Chronic hippocampal subfield damage in transient global amnesia revealed by 7T MRI: All is not reversible?

Transient global amnesia (TGA) is a neurological condition characterized by temporary memory loss and classically associated with a reversible unilateral punctate focus of restricted diffusion in the cornu ammonis 1 (CA1) region of the hippocampus. Historically, the lesions were considered to be transient in nature with no long-term imaging abnormality. However, more recent studies have challenged the concept that there are no long-term neurological sequelae. In line with this evidence, we explore the role of ultra-high-resolution imaging using 7 Tesla MRI to evaluate for long-term imaging abnormalities in a 63-year-old woman with a typical clinical course and acute TGA imaging findings. The 7 Tesla MRI revealed a residual lesion on susceptibility-weighted imaging (SWI) with evidence of gliosis and volume loss at the site of the acute lesion in CA1 eight months after the acute episode. This case challenges the traditional mantra of TGA as a fully reversible condition with no long-term imaging findings, suggesting the need for further research using ultra-high-field MRI to determine TGA's potential long-term imaging sequelae and any association with neurocognitive sequelae.

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

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

New-Onset Transient Global Amnesia: A Clinical Challenge in an Air Medical Transportation Pilot With a History of Coronavirus Disease 2019

A 43-year-old male Bell 214C helicopter pilot presented to the emergency ward with flu-like syndrome. His nasopharyngeal severe acute respiratory syndrome coronavirus 2 real-time polymerase chain reaction test was positive, and a chest computed tomographic scan confirmed coronavirus disease 2019 pneumonia. He was admitted, received treatment, was discharged, and returned to flying. During the mission debrief, copilots who had flown with him reported that he experienced episodes of in-flight dizziness and blacked out. They occurred briefly during the cruise and hovering flight, perhaps for a few seconds of disorientation and unconsciousness. Rapid identification of the copilot and control of the helicopter prevented any incident or accident. Afterward, he explained the sudden onset and unexpected brief periods of loss of consciousness after a headache. The flight safety office referred him to the aviation medical center for further investigations. The cardiovascular, neurologic, laboratory, and toxicologic assessments were inconclusive with the approach to sudden-onset transient loss of consciousness. The only abnormal finding was hippocampus lesions on brain magnetic resonance imaging (MRI). Because of the possible diagnosis of transient global amnesia, the aviation medical examiner suspended him from flight duties until complete recovery and the absence of any probable complications.

[Memory Loss - a Case of Sudden Amnesia]

Memory Loss - a Case of Sudden Amnesia Abstract. Transient global amnesia (TGA) is a clinical diagnosis with typical signs of an anterograde and retrograde amnesia. The underlying mechanisms are yet unknown, different hypotheses are being discussed. Ultimately there is a temporary dysfunction of the hippocampi. Consistent with this, transient uni- or bilateral punctiform hyperintense lesions may be found on DWI-MRI sequences, usually without correlation on FLAIR-weighthed MR-images. Symptoms usually resolve within twenty-four hours. There is no need for a specific therapy. A prophylactic therapy, such as antithrombotic treatment, is not indicated. The prognosis is usually good, the risk of a recurrence is about 18%.

[GABAB receptor autoimmune encephalitis presenting as transient epileptic amnesia]

This case was a 50-year-old healthy woman. After repeated transient amnesia, she developed tonic-clonic seizures and was admitted to our hospital. The brain MRI showed FLAIR hyperintensities in the left temporal lobe and EEG showed an epileptic discharge starting from the left temporal region. Based on these findings, we diagnosed temporal lobe epilepsy associated with acute limbic encephalitis. While she experienced recurrent transient amnesia, her cognitive functions were preserved except for her memory. These symptoms and EEG findings were consistent with transient epileptic amnesia (TEA). Acute limbic encephalitis that occurred in a healthy middle-aged woman may be antibody-mediated encephalitis, requiring immediate immunotherapies. In this case, GABA_B receptor antibodies in cerebrospinal fluid were found positive. This is the first report showing that TEA was caused by GABA_B receptor autoimmune encephalitis.

