Transient global amnesia: disease or syndrome?

Comprehensive Ultrasound Assessment of the Craniocervical Circulation in Transient Global Amnesia

OBJECTIVES

Structural changes and metabolic stress have been reported on diffusion-weighted magnetic resonance imaging in the cornu ammonis 1 area of the hippocampus in patients with transient global amnesia (TGA), but a consensus on pathogenesis is still lacking. The aim of our study was to perform a comprehensive ultrasound analysis of the cerebrovascular circulation in our population of patients with TGA.

METHODS

One hundred patients with TGA and 50 age- and sex-matched control participants underwent ultrasound examinations of the cervicocranial circulation.

RESULTS

The most significant risk factor for TGA was arterial hypertension (P < .01). There were no significant atherosclerotic lesions on the large arteries of the neck (mean internal carotid artery stenosis ± SD, 28.7% ± 11.7%) or on the large intracerebral arteries (good structural and hemodynamic status; P > .05). Rarely detected microembolic signals or a right-left cardiopulmonary shunt excluded an emboligenic mechanism of TGA (P > .05). The internal jugular vein valves were incompetent in 54% of patients with TGA, and this condition was associated with an increased risk of TGA (odds ratio, 4.16; 95% confidence interval, 1.91-9.04). The mean values of the breath holding index and pulsatility index, as parameters of small-vessel function, were within normal ranges and without differences between the TGA and control groups (P > .05).

CONCLUSIONS

Our ultrasound examination did not detect significant structural atherosclerotic changes of cervicocranial arteries, and an emboligenic mechanism was excluded. Only a significant rise of blood pressure in TGA and significant valvular insufficiency of the internal jugular vein were established. New research should clarify whether these simultaneous functional circulatory changes have relevance for metabolic stress in the cornu ammonis of the hippocampus.

Incompetence of internal jugular vein valve in patients with transient global amnesia

Background/Aim. Transient global amnesia (TGA) could be related to acute ischemic disturbances in mesial parts of temporal lobes, which are important for memory. Incompetence of internal jugular vein (IJV) valve with venous congestion causes venous microthrombosis of hippocampus. The aim of this study was to investigate the frequency of IJV valve incompetence, as well as other hemodynamic and structural properties of cerebral circulation in TGA patients. Methods. IJV valve competence was investigated in 40 TGA patients and 30 persons of the control group (matched by age and sex), as well as detection of microembolic signals and detection of right to left cardiopulmonal shunt, cerebral vasomotor reactivity and echocardiography by color triplex ultrasonography and transcranial doppler. Results. A significant difference in frequency of IJV valve incompetence was found between the TGA patients and the control persons (55% TGA vs 30% controls; p < 0.001). We did not find a significant structural (plaques frequency) or hemodynamic (flow velocity, pulsatility index) differences on arteries of the neck and cerebral arteries between the TGA patients and the controls, except for the increased pulsatility index on the basilar artery (40% TGA vs 16.6% controls; p < 0.01) and decreased vasomotor reactivity in TGA patients (50% TGA vs 26.6% controls; p < 0.001). Microembolic signals were detected very rarely (17.5% TGA patients vs 13.3% controls; p > 0.05), as well as right to left cardiopulmonal shunt (15% TGA vs 16.6% controls; p > 0.05), indicating that embolism was not important for pathogenesis of TGA. Transesophageal echocardiography confirmed it, because only one TGA patient had a potent foramen ovale. Conclusion. We found a significantly increased frequency of IJV incompetence in the TGA patients, which confirmed the role of vein drainage disturbances in pathogenesis of TGA.