A Case of Progressive Supranuclear Palsy-like Syndrome: Aetiology Revealed

ABSTRACT

In 2015, we published an enigmatic case in Neuro-Ophthalmology regarding an 18-year-old woman who underwent an initially uneventful ascending aortic aneurysm repair. After 48 h, she developed a progressive supranuclear palsy-like syndrome with no findings on magnetic resonance imaging (MRI), MRI tractography, or functional MRI which correlated with this syndrome. After following our patient over the ensuing years, it became clear that the likely aetiology of these neurologic deficits was the profound deep hypothermia associated with her aortic aneurysm repair.

To the Editor:

In 2015, we published an enigmatic case in Neuro-Ophthalmology regarding an 18-year-old woman who underwent an initially uneventful ascending aortic aneurysm repair.¹ She was neurologically normal for 48 h after surgery, and then she developed dysarthria, dysphagia, gait ataxia, emotional lability, and ophthalmoplegia (progressive supranuclear palsy-like syndrome) with no neuroimaging findings to explain her neurologic deficits. Magnetic resonance imaging (MRI) in progressive supranuclear palsy-like syndrome has been reported to show infarcts in the pons, substantia nigra, centrum semiovale, frontal subcortex, striatum, corona radiata, internal capsule, and basal ganglia.¹ Our patient’s extensive neuroimaging, including a contrasted fat-suppressed cranial and orbital MRI, MRI tractography, and functional MRI, however, revealed no clear radiological involvement except for a single tiny low signal midbrain dot on gradient-echo imaging, which was not considered anatomically sufficient to account for the patient’s deficits.¹ The small haemorrhage in retrospect was likely the result of the hypothermia (associated with the ascending aortic aneurysm repair) and which is linked to increased bleeding risk.² Interestingly, cranial MRIs in neonates treated with whole-body hypothermia show deep nuclear injury in 93%.³ Thus, at the time of our publication, we were looking for structural brain damage that would be visible at least on one of the imaging modalities we utilised. However, the mechanism of injury remained unclear. Progressive supranuclear palsy-like syndrome after aortic aneurysm repair has been coined Mokri syndrome, named after the lead author who first described the syndrome in 2004.^4,5 These patients typically present with supranuclear gaze palsy (100%), dysarthria (96%), and gait imbalance (80%) with part or all of the triad observed before hospital discharge and stabilising over days to weeks, but with later progression in some biphasic course.^4,5 Our patient’s symptoms did not improve. Subsequent to the publication of our paper, the elucidation as to the mechanism of Mokri syndrome has been described in a 2020 manuscript reporting 25 patients with Mokri syndrome, all who had had surgery under deep hypothermia.⁴ Six had normal MRIs and one had microhaemorrhage, as in our patient.⁴ Since our publication and during subsequent interviews with our patient and her family along with a records review, it was discovered that the patient’s surgery was performed under very deep hypothermia. Thus, it seems that the likely aetiology of our patient’s injury was from the profound deep hypothermia (much colder than other cardiac surgeries) that is common during this form of cardiac-aortic surgery. The mechanism at a cellular level has yet to be elucidated.

Funding Statement

This work was supported by the Harper-Inglis Memorial for Eye Research, The Peierls Foundation, That Man May See, and Research to Prevent Blindness.

Declaration of interest statement

No potential conflict of interest was reported by the authors.