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PubMed1990

Bitemporal hypoperfusion in transient global amnesia: 99m-Tc-HM-PAO SPECT and neuropsychological findings during and after an attack.

We report a patient who was evaluated neuropsychologically and with single photon emission computed tomography (SPECT) during and after an episode of transient global amnesia. During the attack, there was patchy retrograde amnesia and an inability to learn both verbal and non-verbal material. SPECT showed severe bitemporal hypoperfusion. Serial neuro-psychological testing documented a rapid recovery of recognition, but delayed recovery in reproduction of learned information. Recovery of spontaneous verbal and figural fluency was even further delayed. Follow up SPECT examination showed a recovered cerebral perfusion. This case supports the hypothesis that TGA is associated with transient hypoperfusion of bilateral medial-temporal brain structures and suggests an additional involvement of structures responsible for drive and initiation.

Aged↗
PubMed1991

Anterograde amnesia with fornix damage following removal of IIIrd ventricle colloid cyst.

Two patients developed anterograde amnesia following the apparently uncomplicated transcallosal-transventricular removal of a colloid cyst. Damage to the fornical columns was demonstrated on CT and MRI scans, whilst other memory related structures were entirely normal. Longitudinal neuropsychological evaluation, over 12-24 months, has revealed a very similar pattern of deficit in the two cases: verbal memory has remained persistently impaired whilst nonverbal anterograde memory has improved to some degree. Formal tests of remote public (famous faces and events) and personal autobiographical memory have supported the clinical impression that neither patient has a temporally extensive retrograde amnesia. These findings address the role of the fornix, and the dissociation of memory processes in humans.

Adult↗
PubMed1981

Reduction of ECS-induced retrograde amnesia of passive avoidance conditioning after 5,7-dihydroxytryptamine median raphe nucleus lesion in the rat.

5,7-Dihydroxytryptamine (5,7-DHT), median raphe nucleus (MRN)-lesioned and sham-lesioned rats were submitted to one-trial passive avoidance conditioning followed by electroconvulsive shock (ECS) or sham-ECS. On test session (24 h later) MRN-lesioned rats presented a longer conditioned response and, chiefly, a remarkable reduction of ECS-induced retrograde amnesia in comparison to sham-lesioned animals. This effect appeared unrelated to major changes in spontaneous behavior: on training session MRN-lesioned rats exhibited a faster stepping-down from the platform; their exploratory activity into a novel cage was characterized by a slightly higher initial response; moreover MRN lesion did not significantly effect pain threshold. A reduced brain 5-HT functional activity following MRN lesion was suggested by the study of the hyperactivity syndrome induced by tranylcypromine plus L-tryptophan. Lastly, MRN-lesioned rats showed a significantly lower brain 5-HT steady level without differing from the sham-lesioned ones with respect to turnover rate. The reduction of ECS-induced retrograde amnesia observed in 5,7-DHT, MRN-lesioned rats was considered as due to a lower synaptic availability of 5-HT at the time of ECS administration.

5,7-Dihydroxytryptamine↗
PubMed1982

Aging-related changes in retrograde amnesia for mice.

Aging mice showed a retrograde amnesia for passive avoidance behavior when a single electroconvulsive shock (ECS) was given at post-training intervals up to 1 h, whereas adult mice showed no significant amnesia when ECS was given 10 min or more after training. Catecholamines (norepinephrine and dopamine), but not serotonin (5-HT) changed with aging in the several brain regions, but only 5-HT was significantly changed (elevated) by ECS. Protein synthesis was significantly inhibited by ECS, notably in limbic structures. The increased susceptibility of aging mice to the amnesic effect of ECS could be related to aging-related changes in the rate of memory consolidation or to the duration of neural chemical changes that disrupt processes such as consolidation, storage, and/or retrieval of the memory trace.

Aging↗
PubMed1985

Transient global amnesia and meningioma.

A patient with episodes of transient global amnesia and transient partial amnesia was found to have a meningioma impinging on the right medial temporal lobe. Multiple partial complex seizures and EEG abnormalities suggested an epileptogenic disorder.

Amnesia↗
PubMed1999

Anterograde and retrograde amnesia after lesions to frontal cortex in rats.

A socially acquired food-preference test was used to assess effects of lesions to the frontal cortex on anterograde and retrograde memory in rats. In Experiment 1, there was no effect of lesion when rats were administered a two-choice test in which the target food was to be selected in the presence of a single distractor. In Experiment 2, a three-choice memory test was administered in which the target food was presented along with two equally palatable alternatives. In the latter test, lesioned groups displayed anterograde amnesia that increased with the length of the interval between postoperative acquisition and test, and a severe retrograde amnesia that extended equally over the entire range of intervals between preoperative acquisition and test. This outcome, which contrasted with the pattern of memory loss previously observed in rats with hippocampal lesions on this test, was interpreted as evidence for the strategic role of the frontal lobes in directing response selection and retrieval processes in memory.

