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Re: Reply to Lewis

We read with interest the comments of Dr. Lewis regarding our recently published report. [1] In contrast to our hypothesis of an ischemic etiology for the TGA-like symptoms in our patients, he suggests that increased venous return to an acutely compressed superior vena cava, causing transient retrograde high-pressured venous flow to bilateral hippocampal or diencephalic structures, is a plausible explanation.

Bonnet et al [3] discuss a stress-induced etiology of the typical paroxysmal memory loss caused by the pain of acute aortic dissection. Ever since its first description, the central enigma of TGA has been its etiology. Although recent diffusion-weighted imaging findings in TGA could be compatible, we do not agree with Lewis' hypothesis for the etiology of TGA in our cases. [4, 5] Compared to “pure” transient global amnesia, our patients showed additional but reversible symptoms including mild left sided motor deficit, slight anisocoria and mild facial paresis. These make an arterial-embolic etiology more likely than hippocampal venous ischemia.

Our first described patient as well as another young woman with Marfan syndrome also presenting with “TGA-plus syndrome” had painless aortic dissection and no anamnestic hints of an initial Valsalva maneuver. The simultaneous occurrence of a dissecting/non-dissecting aneurysm of the aortic arch and superior vena cava obstruction was observed several times but could not be proved by CT. There was only slight widening of the ascending aorta.

In addition to the peculiar trigger of TGA in our patients, our aim was to draw attention to the diagnostic quandary of the simultaneous occurrence of TGA and aortic dissection. The presence of the conspicuous minor neurological deficits in addition to “pure” transient global amnesia was the reason for more diagnostic efforts. We have learned that transient global amnesia may extinguish important details of a patient's recent history and may mask a life-threatening disease.

References

1 Gaul C, Dietrich W, Tomandl B, Neundorfer B, Erbguth FJ. Aortic dissection presenting with transient global amnesia-like symptoms. Neurology 2004; 63:2442-2443

3. Bonnet P, Niclot P, Chaussin F, Placide M, Debray MP, Fichelle A. A puzzling case of transient global amnesia. Lancet 2004; 364:554.

4. Lewis SL. Aetiology of transient global amneseia. Lancet 1998;352: 397- 399

Send Correspondence to journal:
Re: Aortic dissection presenting with transient global amnesia-like symptoms

I read with interest the report by Gaul et al [1] of two patients with acute amnesic events consistent with transient global amnesia (TGA) occurring in the setting of acute Stanford Type A ascending aortic dissections. The authors favored an ischemic etiology for the TGA in their patients, evidenced by subtle focal motor findings during the events, and the possibility of emboli to the posterior circulation from the aortic vascular lesion.

There have been two other reports of TGA with acute ascending aortic aneurysm rupture. Rosenberg [2] reported a 55-year-old man who developed symptoms of TGA in the setting of an acute ascending aortic dissection. More recently, Bonnet et al[3] described a 47-year-old man who presented with TGA occurring immediately after the onset of an ascending aortic dissection; the authors of this report suggested that the TGA was simply triggered due to the severe pain at the onset of dissection. Both Rosenberg’s and Bonnet’s patients developed TGA at the onset of the acute painful event, heralded by transient pallor and faintness; there were no other neurologic signs described.

I suggest that the onset of TGA in patients with acute ascending aortic dissection is compatible with the venous ischemic hypothesis for TGA that I proposed in 1998. [4] This hypothesis was developed because of two observations regarding the common TGA triggers (e.g. severe pain, emotional stress, sexual intercourse, and physical exertion): 1) these triggers would be expected to cause increases in venous return toward the superior vena cava (SVC); and 2) common TGA triggers would likely cause a concomitant Valsalva maneuver transiently blocking SVC drainage into the right heart. The hypothesis simply states that increased venous return toward a blocked SVC could cause transient retrograde venous congestion and venous ischemia to bilateral hippocampal or diencephalic structures, resulting in TGA. Recent diffusion-weighted imaging findings in TGA remain compatible with this hypothesis. [5]

Due to its location and thin walls, the SVC is particularly vulnerable to compression from an ascending aortic aneurysm; aneurysms of the aortic arch are well-recognized causes of superior vena cava obstruction. In cases of TGA occurring in the setting of acute painful ascending aortic dissection, I suggest that increased venous return to an acutely compressed SVC, causing transient retrograde high- pressured venous flow to bilateral hippocampal or diencephalic structures, is a plausible explanation.

References

1. Gaul C, Dietrich W, Tomandl B, Neundorfer B, Erbguth FJ. Aortic dissection presenting with transient global amnesia-like symptoms. Neurology 2004;63:2442-2443.

2. Rosenberg GA, Transient global amnesia with a dissecting aortic aneurysm. Arch Neurol 1979;36:255.

3. Bonnet P, Niclot P, Chaussin F, Placide M, Debray MP, Fichelle A. A puzzling case of transient global amnesia. Lancet 2004;364:554.

4. Lewis SL. Aetiology of transient global amnesia. Lancet 1998;352:397-399.