Transient Global Amnesia

1
Transient Global Amnesia

• Allan B. Wolfson, MD
• University of Pittsburgh
• Department of Emergency Medicine

2
Presentation of TGA

3
Clinical features

• Sudden onset
• Anterograde amnesia
• Repetitive questioning
• Retrograde amnesia
• (variable, often spotty)
• Normal alertness, behavior, cognition
• Non-focal neuro exam
• Resolution within 24 hrs

4
Reported triggers

• Emotional upset
• Sexual activity
• Vigorous exercise
• Valsalva

5
Differential Diagnosis

• Head injury
• Toxic / metabolic
• Vascular / TIA posterior circulation
• Non-convulsive seizure
• Post-ictal state
• Migraine
• Tumor
• Encephalitis
• AV fistula
• Functional

6
Epidemiology of TGA

• Age group
• usually over 50, but seen in kids too
• Family history ?2
• Incidence
• 5 - 30 per 100,000
• Recurrence
• 5 - 8 per year
• Apparent triggering factors
• in 33 - 50

7
TGA -- Criteria for Dx

• Witnessed onset
• Antegrade amnesia
• No clouding of consciousness or loss of personal
  identity
• No cognitive impairment
• No focal findings
• No epileptic features
• No recent head trauma, no sz within 2 yrs
• Resolution within 24 hrs

8
Anatomy of Memory

• What structures subsume memory?
• Medial temporal lobes (hippocampus)
• Thalamus
• Diencephalon
• Frontal / pre-frontal
• Deep cortical structures

9
Physiology of Memory

• Memory acquisition
• Memory storage or consolidation
• Memory retrieval
• 3-compartment model?
• immediate, recent, remote

10
Emergency Dept Evaluation

• History
• Neuro exam
• Basic labs?
• Head CT
• EEG
• MRI

11
Bedside evaluation of episodic memory

• Orientation?
• Remember 3 things for 3 minutes?
• Remember what happened yesterday?

12
Other types of memory to check on

• Semantic memory
• Procedural memory
• Biographical memory
• Topographic memory
• Meta-memory

13
Etiology of TGA?

• Vascular
• Seizure
• Migraine
• Venous hypertension
• (Valsalva, paradoxical embolism)

14
Etiology of TGA?

• Case-control studies show no association with
  stroke or TIA
• Sub-group with epilepsy excluded by definition
• Nonconvulsive status epilepticus?
• Association with migraine
• Reported precipitating factors

15
Differentiating features

• Repetitive questioning
• Complex acts and instructions
• Memory gap for the event
• Severity of retrograde amnesia
• Rapid onset
• Duration

16
Transient epileptic amnesia

• Short attacks, multiple attacks
• No repetitive questioning
• Anterograde amnesia may be only partial
• Altered behavior
• Alteration in consciousness
• Other features of epilepsy
• (eg, automatisms, other seizures, EEG,
• response to anticonvulsants)

17
Functional Amnesia

• Severe retrograde amnesia
• Absence of anterograde amnesia
• Duration often weeks or longer

18
Fancy Diagnostic Studies

• EEG
• CT scanning
• SPECT scanning, PET scanning
• MRI, DW-MRI, PW-MRI

19
SPECT scanning

• Some studies have shown decreased perfusion in
  medial temporal lobes, thalamus, or frontal
  lobes
• Usually returns to normal after attack
• Reflection of abnormality or cause?

20
Diffusion-weighted MRI

• Inconsistent findings
• Sometimes shows abnormalities
• (esp in left hippocampus)
• Sensitive for ischemia
• (decreased diffusibility of water)
• But also consistent with
• spreading depression
• (rapid resolution, unlike ischemia)

21
Diffusion-weighted MRI

• Sensitive for ischemia
• (decreased diffusibility of water)
• But also consistent with
• spreading depression
• (rapid resolution, unlike ischemia)

22
What is spreading depression?

• Wave of depolarization progressing across cortex
  at 3-5 mm/min
• Associated with aura of migraine

23
Diffusion-weighted MRIin TGA

• Inconsistent findings
• Sometimes shows abnormalities,
• especially in left hippocampus
• Bilateral or left-sided only
• Sometimes no changes
• May be time-dependent

24
Treatment

• None necessary
• Migraine therapy?

25
Prognosis

• Essentially benign
• Subclinical persistent memory deficits?
• Associated conditions?

26
Disposition from the ED

• Theoretically
• after amnesia resolves, can
• discharge with neurology follow-up
• and no immediate testing
• Actually
• admission, MRI, EEG

27
Unanswered questions

• Etiology? Spectrum of causes?
• True role of precipitating factors?
• Acute treatment?
• Physiology of memory?

28
QUESTIONS ???