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Transient Global AmnesiaMRI Case Series
Dr Lan Nguyen (Radiology Registrar)Dr Tarun Jain (Consultant Radiologist)
What is Transient Global Amnesia (TGA)?
Self-limiting antegrade amnesia› In absence of other causes
Clinical Symptoms
Witnessed Antegrade amnesia
› Unable to form new memories› Perserveration
“Broken record”› Sometimes also retrograde
No other cognitive impairment or altered consciousness› Otherwise, alert and well
Duration of episode resolves within 24hrs› 1-10 hrs, average 6hrs
No other neurological deficit/epileptic features/head trauma› Diagnoses of exclusion
Precipitating event
Pathophysiology
No concensus Theories include:
› Vascular dysfunction Arterial or Venous
› Paroxysmal neuronal discharge/Epileptic phenomena Self propagating wave of neuronal depolarisation
Treatment
Nothing › Self resolving
Role of Imaging
Exclude other causes› Diagnosis
treatment› Prognosis
Differentials
DDx Clinical Findings MRI findings
Transient epileptic amnesia
<1hr, multiple attacks at time of presentation
Increased T2/FLAIR in hippocampus, thalamus and cortex
TIA/CVA Amnesia in absence of other focal neurodeficits rare
DWI in vascular territories
Wernickes encephalopathy
More global amnesia and inattention
Symmetrical increased T2/FLAIR in mammillary bodies, medial thalami, tectal plate and periaqueductal area
tectal region (white arrows), periaqueductal area (black arrowheads), and mamillary bodies (white arrowheads
TGA Antegrade amnesia<24hrs
DWI punctate (1-3mm) foci in hippocampus, uni/bilateral
DDx
Transient epileptic amnesia
TIA/CVA
Wernickes encephalopathy
TGA
Hippocampus
Fn› Involved in learning & memory
Part of mesial temporal lobe› Below temporal horn of lateral ventricles› Seahorse› Made up of dentate gyrus, C1-4.
Hippocampus Continue
Blood supply: › PCA
hippocampal arteries› AChA
Branch of ICA
Cases
5 TGA cases presented to the Calvary Hospital› Between March 2013 to February 2015
All had MRI findings typical of TGA
Case 1 - WQ
61 yo male No significant PMHx
Acute confusion and amnesia› Repetitive questioning
Alert
Ix:› CTB: NAD› LP: NAD
Case 1 - MRI
Day 1 MRI 2 punctate DWI lesions in left hippocampus
Case 2 - NY
66yo male PMHx: T2 DM, hypertension and
hypercholesterolaemia Acute onset of amnesia and confusion
Alert Repetitive questioning
CTB: NAD
Case 2 - MRI
Day 1 MRI Punctate DWI lesion in left hippocampus
Case 3 - JT
62yo female PMHx: Meniere’s disease, migraine and hypertension Sudden onset of anterograde and retrograde amnesia Nausea and vomiting, worse than usual Meniere’s
Alert
CTB: NAD
Case 3 - MRI
Day 2 MRI 5mm DWI hyperintense focus in the left hippocampus
Case 4 - SZ
63yo female Sudden onset confusion and amnesia at work PMHx: NAD
Alert› No memory of days events
CTB: NAD
Case 4 - MRI
Day 2 MRI 4.5mm DWI hyperintense focus in the left
hippocampus
Case 5 - ED
64yo female PMHx: OA Amnesic events at the gym and whilst doing errands
Case 5 - MRI
Day 2 MRI 5mm DWI lesion in left hippocampus
Case 6 - MRI
Left hippocampal DWI lesion
Case 6 - MM
81yo female PMHx: AF, AV replacement Acute confusion and dysphasia
› Resolved next day
Acute left hippocampal infarction
Case 7 - MRI
Left hippocampal DWI focus
Case 7 - KC
78yo male PMHx: EtOH, COPD
Recurrent episodes of decreased levels of consciousness › Staring and not responding› Over last few months› Lasts 10mins
Followed by 2-3 hrs of fatigue
Complex partial seizures
Hippocampal DWI Lesions
Cases demonstrating DWI focus in hippocampus› BUT not TGA clinically
Hippocampal DWI Lesions ≠ TGA
Other Studies
Total 99 patients› 52 had DWI changes
45 in hippocampal region 25 left, 9 bilateral, 11 right
› Sedlaczek et al. 26 out of 31 had punctate hippocampal
DWI lesions
All 5 TGA cases showed hippocampal DWI lesion
Sand
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Limitations / Implications
Small case series Reflective of literature
Diagnosis to consider Review area
Clinical diagnosis
“Clinical correlation is recommended”
Acknowledgements
Dr Yash Gawarikar Dr Alexander Lam Dr Brett Jones Dr Yun Tae Hwang
Thanks!
Our Case Series
Consistent with other studies
MRI findings supports clinical diagnosis› Treatment and prognosis
100% MRI detection rate› Why?
Optimised protocol t = 24-72 hrs b = 2000 3mm thick slices
Imaging
Previously brain imaging normalNow…Improvements in MRI:
Small punctate (1-3mm) DWI hyperintense foci in lateral hippocampus (CA1 sector of hippocampus)
Often Unilateral and left sided› Selective vulnerability of this region to metabolic stressors
glutamate excitotoxicity and Ca2+ influx
MR-spectroscopy of hippocampal DWI lesion› Lactate peak further evidence for CA1 neuronal
dysfuction No abnormality in vessels on MRA Dy/dx with Wernicke encephalopathy DWI in medial thalami, mammillary bodies,
periaqueductal region, tectal plate
Frequency of detection 0-84%› Large range!› Likely related to timing of MRI from onset of symptoms› Sedlaczek (2004) - 6% detection rate when Mri done within 8 hrs of onset› Increased to 84% at 48hrs post onset
B values >1000› Weon (2008) – detection rate @ B= 1000 (3mm thickness) was 38%, @ B=2000 (3mm
thickness) was 54%. No difference between B=2000 and B=3000. As B value increases diffusion weighting increases increases detection Slice thickness <5mm
› Weon- detection rate within 24 hrs @5mm thickness – 13%, then increased to 38% at 3mm
Increase detection of small punctate lesions by decreasing partial volume averaging effects
Timing of MRI
Ahn – overall time to MRI was 6hrs . However, those with MRI changes is 9 hrs
16 out of 203 TGA over 7yrs with DWI hippocampal changes Bartsch – found that lesions localised to CA1 of
hippocampus in 29 TGA patients in 24-72 hrs Peak incidence at 12-72hrs DWI normalisation on Day 10 Similar to time course of ischaemic careful timing to find abnormalities Lesions resolve on F/U imaging in 1-6 months
MRI Imaging protocol in TGA
3T magnet Acquisition between 24 to 72 hours 3mm DWI slice thickness
Detection increased 88% when scan performed 2-3 days post event, DWI with resolution B=2000, slice thickness 2-3mm.