Emergency department visits for transient global amnesia alone or in association with substance abuse

OBJECTIVES

To study the epidemiology of emergency department visits for transient global amnesia (TGA) by itself or associated with substance abuse or sexual assault.

MATERIAL AND METHODS

Retrospective study of cases treated from January to December 2018. Data for all patients with TGA were extracted, and cases were classified as associated with substance abuse (TGASUB), sexual assault (TGASEX), or neither (TGAONLY).

RESULTS

A total of 287 TGA cases were found: 169 (58.9%) were TGASEX, 62 (21.6%) TGAONLY, and 56 (19.5%) TGASUB. Two hundred eighteen (76%) were female and 69 (24%) were male. Ages ranged from 16 to 90 years; 174 (60.6%) were under the age of 30 years. Two hundred one patients (72.8%) reported consuming alcohol; and 105 (49.1%) were positive on testing (mean blood alcohol concentration, 0.74 g/L; maximum, 3.9 g/L. Twenty patients (7.1%) reported using cannabis, and 39 (17.3%) had positive test results; 14 reported using cocaine (4.9%) and 28 (12.4%) tested positive; 5 (1.7%) reported using amphetamines and 20 (8.8%) tested positive. Fifty-eight (20.1%) had symptoms of intoxication. Four were admitted in coma. A computed tomography scan was ordered for 66 patients (23%), 7 patients were hospitalized, and none died.

CONCLUSION

The prevalence of TGA is higher if cases of substance abuse and sexual assault are counted. Toxicolgy testing changes the epidemiology of TGA in emergencies.

Transient Global Amnesia After Cerebral Angiography With Iomeprol: A Case Report

Transient global amnesia is now considered a very rare complication of cerebral angiography. Various etiological mechanisms have been suggested to account for this complication, but no consensus has been reached yet. This case report documents one of the few reported cases of cerebral angiography-related transient global amnesia associated with magnetic resonance imaging (MRI) evidence of unilateral hippocampal ischemia, most probably as a consequence of a transient reduction in regional hippocampal blood flow. However, the possibility of a direct neurotoxic effect of the nonionic contrast media Iomeprol on the Cornu ammonis - field 1 neurons cannot be firmly ruled out.We describe the case of a 54-year-old woman admitted to our department for left upper limb weakness with acute onset 8 days before. The brain computed tomography (CT) scan performed at admission revealed subacute ischemic lesions in the right watershed superficial territories and a right thalamic lacunar infarct. Diagnostic digital subtraction cerebral angiography was performed 4 days after admission with the nonionic contrast media Iomeprol. A few minutes after completion of the procedure, the patient developed symptoms suggestive for transient global amnesia. The brain MRI performed 22 hours after the onset of symptoms demonstrated increased signal within the lateral part of the right hippocampus on the diffusion-weighted imaging (DWI) sequences, associated with a corresponding reduction in the apparent diffusion coefficient (ADC) and increased signal on the fluid-attenuated inversion recovery (FLAIR) sequences, consistent with acute hippocampal ischemia and several T2/FLAIR hyperintensities in the right watershed superficial territories and in the right thalamus, corresponding to the lesions already identified on the CT scan performed at admission. A follow-up MRI, performed 2 months later, demonstrated the disappearance of the increased signal within the right hippocampus on the DWI, T2/FLAIR, and ADC sequences.The precise mechanism of transient global amnesia related to cerebral angiography is still unclear, and further studies aimed to determine the definite pathophysiology of this syndrome and consequently to establish specific preventive measures are needed. Although the condition itself is considered to be self-limited, the long-term prognosis and the risk of recurrence in the cases where subsequent angiographic procedures are performed are not established yet.

