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 brain over CT to detect subtle abnormalities, as recommended by the most recent guidelines 1. The workup should begin with a detailed history from both the patient and witnesses to establish the onset, duration, and characteristics of memory loss. Vital signs and a complete physical examination are essential to rule out medical emergencies. Laboratory tests should include:
- Complete blood count
- Comprehensive metabolic panel
- Thyroid function tests
- Vitamin B12 level
- Folate level
- Toxicology screening Neuroimaging is crucial, with MRI brain being preferred over CT to detect subtle abnormalities like hippocampal changes seen in transient global amnesia or small strokes, as suggested by the American College of Radiology 1. An electroencephalogram (EEG) should be performed to rule out seizure activity, particularly nonconvulsive status epilepticus. Lumbar puncture may be necessary if infectious or inflammatory causes are suspected, examining CSF for cell count, protein, glucose, and potential pathogens. Formal neuropsychological testing can help characterize the memory deficit pattern. This comprehensive approach is necessary because global amnesia can result from various etiologies including transient global amnesia (typically self-limiting within 24 hours), stroke, seizures, head trauma, drug toxicity, or early neurodegenerative disease, each requiring different management strategies, as outlined in the ACR Appropriateness Criteria 1.
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.