1. Cone AM Exercise-induced transient global amnesia in a patient with subclavian steal Anaesth Intensive Care 1994; 22:95-6 2. Inzitari D, Pantoni L, Lamassa M, et al. Emotional arousal and phobia in transient global amnesia Arch Neurol 1997; 54:866-73 OBJECTIVE: To evaluate the role of emotionally stressful or phobogenic events and phobic personality traits in transient global amnesia (TGA). DESIGN: Case-control study. SETTING: Tertiary care center. PATIENTS: Fifty-one case patients with TGA (mean +/- SD age, 62.7 +/- 6.7 years) compared with 51 control patients with transient ischemic attacks (mean +/- SD age, 63.8 +/- 6.7 years). MAIN OUTCOME MEASURES: Precipitant factors, life events, and phobic attitudes. RESULTS: Of the 25 TGA attacks that were triggered by a precipitant, 11 were possibly related to emotionally stressful or phobogenic situations. On a scale that measured phobic attitudes, the case patients with TGA scored significantly higher than the control patients with transient ischemic attacks (mean +/- SD total score, 15.21 +/- 11.0 vs 4.41 +/- 5.2; P < .001 by corrected analysis of variance for age, sex, and education). The amount of stressful live events in the year that preceded the attack did not differ between the case patients with TGA and the control patients with transient ischemic attacks. CONCLUSION: The results support the hypothesis that emotional arousal and phobia are involved in TGA. 3. Lauria G, Gentile M, Fassetta G, Casetta I, Caneve G Incidence of transient global amnesia in the Belluno province, Italy: 1985 through 1995. Results of a community-based study Acta Neurol Scand 1997; 95:303-10 INTRODUCTION: We sought to determine the incidence rate of all the new cases of first-ever-in-a-lifetime transient global amnesia in the Belluno province, Italy. Only two prospective epidemiological studies on TGA incidence have been performed to date, non in Italy. Our study aimed to provide reliable and comparable information on TGA incidence. MATERIAL AND METHODS: We undertook a prospective population-based study in the territory of the province of Bulluno, Italy, between June 1, 1992 and December 31, 1995. We also retrospectively reviewed the clinical records of all the patients with a diagnosis of amnesia seen in the hospitals of the study area from January 1, 1985 through May 31, 1992. RESULTS: During the prospective study period we identified 77 patients who experienced a first-ever TGA. The crude annual incidence rate was 10.4/100,000 (9.35/100,000 for men and 11.37/100,000 for women). After adjustment to the European population, the incidence rate decreased to 8.60/100,000 per year. The crude annual incidence rate during the retrospective study period was 5.81/100,000. The demographic and clinical features of the two groups did not differ one to the other. CONCLUSIONS: The incidence rate of first-ever TGA registered in the province of Belluno, Italy, was closely similar to that reported in Turku, Finland and confirms that TGA is more common than has been usually proposed. We emphasize the usefulness of prospective, rather than retrospective, epidemiological studies for research on TGA. 4. Tosi L, Righetti CA Transient global amnesia and migraine in young people Clin Neurol Neurosurg 1997; 99:63-5 Two cases of transient global amnesia (TGA) in a 16-year-old boy and in a 13-year-old girl are reported; both occurred during competitive sport and were associated with migraine. TGA in young people could provide crucial information on the still equivocal pathogenesis, a vascular thromboembolic hypothesis being untenable in such cases. A migrainous mechanism is likely to underlie TGA in young people and "pure' TGA in general. TIA or stroke, like epilepsy or other pathological conditions, should concern the differential diagnosis of transient amnestic episodes rather than the pathogenesis of TGA. 5. Meder JF, Mourey-Gerosa I, Blustajn J, et al. Transient global amnesia after cerebral angiography. A case report Acta Radiol 1997; 38:273-4 We report on a case of transient global amnesia after cerebral angiography in which a nonionic contrast medium was used. The complication observed showed no evidence of any definite cause. 