From the Guidelines
Hypoattenuation on brain MRI is a critical finding that requires prompt evaluation and management, particularly in the context of acute ischemic stroke, where it can indicate areas of infarction or edema. When hypoattenuation is observed, further clinical correlation and additional imaging sequences are necessary for proper diagnosis. Common causes include acute ischemic stroke, where restricted blood flow leads to cytotoxic edema; multiple sclerosis plaques, which represent areas of demyelination; and vasogenic edema surrounding tumors or infections. The radiologist will typically characterize the location, size, shape, and distribution of hypoattenuated areas to narrow the differential diagnosis. It's essential to note that hypoattenuation is more commonly discussed in CT imaging terminology, while in MRI, terms like hypointensity or hyperintensity (depending on the sequence) are more precise. The appearance of brain lesions on MRI varies based on the specific sequence used (T1-weighted, T2-weighted, FLAIR, diffusion-weighted), which helps differentiate between pathologies and determine the age of lesions. According to the guidelines for the early management of patients with acute ischemic stroke 1, the extent and severity of acute hypoattenuation or early ischemic changes should not be used as a criterion to withhold therapy for such patients who otherwise qualify. Additionally, the use of diffusion-weighted MR imaging (DWI-MRI) has emerged as the most sensitive and specific imaging technique for acute infarct, far better than non-contrast CT (NECT) or any other MRI sequence 1. In the management of acute ischemic stroke due to large-vessel occlusion, the assessment of ischemic core using NCCT, mCTA, CTP, and DWI-MRI is crucial for determining the best course of treatment 1. The decision to administer IV alteplase should not be based solely on the presence or extent of hypoattenuation, but rather on a comprehensive evaluation of the patient's clinical presentation, imaging findings, and other relevant factors, as recommended by the guidelines 1. In summary, hypoattenuation on brain MRI is a significant finding that requires careful evaluation and management, and its interpretation should be guided by the latest evidence-based guidelines and recommendations.
From the Research
Hypoattenuation on Brain MRI
- Hypoattenuation on brain MRI refers to areas of low signal intensity, which can be indicative of various conditions, including ischemic stroke 2.
- In the context of acute ischemic stroke, hypoattenuation on brain MRI can be used to assess the extent of brain tissue affected by the stroke 3, 4.
- However, hypoattenuation can also be caused by other factors, such as artifacts or normal anatomical variations 2.
Clinical Relevance
- The clinical relevance of hypoattenuation on brain MRI depends on the underlying cause and the patient's symptoms 2.
- In patients with acute ischemic stroke, hypoattenuation on brain MRI can be used to guide treatment decisions, such as the use of thrombolytic therapy 3, 4, 5.
- In elderly patients with acute ischemic stroke, the safety of intravenous thrombolysis with alteplase has been shown to be comparable to that of non-elderly patients, with no increased risk of intracranial hemorrhage or mortality 6.
Management
- The management of hypoattenuation on brain MRI depends on the underlying cause and the patient's clinical presentation 2.
- In patients with acute ischemic stroke, treatment with thrombolytic therapy, such as alteplase, may be indicated 3, 4, 5.
- In elderly patients with acute ischemic stroke, the use of thrombolytic therapy should be carefully considered, taking into account the patient's overall health status and the potential risks and benefits of treatment 6.