logistic regression analysis showed that the more increased number of TGA the more number of trigger events (P < 0.11; chi2 = 6.38; beta = -3.29). These observations claim that TGA may be considered a complex epiphenomenon, and the sum of the trigger factors can be responsible for recurring of this almost unique-in-life event.

What does transient global amnesia really mean? Review of the literature and thorough study of 142 cases

Since the first reports of transient global amnesia (TGA) were published in 1956, several neuropsychological and functional imaging studies have shed light on different aspects of this neurological syndrome. By establishing diagnostic criteria, Hodges and Warlow (1990b) have made it far easier to identify clinical TGA-related features. However, no comprehensive survey has been yet carried out in order to validate their criteria/findings or provide information about previously unknown features. In the present paper, (i) we review the literature published since Hodges and Warlow's study and seek to characterize the demographic and clinical features of TGA more accurately, (ii) we report 142 personal TGA cases, with supplementary information regarding both episodes and patients, such as precipitating events, associated symptoms and personality, and (iii) we suggest the existence of different groups of TGA patients, on the basis of a hierarchical cluster analysis. This revealed that in women, episodes are mainly associated with an emotional precipitating event, a history of anxiety and a pathological personality. In men, they occur more frequently after a physical precipitating event. In younger patients, a history of headaches may constitute an important risk factor. No link was found with vascular risk factors. The relevance of each of the above-mentioned variables is discussed in the light of our classification. An extensive description of cases from both the literature and our patient population allows us to refine the characterization of clinical TGA features.

The relationship between working memory and episodic memory disorders in transient global amnesia

In a previous study, we investigated the relationship between the disorders of both episodic memory and working memory in the acute phase of transient global amnesia (TGA). Since executive functions were spared, another dysfunction may be responsible for the binding and maintenance of multimodal informations and contribute to the encoding disorders observed in some patients [Quinette, P., Guillery, B., Desgranges, B., de la Sayette, V., Viader, F., & Eustache, F. (2003). Working memory and executive functions in transient global amnesia. Brain, 126, 1917-1934.]. The aim of this present study was to assess the functions of binding and maintenance of multimodal information during TGA and explore their involvement in episodic memory disorders. We therefore conducted a more thorough investigation of working memory in 16 new patients during the acute phase of TGA using two tasks designed to assess the binding process and both dimensions of the maintenance, namely the active storage and the memory load ability. We also investigated the nature of the episodic memory impairment in distinguishing between the performance of patients with preferential encoding deficits and those of patients with preferential storage disorders on the episodic memory task. This distinction was closely related to the severity of amnesia, i.e. an encoding disorder was observed rather in the early phase of TGA. The results showed that while the functions of binding and maintenance of multimodal information were intact in patients with storage disorders, they were impaired in the case of encoding deficits. These results are interpreted in the recent framework of episodic buffer proposed by Baddeley [Baddeley, A. D. (2000). The episodic buffer: A new component of working memory? Trends in Cognitive Sciences, 4, 417-423] that represents an interface between working memory and episodic memory.

Delayed transient worsening of neurological deficits after ischaemic stroke

BACKGROUND

Although the causes of stroke recurrence are well known, no particular study deals with the specific issue of late-onset transient worsening of the neurological deficit (TWND) after an ischaemic stroke.

PATIENTS AND METHODS

In this retrospective study the aetiology of the TWNDs in 101 patients was compared to the causes of transient ischaemic attacks (TIAs) in 115 patients. All patients had a full cardiovascular and neuroimaging examination according to current guidelines. An electroencephalogram (EEG) was performed when necessary. The diagnosis of inhibitory seizures was retained when the EEG showed periodic lateralized epileptiform discharges or intermittent rhythmic delta activities, or when the patient developed typical seizures afterwards.

RESULTS

Arterial hypertension and diabetes were more prevalent vascular risk factors in TWND patients. Small-vessel disease and inhibitory seizures were a more frequent cause of TWNDs than of TIAs. Extracranial large-vessel disease predominates in TIA patients. The global prevalence of cardiac diseases as cause of TIAs and TWNDs was the same, although severe ulcerous plaques of the aortic arch and patent foramen ovale with atrial septum aneurysm occurred more frequently in TWND patients.

CONCLUSIONS

The most frequent causes of late-onset TWNDs were different from those of TIAs. Apart from repeated neuroimaging of the brain, exhaustive cardiac investigations and EEG are mandatory in TWND patients.

