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PubMed1993

Transient global amnesia: neuropsychological findings after single and multiple attacks.

We examined by neuropsychological tests 41 patients who had presented attacks of transient global amnesia (TGA; 31 had single and 10 multiple episodes), comparing them with 41 matched normal controls. Patients with single attacks showed only two impaired memory tasks with respect to controls (immediate and long-term verbal memory), while patients with multiple attacks showed more impaired tasks in memory and visuoperceptual ability. These data confirm that TGA is a benign syndrome, but could leave a few subclinical memory deficits probably exacerbated by repeated attacks.

Aged↗
PubMed1990

Epileptic transient amnesia.

A patient with epileptic amnesic attacks suffered three prolonged episodes similar to transient global amnesia. Clinical, electroencephalographic and neuropsychological observations during 2 years' follow-up are reported.

Aged↗
PubMed1995

Amnesia after diazepam infusion into basolateral but not central amygdala of Rattus norvegicus.

Recent findings indicate that the memory-impairing effects of benzodiazepines may preferentially involve the basolateral nucleus of the amygdala. To test this hypothesis we examined the effects on pretrial injection of diazepam into the central as compared to the lateral/basolateral amygdaloid nuclei on memory for a conditioned avoidance response. Rats were implanted bilaterally with cannulae directed to either the central or lateral/basolateral amygdaloid nuclei. Five to 7 days later they were trained on a multitrial inhibitory avoidance (step-down) task to criterion and tested 48 h later. Fifteen minutes before training they were given an injection of either vehicle or diazepam (0.7 or 1.4 nmol) into the central or lateral/basolateral nuclei. Administration of diazepam into the lateral/basolateral nuclei but not the central nucleus induced anterograde amnesia. These results add to the body of data linking the GABA-benzodiazepine system of the lateral/basolateral nuclei to the amnestic effects induced by peripheral as well as central administration of benzodiazepines.

Amnesia↗
PubMed1988

Amnesia following thalamic hemorrhage. Another stroke syndrome.

The clinical manifestations of thalamic hemorrhage frequently comprise hemiparesis, hemianesthesia, and oculomotor abnormalities. Since the advent of computed tomography, an amnestic syndrome following thalamic hemorrhage has been recognized, but the thalamic structures involved and the mechanism of amnesia have remained uncertain. We report a patient with sudden memory dysfunction following hemorrhage into the anterior nucleus of the left thalamus that was shown neuropathologically to disrupt the mamillothalamic fasciculus, one of the principal components of the limbic system. It is considered that the amnestic syndrome following thalamic (anterior nucleus) hemorrhage is due to interruption of the mamillothalamic fasciculus.

Amnesia↗
PubMed1995

Transient global amnesia and transient ischemic attack. Natural history, vascular risk factors, and associated conditions.

BACKGROUND AND PURPOSE: The purpose of the present study was to make an attempt to ascertain the etiology of transient global amnesia (TGA), which is still disputed more than 30 years after the first description of this clinical entity. METHODS: In a case-control study, we compared the prevalence of vascular risk factors in 64 TGA patients with 64 first-ever transient ischemic attack (TIA) control subjects and 108 normal community-based control subjects matched for age and sex. We prospectively studied the vascular events and mortality rates of the TGA cases and of the TIA control subjects. Then we compared the outcome of the two groups using actuarial analysis based on survival curves. RESULTS: We did not find evidence of an increased risk of TGA associated with any vascular risk factor. In contrast to TIA control subjects, no TGA patient suffered stroke, myocardial infarction, or TIA during the follow-up period. Migraine was more common in TGA patients than in both normal and TIA control subjects. In three patients (4.5%), the TGA was eventually considered to be of epileptic origin. CONCLUSIONS: The results of our case-control and longitudinal studies point to the conclusion that TGA and TIA do not share the same etiology. Since half of our patients had a precipitating event in their history, it is reasonable to hypothesize that spreading depression may play a role in TGA. The significant positive association between migraine and TGA may support this hypothesis. Epilepsy may mimic TGA in a minority of cases.

Actuarial Analysis↗
PubMed1999

Lack of evidence of acute ischemic tissue change in transient global amnesia on single-shot echo-planar diffusion-weighted MRI.

