Lentiform Fork sign: a unique MRI picture. Is metabolic acidosis responsible?

BACKGROUND AND PURPOSE: Bilateral basal ganglia lesions are neither diagnostic nor pathognomonic of uremic encephalopathy (UE). Nonetheless, bilateral basal ganglia T2/FLAIR hyperintensities have been widely reported to be associated with UE. The aim of this study was to describe a unique neuroradiological sign seen on the MRI brain in UE, present a retrospective chart review of patients with UE over the past 10 years for evidence of similar MRI appearance, review literature for evidence of this sign, and generate a hypothesis to explain its pathophysiological basis.

METHODS: We describe a previously unreported and unique MRI picture, the Lentiform Fork sign, in a patient with UE. We conducted a focused retrospective chart review of patients with UE over the past 10 years, for evidence of similar MRI changes. We review literature (through PUBMED, OVID, and CENTRAL) for evidence of this sign and propose a hypothesis to explain the basis of this MRI sign.

RESULTS: We describe the Lentiform Fork sign in a patient with UE. Of our 21 retrospectively reviewed patients with UE who underwent MRI, only one had this sign. Literature review identified 22 patients with this sign who had various conditions, all associated with metabolic acidosis. Fourteen of these patients had documented evidence of severe metabolic acidosis. We propose the hypothesis that metabolic acidosis is the basis of this Lentiform Fork sign.

CONCLUSION: Lentiform Fork sign is a unique, previously unreported MRI picture that is seen not only in patients with UE but also in other conditions that result in metabolic acidosis, helping discriminate a specific etiology from the myriad of conditions that are lumped under the rubric of "basal ganglia hyperintensity." We propose the hypothesis that metabolic acidosis may be the key factor in the pathogenesis of this sign.