self-limiting antegrade amnesia › in absence of other causes
TRANSCRIPT
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Transient Global AmnesiaMRI Case Series
Dr Lan Nguyen (Radiology Registrar)Dr Tarun Jain (Consultant Radiologist)
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What is Transient Global Amnesia (TGA)?
Self-limiting antegrade amnesia› In absence of other causes
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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
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Pathophysiology
No concensus Theories include:
› Vascular dysfunction Arterial or Venous
› Paroxysmal neuronal discharge/Epileptic phenomena Self propagating wave of neuronal depolarisation
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Treatment
Nothing › Self resolving
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Role of Imaging
Exclude other causes› Diagnosis
treatment› Prognosis
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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
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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.
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Hippocampus Continue
Blood supply: › PCA
hippocampal arteries› AChA
Branch of ICA
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Cases
5 TGA cases presented to the Calvary Hospital› Between March 2013 to February 2015
All had MRI findings typical of TGA
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Case 1 - WQ
61 yo male No significant PMHx
Acute confusion and amnesia› Repetitive questioning
Alert
Ix:› CTB: NAD› LP: NAD
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Case 1 - MRI
Day 1 MRI 2 punctate DWI lesions in left hippocampus
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Case 2 - NY
66yo male PMHx: T2 DM, hypertension and
hypercholesterolaemia Acute onset of amnesia and confusion
Alert Repetitive questioning
CTB: NAD
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Case 2 - MRI
Day 1 MRI Punctate DWI lesion in left hippocampus
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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
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Case 3 - MRI
Day 2 MRI 5mm DWI hyperintense focus in the left hippocampus
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Case 4 - SZ
63yo female Sudden onset confusion and amnesia at work PMHx: NAD
Alert› No memory of days events
CTB: NAD
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Case 4 - MRI
Day 2 MRI 4.5mm DWI hyperintense focus in the left
hippocampus
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Case 5 - ED
64yo female PMHx: OA Amnesic events at the gym and whilst doing errands
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Case 5 - MRI
Day 2 MRI 5mm DWI lesion in left hippocampus
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Case 6 - MRI
Left hippocampal DWI lesion
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Case 6 - MM
81yo female PMHx: AF, AV replacement Acute confusion and dysphasia
› Resolved next day
Acute left hippocampal infarction
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Case 7 - MRI
Left hippocampal DWI focus
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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
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Hippocampal DWI Lesions
Cases demonstrating DWI focus in hippocampus› BUT not TGA clinically
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Hippocampal DWI Lesions ≠ TGA
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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
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Limitations / Implications
Small case series Reflective of literature
Diagnosis to consider Review area
Clinical diagnosis
“Clinical correlation is recommended”
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Acknowledgements
Dr Yash Gawarikar Dr Alexander Lam Dr Brett Jones Dr Yun Tae Hwang
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Thanks!
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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
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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
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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
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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
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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
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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.