Pallidal degenerations and related disorders: an update

Area of Science:

• Neurology
• Genetics
• Neuroscience

Background:

• Rare neurodegenerative disorders preferentially affect the globus pallidus and its connected neural systems.
• These disorders manifest as progressive movement disorders (e.g., choreoathetosis, dystonia, Parkinsonism) and can include seizures and cognitive impairment.
• They represent a heterogeneous group with diverse clinical presentations and genetic underpinnings.

Purpose of the Study:

• To classify and describe rare neurodegenerative disorders affecting the globus pallidus and related neuronal systems.
• To review the clinical manifestations, genetic mutations, and pathological features of these disorders.
• To discuss diagnostic challenges, potential etiological mechanisms, and current therapeutic limitations.

Main Methods:

• Literature review and synthesis of existing studies on pallidal neurodegenerative disorders.
• Classification of disorders based on affected neuronal systems and genetic findings.
• Analysis of clinical, genetic, and pathological data from reported cases.

Main Results:

• Several subgroups were identified, including pure pallidal atrophy, pallidonigral degeneration, and others like dentatorubral-pallidoluysian atrophy (DRPLA) and neuroferritinopathy (NF).
• Specific gene mutations (e.g., ATP13A2, FTL1, ATN1, MAPT) are linked to certain forms, with some classified as 4-R tauopathies.
• Differential diagnosis is broad, encompassing conditions like Huntington's disease and multiple system atrophy; neuroimaging and biomarkers are limited for most syndromes.

Conclusions:

• These rare disorders present a diagnostic challenge due to their heterogeneity and overlapping symptoms.
• While some genetic causes are identified, the etiology of most remains unknown, with proposed mechanisms including oxidative stress and protein aggregation.
• Currently, no disease-modifying therapies exist, and management is primarily symptomatic.