Obstruction of Venous Drainage Linked to Transient Global Amnesia

Abnormal extracranial venous drainage modality has been considered an etiology of transient global amnesia (TGA). Evidence suggests that the transmission of the intrathoracic/intraabdominal pressure during a Valsalva maneuver (VM) is mainly through the vertebral venous system, and patency of internal jugular vein (IJV) is essential for venous drainage and pressure releasing. We hypothesize that obstruction of IJV venous drainage is a contributing factor in TGA pathogenesis. A magnetic resonance (MR) imaging protocol was used in 45 TGA patients and 45 age- and sex-matched controls to assess the morphologies of IJV, brachiocephalic vein (BCV) and asymmetry of transverse sinus (TS). The IJV was divided into the upper- and middle-IJV segments. Compared to the controls, TGA patients had significantly higher rates of moderate and severe compression/stenosis at the bilateral upper-IJV segment (left: 37.8% vs. 17.8%, P = 0.0393; right: 57.8% vs.15.6%, P<0.0012), in left BCV (60% vs. 8.9%, P<0.0004), and in TS hypoplasia (53.3%% vs. 31.1%, P = 0.0405). The prevalence of at least one site of venous compression/stenosis in IJV or BCV was significantly higher in patients than in controls (91.1% vs. 33.3%, P<0.0004). The diameter of the left TS in MRV, but not in T1 contrast imaging, was significantly smaller in TGA patients than in controls (0.31±0.21 vs. 0.41±0.19, P = 0.0290), which was compatible with downstream venous stenosis/obstruction. TGA patients have a higher prevalence of compression/stenosis of the bilateral IJV and the left BCV and TS hypoplasia, which is new evidence that supports the role of extracranial veins in TGA pathogenesis.

Is a cancer diagnosis associated with subsequent risk of transient global amnesia?

BACKGROUND

Psychological stress has been associated with transient global amnesia (TGA). Whether a cancer diagnosis, a severely stressful life event, is associated with subsequent risk of TGA has not been studied.

METHODS

Based on the Swedish Cancer Register and Patient Register, we conducted a prospective cohort study including 5,365,608 Swedes at age 30 and above during 2001-2009 to examine the relative risk of TGA among cancer patients, as compared to cancer-free individuals. Incidence rate ratios (IRRs) and their 95% confidence intervals (CIs) derived from Poisson regression were used as estimates of the association between cancer diagnosis and the risk of TGA.

RESULTS

During the study 322,558 individuals (6.01%) received a first diagnosis of cancer. We identified 210 cases of TGA among the cancer patients (incidence rate, 0.22 per 1000 person-years) and 4,887 TGA cases among the cancer-free individuals (incidence rate, 0.12 per 1000 person-years). Overall, after adjustment for age, sex, calendar year, socioeconomic status, education and civil status, cancer patients had no increased risk of TGA than the cancer-free individuals (IRR, 0.99; 95% CI, 0.86-1.13). The IRRs did not differ over time since cancer diagnosis or across individual cancer types. The null association was neither modified by sex, calendar period or age.

CONCLUSION

Our study did not provide support for the hypothesis that patients with a new diagnosis of cancer display a higher risk of TGA than cancer-free individuals.

Transient amnesia after coiling of a posterior circulation aneurysm

BACKGROUND

Acute amnesia can be caused by medication effect, transient global amnesia, ischemia, metabolic abnormalities, and seizures.

METHODS

Case report.

RESULTS

A 56-year-old woman developed acute amnesia resembling transient global amnesia (TGA) after aneurysm coiling. She was started on abciximab for possible thromboembolic complications related to coiling. Abciximab was discontinued after she developed chest pain. Her chest pain resolved after discontinuing abciximab. She was subsequently found to have small medial temporal lobe strokes on diffusion weighted MRI.

CONCLUSIONS

Ischemia in the posterior circulation should be considered in the differential diagnosis of TGA, especially in situations predisposing to thromboembolism such as coiling.

