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Manganism

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Cognitive Engineering, LLC

Parkinson’s disease (PD) is a neurodegenerative disease caused by deficiency of dopamine production in the substantia nigra region of the brain.  Characteristic features of PD include resting tremor, rigidity, bradykinesia, and postural instability. Interestingly, a very similar syndrome in its clinical presentation can be produced by exposure to the metal Manganese (manganism), often thru inhaling of welding rod fumes. 

 

Clinical features of manganism, in contrast to PD,  include:

n      gait ataxia plus other neurologic findings (ataxia-plus)

n      cognitive impairment with psychiatric features.

n      liver failure.

 

Manganese toxicity is thought primarily to affect two regions of the basal ganglia, in contrast to PD: the striatum and globus palladus.  Because the two syndromes have overlap in clinical features, it is important to have a strong identification of causation when evaluating these patients / clients.  Although there may be significant overlap, recent studies have shown that these two etiologically distinct syndromes may be distinguished by:

*      The clinical presentation,

*      Therapeutic response to levodopa,

*      Biological Markers, including blood and urine Mn levels.

Recently, several publications in the peer-reviewed medical literature have pointed to the potential use of Magnetic Resonance Imaging (MRI) as a tool to distinguish these two syndromes. Specifically, the radiologic literature indicates that the T1 (spin lattice relaxation) signal in the basal ganglia on MRI can distinguish Mn-induced Parkinson’s-like disease (Manganism) from dopamine-deficient PD. (Josephs 2005). This technique has the potential to allow a more definitive answer to the essential question of differentiating patients with Parkinsonism due to manganese intoxication from patients with idiopathic PD who have incidental manganese exposure.  Typically, this involves an analysis of the clinical syndrome, the patient’s  response to levodopa, and pathologic features. Incorporating MRI studies in the diagnostic workup can be highly beneficial in ruling out spontaneous PD or a toxic-metabolic encephalopathy from liver disease

 

By using MRI, one can specifically look for the differentiating component of PD vs MN. Remembering that a Manganese-induced movement disorder primarily affects two regions of the basal ganglia: the striatum and globus palladus, one can select this area as a region of interest (ROI) on MRI. Racette et al (2005) has shown that the globus pallidum interna had increased signal on T1-weighted magnetic resonance imaging (MRI) images.  In practice, a sagittal T1-weighted MRI is taken over that ROI.  A Pallidal Index (PI) can then be calculated as the ratio of the signal intensity of the globus pallidus to the subcortical frontal white matter in sagittal T1-weighted MRI planes (Kodua 2004). This PI may serve as a semi-quantitative indicator of brain manganese concentration in vivo, and may functionally represent the target organ (brain) dose of occupational manganese exposure (Kim 2006).

Ultimately, in practice, a clinical differentiation of idiopathic Parkinsons from Manganism is a clinical determination which must include :

*      Complete review of the medical records,

*      Occupational History / exposure to Mn,

*      A complete physical and neurologic exam, including a hepatologic evaluation,

*      Evaluation by a testifying neurologist,

*      Targeted neuro-psychiatric testing

*      MRI,

*      Generation of an expert report on the etiology of symptoms, which incorporates the principles of causation and scientific evidence.

If you are interested inthe use of MRI for evaluation of Manganese or other toxin exposure, please contact us.

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