6. Okura M, Tomotake M, Mori K, Ikuta T Recovery of high speed memory scanning after transient global amnesia: a case report Psychiatry Clin Neurosci 1996; 50:317-21 We described the case of a 59 year old female with transient global amnesia (TGA) who had been examined neuropsychologically using Sternberg's paradigm and a random number generation (RNG) task on the following day, 1 week and 4 weeks after a TGA episode. The slope value of the linear function, a measure of cognitive memory scanning speed, decreased with time and showed a marked decrease 1 week after TGA, suggesting that the stage of serial and exhaustive scanning recovered within 1 week. The zero-intercept value, on the other hand, increased during 1 week but decreased 4 weeks later and was not related directly to recovery from TGA. The performance in RNG task improved 1 week later, but deteriorated 4 weeks after the episode. Such a change in RNG was in accordance with that of the zero-intercept value, predicting a relationship. It is concluded that the subclinical memory deficit, detected with these tasks, persisted longer than clinical recovery from TGA. 7. Chen WH, Liu JS, Wu SC, Chang YY Transient global amnesia and thalamic hemorrhage Clin Neurol Neurosurg 1996; 98:309-11 A left rostral thalamic hematoma was found in a 52-year-old hypertensive man who suffered from a 10-h episode of transient global amnesia (TGA). A neuropsychological study revealed no cognitive impairment in a follow-up period for 5 years. The left rostral part of the thalamus appears to be responsible for his TGA, due probably to an interference of the mamillothalamic tract, ventroamygdalofugal pathway or dorsal noradrenergic bundle. 8. Saito M, Ishida T, Asai M Alterations of peak distribution of auditory ERPs during transient global amnesia: a case report Biol Psychiatry 1997; 41:237-40 9. Orefice G, Soriente L, Cerbone AM, et al. Transient global amnesia in a young woman on prolonged treatment with oral contraceptive drugs [letter] Thromb Haemost 1996; 75:980 10. Jung HH, Baumgartner RW, Burgunder JM, et al. Reversible hyperperfusion of the right medial temporal lobe in transient global amnesia [letter] J Neurol Neurosurg Psychiatry 1996; 61:654-5 11. Buchholz DW, Reich SG The menagerie of migraine Semin Neurol 1996; 16:83-93 Migraine is conventionally regarded as a specific type of headache with a small set of associated neurologic symptoms. Yet, the true scope and frequency of migrainous phenomena are much greater than is generally acknowledged. Six cases are presented to illustrate some of the diverse manifestations of migraine: (1) transient global amnesia, (2) persistent visual phenomena, (3) migraine and seizures, (4) vestibular dysfunction, (5) hearing loss, and (6) migraine masquerading as multiple sclerosis. These and other migraine-associated neurologic symptoms are discussed in relation to previous reports in the literature. Pitfalls in recognizing the diverse manifestations of migraine, which are often underdiagnosed or misdiagnosed, are reviewed. Whether or not the established diagnostic criteria for migraine are too strict, other factors contributing to failure to identify migraine when it causes nonclassic neurologic symptoms include: (1) the belief that these are rare, (2) lack of an objective measure for migraine, (3) inadequate attention to the positive diagnostic features of migraine in the absence of headache, (4) confusion regarding prior migraine history, and (5) dismissing the diagnosis because of reported failure of prior migraine treatment. Recognition of the diversity of migraine helps avoid unnecessary testing and opens the door to effective treatment. 12. Takahashi Y, Yamamoto T, Abe T, et al. Transient global amnesia and dural arteriovenous fistula of the anterior cranial fossa Kurume Med J 1996; 43:223-9 Dural arteriovenous fistula (AVF) of the anterior cranial fossa is associated usually with cerebral hemorrhage or subarachnoid hemorrhage, while an association with transient global amnesia has not been reported previously. A case presenting the latter unusual symptom is described and the surgical treatment of AVF is discussed. A 64-year-old woman was hospitalized complaining of transient memory impairment. Magnetic resonance (MR) imaging demonstrated a flow void in the left frontal lobe and temporal pole. Cerebral angiography revealed an AVF in the anterior cranial fossa, which was fed