Transient Global Amnesia Patients Research Articles

Clinical impact of patent foramen ovale diagnosis with transcranial Doppler

The role of patent foramen ovale (PFO) in cryptogenic stroke is still debated, but from recent follow-up studies it seems that the amount of right-to-left shunt (RLS) and the association with atrial septal aneurysm (ASA) are major determinants of stroke recurrence. PFO and RLS through the atrial chambers have been recently studied in a number of conditions not or marginally related to cerebrovascular disease. Historically the first studies addressed the presence of RLS in scuba divers as a possible abnormality related to decompression sickness (DS) of unknown aetiology. Despite initial debate there is now robust evidence to claim that patency of foramen ovale increases the risk of developing DS by two and half to four times. Patients with PFO-related DS tend to have early occurrence of symptoms after surfacing and a clinical presentation that indicates brain or upper cervical spinal cord involvement. Recent reports suggest that divers with hemodynamically significant RLS may have an increased risk of developing clinically asymptomatic multiple brain lesions. PFO has been found in patients suffering from migraine with aura with approximately the same frequency as that encountered in cryptogenic stroke patients. This finding has prompted speculations on the possible role of RLS in increasing the stroke risk in migraineurs and in the pathophysiology of the aura. Recent reports showing that migraine with aura is dramatically improved after transcatheter closure of PFO suggest that migraine with aura may indeed be triggered by humoral factors that reach the brain by escaping the pulmonary filter. A RLS is involved in a rare condition known as platypnea-orthodeoxia and perhaps underlies an increased risk of cerebral complications after major orthopedic surgery. Valsalva-like activities often precede the occurrence of attacks of transient global amnesia (TGA) and abnormalities consistent with hypoperfusion of deep limbic structures have been reported during a typical TGA episode. This had raised the hypothesis that TGA may be triggered by paradoxical embolism of platelets aggregates in the posterior circulation, but the search for an increased frequency of PFO in TGA patients has yielded conflicting results. Conditions that determine an increase in pulmonary pressure may facilitate the opening of the virtual interatrial valve and thus promoting shunting of blood to the left heart chambers which in turn might contribute to further desaturation of arterial blood. It is therefore not surprising that RLS has been found in 70% of patients with chronic obstructive pulmonary disease and increased pulmonary pressure and in the same proportion of patients with obstructive sleep apnoea, a condition that ultimately may result in pulmonary hypertension. In conclusion, from the evidence gathered so far the picture is emerging of an important role of PFO in a number of non-stroke conditions, either as causative factor or as associated condition predisposing to complications. The availability of simple diagnostic techniques such as transcranial Doppler (TCD) to assess RLS will undoubtedly contribute a great deal of knowledge on the relevance in medicine of this hitherto neglected condition.

Clinical features, vascular risk factors, and prognosis for transient global amnesia in Chinese patients

Transient global amnesia (TGA) is an intriguing clinical syndrome that has not been studied in a series of Chinese patients. From 1989 to 1995, we observed 28 consecutive patients with TGA. Their clinical characteristics, risk factors, and outcome were retrospectively reviewed and analyzed. There were 13 men and 15 women with a mean age of 62 years (range, 39 to 76). The duration of amnesic attack ranged from 20 minutes to 24 hours (mean, 8 hours), with the majority (76%) of attacks lasting for 2 to 12 hours. In 9 (32%) of the 28 patients, the TGA was triggered by a potential precipitating factor including bathing, emotional stress, and headache. The most prominent symptom exhibited by patients during an attack was repetitive questioning, which occurred in 21 (75%) of the 28 patients. No focal neurological abnormality was noted during or after the attack. Electroencephalograms were obtained in 26 patients after experiencing TGA, which showed nonspecific findings in 6 patients and were normal in 20. In 21 patients who had cranial computed tomography scans, cortical atrophy was found in 5 (24%), focal infarction in 4 (19%), and the results were negative in 12 (57%). Hypertension was the predominant vascular risk factor (11 cases, 39%), then hyperlipidemia (7 cases, 25%), and smoking (3 cases, 11%). No vascular risk factor was found in 13 patients (46%). Recurrent TGA was found in 5 patients (18%), and stroke in 2 (7%). Our study largely confirms the demographic pattern, clinical characteristics, and prognosis of TGA patients reported from the western countries. Although the cause is uncertain, TGA is a relatively benign entity.