BACKGROUND AND PURPOSE: There is uncertainty concerning the etiology of transient global amnesia (TGA). Previous CT and MRI studies have indicated that permanent structural abnormality is rare in TGA. Diffusion-weighted (DW) MRI is very sensitive to early ischemic parenchymal changes and has recently demonstrated embolic infarction in the posterior cerebral artery territory in 2 TGA patients. We report the findings of DW MRI in 8 patients in acute stages of TGA. METHODS: Conventional and echo-planar DW MRI was performed in 2 patients in the active phase and 6 patients in the recovery phase (1 to 8 hours after cessation of anterograde memory dysfunction) of spontaneously occurring TGA. RESULTS: None of the patients showed signs of hyperintensity on DW images or hypointensity on quantitative apparent diffusion coefficient (ADC) maps to suggest regional decreases of water mobility or acute T2 changes on transverse or coronal slices. CONCLUSIONS: We were unable to detect ADC or acute T2 changes with echo-planar DW MRI in patients with TGA, which suggests that mechanisms other than ischemic infarction may cause TGA. We did not identify spreading depression-associated changes of the ADC. Further refinement of MRI sequences may be necessary to detect subtle or transient signal change in brain parenchyma.

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PubMed2001

Preserved recognition in a case of developmental amnesia: implications for the acquisition of semantic memory?

We report the performance on recognition memory tests of Jon, who, despite amnesia from early childhood, has developed normal levels of performance on tests of intelligence, language, and general knowledge. Despite impaired recall, he performed within the normal range on each of six recognition tests, but he appears to lack the recollective phenomenological experience normally associated with episodic memory. His recall of previously unfamiliar newsreel events was impaired, but gained substantially from repetition over a 2-day period. Our results are consistent with the hypothesis that the recollective process of episodic memory is not necessary either for recognition or for the acquisition of semantic knowledge.

Adult↗
PubMed2005

Inattentional amnesia to words in a high attentional load task.

We investigated the dependence of visual word processes on attention by examining event-related potential (ERP) responses as subjects viewed words while their attention was engaged by a concurrent highly demanding task. We used a paradigm from a previous functional magnetic resonance imaging (fMRI) experiment [Rees, G., Russel, C., Frith, C. D., & Driver, J. Inattentional blindness vs. inattentional amnesia for fixated but ignored words. Science, 286, 2504-2506, 1999] in which participants attended either to drawings or to overlapping letters (words or nonwords) presented at a fast rate. Although previous fMRI results supported the notion that word processing was obliterated by attention withdrawal, the current electrophysiological results demonstrated that visual words are processed even under conditions in which attentional resources are engaged in a different task that does not involve reading. In two experiments, ERPs for attended words versus nonwords differed in the left frontal, left posterior, and medial scalp locations. However, in contrast to the previous fMRI results, ERPs responded differentially to ignored words and consonant strings in several regions. These results suggest that fMRI and ERPs may have differential sensitivity to some forms of neural activation. Moreover, they provide evidence to restore the notion that the brain analyzes words even when attention is tied to another dimension.

Adult↗
PubMed1987

Diazepam-induced amnesia: a neuropharmacological model of an "organic amnestic syndrome".

Diazepam has well-known amnestic properties. These effects, however, are selective for certain psychobiologically distinct memory functions. In this study, incremental doses of diazepam administered to 10 normal volunteers selectively impaired anterograde episodic memory and attention while totally sparing access to information in long-term memory (semantic or knowledge memory). This pattern of disruption mimics that seen in patients with organic amnesias and is in sharp contrast to the pattern seen in patients with dementia. These findings provide a framework for defining specific psychobiological determinants of cognitive failure.

Adult↗
PubMed1998

Implicit memory in posttraumatic stress disorder with amnesia for the traumatic event.

This report documents a case of posttraumatic stress disorder (PTSD) following psychological trauma with cerebral insult and amnesia for the traumatic event. The case history demonstrates the role of implicit memory in PTSD and indicates that the mechanisms of psychopathology are one-trial sensitization and conditioned emotional responses.

Accidents, Occupational↗
PubMed2002

Posttraumatic amnesia and recall of a traumatic event following traumatic brain injury.

