Akinetic mutism: types, symptoms and causes

Akinetic mutism is a syndrome characterized by a reduction in the frequency of movements, including verbal behaviors, associated with motivational deficits that occur as a consequence of damage cerebral.

In this article we will describe what is akinetic mutism and what are its symptoms, causes and main types.

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What is akinetic mutism?

In the year 1941 Cairns, Oldfield, Pennybacker and Whitteridge described the case of Elsie Nicks, a 14-year-old girl with a cyst on her right lateral ventricle. As she grew older, the malformation caused Elsie to Headaches increasingly intense that led the doctors to apply a treatment with morphine.

The patient began to show signs of apathy along with significant impairments in her ability to speak and to control movement. The symptoms progressed to a state that Cairns and his colleagues dubbed "akinetic mutism."

These authors described the disorder as a state in which the person remains immobile, although he can fix his gaze on objects and follow movements. Stillness also affects the movements necessary for speech and other vocalizations. Although actions are sometimes carried out and sounds are emitted, these are not usually voluntary.

As we will see below, the Cairns team's proposal has been updated over the years and the consequent scientific progress. Today the term "akinetic mutism" is often used to describe any case showing the absence of motor and verbal behaviors that give it its name, and that can also consist of less serious deficits.

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Main symptoms and signs

Cairns et al. (1941) pointed out five key signs for the diagnosis of akinetic mutism: the presence of states of alertness, the ability to gaze at other people, the execution of eye movements in reaction to auditory stimuli, actions in response to repeated commands, and difficulties in speaking and communicating in general.

However, we now have more specific knowledge about akinetic mutism. In their review of the relevant scientific literature, Rodríguez-Bailón et al. (2012) conclude that significant reduction in the number of verbal behaviorsand the ability to follow objects with your eyes are the two basic diagnostic criteria.

The authors of this paper highlight the variability of emotional disturbances in these cases. Thus, patients with evident impairments in the expression of emotions, but also others with signs of disinhibition. This clinical diversity has to do with the specific location of the brain lesions that cause akinetic mutism.

The immobility characteristic of this alteration is manifested in all facets of motor skills, so that those with akinetic mutism cannot speak, gesture, or form facial expressions, or suffer serious difficulties in doing so. When they do, movements tend to be slow and sparse, and responses monosyllabic.

People with akinetic mutism are not paralyzed at the motor level, but the alterations that cause it seem to affect the will and the motivation to carry out behaviors, among them the verbal. Many patients with this disorder have reported that they feel a resistance that prevents them from moving when they try to do so.

Types of akinetic mutism and their causes

The symptoms and signs of each case of akinetic mutism depend on the brain regions damaged by the causative factor of the disorder. Broadly speaking, we can distinguish two variants of akinetic mutism: frontal and mesencephalic, which are associated with lesions in the frontal lobe of the brain and in the brain. midbrain, respectively.

Frontal akinetic mutism is frequently due to alterations in blood supply, specifically in the anterior cerebral artery. Disorders and cerebrovascular accidents are the most frequent causes of akinetic mutism, although it can also appear as a consequence of infections, contact with toxic substances and neurodegenerative diseases.

When akinetic mutism arises as a consequence of frontal lesions, it often occurs in conjunction with signs of disinhibition typical of frontal syndrome. Thus, in these cases there are often impulsive emotional responses related above all to passivity.

The midbrain is a subcortical structure that contains brain nuclei as relevant as the colliculi, involved in visual and auditory perception, and the substantia nigra, fundamental in the production of dopamine and therefore in the reinforcement. This kind of akinetic mutism associated with hypersomnolence and motivational deficits.

Akinetic mutism can also be caused by respiratory arrest (which can lead to cerebral hypoxia), head trauma, tumors, meningitis, hydrocephalus, damage to the thalamus, destruction of the cingulate gyrus, and Creuztfeldt-Jakob disease, a neurodegenerative disorder caused by infections of prions.

Bibliographic references:

• Cairns, H.; Oldfield, R. c.; Pennybacker, J. b. & Whitteridge, D. (1941). Akinetic mutism with an epidermoid cyst of the 3rd ventricle. Brain, 64(4): 273–90.

• Rodríguez-Bailón, M.; Trivino-Mosquera, M.; Ruiz-Perez, R. & Arnedo-Montoro, M. (2012). Akinetic mutism: review, neuropsychological protocol proposal and application to a case. Annals of Psychology, 28(3): 834-41.