Aims:
To describe the frequency and characteristics of acute ischemic strokes (AIS) and transient ischemic attacks (TIAs) presenting predominantly with amnesia, and to identify clinical clues for differentiating them from similar conditions like transient global amnesia (TGA).
Methods:
Over a 12.5 year period, we retrospectively identified in our stroke center patients with DWI-MRI-confirmed AIS and TIAs whose main presenting symptom was acute antero- and retrograde amnesia. We excluded patients with important focal or cognitive symptoms, absence of significant amnesia or absence of a witness (for patients with self-reported transient amnesia).
Results:
After exclusion of 6 amnestic DWI-positive stroke patients not fulfilling all inclusion criteria, we identified 10 amnestic strokes and TIAs, representing 0.2% of all patients admitted during the observation period. Half of the events could not be distinguished clinically from TGA (no “red flags”). When compared with 3’250 AIS from our registry (ASTRAL), the initial stroke diagnosis was significantly more often uncertain in amnestic patients (80% vs. 2.4%), involved more frequently the posterior circulation (90% vs. 27.2%) and/or multiple territories (40% vs. 1.4%, all p< 0.01 in univariate analysis). Most events were cardioembolic (n=5), and affected at least one structure in the limbic system (n=9). Acute CT was negative in all patients where it was performed. Clinical clues for an ischemic origin of the amnestic syndrome were higher age (median 70 years vs. 60 for TGA in the literature), minor focal neurological signs (n=3), circumstances such as interruption of antithrombotic treatment (n=3) and multiple cerebrovascular risk factors (n=5); 5 patients had none of these clues. Three months after the event, all patients were living independently at home despite persistent memory deficits in 3, and none had stroke recurrence.
Conclusion:
Predominant amnesia as the main symptom of acute ischemic cerebral events is rare, often transient, and is easily be missed or mistaken as TGA. Although associated mild localizing signs and circumstances increase the likelihood of an ischemic amnestic event, the threshold for performing direct DWI imaging in patients with acute transient amnesia should be low.