Transient global amnesia

Transient global amnesia (TGA) is a memory dysfunction characterized by a sudden onset of dense anterograde amnesia (AA) that gradually resolves across several hours. TGA is typically accompanied by repeated questions (concerning present circumstances) with retrograde amnesia for events preceding the attack, and it usually strikes individuals in their late 50s and early 60s. The etiology of TGA remains unclear, although it probably reflects a temporary disruption of the blood supply to the temporal lobe. The physical and psychological events preceding the attack are diverse, but they often include acute emotional and physical stressors. TGA appears to be benign, with low risk for recurrence or residual complications. While systematic memory research on TGA patients is rare, these individuals present a unique opportunity to study amnestic behaviors in otherwise normal individuals. A guide to conducting future research is provided.

Transient Global Amnesia and Migraine

This study examined the putative association of transient global amnesia (TGA) and migraine. 57 TGA patients were compared to a double-size control group of normal subjects. TGA patients who also had migraine were additionally compared to those without migraine and to a second control group of outpatients with migraine only. The prevalence of migraine, and also of episodic tension-type headache, was markedly increased among TGA patients. Precipitants and accompanying vegetative symptoms of TGA and migraine overlapped. However, there was no evidence of an interaction between TGA and migraine, in that the expression of key TGA features was not affected by comorbidity with migraine, and vice versa. The present findings argue against the hypothesis that TGA represents a type of migraine aura or migraine equivalent. They conform to the hypothesis that the two conditions are essentially independent and result from an inherited brain state that disposes to different types of paroxysmal dysregulation, presumably at the level of the brain stem.

Transient global amnesia: Acute SPECT functional imaging and neuropsychological deficits

Five patients with transient global amnesia (TGA) were seen clinically and studied neuropsychologically and with SPECT scanning within 24 hours in four and one within 48 hours of the attack. The memory deficits were characteristic of TGA and the magnetic resonance brain scans were normal in all patients. The SPECT scans showed hypoperfusion in the frontal and thalamic regions in all patients. In addition biparietal hypoperfusion was seen in one, parieta occipital in two and unilateral temporal in two patients. Transcranial Doppler studies were performed in three of the five patients and revealed abnormalities of possible relevance in one. Two of the SPECT studies had normalised when repeated at approximately 2 months post ictus. These five patients represent relatively "pure" forms of TGA as they all had normal MRI scans which excluded other disease processes such as subclinical or silent strokes. The frontal hypoperfusion in all five patients is of interest given the role of the frontal lobes in memory processing. Transient global amnesia (TGA) remains a clinical diagnosis of unknown pathophysiology with no corroborative laboratory or radiological test. Despite over one thousand case reports in the literature,1-9 neuropshyhological assessment at time of or immediately after the ictus is limited to less than a dozen cases.1,3-5 Strict definition as recommended by the Oxford criteria was not used in the majority of studies.1 Several functional scanning studies, mainly single photon emission computed tomography (SPECT) reports and one positron emission computed tomography (PET) study, report of thalamic and/or neocortical hypoperfusion with hippocampal, temporal, frontotemporal, thalamus, hemicortical and mesial temporal sites of decreased cerebral blood flow.3,10-19 Functional imaging with SPECT and PET may be useful in elucidating the cause for the most popular proposed mechanisms which include cerebral ischaemia, seizures and migraine. To date 10 such studies have been published describing 13 patients. In these studies, magnetic resonance imaging (MRI) scans were not reported on, or not performed in six studies and were abnormal in a further two. In the remaining two studies MRI scans were performed 10 days and three months post ictus.3, 10-19 This report describes five patients in the acute phase, all with normal MRI scans. To our knowledge, this study represents the largest case series at TGA patients with normal MRI scans but abnormal SPECT scans.

