Progressive supranuclear palsy

Clinical History

A 61-year-old male patient presented with gait disturbances, slowness and falls while walking for more than 2 years. The symptoms were of insidious onset and progressive course. Also, alteration of eye movements had started 1 year ago.

Imaging Findings

The MRI images, especially the midsagittal T1-weighted (Fig.1a), show atrophy of midbrain tegmentum with relative preservation of pons, which shows the appearance of the "hummingbird sign" and is typically related with progressive supranuclear palsy.
This was observed in axial T1-weighted images too, which is associated with a slight increase of the interpeduncular cistern (Fig. 1b). Even the width of the superior cerebellar peduncle, best evaluated in coronal T1-weighted image, is less than 3 mm (Fig. 1c).

Discussion

Progressive supranuclear palsy (PSP) is the second most common cause of parkinsonism after Parkinson's disease [1], it is a primary tauopathy that causes a sporadic neurodegenerative disease characterised by abnormal hyperphosphorylation of tau protein (predominantly four-repeated) that accumulates and deposits in the basal ganglia, brainstem and frontal lobe [2] determining neuronal loss of midbrain tegmentum and superior cerebellar peduncle decussation [3].

Typically, the average age of presentation is 63 years with an insidious onset and progressive course. Clinically, the symptoms are bradykinesia, gait disturbances, slow walking with falls, which at the beginning is difficult to differentiate from Parkinson's disease. Also, it is accompanied by alterations of eye movements (vertical gaze palsy), and cognition (gradual loss of executive functions) [4].

The best imaging technique to evaluate it is MRI and DTI. The well-known features in MRI of PSP are the atrophy of midbrain tegmentum and superior cerebellar peduncles with relative preservation of pons, which are best represented in midsagittal T1-weighted images, showing the appearance of a hummingbird (“hummingbird sign”) [3].
Also, in axial T1-weighted images, the neuronal loss of superior cerebellar peduncle superior decussation determines the decrease of anteroposterior midbrain diameter in association with dilatation of interpeduncular cistern (“Mickey Mouse” appearance) [5].

Currently, the morphometric analysis calculates the midbrain and pons areas (midsagittal T1-weighted image) and establishes the pons/midbrain ratio. Besides, middle cerebellar peduncle width (in sagittal T1-weighted image), superior cerebellar peduncle width (coronal T1-weighted image) and middle/superior cerebellar peduncle ratio are calculated to distinguish between Parkinson's disease and multisystem atrophy [6].
Even although there are no standardised measurements, it has been determined that midbrain area and superior cerebellar peduncle smaller than 105mm2 and 3mm respectively predicts PSP with 95% sensibility and 80% specificity[7].
The DTI images clearly show the loss of superior cerebellar peduncle decussation [5].

Differential Diagnosis List

Final Diagnosis

Progressive supranuclear palsy

URL:	https://eurorad.org/case/15247
DOI:	10.1594/EURORAD/CASE.15247
ISSN:	1563-4086