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

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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.