Manganese Related Neurodegeneration (Manganism) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Manganese-related neurodegeneration, commonly known as manganism or Manganese-Induced Parkinsonism, is a rare but serious neurological disorder caused by excessive accumulation of manganese (Mn) in the brain, particularly in the basal ganglia. This condition shares clinical features with Parkinson's Disease but has distinct pathological and mechanistic characteristics. [1]
Manganism results from occupational exposure to manganese fumes or dust, genetic factors, or liver dysfunction that impairs manganese excretion. Unlike idiopathic Parkinson's Disease, manganism primarily affects the globus pallidus and striatum, leading to a distinct pattern of motor and non-motor symptoms. [2]
The condition is considered a form of toxic parkinsonism and is classified within the spectrum of neurodegeneration with brain iron accumulation (NBIA) disorders, though it involves manganese rather than iron as the primary metal.
¶ Epidemiology and Risk Factors
Manganese exposure occurs primarily in the following occupational settings:
- Welding: The most common source of manganese exposure, particularly in enclosed spaces with inadequate ventilation
- Mining: Both coal and manganese ore mining operations
- Steel manufacturing: Ferromanganese production and steelworking
- Battery manufacturing: Production of alkaline batteries
- Glass and ceramics: Industrial applications involving manganese compounds
Workers exposed to manganese concentrations exceeding 1 mg/m³ for extended periods (typically 10+ years) are at highest risk.
- Genetic factors: Mutations in the SLC30A10 gene (manganese transporter) cause hereditary manganism
- Liver disease: Cirrhosis and hepatic failure impair manganese excretion via bile
- Total parenteral nutrition: Excessive manganese in intravenous feeds
- Infant formulas: Historical cases of high manganese in soy-based formulas
¶ Manganese Transport and Homeostasis
Manganese is an essential trace element required for normal brain function, serving as a cofactor for numerous enzymes including:
- Superoxide dismutase (MnSOD): Antioxidant defense
- Glutamine synthetase: Neurotransmitter cycling
- Pyruvate carboxylase: Gluconeogenesis
- Choline acetyltransferase: acetylcholine synthesis
The brain's manganese homeostasis is maintained by:
- SLC30A10: Manganese exporter located on neuronal and astrocytic membranes
- SLC39A14: Manganese importer involved in uptake
- DMT1 (Divalent Metal Transporter 1): Transport across the Blood-Brain Barrier
Manganese accumulates in mitochondria, particularly in dopaminergic neurons, where it:
- Inhibits complex I of the electron transport chain
- Reduces ATP production
- Increases reactive oxygen species (ROS generation
- Triggers mitochondrial permeability transition
Manganese promotes oxidative damage through:
- Direct ROS generation via Fenton-like reactions
- Inhibition of antioxidant enzymes (glutathione peroxidase, catalase)
- Depletion of cellular glutathione stores
- Lipid peroxidation and DNA damage
Chronic manganese exposure activates:
- Microglial activation: Pro-inflammatory cytokine release (IL-1β, TNF-α, IL-6)
- Astrocytic dysfunction: Impaired glutamate transport and potassium buffering
- blood-brain barrier disruption: Increased permeability
Manganese selectively damages dopaminergic neurons in the:
- Globus pallidus: Primary site of manganese accumulation
- Substantia nigra pars reticulata: Secondary affected region
- Striatum: Postsynaptic dopaminergic terminals
The pattern differs from Parkinson's Disease, which primarily affects substantia nigra pars compacta dopaminergic neurons.