bilaterally by the ethmoidal arteries and by branches of the external carotid arteries. The AVF drained into the superior sagittal sinus and the superficial sylvian vein via large varices. Following transfemoral embolization, surgical treatment was carried out. Postoperative angiography revealed complete obliteration of the anomaly. There were no further episodes of amnesia. In our presented case, there is an association between the presenting symptoms and the AVF. The combination of ischemia and congestion in the frontal and temporal lobes may have caused transient memory impairment. From our surgical experience, the excision of the vascular connection between the dura and the frontal lobe following the coagulation of the dura mater of the anterior part of the base of the skull without extensive excision seems to be recommended. 13. Moccia F, Aramini A, Montobbio P, Altomonte F, Greco G Transient global amnesia: disease or syndrome? Ital J Neurol Sci 1996; 17:211-4 Transient global amnesia (TGA) has been defined as the presence of an impairment of short-term memory, retrograde amnesia and repetitive queries, without any other neurological signs or symptoms. The precise pathophysiology of TGA is unclear, although thromboembolic, epileptic, migrainous and metabolic mechanisms have been suggested. We have studied the clinical, biohumoral, electroencephalographic and neuro-imaging data relating to 25 patients with TGA, and found a prevalence of hypertension and hypercholesterolemia. We also found a higher incidence of electrical changes in the patients whose TGA was of shorter duration, whereas brain CT scans revealed ischemic lesions more frequently in the patients with TGA of longer duration. Our findings seem to confirm the hypothesis that TGA is a heterogeneous clinical syndrome consisting of pure and ischemic forms. 14. Neri M, Andermarcher E, De Vreese LP, et al. Transient global amnesia: memory and metamemory Aging (Milano) 1995; 7:423-9 Twenty patients (mean age 64 years) with a previous episode of transient global amnesia (TGA) were examined to assess the functioning of objective memory (by using the Randt Memory Test), the metamemory capacities (Sehulster Memory Scale), the residual level of retrograde amnesia (Questionnaire of Remote Events), and the level of depression (Geriatric Depression Scale). Patients with residual retrograde amnesia scored significantly lower than non-amnesic ones on indices of both short-term and long-term memory, and for one of three main metamemory components, namely self-rating of memory functioning through comparison with memory functioning of peers (Set3). Age, time interval from TGA attack and TGA duration did not prove to influence memory and metamemory scores. Retrograde amnesia and depression were rather substantially associated (1/5), and this association was found to negatively influence nearly all memory and metamemory scores. Depression level showed a positive correlation with short-term memory functioning in non-amnesics. The different pattern and strength of the relationships between metamemory components and objective memory dimensions observed in amnesics and non-amnesics indicate that metamemory evaluations are more closely related to memory functioning in amnesics than in non-amnesics. 15. Mahmoud S, Elizabeth J Transient global amnesia: alarming but benign condition Br J Hosp Med 1996; 56:113 16. Meo R, Bilo L, Striano S, et al. Transient global amnesia of epileptic origin accompanied by fever Seizure 1995; 4:311-7 The case of a previously healthy 69-year-old female patient is described who presented, in a period of 6 months, 3 long-lasting (from 2 hour- to 10 hour-duration) episodes of transient global amnesia accompanied by a temperature rise. During one of these episodes an EEG was obtained, showing a diffuse alteration, focal slowing, and bitemporal asynchronous paroxysmal activity giving rise to electrical ictal discharges. Interictal EEGs were normal. Cerebral computed tomography was normal. Carbamazepine was given with complete control of the attacks. These episodes may be interpreted as complex partial status with unusual semeiology. 