CASE 10837 Published on 09.04.2013

A 74-year-old-woman with two attacks of transient global amnesia

Section

Neuroradiology

Case Type

Clinical Cases

Authors

García Ortega A, Ortega Hernández C, López Farfán A, Vázquez Sáez V, Palazón Cabanes B.

University Hospital Virgen de la Arrixaca,
Murcia, Spain;
Email:caoh27@hotmail.com
Patient

74 years, female

Categories
Area of Interest Neuroradiology brain ; Imaging Technique MR-Diffusion/Perfusion, MR
Clinical History
A 74-year-old woman was in a hairdresser's shop when she had an acute-onset memory loss. She was disoriented to place and asked repeatedly where she was and why she was there. She recovered perfectly after a few minutes. She had experienced a similar episode one year before.
Imaging Findings
Cerebral computed tomography was normal.
A brain 1.5-T MRI was performed after 24 hours of the episode, including conventional magnetic resonance sequences: axial and coronal T1WI, axial and coronal T2WI, axial FLAIR, axial T2*WI, along with DWI.
Axial FLAIR image (A) does not demonstrate any abnormality.
Corresponding axial DWI b=1000 and 3000 (B) and ADC map (C) images demonstrate punctate lesion of restricted diffusion involving the left medial temporal lobe.
Discussion
TGA is defined as a temporary episode of short-term memory loss without other neurological impairment.
Epidemiology: The majority of patients are between the age of 50–80 years, with an average age of approximately 60–65 years [1].
The aetiology and pathogenesis of TGA are uncertain, though several different causes are suggested, such as ischaemia, migraine, epileptic seizure, venous congestion, and psychological disturbances [2]. Recent data suggest that the vulnerability of CA1 neurons to metabolic stress plays a pivotal part in the pathophysiological cascade, leading to an impairment of hippocampal function during TGA [3, 4].
The diagnosis of TGA is clinical (Caplan and Hodges criteria) supported by MRI. The seven diagnostic criteria for TGA are: 1.Presence of anterograde amnesia. 2. Witnessed account of an observer. 3. No clouding of consciousness or loss of personal identity. 4. Only amnesia and no other cognitive impairment. 5. No focal neurological or epileptic symptoms. 6. No recent history of head trauma or seizures. 7. Resolution of symptoms within 24 h [5].

IMAGING PERPSPECTIVE
DWI shows the presence of focal hyperintensities involving the hippocampus in TGA [6]. The lesions detected by DWI are small and punctate (1–3 mm) and located within the lateral portion of the hippocampus, belonging to CA1 subfield, which is known to be susceptible to ischaemia [7].
Regarding the small size of TGA lesions, DWI sequence performed with 3mm thickness and with higher b-values (b=2000 or 3000) may increase detection [8, 9].
The timing of MRI may impact the likelihood of demonstrating these lesions; they are less common in the hyperacute phase and become more prevalent after 12 hours, with a peak incidence between 12 and 72 hours. If no lesion is detected on initial DWI, especially if performed within several hours of symptom onset, follow-up DWI after several days is recommended [8].
Dx: transient epileptic amnesia, transient ischaemia attack, acute confusional state, complex partial seizure, psychogenic amnesia.
Rx: Treatment is generally not required, and the condition usually does not recur and the patients do not have an increased risk of mortality, epilepsy, or stroke following TGA [10, 11].
Differential Diagnosis List
Transient global amnesia
Transient epileptic amnesia
Transient ischaemia attack
Acute confusional state
Complex partial seizure
Psychogenic amnesia
Final Diagnosis
Transient global amnesia
Case information
URL: https://www.eurorad.org/case/10837
DOI: 10.1594/EURORAD/CASE.10837
ISSN: 1563-4086