[Transient amnesia in the elderly]

The two main aetiologies of transient amnesia in the elderly are idiopathic transient global amnesia (TGA) and iatrogenic or toxic amnesia. Vascular and epileptic amnesia are less common. According to the literature, transient psychogenic amnesia, which is a frequent cause of amnesia at age 30 to 50, is very rare in the elderly. TGA is the prototypical picture of transient amnesia. It occurs more often after age 50, with no identified cause, even if some authors accept emotional stress or minor head trauma as occasional precipitants. The mechanism of TGA remains a matter of discussion. It may be the consequence of a spreading depression similar to that described in migraine with aura, but other arguments support an ischemic mechanism. Iatrogenic amnesias are mainly caused by benzodiazepines (BZs) or anticholinergics. The former may occur in a non-anxious subject, who is not a usual consumer of BZ and takes a single dose. The latter are more often due to a hypersensitivity to anticholinergic drugs, in particular in patients presenting with a covert, incipient Alzheimer's disease. A vascular origin must be considered when amnesia is accompanied by other neurological symptoms, and when the regression of the amnesic disorder is slow, lasting several days. It results from lesions involving various mechanisms and locations, mainly subcortical. Partial seizures, most often mesio-temporal, more rarely frontal, may be the cause of transient amnesia in the elderly, in the absence of a past history of epilepsy. The red flag supportive of an epileptic origin is the repetition of stereotyped amnesic episodes. EEG demonstration of seizures may be difficult and the response to antiepileptic drugs effective on partial seizures is usually good.

[A study of the risk factors in transient global amnesia and its differentiation from a transient ischemic attack]

INTRODUCTION

Transient global amnesia (TGA) is a clinical condition that has been described in many studies, but its pathophysiology is not fully understood. In recent years the theory of valvular insufficiency in the jugular vein has been added to the classical hypotheses that link it to migraine, to epilepsy and -the most widely accepted- to transient ischemic attacks (TIA), although the real origin of the condition has still not been determined.

PATIENTS AND METHODS

In a retrospective study we compared 131 patients diagnosed with TGA between 1993 and 2004 with 262 patients who were diagnosed as having TIA over the same period.

RESULTS

Mean age was 65.94 years in TGA versus 71.11 years in the case of TIA. There was a higher rate of arterial hypertension among the patients with TGA and diabetes mellitus was more frequent among those with TIA (p<0.05 in both cases). Emboligenic heart disease was scarce among patients with TGA. The number of patients with a history of ischaemic heart disease and a history and the development of cerebrovascular diseases was greater among those with TIA than in cases of TGA (p<0.05). The TGA recurrence rate was 12%. The percentage of pathological findings in the CAT brain scan was higher in patients with TIA (p<0.05). There are no significant differences between patients with TGA and TIA as far as treatment on hospital discharge is concerned.

CONCLUSIONS

TGA does not seem to be a symptom of an arteriosclerotic pathology nor does it appear to offer a higher risk of heart or cerebrovascular disease and, therefore, antiaggregating therapy would not be indicated in such cases.

Weather conditions and transient global amnesia. A six-year study

OBJECTIVES

The aetiology of transient global amnesia (TGA) is still unknown. Various events or activities have been shown to trigger TGA. A common feature of these events is an increased sympathetic activity which in turn may be influenced by meteorological factors. This prompted us to evaluate the influence of climatic parameters, and their variation on the incidence of TGA.

METHODS

A total of 223 cases of TGA admitted to our hospital over a six-year period were studied. The study consisted of a comparison between the climatic parameters of days with TGA and those without TGA. The meteorological database included daily values of parameters recorded at the meteorological station of the town during this period.

RESULTS

The onset of TGA was significantly correlated with lower daily,monthly and seasonal temperature values. Most cases of TGA were found when the temperature was less than 6.9 degrees C,whereas the frequency of TGA was minimum when it was more than 24 degrees C (P < 0.0001). Only temperature had a significant independent effect: an increase of 1 sd = 8.4 degrees C decreases the TGA admission odds of 0.78 (95 % CI: 0.62 to 0.97), i.e -22% (95 % CI: -38% to -3 %).

CONCLUSIONS

This study suggests an association between TGA occurrence and low ambient temperature. Multicentre studies taking into account climatic differences between countries are necessary to confirm our findings.

Increased incidence of jugular valve insufficiency in patients with transient global amnesia

OBJECTIVE

While transient global amnesia (TGA) is a clinically well defined disorder, its etiology is poorly understood. Cerebral venous hypertension and subsequent damage to hippocampal and diencephalic structures are among the discussed hypothetical causes. Using a direct method for the study of retrograde flow during a Valsalva maneuver, we determined whether jugular valve insufficiency contributes to cerebral venous hypertension in patients with TGA.

