In multiple sclerosis, which MRI finding is considered pathognomonic and represents demyelinating lesions oriented perpendicular to the lateral ventricles?

Explanation

## Dawson's Fingers in Multiple Sclerosis **Key Point:** Dawson's fingers are a characteristic MRI finding in MS, representing demyelinating lesions that radiate perpendicular to the lateral ventricles along perivascular spaces. ### Pathophysiology These lesions follow the distribution of medullary veins, which run perpendicular to the ventricular surface. The perivascular inflammation in MS preferentially affects these vascular territories, creating the distinctive finger-like appearance on axial and sagittal T2/FLAIR sequences. ### MRI Characteristics - **Location:** Periventricular white matter - **Orientation:** Perpendicular (radial) to lateral ventricles - **Sequence:** Best seen on T2-weighted and FLAIR - **Specificity:** Highly suggestive of MS when present ### Diagnostic Significance **High-Yield:** Dawson's fingers are one of the most specific imaging findings for MS and strongly support the diagnosis when identified in the appropriate clinical context. **Clinical Pearl:** While highly specific, Dawson's fingers are not present in all MS cases. Their absence does not exclude MS, but their presence is highly suggestive of demyelinating disease. ### Other MS-Related MRI Findings | Finding | Description | Significance | |---------|-------------|-------------| | Ovoid lesions | Lesions oriented along long axis of white matter tracts | Common in MS | | Infratentorial lesions | Brainstem and cerebellar involvement | Part of dissemination criteria | | Spinal cord lesions | Longitudinally extensive transverse myelitis | Supports MS diagnosis | | Black holes | T1 hypointense lesions | Indicate chronic demyelination | [cite:Harrison 21e Ch 380]