Akinetic mutism: types, symptoms and causes

This neurological disorder makes us unable to speak or move voluntarily.

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 brain damage.

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

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 in the right lateral ventricle. As she grew, the malformation caused Elsie increasingly severe headaches that led doctors to treat her with morphine.

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

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

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

Main symptoms and signs

Cairns et al. (1941) pointed out five key signs for the diagnosis of akinetic mutism: the presence of alert states, the ability to fix the gaze on 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 the significant reduction in the number of verbal behaviors and the ability to follow and the ability to follow objects with the gaze are the two basic diagnostic criteria.

The authors of this work highlight the variability of the emotional alterations in these cases. Thus, patients with evident impairments in the expression of emotions have been identified, but also others with signs of disinhibition. This clinical diversity is related to the specific location of the brain lesions causing akinetic mutism.

The characteristic immobility of this alteration is manifested in all the facets of motor skills, so that those who have akinetic mutism cannot speak, make gestures or form facial expressions, or suffer serious difficulties to do so.or suffer serious difficulties to do so. When they manage to do so, movements tend to be slow and scarce, and monosyllabic responses.

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

Types of akinetic mutism and its causes

The symptoms and signs of each case of akinetic mutism depend on the brain regions damaged by the factor causing 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 midbrain, respectively.

Frontal akinetic mutism is frequently due to alterations in the Blood supply, specifically in the anterior cerebral artery. Disorders and cerebrovascular accidents are the most frequent causes of akinetic mutism, if 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 frequently appears in conjunction with signs of disinhibition typical of frontal syndrome. Thus, in these cases there are often impulsive emotional responses related mainly to passivity.

The midbrain is a subcortical structure containing such relevant brain nuclei as the colliculi, involved in visual and auditory perception, and the substantia nigra, fundamental in the production of dopamine and therefore in reinforcement. This kind of akinetic mutism is 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 prion infections.

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