METHODS

Jugular valve closure was assessed by duplex sonography in 20 patients with TGA and 20 age and gender matched controls. The diagnosis of valvular insufficiency was made on the basis of recently established criteria.

RESULTS

Valvular insufficiency (either left or right-sided, or bilateral) was identified in 85% of patients with TGA,and in 45% of controls (p = 0.008). All patients with involuntary Valsalva episodes immediately prior to TGA developed valvular insufficiency (n = 8; p = 0.13 compared with patients who did not recall such an event). The mean duration of the insufficiency jet did not differ significantly between patients with TGA (3.26 s) and controls (2.78 s; p = 0.315). However, patients with TGA who experienced a trigger event were characterized by significantly longer insufficiency reflux times (3.84 s) than those without (2.55 s; p = 0.03).

CONCLUSIONS

TGA is associated with an increase in the prevalence of jugular insufficiency. Valvular insufficiency may lead to increased venous pressure transmission during a Valsalva maneuver and thus contribute to venous ischemia in TGA. The association of valvular insufficiency and longer reflux times with the occurrence of a trigger event further suggests that cerebral venous congestion is an important etiological factor in transient global amnesia.

Clinical features, risk factors, and prognosis in transient global amnesia: a follow-up study

We previously observed a high frequency of psychopathological features in transient global amnesia (TGA). We aimed at assessing differences in risk factor profile and prognosis between TGA and transient ischemic attack (TIA) patients with a focus on aspects with possible psychopathological relevance. We studied 51 TGA patients (mean age +/- SD, 62.7 +/- 6.7 years; M/F = 24/27) and 51 control patients with TIA (mean age +/- SD, 63.8 +/- 6.7 years; M/F = 41/10) and followed them up for about 7 years. Compared with TIA controls, TGA patients more frequently had a history of psychiatric diseases (age and sex-corrected OR = 2.86, 95% CI: 1.01-8.05) and alcohol use (OR = 3.26, 95% CI: 1.10-9.66) and less frequently a history of cardiac (OR = 0.29, 95% CI: 0.11-0.76) or peripheral artery disease (OR = 0.11, 95% CI: 0.01-0.96). A family history of psychiatric diseases was reported more frequently by TGA than TIA patients (OR = 2.99, 95% CI: 1.04-8.59). On follow-up, in comparison with TIA patients, TGA patients had a significantly lower risk of combined stroke, myocardial infarct, and death (log-rank test, P = 0.0059). In the multivariate analysis, the dissimilar baseline risk factor profile explained most of the difference in prognosis between the two groups. In comparison with TIA patients, patients with TGA have more frequently a personal or family history of psychiatric diseases and a more favorable vascular risk factor profile and prognosis. These results have therapeutic implications and reinforce the hypothesis that TGA is a benign disorder.

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.

Internal jugular vein valve incompetence and intracranial venous anatomy in transient global amnesia

BACKGROUND

Recently a causal relation between internal jugular vein valve incompetence (IJVVI) and transient global amnesia (TGA) has been suggested. IJVVI is postulated to provoke a transient mesiotemporal ischaemia by venous congestion. This mechanism requires a patent venous pathway from the affected IJV through the transverse sinus, confluens, straight sinus (SS), vein of Galen into the basal vein of Rosenthal and the internal cerebral veins.

OBJECTIVE

To study IJVVI in TGA patients in relation to the intracranial venous anatomy.

METHODS

IJVVI was defined if a repeated Valsalva manoeuvre (VM) led to a retrograde jugular flow detected by extracranial duplex ultrasound. Non-contrast venous MR angiography (MRA) was performed to analyse intracranial drainage patterns of the SS in relation to the side of the IJVVI. SS drainage was differentiated into three groups: predominantly right, left, and bilateral drainage. Ultrasound studies were performed in 25 TGA patients and 85 age matched controls. Twenty patients underwent venous MRA.

RESULTS

Sixty eight per cent of patients and 33% of controls showed unilateral or bilateral IJVVI (p = 0.0025). In 36% of patients a TGA preceding VM was reported. Drainage pattern of SS and side of IJVVI corresponded in five of eight patients (63%) with VM and four of 12 patients without VM (33%, p = 0.0994).

CONCLUSION

Our study confirms the significantly higher prevalence of IJVVI in TGA patients. However, no specific IJVVI related intracranial venous drainage patterns could be found to further support the hypothesis of a direct causal relation between IJVVI and TGA.

