Akinetic mutism is a symptom complex consisting in the absence of voluntary movements and expressive speech in the presence of a potential opportunity to move and speak. Patients are in a state of wakefulness, they retain the ability to fix their gaze, follow objects with their eyes, react to sounds, understand speech. The diagnosis is confirmed by neurological and neuropsychological examination, head MRI, EEG, lumbar puncture. Akinesia and mutism disappear as the cause is eliminated (neurosurgery, pharmacotherapy, neurorehabilitation) with the development of amnesia for the period of the disorder.
ICD 10
F80.1 R41.8
General information
Akinetic mutism (AM) – absence of speech (mutism) and motor activity (akinesia). In modern neurology, it is considered as a form of consciousness disorder, a transitional stage between the apallic syndrome (waking coma) and the exit from the “small consciousness”. For the first time , this neurological phenomenon was described by the British neurosurgeon H. Cairns, who observed a 14-year-old patient with craniopharyngioma of the III ventricle. After drainage of the cavity of the cystic formation, speech and motor functions returned to the teenager for a short time, but then akinetic mutism developed again. The disorder is rare, its exact prevalence is unknown.
Causes
Akinetic mutism is associated with severe structural damage to various areas of the brain of vascular, traumatic, toxic, infectious genesis. Most often develops at the stage of coming out of a coma. The lesion can be localized in the frontal lobes, midbrain, thalamus, cingulate gyrus. AM occurs in the following neurological and neuropsychiatric syndromes:
- Cerebrovascular pathologies: bilateral infarction in the PMA basin, thalamic stroke, subarachnoid hemorrhage.
- Traumatic brain injuries: brain contusion, gunshot wounds of the frontal lobes, intracranial hematomas.
- Volumetric formations: cyst of the III ventricle, hemangioma of mesencephalic localization, meningioma of the olfactory sulcus, brain abscess.
- Neurotoxic effects: taking immunosuppressants, neuroinfections.
- Creutzfeldt-Jakob disease (terminal stage, mesencephalic form).
- Mental disorders: hysterical and affective psychoses, schizophrenia.
- Other causes: obstructive hydrocephalus, hypoxic encephalopathy.
Pathogenesis
The pathophysiology of akinetic mutism is associated with damage to the frontal-subcortical structures involved in the translation of a motivational stimulus into a behavioral response. Purposeful behavior is the end result of receiving and processing information from the cognitive, motor, limbic areas. Loss of function of any element of this frontal-subcortical chain can seriously affect motivation, planning and implementation of actions.
The frontal lobes act as an integrator of information coming both from outside and from the limbic system. Decreased motivation, abulia, and general loss of interest are closely associated with damage to various areas of the frontal cortex. The anterior cingulate cortex (PC) presumably provides the relationship between decision-making in the frontal lobe and the “emotional brain” (limbic system), participates in the choice of behavioral reactions. In addition, it plays a crucial role in speech initiation and vocalization. Bilateral damage to the cingulate cortex is often described in patients with hemorrhage, stroke, severe TBI and akinetic mutism.
The PC not only has direct subcortical projections, but can also indirectly, through the ventromedial striatum, affect such subcortical structures as the hypothalamus and mesencephalic region. It has been noted that apathy, depression, akinesia, anhedonia, and mutism also develop when the striatum is damaged. Dopaminergic neurons located in the midbrain play an important role in modeling a wide range of behavioral and motor processes. Their damage during a mesencephalic infarction is often associated with akinetic mutism.
The most important link of the frontal-subcortical connections is the thalamus. Integrating information between different functional areas, it ensures synchronization of motivation and behavior, participates in the formation of purposeful reactions. In thalamic strokes, behavioral syndromes such as apathy, disinhibition, personality changes, akinetic mutism, and amnesia are described. The role of various brain structures in the development of the disorder remains the subject of ongoing research.
Symptoms
AM is characterized by the absence of voluntary motor activity, the absence of speech reactions with the preservation of sensory functions and consciousness. This condition is regarded as a stage of exit from the vegetative status. At the same time, the patient is able to open and close his eyes, fix his gaze, follow objects and sounds. Hypersomnia is pronounced, although the cyclicity of sleep and wakefulness persists. In response to a painful stimulus, the patient reflexively pulls back the limb.
With intensive stimulation, patients with akinetic mutism are able to perform the simplest commands, give a monosyllabic verbal or gestural response. Rigidity and spasticity of muscles, as a rule, are expressed slightly. Urinary and fecal incontinence is noted.