The relationship between posttraumatic amnesia (PTA) and symptoms of posttraumatic stress disorder (PTSD) was examined in 282 outpatients at a mean of 53 days after traumatic brain injury (TBI). Patients were assessed for TBI severity, intrusive and avoidant PTSD-type symptoms, and psychological distress, and were stratified into four comparison groups by duration of PTA. Levels of PTSD-type symptoms and psychological distress did not differ significantly between groups. Even patients with PTA >1 week reported intrusive and avoidant PTSD-type symptoms. However, when patients were stratified into those with PTA of <1 hour or >1 hour, the former were more likely to report such symptoms. TBI patients with brief PTA are more likely to experience PTSD-type reactions, but severe TBI with prolonged PTA is not incompatible with such reactions in a subset of patients. Possible mechanisms that could account for this finding are discussed.

Adult↗
PubMed2000

Transient global amnesia and amaurosis fugax in a patient with common carotid artery occlusion--a case report.

The etiology of transient global amnesia (TGA) is debatable. The hypothesis of a thromboembolic cause of TGA has been questioned by recent case control studies. Occlusion of the common carotid artery (CCA) is rare. Although amaurosis fugax (AF) is a hallmark of ipsilateral internal carotid artery disease, its occurrence in CCA occlusion is less known. Association of these three conditions in a patient may imply pathophysiologic significance. Here, the authors report a 76-year-old man who suffered from a spell of TGA and then several attacks of AF of the right eye. Progressive occlusion of the right CCA was documented by repeat carotid duplex scans and was finally confirmed by cerebral angiography. In this patient, the occurrence of CCA occlusion and AF implicates a vascular etiology for the event of TGA. A noninvasive carotid ultrasonographic screen may, therefore, be worthwhile for patients with TGA.

Aged↗
PubMed1988

Kluver Bucy syndrome with severe amnesia secondary to herpes encephalitis.

The authors present a case of Kluver Bucy syndrome with severe amnesia secondary to herpes encephalitis. The clinical features, neuropsychological test results and magnetic resonance images in this case also elucidate important aspects of limbic system pathology that are discussed in light of the literature.

Adult↗
PubMed1989

EEG features in transient global amnesia.

Forty-seven patients with one or more episodes of transient global amnesia (TGA) were studied by means of standard and 24-hour ambulatory cassette recording electroencephalography (EEG). Only one individual, with a left frontal hemorrhage, had intracranial lesions. TGA was multiple in 16 of the patients (34%), the attacks recurring with an average time span of one every 3 years. No patient required anticonvulsant therapy and all episodes of TGA were self-limited and rather benign. Only 13 patients were known to be hypertensive and 2 had a history of classic migraine. The average time span of EEG recordings after TGA was 2.7 days. Three individuals had recordings during the actual clinical attack, 2 of whom had paroxysmal abnormalities (one with periodic lateralized epileptiform discharges and the other with left temporal sharp wave and central spike and wave discharges). The remaining patient had no change in the EEG. The percentage of EEG abnormalities encountered was 36% (17 patients) but only 10.6% (5 patients) disclosed specific paroxysmal activity. Activation procedures, sleep and 24-hour ambulatory studies were overall of no additional value to the standard recordings. TGA seemingly represents a benign circulatory disturbance affecting the memory zones of the brain, rather than a primary epileptic disorder.

Aged↗
PubMed1998

Assault, post-traumatic amnesia and other variables related to outcome following head injury.

OBJECTIVE: To estimate how many patients who sustain a head injury might benefit from intervention and support each year and to consider whether relationships can be found between demographic data relating to patients' circumstances at the time of head injury, and their outcomes six months later. DESIGN: Data collected on 625 patients through follow-up interviews and assessments by the Oxford Head Injury Service for a randomized controlled trial of intervention conducted in 1993-94. SETTING: A mixed rural and urban Health District with a population of approximately 560,000. PATIENTS: Patients were aged between 16 and 65 years and resident in Oxfordshire. They presented over 13 months to accident and emergency departments, or were admitted to hospital. All were diagnosed as having suffered a head injury. OUTCOME MEASURES: The Rivermead Head Injury Follow Up Questionnaire and the Rivermead Post Concussion Symptoms Questionnaire. RESULTS: Data are given on age, sex, social circumstances, employment, cause of injury, severity of associated injuries, post-traumatic amnesia (PTA), anticonvulsants, postconcussion symptoms and activities of everyday life. Outcome at six months was significantly worse for those who had been assaulted as against all other causes of injury combined (p = 0.0001); and/or had been admitted to hospital (p = 0.0001)l and/or had sustained more severe additional injuries (p = 0.04); and/or had experienced any PTA (p = 0.00001). The minimum incidence of such injuries in those aged 16-65, calculated for Oxfordshire, is 292 per annum (74/100,000 aged 16-65 per year). CONCLUSIONS: In the general population 52/100,000 patients per annum will experience more serious head injuries as indicated by hospital admission and/or one or more fractures and/or any length of PTA and/or having been assaulted. This group may benefit from monitoring and support and their needs should be considered when planning services.

