Here we go again!

Dr Michele Romoli and Dr Linxin Li

A gentleman in his sixties, who is an ex-smoker and overweight but with no other known cardiovascular risk factors is referred to your TIA clinic.

Two days ago, waking up from a nap in the afternoon, he was found by his wife being disoriented, in a state of confusion, repetitively questioning about the date, the time, and what his job was. Symptoms gradually resolved over the following 90 minutes, and no speech or motor impairment was noted by the wife. The patient himself was unable to recall the conversations happened during the event but did remember having some memory problems. Neurological examination in clinic was normal. MRI brain was unremarkable.

What are your differentials?

Transient amnestic syndromes are a challenging scenario for physicians¹. Transient global amnesia (TGA), transient epileptic amnesia (TEA) and transient ischemic attack (TIA) are all differentials to be taken into account.

TGA is a clinical syndrome characterized by an anterograde memory deficit lasting <24h². Brain MRI can highlight tiny isolated DWI lesion in the hippocampus¹. TEA is characterized by recurring episodes of brief anterograde memory deficit, usually < 1h, often with wake-up onset and incomplete memory deficit (the patient can describe the feeling of “remembering of not being able to remember”)^1,3. TIA, although rare, can also manifest as isolated anterograde memory loss and acute ischaemic lesions can be detected in the thalami and parietal cortex⁴. In the case we just saw, the wake-up onset and patchy recollection of memory disturbance might be more suggestive of TEA but the duration is not typical.

Subsequently the patient underwent both baseline and sleep-deprivation EEG, which was, however, unremarkable. He was diagnosed with possible TGA and was not treated.

All happy now?

Unfortunately, in the following 12 months, he presented with 3 more episodes similar to the first one, all occurred while awake and after being exposed to high stress due to family-related issues, all were brief in duration (from 30 to 90 minutes), and were associated with a partial recollection of memory disturbance. In all cases the patient repetitively asked his wife what his job was. After the third episode, he underwent a further EEG, which was completely normal. He was also found to be hypertensive and started blood pressure treatment. After better control of blood pressure and resolving family-related issues, he had no further episodes, and he is cognitively normal.

Take home message:

TEA is not the sole anterograde memory deficit that recurs over time. TGA can indeed recur in up to 30% of patients, and, though variable in its clinical features, can present with memory deficit also at wake-up, and ranging from few minutes to several hours¹. Thus, when facing recurrent events, TGA should still be taken into account, and cardiovascular risk factors should be correctly managed to avoid further recurrences.

 References

1. Bartsch T, Butler C. Transient amnesic syndromes. Nat Rev Neurol. 2013;9:86–97.
2. Hodges JR, Warlow CP. Syndromes of transient amnesia: Towards a classification. A study of 153 cases. J Neurol Neurosurg Psychiatry.1990;53:834–43.
3. Savage SA, Butler CR, Hodges JR, et al. Transient Epileptic Amnesia over twenty years: Long-term follow-up of a case series with three detailed reports.Seizure. 2016;43:48–55.
4. Michel P, Beaud V, Eskandari A, et al. Ischemic Amnesia: Causes and Outcome. Stroke. 2017;48:2270–3.