Akinetic mutism is a "syndrome of negatives", characterized by lack of voluntary movement (akinesia), absence of speech (mutism), lack of response to question, and command, but with normal alertness and sleep-wake cycles (cf. coma). Blinking (spontaneous and to threat) is preserved. Frontal Release Signs, such as grasping and sucking, may be present, as may double incontinence, but there is a relative paucity of upper motor neurone signs affecting either side of the body, suggesting relatively preserved descending pathways. Abulia has been characterized as a lesser form of akinetic mutism.
Pathologically, akinetic mutism is associated with bilateral lesions of the "centromedial core" of the brain interrupting reticular-cortical or limbic-cortical pathways but which spare corticospinal pathways; this may occur at any point from frontal lobes to brainstem:
anterior cingulate cortex (medial frontal region)
paramedian reticular formation, posterior diencephalon, hypothalamus
Other structures (e.g., globus pallidus) have been implicated but without pathological evidence.
These pathologies may be vascular, neoplastic, or structural (subacute communicating hydrocephalus). Akinetic mutism may be the final state common to the end-stages of a number of neurodegenerative pathologies.
Occasionally, treatment of the cause may improve akinetic mutism (e.g., relieving hydrocephalus). Agents, such as dopamine agonists (e.g., bromocriptine) and ephedrine, have also been tried.
Cairns H. Disturbances of consciousness with lesions of the brain stem and diencephalon. Brain 1952; 75: 109-146
Freemon FR. Akinetic mutism and bilateral anterior cerebral artery occlusion. Journal of Neurology, Neurosurgery and Psychiatry 1971; 34: 693-698
Ross ED, Stewart RM. Akinetic mutism from hypothalamic damage: successful treatment with dopamine agonists. Neurology 1981; 31: 1435-1439