MRI in neurology

CNS involvement in infective endocarditis

Infective endocarditis (endocarditis infectiosa) is frequently accompanied by severe neurological complications requiring careful imaging. In 50–80% of cases, these central nervous system lesions are ischemic in nature. Small focal ischemic lesions are detected on scans significantly more often than extensive areas of cerebral infarction.

In fewer than 10% of cases, other structurally more complex changes occur:

• Parenchymal or subarachnoid hemorrhages.
• Abscess formation.
• Development of mycotic aneurysms.

According to current clinical guidelines, brain MRI is strictly indicated for all patients with confirmed infective endocarditis and any neurological symptoms (ESC level of evidence I B, CCC C, LCE 4).

Diagnostic value of the method and impact on management

Magnetic resonance imaging has unsurpassed sensitivity and reliably outperforms standard computed tomography (CT) in diagnosing cerebral infarctions, transient ischemic attacks (TIAs), and encephalopathy manifestations. The clinical significance and interpretation of study results directly depend on the patient's baseline neurological status:

1. In patients with neurological symptoms: MRI allows the detection of additional subclinical lesions that do not present with a clear clinical picture. Although this rarely changes the diagnosis itself (since diagnostic criteria in such patients are usually already met), the results are critical for choosing further treatment tactics. First and foremost, the scan helps determine the safe timing of cardiac valve surgery.
2. In patients without neurological symptoms: The study can detect occult lesions (predominantly of ischemic origin) in at least 50% of patients. In complex, diagnostically uncertain clinical situations, the use of MRI increases the successful diagnosis rate by 25%. It is important to remember that asymptomatic brain involvement is officially included in the minor diagnostic criteria according to the Duke classification.

Cerebral microbleeds

A specific and extremely common neuroimaging finding is cerebral microbleeds, which are specifically detected in 50–60% of patients. Morphologically on scans, they appear as small areas of hemosiderin pigment deposition.

In modern neurological practice, their pathogenesis is associated with systemic small vessel disease of the brain, suggesting a non-embolic nature of their origin. There is a crucial diagnostic nuance: despite the proven high incidence in infective endocarditis, isolated microbleeds should not be considered by the physician as a minor Duke criterion.

Uremic encephalopathy and alternative imaging

When managing patients with uremic encephalopathy (encephalopathia uremica), neuroimaging is required on an emergency basis if the patient develops any focal neurological symptoms. The main goal of instrumental examination in such an acute situation is the reliable and rapid exclusion of intracranial hemorrhage. Both brain MRI and CT are used to solve this task.

In routine diagnostic practice, contrast-enhanced computed tomography is considered exclusively as an alternative imaging method. Its prescription is justified only in cases where the patient has strict absolute contraindications to magnetic resonance imaging. In other clinical situations, MRI remains the absolute method of choice. Additionally, when indicated, patients may be referred for a neurological consultation and electroencephalography (EEG).

Class and exam questions

What else to study on this topic

• Pathogenesis of mycotic aneurysms and brain abscesses.
• Indications for electroencephalography (EEG) in neurological disorders.
• Differential diagnosis of parenchymal and subarachnoid hemorrhages.
• Determining the optimal timing for cardiac surgery when ischemic lesions are detected.
• Duke classification: major and minor criteria for infective endocarditis.

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.