Mutism in the Older Adult

Nages Nagaratnam, MD, FRCP, FRACP, FRCPA, FACC; Gowrie Pavan, MBBS, FRAGP


Geriatrics and Aging. 2005;8(8):61-68. 

In This Article


There are three dopaminergic pathways, namely the striatonigral pathway (substantia nigra to caudate and putamen), the mesolimbic pathway (ventral tegmental area of midbrain to limbic areas of basal forebrain), and the mesocortical pathway (ventral tegmental area of midbrain to frontal and cingulate cortices) (Figure 4B). Destruction of the ascending dopaminergic pathway, blocking of dopamine receptors by drugs, inhibition of dopamine synthesis, or prevention of dopamine storage has been shown to induce akinesia on animals in experimental studies. Drugs that release dopamine or act as dopamine agonists have been shown to increase the motor activity in experimental animals.[50] In Parkinson's disease (PD), the striatonigral outflow does not function normally because of the degeneration of the dopaminergic cells in the substantia nigra. The SMA appears to be the major target of a disordered nigrostriatal-thalamic outflow in PD. The striatum receiving inadequate dopaminergic stimulation results in functional deafferentation of the SMA and thereby gives rise to a defect in motor programming.

Results for the use of dopaminergic agonists in AM have been varied, which may be due to the site of the lesion giving rise to the AM. In one study of four patients who had global akinesia followed by hypokinesia, bradykinesia, and hypometria due to anterior cerebral artery infarction with damage to the SMA, there was poor response to dopamine agonists.[51] A patient with AM following bilateral damage to the anterior hypothalamus responded to treatment with bromocriptine, a direct dopaminergic receptor agonist.[52] The reason for this response, according to the investigators, was that the lesion was anterior to the site at which the nigrostriatal fibres diverge from the median forebrain bundle.

AM is a clinical syndrome, and the lesions implicated are in the mesencephalic-frontal activating system, which is a dopaminergic pathway. However, it has different etiologies and pathologies that are liable to be induced by diverse localized lesions, and as such, there is no one treatment, pharmacological or non-pharmacological, for AM.


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