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 symptoms, causes and main types.
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 older, her malformation gave Elsie increasingly severe headaches that led doctors to give her morphine treatment.
The patient began to show signs of apathy along with significant impairments in her ability to speak and control movements. The symptoms progressed to a state that Cairns and her colleagues named “akinetic mutism.”
These authors described the disorder as a state in which the person remains motionless, although it can focus on objects and follow movements. Statism also affects the movements necessary for speech and other vocalizations. Although actions and sounds are sometimes carried out, these are not usually voluntary.
As we will see below, the Cairns team’s proposal has been updated over the years and subsequent scientific progress. Today the term “akinetic mutism” is often used to describe any case that shows the absence of motor and verbal behaviors that give it its name, and that may also consist of less serious 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 focus on other people, the execution of eye movements in reaction to auditory stimuli, actions in response to commands they repeat and difficulties speaking and communicating in general.
However, we currently 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 objects with your eyes They are the two basic diagnostic criteria.
The authors of this work highlight the variability of emotional alterations in these cases. Thus, patients have been identified 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 who have akinetic mutism cannot speak, gesture, or form facial expressions, or they suffer serious difficulties in doing so. When they succeed, the movements tend to be slow and few, and the responses monosyllabic.
People with akinetic mutism are not paralyzed at a motor level, but the alterations that cause it seem to affect the will and motivation to execute 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 their 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 the midbrain, respectively.
Frontal akinetic mutism is frequently due to alterations in blood flow, specifically in the anterior cerebral artery. Disorders and strokes are the most common 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 frequently appears in conjunction with signs of disinhibition typical of frontal syndrome. Thus, in these cases there are frequently 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, essential 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.
