Apallic syndrome is a clinical symptom complex, including the absence of signs of awareness in the presence of eye opening, alternating sleep / wakefulness. According to neurologists, it is associated with extensive damage to the cerebral cortex. It can be a transitional state when coming out of a coma. It is diagnosed exclusively clinically using scales to assess the level of consciousness. Instrumental examinations (EEG, MRI, PET) are auxiliary, allow to establish causal pathology. Treatment is aimed at stimulating recovery, maintaining vital functions, preventing complications, and reducing hydrocephalus.
ICD 10
R40.2 Coma, unspecified
General information
The new cortex (neocortex), consisting of 6 layers of neurons, covers the surface of the hemispheres of the brain and has the anatomical name “pallium” — a cloak. Accordingly, apallic means the absence of pallium, its functional “shutdown”. The term “apallic syndrome” was proposed by the German doctor Kretchmer in 1940, is used in Germany, CIS countries. In English-language sources on neurology, the term “vegetative state”, introduced in 1972, is used. Apallic syndrome (AS) occurs in 25-100 patients per 1 million. a person in the population, in many countries there is a tendency to increase the number of cases. AS is observed in persons of both sexes of different age groups – from infants to the elderly.
Causes
The basis of AS is a total or subtotal lesion of the neocortex while preserving the function of the brain stem. Etiological factors are:
- Traumatic brain injury. Traumatic genesis has the majority of cases of AS of young age.
- Cerebral hypoxia. It is noted with carbon monoxide poisoning, asphyxia, severe arterial hypotension, cardiac arrest due to heart diseases, during surgical interventions.
- Neuroinfections. Apallic syndrome can become the outcome of acute infectious processes with extensive damage to the cerebral cortex, occur at the final stage of slow CNS infections (Schilder’s leukoencephalitis, progressive rubella panencephalitis).
- Brain tumors. In some cases, extensive tumor processes lead to AS caused by hypoxia, neurotoxicosis, cerebral edema.
- Progressive degenerative diseases. They are the main cause of AS in elderly patients. The syndrome is observed at a late stage of Alzheimer’s disease, Creutzfeldt-Jakob, Peak, vascular dementia, alcoholic encephalopathy.
- Acute dysmetabolic states. Uremic, hypoglycemic, hepatic coma can turn into an apallic state.
- Brain abnormalities: microcephaly, severe cortical dysplasia. They cause apallic syndrome in young children.
Pathogenesis
The morphological picture of cortical lesion in AS is nonspecific, it differs in different patients. Hypoxic injuries are accompanied by necrosis, traumatic — diffuse axonal damage, degenerative — atrophy. The variability of the volume and nature of the lesion, the absence in some cases of significant morphological changes, indicates functional disorders leading to the “shutdown” of the cortex. The pathophysiological foundations of these processes are under study.
The transition from coma to the apallic state is characterized by the restoration of the function of the reticular formation, subcortical structures. The resumption of connections between the subcortex and the cortex leads to further restoration of consciousness. If cortical connections are not restored, do not form again or are formed incorrectly, a chronic vegetative state occurs — apallic syndrome. In the outcome of progressive cortical degeneration, AS develops due to the massive loss of connections that ensure the interaction of neurons within the cortex and with underlying structures.
Symptoms
The basis of the clinical picture is a paradox: the presence of visible signs of consciousness in the absence of objective criteria for the patient’s awareness of himself and the world around him. The patient opens his eyes, moves them in a state of wakefulness, reacts to pain stimuli, goes through sleep-wake cycles, which forms the impression of awareness. However, there are no signs of conscious activity, purposeful activity. The movements are spontaneous, there are no emotional and conscious reactions. Eye movement is chaotic, tracking reaction is not observed. The alternation of sleep and wakefulness does not depend on the time of day.
The patient’s face is masked, without facial expressions. Chewing and swallowing are slowed down, chewing movements, blinking, yawning may be noted. In response to pain stimuli, a non-directional motor reaction occurs, accompanied by increased heart rate and respiration, dilation of the pupils. The function of the pelvic organs is not controlled. Epileptic paroxysms are possible. Typically, an increase in muscle tone: the hands are compressed, the feet are in a state of plantar flexion, the limbs are bent and brought. The functioning of the hypothalamus and brain stem ensures the maintenance of the necessary hemodynamics, respiratory activity, and autonomic function. In the waking phase, the predominance of the sympathetic nervous system is characteristic (increased heart rate, blood pressure, chills are possible), in the sleep state — parasympathetic (decreased blood pressure, heart rate, increased sweating).
Apallic syndrome of traumatic, hypoxic, dysmetabolic genesis occurs acutely, often observed after a previous coma. The apallic symptom complex in degenerative processes develops gradually, sometimes over several years. In the first case, it is possible to restore consciousness, the first signs of which are fixing the gaze, following the object with the eyes, following simple instructions (requests to close your eyes, squeeze your fingers). Since there are cases of the appearance of eye tracking without further recovery, it is customary to consider this symptom as a criterion for getting out of the apallic state only if it is combined with other signs of expansion of consciousness.
