A Rare Case of Asymmetric Progressive Supra Nuclear Palsy Diagnosed In vivo with Magnetic Resonance/Positron Emission Tomography

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are usually multisystem sporadic disorders characterized by tau inclusions in neurons and glia.[1] PSP is characterized by progressive axial rigidity, vertical supranuclear gaze palsy, frontal lobe cognitive decline, and balance issues.[2] The classic clinical syndrome of CBD is the presentation of an apraxic, dystonic, and rigid limb with asymmetrical cortical signs and distal myoclonus known as CBD.[3] As noted clinically, PSP predominantly presents with a supranuclear vertical gaze palsy and early postural instability with falls.[4] Clinical overlap makes it difficult for clinicians to diagnose these properly, and biopsy to characterize the site of tau inclusions is not always feasible.[5] Here, we present the case of a 65-year-old female patient, presenting a 3-year history of insidious onset of asymmetric right upper and lower limb dystonia, followed by slowness, falls and injuries to the back, Parkinsonism, urinary incontinence, and cognitive dysfunction and upward gaze palsy.

Magnetic resonance/positron emission tomography (MR/PET) using F18-fluorodeoxyglucose was done with the following clinical history.

MR imaging (MRI) findings [Figure 1a and b] were suggestive of moderate cerebral and cerebellar atrophy with prominent ventricular system, reduced antero-posterior midline midbrain diameter, at the level of superior colliculus on axial imaging (morning glory sign was positive) on the left side as seen typically.[6]

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Figure 1 Head T1 MPRAGE sagittal showing the humming bird sign with midbrain atrophy. (b) Head T2 dark fluid transverse showing left side midbrain atrophy. (c) ¹⁸F-FDG MR/PET axial fused showing hypometabolism involving the left thalamus, striatum, frontal, and temporal lobes. (d) ¹⁸F-FDG MR/PET axial fused showing hypometabolism involving the midbrain left side. (e) ¹⁸F-FDG MR/PET axial fused showing hypometabolism involving the right cerebellum. (f) ¹⁸F-FDG MR/PET axial fused showing maintained left perirolandic region. ¹⁸F-FDG MR/PET: F18-fluorodeoxyglucose magnetic resonance/positron emission tomography

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PET showed asymmetric hypo metabolism noted in the left superior and middle frontal gyrus [Figure 1e and f], superior temporal and middle temporal gyrus in addition to striatum and thalamus, as well as midbrain, pons, and right cerebellar hemisphere [Figure 1c and d].

Overall MR/PET was suggestive of asymmetric PSP (left) and it corroborated with clinical history of unilateral dystonia and supranuclear gaze palsy.

Based on MRI, the differential considered was also CBD, but PET showed metabolic activity in the motor cortex. In addition, based on the hummingbird sign and morning glory sign, a rare diagnosis of unilateral PSP could be made which also corroborated with the clinical picture. The case report emphasizes the utility of PETMRI simultaneously in situations like these to pick atypical variants or cases with overlapping pathology to reach a diagnosis with in vivo imaging methods.