Transient global amnesia. A case control study.

A case control study of transient global amnesia (TGA), transient ischaemic attacks (TIA) and normal controls is described. Each of the 51 TGA patients, selected between January 1985 and March 1990, was compared with four controls (two TIAs and two normals) for the presence of vascular risk factors (hypertension, diabetes, smoking habits, cholesterol, triglycerides and haematocrit levels, heart disease, previous stroke), previous TGA, migraine, psychiatric illness and recent head trauma. Patients with TGA had less diabetes, hypercholesterolaemia and hypertriglyceridaemia than TIA. TGA subjects had significantly more hypertension (odds ratio = 3.31) and migraine (odds ratio = 8.67) than normal controls. During a mean of 17.4 mths of follow-up (range 1-96 mths), three subjects had recurrent TGA, one sustained a TIA and a minor stroke, but none had seizures. Thrombo-embolism and epilepsy are unlikely to be the cause of this benign disorder. The role is stressed of appropriate precipitants, including haemodynamic changes, and of individual susceptibility (of which migraine is probably a marker) in the genesis of TGA.

Memory loss due to transient hypoperfusion in the medial temporal lobes including hippocampus

A typical case of transient global amnesia (TGA) was investigated with single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) with 1.5-tesler scans. During the amnesic episode, a marked decrease of cerebral blood flow was observed in the areas confined to the territory of the bilateral posterior cerebral arteries including the hippocampus. After the episode, cerebral blood flow returned to normal and a circumscribed lesion was detected in the middle portion of CA 1 field of the left hippocampus. The SPECT findings prove direct evidence that the medial temporal structures are involved in the establishment of new memories, as well as in process of recalling only recently acquired memories, but not in retrieval of memories acquired long ago. The MRI findings indicate that a unilateral partial damage to CA 1 sector of the hippocampus does not develop a definite memory impairment and that high-resolution MRI study on the hippocampus is necessary in TGA patients.

THE AETIOLOGY OF TRANSIENT GLOBAL AMNESIA

A case-control comparison of 114 transient global amnesia (TGA) patients using both normal community-based controls (n = 109) and transient ischaemic attack (TIA) controls (n = 212) showed no evidence of an increased risk of TGA associated with any of the conventional risk factors for cerebrovascular disease. However, migraine was significantly more common in the TGA patients than in either control group. A prospective longitudinal study using actuarial (life table) analysis confirmed that the prognosis of the TGA patients was strikingly better than that of the TIA controls. An important minority (7%) of TGA cases developed epilepsy, usually within one year of presentation. On the basis of this evidence, a thromboembolic aetiology for TGA can be confidently rejected, at least for the vast majority of cases. There are good theoretical reasons to link migraine and TGA casually, and occasionally epilepsy may masquerade as TGA. In the remaining cases the cause remains unknown.

A case-control study of transient global amnesia.

To evaluate risk factors and prognosis of transient global amnesia (TGA), three groups of 30 subjects each affected respectively by: (1) first-ever TGA; (2) first-ever transient ischaemic attack (TIA); (3) depressive neurosis, were compared. Prevalence of cerebrovascular risk factors was similar in patients with TGA and TIA, but significantly lower in the third group. CT showed more hypodense lesions in TIA patients than in those with TGA. In a mean follow-up of 36 months, five TGA patients experienced a TIA and three others had recurrence of TGA, but none suffered stroke or myocardial infarction. In the TIA group, four had recurrence of TIA, two suffered a stroke and two others a myocardial infarction, whereas none had TGA attacks. None of the patients of the third group had any ischaemic event during follow-up. The similar prevalence of risk factors, but the different prognosis between TGA and TIA patients, suggest that TGA is an ischaemic event, probably not triggered by thromboembolism but by a different, possibly vasospastic, mechanism.