Dean Sherzai, MD, MAS

Ayesha Z. Sherzai, MD

DESCRIPTION

• Sudden onset of an anterograde and retrograde amnesia that lasts up to 24 hours
• Mild subclinical neuropsychological deficits with concomitant vegetative symptoms can last for days after the episode

EPIDEMIOLOGY

Incidence

• about 3–8/100,000 annually
• 75% between 50 and 70 years
• Rare in patients younger than 40 years
• No clear sex differences
• 6–10% annual recurrence

RISK FACTORS

• Age >50 years
• History of migraines
• Events involving a stress response
• Sudden immersion in cold or hot water
• Physical exertion
• Emotional or psychological stress
• Acute pain
• Medical procedures
• Sexual intercourse
• Valsalva-associated maneuvers

Genetics

• No genetic factors determined

PATHOPHYSIOLOGY

• Exact mechanism is not well known
  • Migraine-related mechanisms, focal ischemia, venous flow abnormalities, and epileptic phenomena have been implicated
  • Temporal lobe structures involved, especially the hippocampus
  • Hyperintense MRI lesions can be detected in the hippocampal formation

ETIOLOGY

• No cause has been found. There is speculation around cerebral ischemia, seizures, and migraines, yet these patients are not at increased risk for strokes, transient ischemic attacks, or seizures.

COMMONLY ASSOCIATED CONDITIONS

• Events involving a stress response
• Psychological or emotional disorders

HISTORY

• Abrupt onset of memory loss, lasting for hours, inability to learn new material
• Diagnostic criteria
  • Presence of an anterograde amnesia that is witnessed by an observer
  • No clouding of consciousness or loss of personal identity
  • Cognitive impairment limited to amnesia
  • No focal neurological or epileptic signs
  • No recent history of head trauma or seizures
  • Resolution of symptoms within 24 hours
  • Mild vegetative symptoms (headache, nausea, dizziness) during the acute phase
  • Patients repeatedly ask ‘Where am I?’, ‘How did I get here?’ during the amnestic event

PHYSICAL EXAM

• Normal physical exam
• No focal neurological signs
  • Cognitive impairment limited to amnesia, predominantly anterograde; repetition of questions or tasks, sometimes confabulation
  • Intact remote memory, including personal identity

DIAGNOSTIC TESTS AND INTERPRETATION

Lab

Initial Lab Tests

• CBC and metabolic panel, drug screen, infectious work-up
• There are no specific laboratory studies for transient global amnesia (TGA)

Follow-Up & Special Considerations

• Neurological consultation

Imaging

Initial Approach

• CT head scan to rule out stroke and head trauma
• Diffusion-weighted MRI of the brain

Diagnostic Procedures/Other

• EEG to rule out transient epileptic amnesia
• Urine drug screen and toxicology panel
• If patient is on medication, consider checking levels, rule out overdose

Pathological Findings

• Diffusion-weighted MRI of the brain, preferably 3T, may show abnormalities in the hippocampus within 24–72 hours

DIFFERENTIAL DIAGNOSIS

• Hypoglycemia
• Ischemia in the posterior cerebral circulation
• Adverse drug side-effects, intoxication
• Complex partial seizures, transient epileptic amnesia, postictal conditions
• Post-traumatic amnesia
• Psychogenic amnesia, dissociative disorders
• Alcoholic “blackouts”
• Thiamine deficiency (Wernicke–Korsakoff syndrome)
• Encephalitis, especially herpes simplex encephalitis

MEDICATION

First Line

• Treatment of reversible conditions, such as metabolic disturbances and toxicity if suspected.

Second Line

• Based on primary etiological factor

ADDITIONAL TREATMENT

General Measures

• Patient and family reassurance
• Frequent patient re-orientation

Issues for Referral

• Neurology
• Psychiatry

SURGERY/OTHER PROCEDURES

• No surgery or instrumentation indicated

IN-PATIENT CONSIDERATIONS

Initial Stabilization

• Avoidance of activities that may increase breathing effort and intrathoracic pressure

Admission Criteria

• Rule out stroke or seizure

Discharge Criteria

• Stabilization of vital signs, reversal of cognitive deficits and constitutional symptoms, enough to be sent home safely without undue anxiety

FOLLOW-UP RECOMMENDATIONS

• Neurology

Patient Monitoring

• Avoidance of stress factors if any

DIET

• No restrictions

PATIENT EDUCATION

• Knowledge of basic health education and risk factor management
• TGA is not indicative of cerebrovascular disease

PROGNOSIS

• Recurrence rate up to 6–10% annually
• Gradual abatement of constitutional symptoms

COMPLICATIONS

• None

• Bartsch T, Deuschl G. Transient global amnesia: functional anatomy and clinical implications. Lancet Neurology 2010;9(2):205–214.
• Caplan L. Transient global amnesia. In: Vinken PJ, Bruyn GW, Klawans HL, eds. Handbook of clinical neurology. Amsterdam: Elsevier, 1985:205–218.
• Hodges JR, Warlow CP. Syndromes of transient amnesia: towards a classification. A study of 153 cases. J Neurol Neurosurg Psychiatry 1990;53:834–843.
• Lewis SL. Aetiology of transient global amnesia. Lancet 1998;352:397–399.
• Sander K, Sander D. New insights into transient global amnesia: recent imaging and clinical findings. Lancet Neurol 2005;4:437–444.
• Weon YC, Kim JH, Lee JS, Kim SY. Optimal diffusion-weighted imaging protocol for lesion detection in transient global amnesia. AJNR Am J Neuroradiol 2008;29:1324–1328.

ICD9

437.7 Transient global amnesia

• Normal physical exam
• Cognitive impairment limited to amnesia only
• Diffusion-weighted MRI within 24–72 hours of onset may show restriction in the hippocampus