Manganese exposure can:
- Promote α
- Enhance tau] phosphorylation
- Impair autophagy-lysosomal pathways
- Disrupt protein quality control systems
| Symptom |
Description |
Distinction from PD |
| Bradykinesia |
Slowed movements, reduced spontaneous activity |
Present but less prominent |
| Rigidity |
Muscle stiffness, particularly in lower limbs |
More axial (trunk) than appendicular |
| Gait disturbance |
Wide-based, shuffling gait with frequent falls |
"Mickey Mouse" gait pattern |
| Dystonia |
Involuntary muscle contractions, foot curl |
Prominent early, especially in hands/feet |
| Tremor |
Less common than in PD; when present, is postural |
Resting tremor rare |
- Cognitive impairment: Executive dysfunction, attention deficits
- Mood disorders: Depression, anxiety, apathy
- Speech changes: Dysarthria, slowed speech
- Psychiatric features: Hallucinations (less common than in PD)
- Sleep disturbances: Insomnia, REM sleep behavior disorder
- Manganese Exposure Index (MEI): Quantifies occupational exposure
- Unified Parkinson's Disease Rating Scale (UPDRS): Modified for manganism
- ** Abnormal Involuntary Movement Scale (AIMS)**: For dystonia assessment
- T1-weighted hyperintensity: Increased signal in:
- Globus pallidus (most characteristic)
- Substantia nigra pars reticulata
- Red nucleus
- Putamen
- Symmetry: Bilateral and symmetric (distinguishes from PD)
- "Eye of the tiger" sign: May be seen in advanced cases
- DaTscan (FP-CIT SPECT): Reduced dopamine transporter binding in striatum
- FDG-PET: Metabolic patterns differ from PD
- Fluoro-DOPA PET: Reduced F-DOPA uptake in caudate and putamen
- Increased echogenicity in substantia nigra (less consistent than in PD)
- Clinical features: Parkinsonism with prominent gait disturbance and early dystonia
- Exposure history: Occupational or environmental manganese exposure
- MRI findings: T1 hyperintensity in basal ganglia
- Exclusion: Exclusion of other causes of parkinsonism
| Condition |
Key Distinguishing Features |
| Idiopathic Parkinson's Disease |
Asymmetric onset, resting tremor, Lewy bodies |
| Progressive Supranuclear Palsy |
Vertical gaze palsy, early postural instability |
| Multiple System Atrophy |
Autonomic dysfunction, cerebellar signs |
| Corticobasal Degeneration |
Apraxia, alien limb phenomenon |
| Wilson Disease |
Kayser-Fleischer rings, younger age |
- Blood manganese: Elevated levels (though may normalize after exposure stops)
- CSF manganese: More reliable indicator of brain exposure
- Genetic testing: SLC30A10, SLC39A14 mutations in familial cases
¶ Treatment and Management
Chelating agents can accelerate manganese excretion:
- EDTA (Ethylenediaminetetraacetic acid): Effective but requires IV administration
- Dimercaprol (British Anti-Lewisite): Historical use
- Succimer (DMSA): Oral chelator with some efficacy
- Para-aminosalicylic acid (PAS): Shows promise in recent studies
- Levodopa/carbidopa: May provide modest improvement
- Dopamine agonists: Pramipexole, ropinirole (variable response)
- Less effective than in idiopathic PD
- Anticholinergics: Trihexyphenidyl (for dystonia)
- Muscle relaxants: Baclofen, tizanidine
- Benzodiazepines: For anxiety and dystonia
- Physical therapy: Gait training, balance exercises
- Occupational therapy: Adaptive devices
- Speech therapy: For dysarthria
- Psychological support: Cognitive behavioral therapy
- Gene therapy: Targeting manganese transporters
- Antioxidant therapy: N-acetylcysteine, coenzyme Q10
- Neurotrophic factors: BDNF, GDNF analogs
- Stem cell therapy: Research phase
- Variable course: Some patients stabilize after exposure cessation
- Progressive form: May continue to worsen despite treatment
- Irreversible damage: Neuronal loss may be permanent
- Early detection: Better outcomes with prompt intervention
- Continued exposure: Worse prognosis with ongoing exposure
- Genetic forms: May have different trajectory
- Chelation response: Those who respond to chelation have better outcomes
- Engineering controls: Local exhaust ventilation
- Respiratory protection: N95 or greater masks
- Personal monitoring: Regular air sampling
- Medical surveillance: Baseline and periodic neurological exams
- Worker education: Recognition of early symptoms
- Environmental monitoring: Near industrial sites
- Drinking water standards: Manganese limits
- Infant formula regulations: Manganese content limits
- Manganese transporters: Understanding SLC30A10 and SLC39A14 function
- Biomarkers: Identifying early diagnostic markers
- Chelation optimization: Newer, more targeted chelators
- Neuroprotection: Developing agents to prevent neuronal death
- Gene therapy: Correcting genetic defects in hereditary forms
Active and recruiting trials are investigating:
- Novel chelation protocols
- Neuroprotective agents
- Biomarker development
- Deep brain stimulation outcomes
The study of Manganese Related Neurodegeneration (Manganism) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- Michalke B, Review about the manganese speciation project related to neurodegeneration: An analytical chemistry approach to increase the knowledge about manganese related parkinsonian symptoms (2016)
- Thines L et al., Yeast as a Tool for Deeper Understanding of Human Manganese-Related Diseases (2019)
- HaMai D, Bondy SC, Oxidative basis of manganese neurotoxicity (2004)
- Aydemir TB et al., Metal Transporter Zip14 (Slc39a14) Deletion in Mice Increases Manganese Deposition and Produces Neurotoxic Signatures and Diminished Motor Activity (2017)
- Lin JJY et al., Associations of a toenail metal mixture with attention and memory in the Gulf long-term follow-up (GuLF) study (2024)