[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.

Transient global amnesia and its aeromedical implications

INTRODUCTION

Transient global amnesia (TGA) is an episode of severe anterograde amnesia of sudden onset, characteristically lasting 4 to 6 h. Patients become disorientated in time and place, but not in person. Automated motor tasks are preserved; however, the retention of new information is impaired, with clear implications to a pilot's fitness to fly. This study examines the United Kingdom Civil Aviation Authority (UK CAA) experience of pilots with TGA and compares it to the medical literature.

METHODS

The UK CAA medical records database was searched for subjects who had reported a history of TGA between the years 1990 and 2010. Subject age and gender, the frequency and duration of episodes, the follow-up period, precipitants, and associated features were recorded. A literature search for papers with similar information was undertaken.

RESULTS

The UK CAA database showed 29 subjects who had held a UK CAA medical certificate with a history of TGA. There were 28 male individuals and 1 female. The mean age was 59 yr. The mean follow-up period was 3.4 yr. The average duration of an episode was 2.8 h. Activity, stress, or exposure to cold water were reported as possible precipitants by 16 subjects (55%). There were 6 subjects (21%) who had a history of migraine and 10 (34%) who had a history of hypertension. From the literature, 10 papers were reviewed and compared to our study group.

DISCUSSION

The aeromedical implications of TGA, including its etiology, associations, misdiagnosis, and recurrence risk are considered. A policy for the certification of pilots following TGA is proposed.

Transient global amnesia: a brief review and update

Transient global amnesia (TGA) is a transitory syndrome of memory loss, lasting less than 24 h. Although there are many known causes of transient amnesia, the syndrome of TGA remains of unknown etiology. Known causes of transient amnesia, theories of pathogenesis of TGA, and recommended evaluation and treatment are discussed.

[The MoCA scale in diagnosis of the amnestic syndrome--case report]

AIM

Among main symptoms of the amnestic syndrome we can distinguish: short-term and long-term memory deterioration, deficiency of the effectiveness of learning, the anterograde amnesia and the retrograde amnesia, lack of the orientation in the place and in the time and confabulations. The aim of the study is to introduce the unknown tool of cognitive assessment named Montreal Assessment Cognitive (MoCA). The authors want to indicate the diagnostic accuracy of the scale in the examination of the amnestic patient.

METHOD

In the neuropsychological examination of the amnestic patient, the Montreal Cognitive Assessment scale was used.

RESULTS

The patient correctly performed the tasks which estimated effectiveness of the visual-motor coordination, language abilities (naming, repeating of the sentences) and effectiveness of the short-term memory. Difficulties in the remaining tasks indicate at deficiency of the effectiveness of the learning ability, long-term memory (recognition), abstractive thinking and the orientation in the place and time. Deterioration of the working memory and executive functions is also noticeable.

CONCLUSIONS

Montreal Cognitive Assessment scale is a useful tool for the evaluation of the cognitive functions among amnestic patients.

[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.

Bilateral hippocampal abnormalities on diffusion-weighted MRI in transient global amnesia: report of a case

The pathophysiology of transient global amnesia (TGA) is still speculative. Recently, diffusion-weighted image (DWI) of magnetic resonance imaging (MRI) documented tiny lesions in the hippocampus of patients with TGA in the acute stage. Most studies reported unilateral lesions on MRI. We present one patient of TGA with high signal-intensity lesions in bilateral hippocampus on DWI at the acute stage. The serial findings of brain MRI support the ischemic nature of TGA. Related mechanism about TGA is discussed.