Accidents↗
PubMed1991

Mr X-A case of amnesia.

A case of psychogenic amnesia in a 58-year-old man supports the view that complete loss of personal identity can follow a traumatic experience. He regained his memory by being helped to develop an affective link with the painful event.

Adaptation, Psychological↗
PubMed1993

Evaluation of a neural network model of amnesia in diffuse cerebral atrophy.

A digital computer program generating a simulated neural network was used to construct a model which can show behaviour resembling human associative memory. The experimental network uses distributed storage, and, in this respect, its functional organisation resembles that suggested by reported observations of neuronal activity in the human temporal lobe during memory storage and recall. Inactivation of increasing numbers of randomly distributed network units simulated advancing cerebral atrophy. This caused progressive impairment of performance, resembling the gradual deterioration of memory function observed in chronic diffuse cerebral degeneration. Unit inactivation had similar effects on recall whether the same units were inactivated before or after learning. This differs from most relevant observations of amnesia resulting from diffuse cerebral disease. While the model may functionally resemble long-term information storage sites in the brain, other cerebral mechanisms participating in learning and remembering are also damaged by diffuse cerebral atrophy.

Amnesia↗
PubMed2005

Assessment of the onset and persistence of amnesia during procedural sedation with propofol.

OBJECTIVES: To assess patients' ability to repeat and recall words presented to them while undergoing procedural sedation with propofol, and correlate their recall with their level of awareness as measured by bispectral index (BIS) monitoring. METHODS: This was a prospective, single-intervention study of consenting adult patients undergoing procedural sedation with propofol between December 28, 2002, and October 31, 2003. BIS monitoring was initiated starting 3 minutes before the procedure and continuing until the patient had regained baseline mental status. At 1-minute intervals during the procedural sedation, until the patient regained baseline mental status at the end of the procedure, a word from a standardized list was read aloud, and the patient was asked to immediately repeat the word to the investigator. The BIS score at the time the word was read and the patient's ability to repeat the word were recorded. After the procedure, the patient was asked to state all of the words from the list that he or she could recall, and to identify the last word recalled from prior to the start of the procedure and the first word recalled from after the procedure was completed. RESULTS: Seventy-five consenting patients were enrolled; one patient was excluded from data analysis for a protocol violation. No serious adverse events were noted during the procedural sedations. The mean (+/-standard deviation) time of data collection was 16.4 minutes (+/-7.1; range 5 to 34 minutes). The mean initial (preprocedure) BIS score was 97.1 (+/-2.3; range 92 to 99). The mean lowest BIS score occurring during these procedural sedations was 66.9 (+/-14.4; range 33 to 91). The mean lowest BIS score corresponding to the ability of the patient to immediately repeat words read from the list was 77.1 (95% CI = 74.3 to 80.0). The mean highest BIS score corresponding to the inability to repeat words was 81.5 (95% CI = 78.1 to 84.8). The mean BIS score corresponding to the last word recalled from prior to the initiation of the sedation was 96.7 (+/-2.4; range 84 to 98). The mean BIS score corresponding to the first word recalled after the procedure was completed was 91.2 (95% CI = 88.1 to 94.3). All patients recalled at least one word that had been read to them during the protocol. The mean lowest BIS score for any recalled word was 91.5 (+/-11.1; range 79 to 98), and no words were recalled when the corresponding BIS score was less than 90. CONCLUSIONS: There is a range of BIS scores during which sedated patients are able to repeat words read to them but are not able to subsequently recall these words. Furthermore, patients had no recall of words repeated prior to procedural sedation in BIS ranges associated with recall after procedural sedation, suggestive of retrograde amnesia.

Adult↗