[Transient global amnesia: A descriptive study of 12 Polynesian patients]. / Ictus amnésique: étude descriptive de 12 patients polynésiens.

INTRODUCTION: According to the criteria of Hodges and Warlow, transient global amnesia is defined by sudden onset of isolated anterograde amnesia of spontaneous resolution within one to twenty-four hours. Its pathophysiological mechanisms are still uncertain. METHODS: In a retrospective study, we have analyzed epidemiological, clinical and MRI data from twelve patients admitted to the only neurological department of French Polynesia for transient global amnesia corresponding to the criteria of Hodges and Warlow between January 2010 and December 2013. RESULTS: The median age of the cohort was 61.5 (53-72), the sex ratio was 1. Ten patients had one or more cardiovascular risk factors, 3 had migraine headaches and 3 had anxiodepressive disorders. Among triggers found, the occurrence during the rest was noted in one case. Retrograde amnesia was observed in 42% of cases, repetitive questioning in 75% of cases, anxious bewilderment in 67% of cases and disorientation in 33% of cases. The median episode duration was 9 hours and the duration of hospitalization was 3 days. Three patients had a recurrence. MRI was abnormal in all patients and showed diffusion-weighted hyperintensities in right (n=8), left (n=3) and bilateral (n=1) hippocampi. CONCLUSION: Epidemiological, clinical and MRI data from our cohort are similar to those from the literature except for the highest prevalence of cardiovascular risk factors and the most frequent right hippocampus involvement. Transient global amnesia occurring exceptionally while sleeping was also observed in one of our patients.

A Tc-99m SPECT study of regional cerebral blood flow in patients with transient global amnesia.

OBJECTIVES: This study aimed to determine whether regional cerebral blood flow (rCBF) is abnormal in patients who have Transient Global Amnesia (TGA). METHODS: We obtained noninvasive rCBF measurements using Tc-99m-ethyl cysteinate diamer Single Photon Emission Computed Tomography (SPECT) in 7 patients diagnosed with TGA within 4 days of onset of the amnestic episode while the patients were still symptomatic and in 17 age-matched healthy control subjects. We assessed memory functioning using the Hopkins's Verbal Learning Test (HVLT) and Statistical Parametric Mapping to compare rCBF across diagnostic groups. RESULTS: The patients with TGA were significantly impaired in their performance on the 20-minute delayed recall of the HVLT. They also exhibited significantly decreased rCBF on their SPECT scans in the inferior and middle frontal gyrus bilaterally, with more prominent left-sided reductions in the superior temporal, precentral, and postcentral gyri, as well as increased rCBF primarily in the right hemisphere within the middle temporal, superior temporal, and inferior frontal gyri, cerebellum, and thalamus, compared with the normal control group. CONCLUSION: These findings suggest that lateralized abnormalities in brain functioning are an important component of the pathophysiology of TGA. Lateralized abnormalities may disrupt functions that are relatively specific to the left hemisphere, including receptive language, symbolic representation, and the processing of local features in the environment, while preserving anterograde memory processes. Increased flow to the right hemisphere centered on regions that subserve the functions of expressive language and visuospatial processing, and may represent processes that compensate for flow reductions to the left hemisphere.

Transient global amnesia after general anesthesia.

Transient global amnesia (TGA) is an amnestic syndrome, clinically dramatic but benign in nature. The hallmark of TGA is brief inability to form new memories and recall past memories despite otherwise normal neurological function. In a significant number of patients with TGA a stressful precipitating factor can be identified. We report two cases of TGA after uneventful general anesthesia. Anesthesia per se does not appear to be a direct trigger of TGA, as our first patient had a second anesthetic the next day without recurrence of TGA. Because the presentation of TGA can be dramatic and may mimic an acute cerebral ischemic event, a thorough neurologic evaluation should be pursued.

Transient amnesia triggered by acute marijuana intoxication.

We report an unusual case of sudden isolated transient amnesia triggered by acute marijuana use. The memory disorder, apart from the long duration, had the characteristics of a transient global amnesia-like episode. Acute marijuana intoxication can affect memory more globally and severely than previously reported.