From the Guidelines
The initial workup for a patient presenting with global amnesia should include a thorough neurological examination, cognitive assessment, and targeted diagnostic testing, prioritizing MRI over CT for brain imaging, as recommended by the most recent guidelines 1.
Key Components of the Workup
- A detailed history from both the patient and witnesses, focusing on onset, duration, and associated symptoms
- Vital signs and a complete neurological examination to assess for focal deficits
- Cognitive testing, including orientation, memory recall, and attention using tools like the Mini-Mental State Examination
- Laboratory tests:
- Complete blood count
- Comprehensive metabolic panel
- Thyroid function tests
- Vitamin B12 level
- Folate level
- Toxicology screening
Imaging and Further Testing
- Brain imaging with MRI is preferred over CT to detect subtle abnormalities like hippocampal changes in transient global amnesia or early signs of stroke 1
- An electroencephalogram (EEG) should be performed to rule out seizure activity, particularly nonconvulsive status epilepticus
- Lumbar puncture may be necessary if infection or autoimmune encephalitis is suspected, examining CSF for cell count, protein, glucose, and specialized antibody panels
Considerations
- The yield of neuroimaging studies in patients with altered mental status is low, but it is crucial in identifying patients with acute intracranial pathology 1
- The evaluating clinician’s judgement is essential in determining the clinical need and value of brain imaging in patients with global amnesia 1
- A comprehensive approach helps differentiate between transient global amnesia, stroke, seizures, toxic-metabolic disorders, and other neurological conditions that can present with memory loss.
From the Research
Initial Workup for Global Amnesia
The initial workup for a patient presenting with global amnesia involves a thorough evaluation to rule out other serious etiologies. Key considerations include:
- Eliminating toxic ingestions, acute strokes, complex partial seizures, and central nervous system infections as potential causes 2
- Conducting a neurologic examination to assess for repetitive questioning, preserved orientation, and absence of focal motor, speech, sensory, coordination, or cranial nerve deficits 3
- Reviewing the patient's medical history, including any history of migraine, as this may be a triggering factor for transient global amnesia (TGA) 4
Diagnostic Approach
The diagnosis of TGA is dependent on a characteristic collateral history and the absence of abnormal signs or symptoms. In cases with classic features, a minimalist approach may be reasonable, focusing on observation and patient safety rather than extensive testing or medical interventions 2. However, due clinical diligence is required in the investigation of these patients to rule out other potential causes of amnesia 3.
Imaging and Investigations
Imaging studies, such as diffusion-weighted imaging (DWI), may be useful in identifying small high-signal abnormalities in the hippocampus, which have been associated with TGA 5. However, the underlying pathophysiologic mechanism of TGA requires further investigation.
Clinical Presentation
TGA typically presents with an abrupt onset of severe anterograde amnesia, accompanied by repetitive questioning, and usually lasts for 1-8 hours, but should be less than 24 hours 6. Patients with TGA remain alert, attentive, and have intact cognition, but may be disoriented to time and place. The condition is usually benign, and no specific treatment is indicated for a typical episode 6.