Transient global amnesia may be caused by cerebral vein thrombosis

Transient global amnesia (TGA) is a disorder of unknown aetiology, characterized by sudden loss of anterograde memory, in the absence other neurological signs or symptoms, followed by complete recovery in less than 24h. Precipitating actions such as strenuous physical activity or valsalva-like manoeuvres are frequently reported. Since first described in 1958, by Fisher and Adams, the possible pathophysiology has undergone much speculation. Nonconvulsive epileptic seizures, migraine, paradoxical embolism thorough a patent foramen ovale, and transient ischemic attacks have been proposed as potential mechanisms. One of the latest hypotheses is that venous congestion causes either ischemia or induces spreading depression in the medial temporal lobes. It has been demonstrated that retrograde flow in the internal jugular veins occurs more frequently during valsalva manoeuvres in TGA patients than in controls, supporting a dysfunctional venous circulation as part of the pathogenesis. However, earlier hypotheses typically fail to explain the relatively low recurrence rate of TGA, lack of comorbidity and the relation to precipitating events. If cerebral venous hypertension was the solely cause of TGA it would presumably be much more common with very high recurrence rates among those predisposed of the condition. Structural changes observed in MRI and SPECT studies along with reports of mild cognitive impairment lasting much longer than the amnestic episodes, indicate that TGA is less transient and perhaps somewhat less benign than earlier believed. Many cases of TGA seem to be associated with factors of increased risk of cerebral venous thrombosis, such as polycythemia, antiphospholipid antibodies, venous hypertension, female sex and more. We suggest that most cases of TGA may be due to small thrombi in the deep cerebral venous system. Small venous thrombi may difficult to visualize even when using modern imaging technology. Further studies of TGA patients with for example blood analysis of D-dimer together with MR venography or CT venography could be done to evaluate this new hypothesis.

The dynamic time course of memory recovery in transient global amnesia

AIMS

To investigate the dynamic time course of transient global amnesia (TGA)--that is, the process of recovery and the interindividual variability--by testing four patients during the day of TGA itself (on three occasions) and at follow up (on two occasions).

METHODS

A specially designed protocol focusing on semantic (both conceptual and autobiographical knowledge) and episodic (both anterograde and retrograde components) memory.

RESULTS

Every patient showed marked impairment of both anterograde and retrograde episodic memory during the acute phase, with a relative preservation of personal and conceptual semantic knowledge. During the following phase, the authors observed similarities and differences among the patients' patterns of recovery. In general, retrograde amnesia recovered before the anterograde amnesia and anterograde episodic memory was recovered gradually in every case. In contrast, shrinkage of retrograde amnesia was more heterogeneous. In two of the patients, this shrinkage followed a chronological gradient and the most remote events were recovered first. In the two other patients, it depended more on the strength of the trace, and there was no temporal gradient. For the latter, an executive deficit could account for difficulties in accessing both conceptual knowledge and autobiographical memories.

CONCLUSIONS

This profile of recovery suggests a "neocortical to medial temporal" process in every case, and the possibility of an additional frontal dysfunction in some cases. Hence, the acute phase seems to be characterised by a common episodic impairment. This variability between subjects appears in the recovery phase with two different patterns of impairment.

Transient global amnesia -- not always a benign process

OBJECTIVES

Transient global amnesia (TGA) is an episodic dysfunction of declarative memory, which is assumed to be a benign disorder. Brain perfusion single photon emission computed tomography (SPECT) was shown to be abnormal during the acute stage and to become normal with normalization of memory function. No data are known about the brain perfusion pattern among these patients with recurrent TGA.

MATERIAL AND METHODS

Sixteen patients with TGA were studied with an initial brain imaging during the acute stages of their attack, and a second imaging was performed after 3 months. In the event of a patients having a second abnormal brain perfusion HMPAO SPECT, a third imaging was performed after 1 year.

RESULTS

Hypofusion perfusion was demonstrated in all cases during the acute stage. In all patients who had a first TGA, a normal SPECT was demonstrated after 3 months. In three patients with recurrent TGA, the brain perfusion remained abnormal after 3 months and after 1 year.

CONCLUSIONS

A normal perfusion in TGA after 3 months can be expected in a patient with a first attack. In patients with recurrent TGA attacks, a persistent focal hypoperfusion can be expected. This subgroup of patients may demonstrate a non-benign type of TGA, eventually due to a different etiology of event.

Detection of delayed focal MR changes in the lateral hippocampus in transient global amnesia

BACKGROUND

There is still limited knowledge on the location and etiology of transient global amnesia (TGA). MR studies including diffusion-weighted imaging (DWI) have been unable to demonstrate consistently the location and underlying pathology of TGA.

