Imaging Criteria for the Diagnosis of Progressive Supranuclear Palsy: Supportive or Mandatory?

Abstract

We present the case of a 54-year-old male, without any significant medical history, who insidiously developed speech disturbances and walking difficulties, accompanied by backward falls. The symptoms progressively worsened over time. The patient was initially diagnosed with Parkinson's disease; however, he failed to respond to standard therapy with Levodopa. He came to our attention for worsening postural instability and binocular diplopia. A neurological exam was highly suggestive of a Parkinson-plus disease, most likely progressive supranuclear gaze palsy. Brain MRI was performed and revealed moderate midbrain atrophy with the characteristic "hummingbird" and "Mickey mouse" signs. An increased MR parkinsonism index was also noted. Based on all clinical and paraclinical data, a diagnosis of probable progressive supranuclear palsy was established. We review the main imaging features of this disease and their current role in diagnosis.

Keywords: Magnetic Resonance Parkinsonism Index (MRPI); Mickey mouse sign; PSP syndromes; corticobasal degeneration; hummingbird sign; midbrain atrophy; morning glory sign; multiple system atrophy (MSA); postmortem histopathological examination; progressive supranuclear palsy.

Figure 1

T1-weighted sagittal MRI revealing the superior margin of the midbrain (yellow arrows). Notice the convex superior margin of the midbrain that could be seen in 2019 (A) and the concave appearance in 2022 (B), the so-called “hummingbird” sign.

Figure 2

T2-weighted axial MRI revealing the midbrain margins (yellow arrows). Notice the normal-appearing midbrain that could be seen in 2019 (A) and the atrophic midbrain with concave lateral margins (“morning glory” sign) and reduced anteroposterior diameter (“Mickey mouse” sign) which was seen in 2022 (B).

Figure 3

MRI FLAIR in coronal (A) and sagittal (B,C) planes. MR Parkinsonism Index (MRPI) in our patient is calculated by determining the: (A) width of the superior cerebellar peduncle (SCP) (blue line), (B) width of the middle cerebellar peduncle (MCP) (blue line), and (C) pons-to-midbrain area ratio (P/M) (red square/green square). MRPI = (P/M) × (MCP/SCP). A value higher than 13.55 is in-dicative of PSP (as was the case with our patient).