17. Kapur N, Abbott P, Footitt D, Millar J Long-term perceptual priming in transient global amnesia Brain Cogn 1996; 31:63-74 This paper addresses the question as to whether long-term perceptual priming can occur during transient global amnesia. A patient who displayed the classical features of transient global amnesia was assessed during the episode and again 7 days later. During the episode, she was administered a task that required the perceptual identification of fragmented pictures over a number of learning trials. Seven days later, after recovery from the episode, she was required to identify the same fragmented pictures together with a new set of pictures that she had never seen before. She was significantly better at identifying the old pictures than the new pictures, in spite of having amnesia for the period of the attack. Matched control subjects who had never seen either set of pictures before, were also tested and performed at a similar level on the old and the new pictures. Our findings extend the clinical domain of implicit memory phenomena and parallel similar observations in chronic amnesia (Cave & Squire, 1992). We provide the first demonstration of a residual capacity for long-term perceptual priming during an acute episode of apparent total loss of memory. 18. Moreno-Lugris XC, Martinez-Alvarez J, Branas F, Martinez-Vazquez F, Cortes-Laino JA [Transient global amnesia. Case-control study of 24 cases] Rev Neurol 1996; 24:554-7 Transient global amnesia (AGT) is a well-defined syndrome of unknown aetiology. It is generally believed to be of vascular origin. Other theories suggest epilepsy or migraine as the cause. We studied the clinical features and associated risk factors in 24 patients with AGT, comparing them with two control groups with 24 people in each group, paired for age and sex. The first control group contained healthy individuals (CN) and the second patients with transient ischaemic attacks (AIT). Of the patients with AGT, 70% were women and 30% men. Their average age was 60 (range 14-76). The attacks were abrupt in onset in 100%. In 8% there was a recognisable trigger factor (driving, physical exercise, etc). The average duration was 7 hours. On study of the cardiovascular risk factors, it was found that 36% were hypertensive, 24% had cardiopathy, 12% had diabetes mellitus, 8% were smokers, 4% had polycythaemia, 16% had hyperlipidaemia, 4% were alcoholics. There was a history of migraine in 29%. No patient had a past history of epilepsy. Further investigation showed ECG changes in 12%. In 24% there were non-specific changes in the EEG. On cerebral CT scan there were lesions compatible with ischaemia in 12.5% of the patients. Levels of arterial hypertension were significantly higher in the AGT group as compared to the normal control group (Odds ratio 7.86; CI. 1.29-11.38). A past history of migraine was seen to be a risk factor associated with AGT as compared with both groups of controls (AGT/CN Odds ratio 9.47; CI 1.01-444.92; AGT/AIT Odds ratio > 1.72). 19. Blasco MR, Arjona A, Jimenez C, Escamilla C Global transient amnesia and subclavian steal syndrome [letter] Lancet 1996; 347:1636 20. Klotzsch C, Sliwka U, Berlit P, Noth J An increased frequency of patent foramen ovale in patients with transient global amnesia. Analysis of 53 consecutive patients Arch Neurol 1996; 53:504-8 OBJECTIVE: Alerted by the number of patients with transient global amnesia (TGA) in whom Valsalvalike activities immediately preceded the onset of TGA, we have investigated the frequency of patent foramen ovale (PFO) as the prerequisite for paradoxical embolism. DESIGN: Case series with comparison to a control group. SETTING: Hospitalized and ambulatory patients at the neurological departments of the Alfried Krupp Hospital, Essen, Germany, and the Rheinisch-Westfalische-Technische Hochschule, Aachen, Germany. PATIENTS: Fifty-three consecutive patients with TGA were evaluated by the 2 centers between 1988 and 1995. RESULTS: Using contrast transcranial Doppler sonography we have observed a PFO in 55% of the patients with TGA, compared with 27% of a control group of 100 patients. This difference was statistically significant (P < .01). Twenty-five patients with TGA (47%), 15 of them with a proven PFO, reported a precipitating activity, such as the lifting of heavy weights, immediately before the TGA occurred. CONCLUSIONS: In addition to other pathological mechanisms, paradoxical embolism with temporobasal