[Sexual intercourse as a trigger of transient global amnesia]

INTRODUCTION

Transient global amnesia (TGA) is characterised by impairment of anterograde memory and, to a certain extent, retrograde memory, which is associated with mild temporal and spatial disorientation that is completely re-established after a few hours. There are different hypotheses about its pathogenesis, including theories about a possible epileptic, migrainous or ischaemic foundation or its being due to venous congestion in the hippocampuses, although the cause remains unknown. In the same way, many precipitating factors have been related to this disorder, including pain, anxiety, changes in temperature, exercise, Valsalva manoeuvres, diagnostic testing, interventionism and long-distance flights. Sexual intercourse has also been related to this condition, although how it can exert an influence is not known and few cases have been reported in the literature to date.

CASE REPORTS

Six patients who suffered from signs and symptoms of TGA that were clearly related to a sexual relationship, in whom both the neurological examination and the complementary tests that were performed were completely normal. We also gather the evidence in favour and against the association between intercourse and this condition.

CONCLUSIONS

Although the pathophysiological mechanisms that link sexual intercourse with TGA are unknown, the relation between them appears increasingly more often in the literature. We draw attention to the need to take sexual activity into account as a possible precipitating factor in patients suffering from this disorder.

Transient global amnesia--a review

Transient global amnesia (TGA) is an isolated amnesic syndrome with normal neurological examination where patients remain alert and communicative with no loss of personal identity; however, they experience striking loss of memory for recent events and an impaired ability to retain new information. TGA could be triggered by venous congestion and there is evidence of association between younger patients and history of migraine. Most episodes last 2-12 h and the recurrence rate of future amnesic events is very low.

Long lasting recurrent familiar transient global amnesia after betablocker treatment withdrawal: case report

The etiology of Transient Global Amnesia (TGA) is not yet clear. A small part of TGA has a familiar occurrence. We report a case of recurrent, long-lasting familiar amnesia occurring after betablocker treatment withdrawal in a migrainous patient. We suggest that familiar TGA could be caused by the mechanism of vasospasm rather than venous congestion and that the abnormal cerebral vasomotor control could be the hereditary substrate in this condition.

[Transient global amnesia: a review. I. Clinical aspects]

INTRODUCTION

Transient global amnesia (TGA) is a neuropsychological syndrome in which a sudden, temporary loss of the capacity of creating new memories and a retrograde amnesia of variable intensity occur, whereas consciousness, personal identity and attention are preserved.

AIM

To review different clinical aspects about TGA.

DEVELOPMENT

Accordingly, the following topics will be reviewed: definition and diagnosis criteria, types of amnesias which should be ruled out and their peculiarities and differences with TGA, epidemiological data such as incidence, age, sex, educational level of the patients and number of TGA episodes, most frequent scene where TGA appears, and most common triggering events. Additionally, classical proposals about its possible etiology (epilepsy, vascular disease and migraine) and other new theories (Leao's spreading depression or influence of stress) will be revised. Finally, different data about neuroimaging studies in patients with TGA will be reviewed.

CONCLUSIONS

There are data and arguments in favour and against the hypotheses regarding etiology of TGA, but there is no current consensus on a theory which explains in a satisfactory way the nature of this kind of amnesia.

[Acute amnesic syndrome--patient's disorientation baffles a doctor]

We report a 53-year-old female patient who presented a sudden dramatic memory disorder following coronary and cerebral angiography. The patient was disoriented and kept repeating the same questions about time and place. Transient global amnesia was ultimately diagnosed using the Hodges and Warlow criteria. We briefly discuss how to distinguish transient global amnesia from psychogenic amnesia, transient epileptic amnesia and transient ischemic attack.

Classical diseases revisited: transient global amnesia

Transient global amnesia usually affects patients between the ages of 40 and 80. Patients with this condition are often described--wrongly--as being confused. It presents classically with an abrupt onset of severe anterograde amnesia. It is usually accompanied by repetitive questioning. The patient does not have any focal neurological symptoms. Patients remain alert, attentive, and cognition is not impaired. However, they are disoriented to time and place. Attacks usually last for 1-8 h but should be less than 24 h. It is possible that it may result from different mechanisms such as venous congestion with valsalva-like activities before symptom onset, arterial thromboembolic ischaemia and vasoconstriction due to hyperventilation. Diagnosis may be made safely in the presence of a characteristic collateral history. No specific treatment is indicated for a typical episode.

