Objective: To present a rare case of eye-of-the-tiger sign in a patient with progressive supranuclear palsy (PSP).

Background: The eye-of-the-tiger is a neuroradiologic sign appearing marked low signal intensity in the globus pallidus surrounding a hyperintense central area with an otherwise normal-appearing MRI T2-weighted imaging, with confirmation of iron accumulation by T2*-weighted/SWI sequences. It has been classically associated with neurodegeneration with brain iron accumulation (NBIA) type I.

Method: Case report from a tertiary medical center.

Results: A 72-year-old women with a 4-year history of predominant and relatively symmetrical akinetic-rigid syndrome, gait impairment and postural instability with frequent falls. Symptoms were unresponsive to levodopa. She is wheelchair-bound for more than a year. More recently, she reported memory loss and urinary incontinency.
Current examination shows hypomimia, eyebrow furrowing, lid retraction, severe reduced eye blinking, myokymia and visual fixation instability with frequent square-wave jerks. Saccades are hypometric (most evident in superior saccades) with an increased latency (most evident in right saccades). The patient has symmetric rigidity and bradykinesia, tremor of the chin and tongue, mild intermittent asymmetric thumb rest tremor with an associated mild postural tremor of the upper limbs and polyminimyoclonus. A dystonic posturing of the left foot is evident. Gait is markedly unstable, only possible with assistance. She tends to fall back when raising the chair and her pull test is markedly positive as she tends to fall backward. There is bilateral upper limb apraxia. Short cognitive assessment shows slowed processing, reduced verbal fluency and executive dysfunction (video available).
Brain MRI showed diffuse hypointensity with an anteromedial area of high signal intensity of the globus pallidus (“eye-of-the-tiger” sign). T2*-weighted/SWI sequences confirmed accumulated iron in the affected regions. 123I-Ioflupane SPECT revealed bilaterally, relatively symmetrical, decreased dopamine transporter availability in the putamen. Genetic study for NBIA was negative.

Conclusion: Eye-of-the-tiger on MRI and marked visual fixation instability may be suggestive of NBIA. However, the clinical evolution points towards probable PSP. This case challenges the specificity of this radiological sign for NBIA, expanding the phenotypic spectrum to include PSP.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/eye-of-the-tiger-sign-in-progressive-supranuclear-palsy/