ischemia could possibly play a role in the clinical syndrome of TGA. This hypothesis could explain the frequent observation of preceding Valsalvalike activities in patients with TGA. 21. Raffaele R, Tornali C, Genazzani AA, Vecchio I, Rampello L Transient global amnesia and cerebral infarct: a case report Brain Inj 1995; 9:815-8 Transient global amnesia refers to a sudden and isolated dysfunction of memory for recent events, lasting a few hours. The pathogenesis of this neurological disorder is still uncertain. The most accepted hypotheses concern ischaemic, epileptic and migraine causes. We now report a case of transient global amnesia associated with computed tomography evidence for a hypodense area in the left thalamus 10 days after the transient memory dysfunctions. 22. Attarian S, Michel B, Delaforte C, Chave B, Gastaut JL [A case of transient amnesia caused by cerebral thrombophlebitis: contribution of neuroimaging to physiopathogenesis of transient amnesia] Rev Neurol (Paris) 1995; 151:552-8 We report a case of transient global amnesia (TGA), in a right-handed woman, which was due to a cerebral venous thrombosis. In our knowledge it is the first case reported. MRI and SPECT revealed the existence of a dysfunction in the right internal temporal region. Such a localization leads us to discuss the specialisation of each hippocampus. 23. Wetterling T [Amnestic syndrome--research update] Fortschr Neurol Psychiatr 1995; 63:402-10 Amnesia characterized by a severe impairment of the memory without a loss of consciousness is one of the 'classical' organic brain syndromes. According to the course, further symptoms and the circumstances of appearance, several subtypes can be differentiated: transient global amnesia, posttraumatic amnesia, Korsakow's psychosis, and psychogenic amnesia. Many disorders may cause amnesia. Guidelines for the differentiation of the underlying disorders and therapeutic strategies are discussed. 24. Sandson TA, Price BH Transient global amnesia Semin Neurol 1995; 15:183-7 25. Jones RJ, Brace SR, Vander Tuin EL Probable propafenone-induced transient global amnesia Ann Pharmacother 1995; 29:586-90 OBJECTIVE: To describe a probable case of transient global amnesia caused by propafenone. This adverse effect has not been previously described for this agent. CASE SUMMARY: A 61-year old man with a history of sick sinus syndrome with persistent atrial fibrillation and infrequent premature ventricular contractions was admitted to the hospital for symptoms of amnesia and disorientation to time, place, and date. He began taking propafenone only 6 days prior to admission because of uncontrolled atrial fibrillation and symptoms of fatigue. His atrial fibrillation subsequently had converted to normal sinus rhythm while he received propafenone without adverse effects prior to this episode. His symptoms of amnesia resolved approximately 6-7 hours after discontinuing the propafenone therapy. DISCUSSION: Propafenone is a class 1C antiarrhythmic agent that blocks fast sodium channels in heart muscle and Purkinje fibers similar to the action of encainide and flecainide. It also produces weak beta- and calcium-channel blockade. It has a significant adverse effect profile, with 30-45% of patients reporting cardiac adverse effects and 15-20% experiencing noncardiac events. Central nervous system effects that parallel amnesia have been reported in 10-15% of the patients, including dizziness, ataxia, drowsiness, fatigue, confusion, and paranoia. Propafenone's distribution, clearance, and structural similarity to propranolol contribute to its central nervous system effects. CONCLUSIONS: The rapid resolution of this patient's symptoms after discontinuing propafenone therapy and the absence of recurrence lend credence to the probability of this effect. Comparable adverse effects, such as disorientation and temporary amnesia, have been reported in patients in the analogous agent, propranolol. Consequently, this is a likely, although rare, possible adverse effect with propafenone for which patients should be monitored. 26. Zorzon M, Antonutti L, Mase G, et al. Transient global amnesia and transient ischemic attack. Natural history, vascular risk factors, and associated conditions Stroke 1995; 26:1536-42 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. 