Amnesia, Anterograde↗
PubMed1989

[Basilar artery migraine associated with transient global amnesia].

Transient global amnesia (TGA) is an unusual form of the amnestic syndrome, clinically characterized by profound disturbance of short-term memory with preservation of immediate recall and long-term memory. Spontaneous recovery is the rule and is usually complete within several hours. The etiology of TGA is not clear. It is considered to be caused by transient ischemia confined to the medial temporal lobe, an area supplied by branches of the vertebrobasilar system. Basilar artery migraine is a well-known syndrome, first described by Bickerstaff. Besides pulsating headache, the dominant symptoms are vertigo, ataxic gait, tinnitus, dysarthria, paraeshesia in the hands, homonymous hemianopsia and sometimes drop-attacks. These symptoms are associated with vertebrobasilar system dysfunction. In this paper, three migraine patients, suffering from one episode of TGA, were reported. All patients were women. Case 1 was a 48-year-old woman with a history of common migraine. Case 2 was a 48-year-old woman with a history of classic migraine. Case 3 was a 59-year-old woman with a common migraine. Family history of migraine exists in case 1 and case 3. Their migrainous attacks began in their twenties and thirties. They suddenly suffered migraine with the symptoms of vertebrobasilar dysfunction. These symptoms are ataxic gait (Case 1, 2, 3), dysarthria (Case 1, 2), vertigo (Case 1, 3) and homonymous hemianopsia (Case 1, 3). Simultaneously three patients had TGA. Duration of retrograde amnesia were about twenty-four hours (Case 1), about thirty minutes (Case 2) and about three hours (Case 3).(ABSTRACT TRUNCATED AT 250 WORDS)

Amnesia↗
PubMed1979

[Genesis of amnesia caused by electroconvulsive shock].

The effect of a series of repeated electric shocks (ES) on retention of the conditioned reflexes and the content of free amino acids (AA) was investigated in the rat brain. Following repeated electric shocks, the first of which was applied 24 hours after learning, the rats developed amnesia. The content of brain excitatory AA did not change, whereas that of inhibitory AA, phenylalanine and tyrosine sharply decreased. The content of AA in the blood plasma increased. It is suggested that amnesia was caused by a change in the balance between excitatory and inhibitory AA in favour of the former ones. The changes in the functional state of the hematoencephalic barrier may play a certain part in the origin of the shifts mentioned.

Amino Acids↗
PubMed1976

A cognitive approach to experimental amnesia.

A review of selected experiments indicates that not all examples of experimental amnesia are due to the failure of a memory to fixate. Briefly, the argument is that the fixation of a memory occurs within a very short time and that its retrieval is aided if it is coded into a contextual memory system. An amnesic agent serves to block (inhibit) memories rather than disrupt them and has its effects on active memories, whatever their age. In sum, the empirical retrograde amnesia gradient does not necessarily support traditional consolidation theory.

Amnesia↗
PubMed1976

[Amnestic episodes in migraine. A contribution to the differential diagnosis of transient global amnesia (ictus amnésique)].

In comparison with 27 similar cases, sampled from literature, 4 observations of amnesic episodes in migraine are presented and discussed. These disturbances known as so-called "Migranedammerattacken" seem to be identical with transient global amnesia in all respects. In most of cases, they occur as migraine-precursors or - equivalents. Headache, vegetative und neurological symptoms are frequent but not necessary companions. It is proposed to look for migraine disposition in all cases of transient global amnesia. Perhaps, this approach might be of some use to understand their enigmatic pathogenesis.

Aged↗
PubMed1977

Transient global amnesia due to a dominant hemisphere tumor.

Transient global amnesia is generally regarded as a benign syndrome of probable vascular etiology. We describe a man who experienced a single episode of transient global amnesia and subsequently developed a progressive dominant hemispheric syndrome. Neuroradiologic investigations and the patient's subsequent death strongly suggest that his disease was due to a left temporal-parietal mass lesion. Although the syndrome is most often benign, such patients should be examined for mass lesions.

Aged↗
PubMed1982

Transient global amnesia. Precipitating activities and other observations.

