Differential Diagnosis for Prepontine Cistern Signal Abnormality and Scattered White Matter Changes

Single Most Likely Diagnosis

• Pulsation artifact from a dominant left vertebrobasilar system: This is considered the most likely diagnosis due to the unchanged nature of the signal abnormality from previous MRI scans and the specific location in the prepontine cistern, which is prone to artifacts from vascular flow.

Other Likely Diagnoses

• Ecchordosis physaliphora: A benign, congenital lesion that can cause signal abnormalities in the prepontine cistern. Its consideration is based on the location and the description of the signal abnormality.
• Microvascular ischemia: Given the patient's history of recent stroke, microvascular ischemia is a plausible explanation for the scattered white matter changes, which are described as typical for this condition.

Do Not Miss Diagnoses

• Metastatic disease to the clivus or brainstem: Although the report mentions no aggressive appearing clival lesion, in a patient with breast cancer, the possibility of metastasis must be carefully considered due to its potential impact on management and prognosis.
• Inflammatory or infectious processes: Conditions such as meningitis or encephalitis could present with signal abnormalities in the brain and require urgent diagnosis and treatment.

Rare Diagnoses

• Chordoma: A rare malignant tumor that can occur in the clivus and could potentially cause signal abnormalities in the prepontine cistern. The absence of an aggressive appearing lesion makes this less likely, but it remains a consideration in the differential diagnosis.
• Other rare vascular malformations or tumors: Given the location and the patient's complex medical history, other rare conditions affecting the brainstem or prepontine cistern, such as hemangiomas or rare metastatic patterns, should be considered, albeit with lower likelihood.