The next stage of recovery is akinetic mutism with emotional reactions. The fixation of the gaze becomes more distinct, there is a differentiated emotional response to external stimuli, changes in facial expressions. With a favorable development of events, the outcome of akinetic mutism is the restoration of motor function, understanding of speech and one’s own speech activity. In the future, patients develop amnesia for the entire period of akinetic mutism.
Complications
Immobility of the patient leads to the formation of pressure sores, the development of hypostatic pneumonia. The need for artificial urination and pulmonary ventilation create conditions for the addition of secondary infection. Such patients often have pyelonephritis, ventilator-associated pneumonia. Complications associated with the underlying disease cannot be excluded: paresis, paralysis, food aspiration, venous thromboembolism.
These circumstances complicate the recovery period and recovery. In the residual period after coming out of akinetic mutism, aphasia, amnestic confusion, bradykinesia, depression, psychopathic disorders may persist.
Diagnostics
Clinical diagnosis of akinetic mutism is carried out by neurologists, neuropsychologists, psychiatrists. The neurological status data correspond to the state of minimal consciousness: the patient is immobilized and does not speak, but there is a fixation of the gaze and a tracking reaction. To assess the condition , it is carried out:
- Cerebral tomography. In order to identify primary brain damage, neuroimaging is performed: contrast brain MRI, MR angiography, MR tractography, PET-CT. In this case, foci of ischemia, tumors, intracerebral hematomas, hydrocephalus, and areas of neurodegeneration can be determined. Their localization is the frontal lobes, mesencephalic, thalamic region.
- EP. They allow differentiating akinetic mutism from the vegetative state. AM is characterized by the appearance of flashes of beta-1 waves on the EEG, the predominance of the influence of subcortical and basal structures against the background of inhibition of cortical activity. Additionally, evoked potentials are investigated, TCMS is carried out.
- Lumbar puncture. The study of cerebrospinal fluid provides useful information in the diagnosis of neuroinfections, Creutzfeldt-Jakob disease. In addition, the procedure allows you to measure the cerebrospinal fluid pressure in hydrocephalus, to drain fluid through a spinal catheter.
- Neuropsychological testing. To assess arbitrary behavioral and mental reactions, special test methods are used (the scale of recovery after coma, the scale of cognitive functions, the scale of recovery of mental activity). The main parameters of the assessment are the level of consciousness, response to stimuli, ability to communicate, and follow simple instructions.
Differential diagnosis
Actinetic mutism must be distinguished from other forms of chronic disorders of consciousness, mental and neurological disorders:
- vegetative state;
- psychogenic areactivity;
- mental akinesia;
- locked-in syndrome;
- catatonic stupor;
- anarthria;
- severe depression.
Treatment
The issue of therapy of the disorder remains unresolved until the end. Reports on the drugs used and the duration of treatment are limited. Obviously, the first step in the treatment of akinetic mutism remains the elimination of its underlying cause:
- Neurosurgical interventions. Surgical tactics are determined by the nature of the pathology. With volumetric formations, a cyst of the III ventricle is removed, meningioma is excised, and a brain abscess is drained. Intracranial hematomas compressing brain matter are evacuated by transcranial, stereotactic, and endoscopic access. With depressed fractures of the skull, bone fragments are removed. Correction of hydrocephalus is carried out with the help of shunting operations.
- Pharmacotherapy. To restore and activate brain activity, nootropics, antihypoxants, calcium channel blockers, antiplatelet agents are used. Dopamine agonists, norepinephrine reuptake inhibitors, intravenous administration of magnesia are prescribed directly for the relief of manifestations of akinetic mutism. Selective GABA receptor agonists have a temporary disinhibiting effect.
- Neurorehabilitation. To activate patients with akinetic mutism, classes with a neuropsychologist, speech therapist, and rehabilitologist are recommended. Massage, passive physical therapy, transcranial magnetic stimulation, sensory stimulation are shown.
Patients with akinetic mutism need additional care related to the provision of physiological needs. Nutrition is carried out through a nasogastric probe. To remove urine, a long-term catheterization of the bladder or the imposition of a cystostomy is performed. Additional respiratory support through a tracheostomy is often required.
Prognosis and prevention
The outcome of akinetic mutism correlates with the prognosis of the underlying disease. With a favorable course of TBI, neuroinfection, stroke, clear consciousness, speech and motor activity are gradually restored. At the same time, AM can develop in the terminal stage of prion diseases and act as a predictor of an unfavorable prognosis.
Due to the heterogeneity of the etiology of akinetic mutism, there are no specific preventive measures. It is recommended to reduce the effect of risk factors: blood pressure monitoring, exclusion of contact with neurotoxic substances and carcinogens, prevention of head injuries.