OBJECTIVE

To investigate patients with TGA using serial DWI performed from the day of symptom onset through days 1 and 2.

METHODS

After reporting negative DWI results in a previous study, the authors used a modified study design to investigate patients with TGA using serial DWI performed from the day of symptom onset through days 1 and 2.

RESULTS

Of 31 consecutive patients studied, 26 developed a small, punctate DWI lesion in the lateral aspect of the hippocampal formation (pes and fimbria hippocampi) on either side (left, n = 15; right, n = 6) or bilaterally (n = 5). Lesions were rarely noted in the hyperacute phase (n = 2), but all became visible regularly at 48 hours.

CONCLUSIONS

The study confirms the involvement of hippocampal parenchyma in the pathophysiology of TGA. The delayed detectability of the lesions may explain the incongruence of previous MR DWI studies in TGA patients.

Neurological Conditions at Altitude That Fall Outside the Usual Definition of Altitude Sickness

Altitude sickness in its commonly recognized forms consists of acute mountain sickness and the two life-threatening forms, high altitude cerebral and pulmonary edema. Less well known are other conditions, chiefly neurological, that may arise completely outside the usual definition of altitude sickness. These, often focal, neurological conditions are important to recognize so that they do not become categorized as altitude sickness because, besides oxygen and descent, treatment may be vastly different. Transient ischemic attacks, cerebral venous thrombosis, seizures, syncope, double vision, and scotomas are some of the well-documented neurological disturbances at high altitude discussed here in order to enhance their recognition and treatment.

Motor cortex excitability in transient global amnesia

OBJECTIVE

To investigate the physiology of motor cortical areas in patients with transient global amnesia (TGA).

MATERIALS AND METHODS

We performed transcranial magnetic stimulation (TMS) and single photon emission computed tomography (SPECT) in 13 patients during and after the acute phase of a typical episode of TGA. Measures of cortical excitability included motor threshold (MT) to magnetic stimulation, cortical silent period (SP) duration and intracortical inhibition (ICI) using a paired-pulse TMS technique.

RESULTS

We found thalamic hypoperfusion and an ipsilateral significantly decreased ICI during the acute phase of TGA.

CONCLUSIONS

Reduced activity in inhibitory circuits may explain why PET studies of patients with TGA showed neocortical hypometabolism. Our findings are consistent with the hypothesis that frontal cortex dysfunction probably due to damage affecting the thalamocortical circuits may play an important role in the pathogenesis of the syndrome.

Transient global amnesia: a clinical and sonographic study

BACKGROUND

The aetiology of transient global amnesia (TGA) is still unknown. The aim of this study was to identify potential risk factors for TGA, vascular risk factors, the role of patent foramen ovale (PFO) and of retrograde jugular venous flow.

METHODS

138 subjects entered the study, including 48 patients with TGA, 42 age-matched patients with transient ischaemic attack (TIA) and 48 controls. PFO was studied by contrast transcranial duplex sonography. Retrograde jugular venous flow was tested with air contrast ultrasound venography (ACUV).

RESULTS

TGA patients and controls showed a lower prevalence for vascular risk factors than TIA patients. No statistical difference was found between the 3 groups with regard to PFO. ACUV detected jugular valve incompetence in 72.9% TGA, 35.7% TIA and 39.5% controls (TGA vs. TIA and TGA vs. controls p < 0.01).

CONCLUSIONS

TGA patients have fewer vascular risk factors than TIA patients. Paradoxical embolism due to PFO as a cause of TGA is not confirmed in our study. Cerebral venous hypertension due to incompetence of the internal jugular valve may play a role in the pathogenesis of TGA.

Neurophysiological characterization of transitory global amnesia syndrome

A total of 27 patients with transitory global amnesia (TGA) in the acute and late (from 7 days) periods and 31 patients with dyscirculatory encephalopathy and subjective memory impairments (control group) were studied. EEG data and assessment of the P300 cognitive evoked potential wave established differences in the nature of beta1 activity between these groups. The extent of beta1 activity on the EEG showed different relationships with the latent period of the P300 wave: in the control group, there were increases in beta1 activity with increases in the latent period (r = 0.43). while beta1 activity in TGA decreased with increases in latent period (r = -0.23). These changes were most marked in the frontocentral areas. The authors believe that these patterns of changes in EEG and cognitive evoked potentials in the acute period of TGA and at later periods, as well as in the control group, provide evidence of the functional nature of TGA syndrome, which is not related to any damaged brain structure.