Prevalence and clinical impact of white matter hyperintensities, cerebral microbleeds, and medial temporal lobe atrophy in transient global amnesia

Abstract

Background: Transient global amnesia (TGA) is a transitory, short-lasting neurological disorder characterized by a sudden onset of antero- and retrograde amnesia. The pathophysiology of TGA remains unclear. This study examined the prevalence and clinical impact of white matter hyperintensities (WMH), cerebral microbleeds (CMB) and medial temporal lobe atrophy (MTLA) in TGA patients vs. normal controls. Methods: We analysed the data for 13 patients with TGA and 11 age-matched cognitively normal controls recruited from Memory and Geriatric Medicine Clinics of the Department of Medicine, Queen Mary Hospital. Controls had no history of dementia, stroke, Parkinson’s disease, head injury, seizures, cancers within 5 years, end-stage organ failure, excessive alcohol or drug use, or psychiatric disease. 3T MRI brain images were retrospectively examined for the severity and location of WMH (Fazekas Score 0-3, >1 abnormal), CMB (Microbleed Anatomical Rating Scale 0-3, >0 abnormal) and MTLA (Scheltens Score 0-4, >1 abnormal). Results: Mean (± s.d.) ages were similar for TGA patients (63.8 ± 5.5 yrs) and controls (66.4 ± 1.7 yrs). Gender, statins use, and history of diabetes, hypertension, hyperlipidaemia, and ischaemic heart disease were similar. TGA patients were more likely to be smokers (p=.009). Controls were more likely to have atrial fibrillation (p=.04) and take anticoagulants (p=.04). In the TGA group, only 1 of 13 patients had a history of stroke or TIA. Comparing TGA vs. control groups, the prevalence of: a) abnormal periventricular WMH was 0% vs. 9% (p=.27); b) abnormal; subcortical WMH was 23% vs. 73% (p=.015); c) CMB was 15% vs. 64% (p=.15); and d) abnormal MTLA was 8% vs. 18% (p=.44). Severity grades of MRI abnormalities were significantly different between TGA and control groups for periventricular WMH (TGA worse, p<0.001), subcortical WMH (controls worse, p=.02), CMB (controls worse, p=.046), but not MTLA. Conclusion: Overall, TGA patients have a low prevalence of small vessel disease and medial temporal lobe atrophy on MRI, as compared to age-matched cognitively normal controls. Higher rates of AF and anticoagulants use may have accounted for more severe subcortical WMH and CMB amongst controls. Higher rate of grade 1 severity of periventricular WMH amongst TGA patients may possibly be a result of smoking exposure. Future prospective studies are warranted to examine the role of MRI abnormalities in understanding the pathophysiology of TGA.