27. Kucinski D [Transient global amnesia] Psychiatr Pol 1995; 29:333-42 This paper reviews the literature concerning TGA. The author attempts to answer the question why this diagnostic category is rarely employed in Poland, and stresses the difficulty in differential diagnosis of TGA. The place of this term in the new systems of classification is also analysed. 28. Jackson A, Stewart G, Wood A, Gillespie JE Transient global amnesia and cortical blindness after vertebral angiography: further evidence for the role of arterial spasm AJNR Am J Neuroradiol 1995; 16:955-9 We describe a series of six patients who experienced severe retrograde amnesia (five cases) or cortical blindness (one case) during selective vertebral angiography. All angiograms were obtained with the same nonionic contrast medium. Analysis of the contrast batch demonstrated no abnormalities, but investigation of the angiographic suite revealed a faulty contrast warming cabinet resulting in injection of contrast material above body temperature. The warming cabinet was withdrawn, and the complication has not recurred. We believe that these symptoms reflect ischemia caused by vertebral arterial spasm. 29. Kazui H, Tanabe H [Hippocampus and memory disturbance: study on cases of transient global amnesia with dysfunction in the medial temporal lobe] No To Shinkei 1995; 47:421-8 30. Sheth RD, Riggs JE, Bodensteiner JB Acute confusional migraine: variant of transient global amnesia Pediatr Neurol 1995; 12:129-31 Acute confusional migraine in children and transient global amnesia in adults share a number of similar clinical manifestations. Acute confusional migraine in 6 children (mean age: 11.7 years; range: 7.5-17 years) was characterized by transient episodes of amnesia and acute confusion lasting 1-12 hours. Episodes were preceded by headache and vomiting in 4 patients. In 2 patients acute confusional migraine was the initial symptom. A history of preceding trivial head injury was reported in 3 patients and migraine in 4. Urine and serum drug screens were negative. Cerebral imaging studies and interictal electroencephalograms were normal. Ictal electroencephalograms in 3 patients revealed diffuse or bioccipital delta wave slowing. Recurrent episodes of acute confusional migraine occurred in 2 children during 1-3 years of follow-up. The clinical manifestations of acute confusional migraine in this series of children are similar to those reported in transient global amnesia. The similarity of the clinical manifestations of acute confusional migraine in children and transient global amnesia in adults suggests that these disorders may share a common pathophysiology. 31. Kimura S, Kumano T, Miyao S, Teramoto J Herpes simplex encephalitis with transient global amnesia as an early sign Intern Med 1995; 34:131-3 Cerebral ischemia has been proposed as the etiology of transient global amnesia. Recently, however, migranous and epileptic etiologies have attracted attention. A 56-year-old man had transient global amnesia and the next day began to display symptoms of meningoencephalitis. Herpes simplex encephalitis was diagnosed based on the titer of herpes simplex virus antibodies. The transient global amnesia appears to have occurred as an early sign of herpes simplex encephalitis and may have been provoked by an epileptic mechanism. 32. Warkentin TE, Hirte HW, Anderson DR, et al. Transient global amnesia associated with acute heparin-induced thrombocytopenia Am J Med 1994; 97:489-91 33. Stracciari A, Lorusso S, Pazzaglia P Transient topographical amnesia J Neurol Neurosurg Psychiatry 1994; 57:1423-5 Ten healthy middle aged or elderly women experienced isolated episodes of topographical amnesia without an obvious aetiology. It is likely a benign cognitive disorder, similar to transient global amnesia. 34. Silberstein EP Transient global amnesia in a young child J Paediatr Child Health 1994; 30:366-7 Unprovoked and unexplained sudden loss of memory and inappropriate behaviour in a 5 year old child is described as fitting into the clinical picture of 'transient global amnesia'. The likely pathophysiology of this condition is discussed with some support for Fisher's suggestion of 'hippocampal-fornical' dysfunction. 