What causes the wine glass sign on coronal FLAIR MRI of the brain?
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Answer:
The wine glass sign is bilateral symmetric hyperintensity along the corticospinal tracts on coronal FLAIR or T2-weighted images, extending from the precentral gyri through the corona radiata and the posterior limbs of the internal capsules to the cerebral peduncles, so that the overall shape resembles the bowl and stem of a wine glass. It reflects Wallerian degeneration of the upper motor neurons and is the classic imaging correlate of amyotrophic lateral sclerosis, where it accompanies the bright tongue sign of the corticobulbar tracts and, on T2 or susceptibility imaging, motor cortex hypointensity from iron deposition. The sign supports the diagnosis but is neither sensitive nor specific: it is present in only a proportion of patients, is more common in those with prominent upper motor neuron signs, and can be produced by any diffuse corticospinal tract insult, including hereditary spastic paraplegia, adrenomyeloneuropathy, Krabbe disease, subacute combined degeneration, multiple sclerosis, toxic leukoencephalopathies and Wallerian degeneration after a large stroke, though that last is unilateral. The diagnosis of amyotrophic lateral sclerosis remains clinical and electrophysiological, using revised El Escorial or Gold Coast criteria; MRI serves mainly to exclude structural mimics such as cervical spondylotic myelopathy, foramen magnum lesions and multifocal motor neuropathy.
Why is it called so?
The bright tracts converging from the two hemispheres down to the brainstem outline the bowl and stem of a wine glass on the coronal image.
Pathophysiology
Loss of Betz cells and other pyramidal neurons in the primary motor cortex causes their axons to degenerate distally along the corticospinal tract, a process of Wallerian degeneration in which axonal breakdown is followed by myelin disintegration, macrophage infiltration and eventual gliosis. Each stage changes tissue water and macromolecular content, so the tract becomes T2 and FLAIR hyperintense; in the earlier phase diffusion tensor imaging shows reduced fractional anisotropy before conventional images change. The distribution is symmetric because the disease affects the motor system diffusely rather than focally, and the sign is best seen coronally because that plane displays the full craniocaudal course of both tracts in a single image.
Alternative names: Wine glass appearance of the corticospinal tracts
Other associated named signs: Bright tongue sign of the corticobulbar tracts and motor band sign of precentral gyrus susceptibility change
References
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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