Impressed with the number of patients whose spells of transient global amnesia were triggered by special circumstances, I have reviewed 78 such cases. Precipitating events were reported in 26 of 85 spells: eight occurred during highly emotional experiences; seven, during sexual intercourse; six, while the patient was in pain; two, while a trigeminal ganglion was being stimulated; and three, during a dip in the cold Atlantic Ocean. These observations suggest an electrophysiologic disturbance. The characteristics of the amnesia, the organization of memory, and behavior during spells were also considered.

Aged↗
PubMed1983

Medial thalamic hemorrhage with amnesia.

Three patients had amnesia and confusion as presenting features of thalamic hemorrhage. They had a relatively benign clinical appearance and lacked characteristics of the syndrome usually associated with thalamic hemorrhage. We reviewed hypotheses regarding a mechanism for the amnesic syndrome and concluded that lesions involving the medial thalamic nucleus were responsible for the amnesia observed.

Aged↗
PubMed1983

Transient partial amnesia.

A patient struck with transient amnesia was able to write a detailed account of her experiences during the episode and retained partial memory of the event. The analysis of her report permits an unusual view of transient partial amnesia.

Amnesia↗
PubMed1992

Technetium-99m HM-PAO single photon emission computed tomography imaging in transient global amnesia.

Five right-handed patients with pure transient global amnesia were evaluated with technetium-99m hexamethylpropyleneamine oxime single photon emission computed tomography after the amnesic attack. Independent of the interval between the procedure and the amnesic episode, single photon emission computed tomography demonstrated a decreased cerebral blood flow in the left temporal lobe in one patient and in the left parietotemporal region in three patients, with a more marked reduction in the temporal lobe. The remaining three patients were normal. A control single photon emission computed tomographic study was carried out in one patient 3 months after the amnesic attack and showed a left-sided persistent temporal hypoperfusion. These findings suggest that in some patients, transient global amnesia can be due to a vascular mechanism requiring strong investigations for vascular risk factors and appropriate treatment. During a follow-up period of 12 to 32 months, none of the patients with regional hypoperfusion suffered cerebrovascular events, suggesting that single photon emission computed tomography has no predictive value for further stroke.

Aged↗
PubMed1998

Amnesia and the organization of the hippocampal system.

Early hippocampal injury in humans has been found to result in a limited form of global anterograde amnesia. At issue is whether the limitation is qualitative, with the amnesia reflecting substantially greater impairment in episodic than in semantic memory, or only quantitative, with both episodic and semantic memory being partially and equivalently impaired. Evidence from neuroanatomical and lesion studies in animals suggests that the hippocampus and subhippocampal cortices form a hierarchically organized system, such that the greatest convergence of information (and, by implication, the richest amount of association) takes place within the hippocampus, located at the top of the hierarchy. On the one hand, this evidence is consistent with the view that selective hippocampal damage produces a differential impairment in context-rich episodic memory as compared with context-free semantic memory, because only the latter can be supported by the subhippocampal cortices. On the other hand, given the system's hierarchical form of organization, this dissociation of deficits is difficult to prove, because a quantitatively limited deficit will nearly always be a viable alternative. A final choice between the alternative views is therefore likely to depend less on further evidence gathered in brain-injured patients than on which view accounts for more of the data gathered from converging approaches to the problem.

Amnesia↗
PubMed1987

Transient global amnesia: the electroencephalogram at onset.

A middle-aged man experienced onset of transient global amnesia while undergoing an electroencephalogram. No important change in electroencephalographic activity occurred. This case provides evidence against the hypothesis that epileptic discharge is responsible for transient global amnesia.

Amnesia↗
PubMed1997

Very long-term amnesia in association with temporal lobe epilepsy: evidence for multiple-stage consolidation processes.

The temporal fractionation of long-term retention remains a relatively uncharted area in human memory research, and in particular there is little in the way of neuropsychological data that address this issue. We describe a patient with temporal lobe epilepsy who complained of amnesia for important events that had occurred in the previous 3-24 months, but who reported that her short-term and medium-term memory were normal. She displayed normal performance on traditional tests of short-term and long-term retention, performing at a very similar level to that of age- and sex-matched healthy control subjects on immediate and half-hour delayed recall measures. Forty days later, however, she showed a dense amnesia for recall of such information, whereas control subjects could readily recall much of the original stimuli. She also showed evidence of memory loss for news events that had occurred over the previous few years. MRI scanning and EEG brain mapping indicated left temporal lobe pathology, with a possible epileptogenic focus in the left anterior hippocampus. These data provide empirical evidence for the existence of a distinct very long-term consolidation process in human episodic memory and point to its neural correlates in the temporal lobe. Transfer of information into a permanent long-term memory store may entail multiple-stage consolidation processes rather than a single-stage, unitary consolidation process.

Amnesia↗