Pathologic and MRI analysis in acute atypical inflammatory demyelinating lesions

Area of Science:

• Neurology
• Neuroimaging
• Pathology

Background:

• Atypical inflammatory demyelinating lesions pose diagnostic challenges, often necessitating brain biopsy to rule out neoplasms.
• The precise relationship between these lesions and conditions like multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) remains unclear.

Purpose of the Study:

• To delineate the radiological and pathological features of patients presenting with acute inflammatory demyelinating lesions.
• To identify common diagnostic characteristics that may help differentiate these lesions from other neurological conditions.

Main Methods:

• Retrospective analysis of patients who underwent brain biopsy for diagnostic uncertainty, revealing demyelinating lesions.
• Comprehensive clinical, biological, radiological, and pathological evaluation of included patients.

Main Results:

• Twenty patients were analyzed, exhibiting diverse MRI findings including infiltrative, ring-like, Baló-like lesions, and acute hemorrhagic leukoencephalitis.
• Consistent features included a peripheral B1000 hyperintense rim (70%), mild edema with mass effect (75%), and open-rim peripheral enhancement (75%).
• Histopathology showed macrophages, extensive demyelination, preserved axons, and preserved Aquaporin-4 (AQP4) staining. AQP4 staining was preserved in all cases, arguing against AQP4-positive NMOSD.

Conclusions:

• Heterogeneous imaging findings in atypical inflammatory demyelinating lesions are common, but specific features like peripheral DWI hyperintense rim and open-rim enhancement suggest demyelination and may obviate the need for brain biopsy.
• Preserved AQP4 staining is a key indicator against AQP4-positive NMOSD.
• Long-term follow-up reveals a low recurrence rate for these lesions, with most patients diagnosed with monophasic lesions rather than MS or NMOSD.