Complications
Due to the constant spastic state of the limbs, joint contractures develop. Prolonged presence of the patient in bed with a sharp restriction of motor activity contributes to the occurrence of bedsores, congestive pneumonia. It is possible to attach a secondary urinary tract infection with the development of pyelonephritis. Apallic syndrome can lead to the final extinction of all brain functions with a fatal outcome. Infectious complications that turn into sepsis can become deadly for the patient. Proper care, nutrition, supportive therapy can delay the appearance of complications, increase the patient’s life expectancy.
Diagnostics
Due to the lack of clear criteria of consciousness and awareness, it is not easy to diagnose apallic syndrome. According to generally accepted rules, in infants, the diagnosis is established after the age of three months, since previously it is impossible to reliably differentiate conscious and reflex behavior. Neurologists, anesthesiologists, resuscitators, neurophysiologists, and, if necessary, neurosurgeons participate in the diagnosis. The following diagnostic measures are carried out:
- Neurological examination. There is no contact with the patient at all. There is a spontaneous movement of the eyeballs, an unintended reaction to pain stimuli. Cranial and spinal reflexes, vegetative function are preserved. Hypertonicity of limb muscles with signs of plasticity, increased tendon reflexes, the presence of symmetrical pathological reflexes is observed.
- Electroencephalography. A low-wave EEG, delta or theta rhythm is characteristic. 10-20% of patients have an alpha or beta rhythm. Recovery is accompanied by the appearance of a distinct alpha rhythm.
- MRI brain. MRI and other methods of neuroimaging (CT) do not reveal specific morphological changes. The picture corresponds to the main disease: foci of necrosis, hematomas, tumors, intracerebral degenerative processes, edema of the medulla are determined. 75% of patients have hydrocephalus. Most cases of AS are accompanied by atrophic changes in the cortex, but such atrophy is observed in conscious patients with dementia.
- PET-CT brain. Allows you to diagnose a decrease in cortical metabolism by 40-50%. The recovery proceeds with the activation of metabolism recorded on PET.
- Transcranial US. It is aimed at assessing cerebral hemodynamics. It has an auxiliary value, is used mainly when deciding on the feasibility of bypass surgery in patients with hydrocephalus.
It is necessary to differentiate the apallic syndrome from coma, the state of minimal consciousness, sopor. Differentiation is carried out using clinical scales. Instrumental methods cannot accurately indicate the level of consciousness of the patient, allow us to establish the nature of the lesion of the cortex, to judge the level of metabolism of cerebral tissues.
Treatment
The therapy is aimed at life support of the patient, prevention of complications and restoration of consciousness. There is no uniform standard for the management of patients. Treatment is carried out for a long time, sometimes for months. Conservative and surgical methods are used:
Conservative therapy:
- Stimulation of recovery processes. The medicinal component includes powerful nootropic, vitamin, vascular therapy, endolumbal oxygen injection. In parallel, regular sensory stimulation is carried out using the entire spectrum of stimuli: auditory, tactile, visual, olfactory.
- Artificial nutrition. It is carried out through a gastrostomy, since probe feeding is often accompanied by complications: aspiration of food into the respiratory tract, gastroesophageal reflux, ulceration of the mucosa in places of contact with the probe.
- Prevention of complications. In order to reduce spasticity and prevent contractures, muscle relaxants are prescribed. The best prevention of pressure sores and hypoventilation pneumonia is adequate care, including a change of underwear, a change of posture, planting with the help of special orthopedic devices, passive physical therapy, massage. It is advisable to involve the patient’s relatives in the care.
Surgical methods:
- Bypass surgery. They are indicated for severe hydrocephalus. Lumboperitoneal and ventriculoperitoneal bypass surgery are the most common.
- Deep electrical stimulation of the brain. It is carried out by stereotactic introduction of microelectrodes, through which the activating systems of the trunk are stimulated.
- Neurotransplantation. It is a new experimental method of treating AS. Activates regeneration of cerebral tissues, provides material for reconstruction of damaged areas. The introduction of embryonic nerve cells is performed intraventricularly (into the cerebral ventricles), intracerebrally (into the cortex or damaged deep areas of the brain).
Prognosis and prevention
The outcome depends on the nature of the brain lesion that caused the apallic syndrome, the age of the patient, the duration of the coma, the presence of convulsive seizures. Acutely developed AS may result in the restoration of consciousness, but in most cases patients remain disabled due to a pronounced psycho-organic syndrome. In the case of progressive cerebral degeneration, apallic syndrome is a terminal stage and ends fatally. Prevention of AS is the prevention of injuries, neuroinfections, intoxication, timely treatment of cardiovascular pathology.
