Hockey stick sign | Radiology Signs

Answer:

The hockey stick sign is symmetric hyperintensity of the pulvinar together with the dorsomedial nuclei of the thalami, so that on the axial image the two involved regions on each side form an L-shaped configuration resembling a hockey stick. It is closely linked to variant Creutzfeldt-Jakob disease, in which it accompanies the pulvinar sign and adds specificity, and it is reported less often in sporadic Creutzfeldt-Jakob disease. The assessment is the same as for the pulvinar sign: the involved thalamic nuclei must be brighter than the anterior putamen, and diffusion-weighted imaging is the most sensitive sequence, often showing restricted diffusion when FLAIR is equivocal. The sign is not pathognomonic and has been described in Wernicke encephalopathy, where thiamine deficiency also affects the medial thalami along with the mamillary bodies, periaqueductal grey and tectal plate, and in deep cerebral venous thrombosis, encephalitides including Japanese encephalitis and influenza-associated encephalopathy, and in extrapontine osmotic demyelination. Because the treatable causes on that list, principally thiamine deficiency and venous thrombosis, must not be missed, symmetric medial thalamic signal change should prompt a careful look at the mamillary bodies, at the internal cerebral veins and straight sinus, and at the clinical history before prion disease is suggested.

Why is it called so?

The combined pulvinar and dorsomedial thalamic hyperintensity forms the blade and shaft of a hockey stick on the axial image.

Pathophysiology

Prion protein deposition in variant Creutzfeldt-Jakob disease is concentrated in the posterior and medial thalamic nuclei, where the resulting spongiform vacuolation, neuronal loss and reactive astrogliosis increase tissue free water and restrict the diffusion of water in the extracellular space. Both effects raise FLAIR signal and reduce the apparent diffusion coefficient. The dorsomedial nucleus is heavily connected to the prefrontal cortex and limbic system and lies adjacent to the pulvinar, so involvement of the two adjoining nuclear groups produces the characteristic angular shape. In Wernicke encephalopathy the same medial thalamic region is damaged by a different mechanism, thiamine-dependent failure of oxidative metabolism in regions of high thiamine turnover, which is why the two conditions converge on a similar appearance.

Alternative names: Double hockey stick sign; pulvinar plus dorsomedial thalamic sign

Other associated named signs: Pulvinar sign, cortical ribboning on diffusion imaging, and the mamillary body enhancement of Wernicke encephalopathy

References

1. Collie DA, Summers DM, Sellar RJ, Ironside JW, Cooper S, Zeidler M, et al. Diagnosing variant Creutzfeldt-Jakob disease with the pulvinar sign: MR imaging findings in 86 neuropathologically confirmed cases. AJNR Am J Neuroradiol. 2003;24(8):1560-9. PMID: 13679271.