35. Schamschula RG, Soo MY Transient global amnesia following cerebral angiography with non-ionic contrast medium Australas Radiol 1994; 38:196-8 Transient global amnesia (TGA) is an uncommon syndrome of recent memory deficit and inability to learn new data, usually resolving within 24 h. Two cases following use of non-ionic contrast media in cerebral angiography are described. The neuroanatomy of memory is reviewed. Possible aetiologies of TGA in relation to cerebral angiography include ischaemia (embolic, arterial spasm), epilepsy that may be primary or tumour-related and direct toxic effects of contrast media. 36. Baron JC, Petit-Taboue MC, Le Doze F, et al. Right frontal cortex hypometabolism in transient global amnesia. A PET study Brain 1994; 117:545-52 A 60-year-old lady with previous hypertension was studied with PET in the acute (early recovery) phase of an otherwise typical episode of transient global amnesia (TGA). Follow-up over > 1 year was uneventful, and delayed CT scans and MRI showed no brain damage. No medical cause was disclosed despite extensive work-up. The PET study revealed a matched reduction in cerebral blood flow and oxygen consumption over the entire lateral frontal cortex on the right side, with an associated, less significant reduction in ipsilateral thalamic and lentiform nucleus metabolism, but sparing the hippocampal area. These changes, which had resolved at a repeat PET study 3 months later, suggest right prefrontal metabolic depression, possibly secondary to thalamic dysfunction, as the underlying mechanism for TGA in this case, consistent with the emerging involvement of the prefrontal cortex in strategies or control of memory traces retrieval. Thus, in analogy with permanent amnesia, TGA may be a core syndrome with several possible foci of dysfunction along the neuronal networks that subserve explicit memory. In the future, combined PET neuropsychological assessment in the acute stage of TGA may prove useful in defining distinct neuropsychological-topographical subtypes of this intriguing clinical entity. 37. Melo TP, Ferro JM, Paiva T Are brief or recurrent transient global amnesias of epileptic origin? J Neurol Neurosurg Psychiatry 1994; 57:622-5 To evaluate if short (less than one hour) or recurrent, or both, episodes of transient global amnesia (TGA) have an epileptic origin or carry a subsequent risk of epilepsy a group of patients with these types of TGA attacks was studied. The group was selected from a prospective series of 103 patients with TGA. Sixteen patients had an episode lasting less than one hour, 13 had more than one episode, and five patients had both short and recurrent attacks. For each patient the number of recurrences was small (four or less) and they were separated by months or years. During short attacks of TGA many subjects showed other typical features of TGA including repeated questioning (12 subjects) and performance of purposeful complex acts (eight subjects). Twelve short attacks were closely related to a characteristic precipitating event. During follow up only one patient had a seizure (partial motor). No other association between either short or repeated attacks of TGA and past history of epilepsy or paroxysmal discharges were seen on the EEG. Short or recurrent, or both, attacks of TGA are not epileptic and do not carry a relevant risk of subsequent seizures. 38. Hodges JR Semantic memory and frontal executive function during transient global amnesia J Neurol Neurosurg Psychiatry 1994; 57:605-8 To assess semantic memory and frontal executive function, two patients underwent neuropsychological testing during transient global amnesia (TGA) and after an interval of 6-8 weeks. In spite of a profound deficit in anterograde verbal and non-verbal memory, semantic memory was normal, as judged by category fluency measures, picture naming, and picture-word and picture-picture matching, and reading ability was normal. Similarly, there were no deficits on a number of tests known to be sensitive to frontal executive dysfunction. A hexamethylpropyleneamine-oxime (HMPAO) single photon emission CT (SPECT) scan, obtained on one patient 24 hours post-TGA, showed focal left temporal lobe hypoperfusion which had resolved three months later. The observed dissociation between episodic and semantic memory is discussed in the light of contemporary cognitive theories of memory organisation.