From the Guidelines
A nonenhancing T2 signal abnormality in the left frontal lobe, suggestive of gliosis due to chronic ischemia or atypical demyelination, is most likely caused by chronic ischemia or demyelination.
Possible Causes
- Chronic Ischemia: Chronic ischemia can lead to gliosis, a condition characterized by the proliferation of glial cells, which can cause T2 signal abnormalities on MRI scans 1.
- Atypical Demyelination: Atypical demyelination, such as that seen in multiple sclerosis, can also cause T2 signal abnormalities, particularly in the absence of gadolinium enhancement 1.
Diagnostic Considerations
- MRI Sequences: The use of specialized MRI sequences, such as double inversion recovery (DIR) or phase-sensitive inversion recovery (PSIR), can help improve the detection of cortical lesions and differentiate them from other conditions 1.
- Lesion Characteristics: The characteristics of the lesion, such as its size, shape, and location, can provide clues about its underlying cause. For example, lesions with ill-defined borders may be more suggestive of progressive multifocal leukoencephalopathy, while those with a curvilinear or worm-shaped appearance may be more characteristic of multiple sclerosis 1.
- Clinical Context: The clinical context in which the lesion is detected is also important. For example, a patient with a history of optic neuritis or other demyelinating events may be more likely to have a lesion caused by demyelination, while a patient with a history of vascular disease may be more likely to have a lesion caused by chronic ischemia 1.
From the Research
Possible Causes of Nonenhancing T2 Signal Abnormality
- Chronic ischemia: This condition can lead to gliosis, which may appear as a nonenhancing T2 signal abnormality on MRI scans 2.
- Atypical demyelination: Demyelinating diseases can cause T2 signal abnormalities, and atypical forms may present with nonenhancing lesions 3, 4.
- Other conditions: Various other conditions, such as arteriovenous malformations, cavernous malformations, and infectious diseases, can also cause T2 signal abnormalities with low signal intensity 5, 6.
Characteristics of T2 Signal Abnormalities
- T2 hyperintensity: Increased T2 signal is commonly present in patients with temporal lobe epilepsy and is associated with histological abnormalities related to the epileptogenic lesion 3.
- T2 hypointensity: Low signal intensity on T2-weighted imaging can be seen in various central nervous system diseases, including arteriovenous malformations, cavernous malformations, and metastases 6.
- Distribution of T2 signal abnormalities: T2 signal increase can be observed in different temporal structures, including the hippocampus, amygdala, and white matter of the anterior temporal lobe 3.
Diagnostic Considerations
- Clinical-radiological correlation: The diagnosis of conditions causing T2 signal abnormalities should be based on clinical-radiological correlation or histopathological findings 6.
- Differential diagnosis: The presence of high signal abnormalities on T2 weighted images should be interpreted with caution, as they can be seen in various degenerative and vascular dementias 4.