Objective: Progressive supranuclear palsy (PSP) is a rare neurodegenerative disorder encompassing several phenotypes with various motor and cognitive deficits. We aimed to study motor and cognitive characteristics across PSP phenotypes and to assess the influence of apolipoprotein E (APOE) gene variants on PSP phenotypic expression. Methods: In this 20-year cross-sectional study, we retrospectively reviewed the charts of all patients classified as PSP patients and recategorized them according to phenotype using the Movement Disorder Society criteria (2017). Phenotypes were divided into three subgroups, Richardson’s syndrome (PSP-RS), PSP-cortical (PSP with predominant frontal presentation [PSP-F] + PSP with predominant speech/language disorder [PSP-SL] + PSP with predominant corticobasal syndrome [PSP-CBS]) and PSP-subcortical (PSP with predominant parkinsonism [PSP-P] + PSP with progressive gait freezing [PSP-PGF] + PSP with predominant postural instability [PSP-PI] + PSP with predominant ocular motor dysfunction [PSP-OM] + PSP with cerebellar ataxia [PSP-C] + PSP with primary lateral sclerosis [PSP-PLS]), based on clinical presentation during the first 3 years after symptom onset, which defines the early disease stage. Clinical and neuropsychological assessment data were collected. Genotyping of APOE was performed using restriction fragment length polymorphism polymerase chain reaction and verified by Sanger sequencing. Results: We included 112 PSP patients comprising 10 phenotypes classified into 48 PSP-RS, 34 PSP-cortical (PSP-CBS, 17.6%; PSP-F, 9.4%; PSP-SL, 8.2%) and 30 PSP-subcortical (PSP-P, 11.6%; PSP-PI, 8%; PSP-OM, 2.7%; PSP-PGF, 1.8%; PSP-C, 1.8%; PSP-PLS, 0.9%) subgroups. PSP-RS patients were older at disease onset (p = 0.009) and had more akinetic-rigid and levodopa-resistant parkinsonism (p = 0.006), while PSP-cortical patients had more tremors and asymmetric and/or levodopa-responsive parkinsonism (p = 0.025). Cognitive domains were significantly less altered in the PSP-subcortical subgroup. Overall, PSP-APOEε4 carriers developed parkinsonism earlier (p = 0.038), had earlier oculomotor dysfunction (p = 0.052) and had more altered cognitive profiles. The APOEε4 allele was also associated with a younger age of parkinsonism onset in the PSP-RS phenotype group (p = 0.026). Conclusion This study demonstrated the wide phenotypic spectrum of PSP among Tunisians. Disease onset and akinetic-rigid and levodopa-resistant parkinsonism were the hallmarks of the PSP-RS phenotype, while milder cognitive impairment was characteristic of the PSP-subcortical subgroup. The APOEε4 allele was associated with earlier parkinsonism and oculomotor dysfunction and seemed to play a role in defining a more altered cognitive profile in PSP patients.

Objective: LRRK2-G2019S is the most frequent mutation in North African Parkinson’s disease (PD) patients. Data on its impact on disease progression and treatment response remain elusive. Therefore, we investigated the clinical features, treatments, and complications of PD in Tunisian patients according to their LRRK2-G2019S profile. Methods: This longitudinal retrospective study was performed in the Department of Neurology, Razi University Hospital. We included clinically diagnosed PD patients according to the Movement Disorders Society criteria and reviewed their medical records for clinical, treatment, and neuropsychological assessments. All patients were screened for the LRRK2-G2019S mutation using Sanger sequencing. The correlation between LRRK2-G2019S and clinical PD features was evaluated. Results: We included 393 PD patients, 41.5% of whom had LRRK2-G2019S mutations. Patients with mutations were younger (p = 0.017), and female PD patients had a greater mutation frequency (p = 0.008). Mutation carriers exhibited distinct clinical features, with a greater frequency of postural instability gait difficulty forms (adjusted-p < 0.001). During disease progression, carriers showed a faster annual progression in the Unified Parkinson’s Disease Rating Scale Section III scores (adjusted-p = 0.009), and significantly higher levodopa equivalent dose values in later stages (1060.81 vs. 877.83 for 6-8 years). Motor complications, such as dyskinesia (adjusted-p < 0.001) and motor fluctuations (31.9% vs. 25.7%, adjusted-p < 0.001), were more prevalent in carriers, particularly in the later stages. LRRK2-G2019S carriers also exhibited a lower prevalence of non-motor symptoms, including episodic memory (adjusted-p < 0.001), attention (adjusted-p < 0.001), and dysexecutive disorders (adjusted-p = 0.038), as well as neuropsychiatric symptoms and dysautonomic signs. Conclusion The present study demonstrated that the variability of the clinical profile among Tunisian PD patients was explained by the incomplete penetrance of LRRK2-G2019S, which increased with age. Further studies using biomarker and disease progression data are necessary to improve PD management.