RARE REASONS OF DEMENTIA: METALS (Al, As, Mn, Hg)

Z. Dimarelou, E. Dermitzakis, J. Rudolf, P. Beredimas, X. Fitsioris, G. Georgiadis

Neurological Department, Papageorgiou Hospital, Thessaloniki, Greece


Dementia is one of the most important problems of the public health especially for the populations of the western countries with important social and economical consequences. Several studies sug­gest the possible influence of substances which exist in the food or in the air (trace elements, metals) in the cognitive function. Trace elements which involve in the metabolic functions and in the oxidative reactions of CNS may influence brain functions.
The scope of this paper is to describe the role of four metals which have been found that they can cause dementia: aluminium (Al), arsenic (As), manganese (Mn) and mercury (Hg).

Aluminium (Al): A subacute form of dementia may appear in patients who are submitted to haemo­dialysis for more than three years. It is believed that this type of dementia is caused by the toxicity of aluminium which exists in the fluids used for haemodialysis, which overloads the patient?s organism with aluminium. The aluminium is deposited in the gray matter of the CNS.
Arsenic (As): It causes dementia from damage to the neuronal membrane. The arsenic is derived from the natural resources of the water, which may be enriched with heavy metals in the underground water reservoirs, and ends up in drinking water. Arsenic also comes from industrial processes and from mining.
Manganese (Mn): Even though the mechanisms of its neurotoxicity have not been cleared up comple­tely, the chronic exposure of the neurons to manganese creates oxidative stress and reduces the production of energy in the mitochrondria. The chronic in­toxication concerns mostly people that for professional reasons are exposed in this metal, like mi­ners, shipyard and industrial workers that inhale manganese dust.
Mercury (Hg): Nowadays there is an increase in the levels of Hg in the atmosphere from the burning of the minerals in the industry. Moreover, the usage of pesticides has as a consequence the increase of its levels on the ground and the water. But the most important source of the general population is the amalgam used by dentists. The influence of Hg on the CNS gives rise to an abundance of symptoms from irritability and insomnia to ataxia, loss of cognitive functions and hallucinations.