Imaging for Short-Term Memory Loss
MRI of the brain without contrast is the preferred initial imaging study for evaluating short-term memory loss, with CT head without contrast as an acceptable alternative when MRI is unavailable or contraindicated. 1, 2
Primary Imaging Recommendation
MRI brain without IV contrast should be obtained first because it has superior sensitivity for detecting:
- Vascular lesions and microhemorrhages 1, 2
- Hippocampal atrophy patterns 1, 2
- Rare conditions causing memory impairment 1, 3
- Treatable structural abnormalities including tumors, subdural hematomas, and normal pressure hydrocephalus 2, 3
Specific MRI Sequences to Request
When ordering MRI, the following sequences should be included 1, 4:
- 3D T1 volumetric sequence with coronal reformations for hippocampal volume assessment
- FLAIR (Fluid-Attenuated Inversion Recovery) for white matter lesions
- T2-weighted imaging or susceptibility-weighted imaging (SWI) if available
- Diffusion-weighted imaging (DWI) to detect acute pathology
CT as Alternative
CT head without contrast is acceptable when MRI cannot be performed (contraindications, unavailability, or patient intolerance), though it is less sensitive 1, 2. If CT is used, coronal reformations should be requested to better assess hippocampal atrophy 1.
When Imaging is Particularly Important
Neuroimaging should be prioritized when 3, 4:
- Cognitive symptoms began within the past 2 years
- Recent significant head trauma occurred
- Unexplained neurological signs are present (new severe headache, seizures, gait disturbances)
- History of cancer exists, particularly with risk for brain metastases
- Risk factors for intracranial bleeding are present
- Symptoms suggest normal pressure hydrocephalus
- Significant vascular risk factors exist
Advanced Imaging Considerations
FDG-PET/CT or amyloid PET/CT should be reserved for cases where the diagnosis remains unclear after initial structural imaging and specialist evaluation 1. These studies:
- Should be ordered by dementia specialists or cognitive disorders experts 1
- Are complementary modalities with greater accuracy when used together 1
- Help differentiate between dementia subtypes when structural imaging is inconclusive 1
SPECT perfusion imaging is an alternative if FDG-PET is unavailable 1, though PET is preferred when accessible.
Important Clinical Caveats
- Advanced MRI sequences (MR spectroscopy, functional MRI, diffusion tensor imaging) are not recommended for routine clinical use 1, 3
- IV contrast is not necessary for initial memory loss evaluation in most cases 1, 2
- Semi-quantitative scales should be used when interpreting images, including the medial temporal lobe atrophy (MTA) scale, Fazekas scale for white matter changes, and global cortical atrophy (GCA) scale 1, 3
- Most patients over age 80 have mixed pathology, making imaging findings supportive but not definitive for specific diagnoses 2