Transient Global Amnesia

Allan B. Wolfson, MD

University of Pittsburgh

Department of Emergency Medicine

Allan Wolfson, MD

Presentation of TGA

Allan Wolfson, MD

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

Allan Wolfson, MD

Reported triggers

• Emotional upset

• Sexual activity

• Vigorous exercise

• Valsalva

Allan Wolfson, MD

Differential Diagnosis

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

Allan Wolfson, MD

Epidemiology of TGA

Age group usually over 50, but seen in kids tooFamily history ?2%Incidence 5 - 30 per 100,000Recurrence 5 - 8% per yearApparent triggering factors in 33 - 50%

Allan Wolfson, MD

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

Allan Wolfson, MD

Anatomy of Memory

What structures subsume memory?

• Medial temporal lobes (hippocampus)• Thalamus• “Diencephalon”• Frontal / pre-frontal• “Deep cortical structures”

Allan Wolfson, MD

Physiology of Memory

• Memory acquisition

• Memory storage or consolidation

• Memory retrieval

• 3-compartment model?

immediate, recent, remote

Allan Wolfson, MD

Emergency Dept Evaluation

• History

• Neuro exam

• “Basic labs”?

• Head CT

• EEG

• MRI

Allan Wolfson, MD

Bedside evaluation of episodic memory

• Orientation?

• Remember 3 things for 3 minutes?

• Remember what happened yesterday?

Allan Wolfson, MD

Other types of memory to check on

• Semantic memory

• Procedural memory

• Biographical memory

• Topographic memory

• Meta-memory

Allan Wolfson, MD

Etiology of TGA?

• Vascular

• Seizure

• Migraine

• Venous hypertension

(Valsalva, paradoxical embolism)

Allan Wolfson, MD

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

Allan Wolfson, MD

Differentiating features

• Repetitive questioning

• Complex acts and instructions

• Memory gap for the event

• Severity of retrograde amnesia

• Rapid onset

• Duration

Allan Wolfson, MD

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)

Allan Wolfson, MD

Functional Amnesia

• Severe retrograde amnesia

• Absence of anterograde amnesia

• Duration often weeks or longer

Allan Wolfson, MD

Fancy Diagnostic Studies

• EEG

• CT scanning

• SPECT scanning, PET scanning

• MRI, DW-MRI, PW-MRI

Allan Wolfson, MD

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?

Allan Wolfson, MD

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)

Allan Wolfson, MD

Diffusion-weighted MRI

• Sensitive for ischemia

(decreased diffusibility of water)

• But also consistent with

“spreading depression”

(rapid resolution, unlike ischemia)

Allan Wolfson, MD

What is “spreading depression”?

• Wave of depolarization progressing across cortex at 3-5 mm/min

• Associated with aura of migraine

Allan Wolfson, MD

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

Allan Wolfson, MD

Treatment

• None necessary

• Migraine therapy?

Allan Wolfson, MD

Prognosis

• Essentially benign

• Subclinical persistent memory deficits?

• Associated conditions?

Allan Wolfson, MD

Disposition from the ED

• Theoretically:

after amnesia resolves, can

discharge with neurology follow-up

and no immediate testing

• Actually:

admission, MRI, EEG

Allan Wolfson, MD

Unanswered questions

• Etiology? Spectrum of causes?

• True role of precipitating factors?

• Acute treatment?

• Physiology of memory?

Allan Wolfson, MD

QUESTIONS ???