SPG11-related parkinsonism: Clinical profile, molecular imaging and l-dopa response

TL;DR: Molecular imaging has proven to be a powerful tool to elucidate degenerated paths in a wide variety of neurological diseases but has not been systematically studied in hereditary spastic paraplegias.

Abstract: Background Molecular imaging has proven to be a powerful tool to elucidate degenerated paths in a wide variety of neurological diseases and has not been systematically studied in hereditary spastic paraplegias. Objectives To investigate dopaminergic degeneration in a cohort of 22 patients with hereditary spastic paraplegia attributed to SPG11 mutations and evaluate treatment response to l-dopa. Methods Patients and controls underwent single-photon emission computed tomography imaging utilizing 99m Tc-TRODAT-1 tracer. A single-blind trial with 600 mg of l-dopa was performed comparing UPDRS scores. Results Reduced dopamine transporter density was universal among patients. Nigral degeneration was symmetrical and correlated with disease duration and motor and cognitive handicap. No statistically significant benefit could be demonstrated with l-dopa intake during the trial. Conclusion Disruption of presynaptic dopaminergic pathways is a widespread phenomenon in patients with SPG11 mutations, even in the absence of parkinsonism. Unresponsiveness to treatment could be related to postsynaptic damage that needs to be further investigated.