The severity of a slightly high Flair signal depends on the specific nature of the lesion.
Flair is a sequence on a cranial MRI. The cause of high Flair signal may be due to demyelination of the cerebral white matter and encephalitis. Patients with cerebrovascular risk factors such as hypertension and diabetes mellitus are susceptible to atherosclerosis, which leads to ischemic demyelination of the cerebral white matter, usually in the anterior and posterior corners of the lateral ventricles.
This cause of Flair high signal is not serious, and controlling risk factors such as hypertension and diabetes is the most critical.
Encephalitis usually also presents with high Flair signal, and this disease is usually accompanied by fever and other symptoms that require aggressive anti-infective treatment, and most of the disease can be cured.
In general, when Flair shows a high signal, it indicates a serious condition, and treatment measures should be taken promptly to avoid delays.