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.

Pathophysiology and classification of stroke

There are a wide variety of causes of stroke and as many different forms of presentation, depending on the area of the brain affected. This article describes how different types of stroke present and outlines the likely outcome for patients for each type.

Diffusion-weighted imaging in transient global amnesia exposes the CA1 region of the hippocampus

INTRODUCTION

Transient global amnesia (TGA) is characterized by a sudden onset of anterograde amnesia without alteration of consciousness or personal identity. Interestingly, recent studies have reported a high frequency of small high-signal abnormalities in the hippocampus with diffusion-weighted (DW) imaging, and ischemia has been proposed as an etiology of TGA. We hypothesized that TGA lesions occur preferentially in the CA1 region of the hippocampus, known to be susceptible to ischemia.

METHODS

Over a 30-month period 34 patients with TGA underwent MRI including DW imaging within 4 days of symptom onset. Patients with high-signal abnormalities in the hippocampus on the initial DW images underwent subsequent DW and T2-weighted imaging in the coronal plane to identify the precise lesion locations.

RESULTS

Fourteen patients had small (1-3 mm) high-signal abnormalities in the hippocampus unilaterally on DW images. One of these patients had two lesions in one hippocampus and therefore in total 15 lesions were identified: four in the hippocampal head, and 11 in the body. Eleven lesions in ten patients with available coronal images were clearly demonstrated on both coronal DW and T2-weighted images and were localized to the lateral portion of the hippocampus, corresponding to the CA1 region.

CONCLUSION

Lesions associated with TGA were localized exclusively to the lateral portion of the hippocampus corresponding to the CA1 region. This finding supports the ischemic etiology of TGA; however, the pathophysiological mechanism involved requires further study.

Transient global amnesia in the district general hospital

Cases of transient global amnesia (TGA) seen by one consultant neurologist over a 4-year period (2002-2005 inclusive) were identified. Of 10 possible cases, eight fulfilled suggested diagnostic criteria. Five cases were seen as ward consultations, three in outpatient clinics; seven were seen in district general hospitals. Six of the eight cases had already been seen by hospital physicians, whose working diagnoses included stroke/TIA and epilepsy. In some cases, this had resulted in inappropriate investigation, treatment and advice. Although rare, TGA is a diagnosis both hospital physicians and general practitioners need to be aware of in order to avoid potential pitfalls. The critical importance of collateral history in reaching the diagnosis is emphasised.

[Transient global amnesia: indications for a syndrome involving cerebral venous stasis]

In 3 patients, a woman aged 58 and 2 men aged 61 and 58, respectively, who presented to the Emergency Clinic with sudden antegrade and retrograde amnesia, the diagnosis 'transient global amnesia' (TGA) was made. In the first and the last patient the TGA was preceded by a Valsalva-like manoeuvre, i.e. vomiting and tying the shoelaces while bending over and holding his breath, respectively. Until recently, TGA was assumed to have three possible causes: arterial ischaemia (transient ischaemic attack; TIA), migraine and epilepsy. A fourth and more recent hypothesis is cerebral venous stasis. This is in accord with the haemodynamic changes that have been described as a provoking factor in TGA. A Valsalva-like manoeuvre increases the intrathoracic pressure, followed by venous reflux in the internal jugular vein. The resultant cerebral venous congestion can cause temporary ischaemia of mesiotemporal structures, such as the hippocampus, and lead to transient cerebral dysfunction. Recent studies support this haemodynamic pathogenesis. The aetiology of TGA is probably multifactorial, with cerebral venous stasis probably playing an important role. There is still no good explanation for the observation that a causative factor usually leads to a TGA in the same person only once.