Unlike fainting, hemorrhagic stroke or epilepsy, in which consciousness is impaired suddenly, slowly progressive impairment of consciousness up to deep coma is characteristic of diseases such as exogenous and endogenous intoxication, intracranial space-occupying processes, inflammatory lesions of the nervous system, and less commonly other causes.
The main causes of progressive clouding of consciousness:
- Exogenous intoxication
- Intracranial volumetric process
- Thrombosis of cerebral sinus(es) and stroke
- Diffuse cerebral ischemia
- Encephalitis, meningitis
- Wernicke Encephalopathy
- Status epilepticus (simple and complex partial seizures)
- Metabolic disorders
- Increased blood viscosity (dehydration)
Exogenous intoxication
Undoubtedly, the most common cause of progressive stupefaction (stunning, stupor, coma) is intoxication. The increase in symptoms and their severity are due to the ongoing absorption of the toxic agent (including a drug or alcohol) and its cumulative dose. The presence and nature of the response to external stimuli determines the depth of loss of consciousness. The patient may experience slow floating movements of the eyeballs, which may or may not be friendly. There may be no oculocephalic reflex, that is, a reflexive abduction of the eyes in the direction opposite to the stimulated labyrinth when the patient’s head is passively turned in the lateral or vertical plane. The oculocaloric reflex (nystagmus to the side opposite to the side of the stimulated labyrinth) may be absent. The pupils are constricted, pupillary photoreactions are usually preserved. As the coma progresses, the pupils dilate and photoreactions become lost. The phenomenon of decerebrate rigidity may be observed in the limbs. As the impairment of consciousness progresses, muscle hypotonia, areflexia (atonic coma) and critical impairment of vital functions (circulation and respiration) develop. Such dynamics of symptoms indicate progressive dysfunction (suppression) of the main systems of the brain stem.
The complete absence of clinical signs of functional activity of the brain (lack of spontaneous breathing, loss of the ability to thermoregulate, extinction of all cerebral reflexes – corneal, cough, oculocardial, oculovestibular, photoreaction of the pupils, swallowing) usually (but not always) indicates its irreversible damage, defined as extreme coma and is considered as one of the criteria for the state of brain death. Diagnostic criteria for brain death also include bioelectrical silence of the brain (isoelectric line on the EEG); lack of cerebral blood flow (the phenomenon of pseudothrombosis during carotid and vertebral angiography); absence of cerebral arteriovenous oxygen difference.
Some of these criteria (in particular, bioelectrical silence of the brain, absence of cerebral reflexes, spontaneous breathing and thermoregulation) are not sufficient to diagnose brain death if the patient was treated with hypothermia or if the coma was caused by poisoning with sedatives. In these cases, restoration of cerebral functions is possible even after a sufficiently long (hours) stay in a state corresponding to the clinical characteristics of an extreme coma. Because this condition is not irreversible, it is defined as coma with loss of autonomic functions and is not considered an indicator of brain death.
Intoxication, as a cause of impaired consciousness should be considered in the absence of other possible etiological factors of stupor or coma.
Without additional research, diagnosing intoxication is often impossible. Neuroimaging and transcranial Doppler sonography revealed no pathological changes. In case of overdose of barbiturates and benzodiazepines, predominant beta activity is recorded on the EEG; during intoxication with other drugs, diffuse changes in the electrical activity of the brain are detected. These electrophysiological studies reveal only dysfunction of cortical and brainstem structures. It is useful to search for traces of taken substances or drugs in clothing pockets, in places where medications are stored, in the nightstand, etc. Key diagnostic methods include blood and urine tests for the presence of toxic agents; in case of sufficient grounds to suspect intoxication, forced diuresis, administration of antidotes, and hemodialysis are used.
Intracranial volumetric process
The presence of symptoms of focal brain damage indicates the possibility of an intracranial space-occupying process (tumor, hematoma, abscess). The cause of confusion may be a rupture of a vessel feeding the tumor, or an increase in cerebral edema, or a violation of venous outflow. Anamnestic information indicating the possibility of brain pathology may be absent, and swelling of the optic discs is not always observed. The EEG reveals focal and diffuse changes in electrical activity. Carrying out a lumbar puncture is associated with risks – it is possible that the temporal lobe is pinched or the cerebellum is herniated into the foramen magnum and compression of the brain stem.
The diagnosis is made by neuroimaging studies or cerebral angiography.
Thrombosis of cerebral sinus(es) and stroke
In rare cases, progressive confusion may be the only symptom of cerebral sinus thrombosis. The onset of the disease can be acute, subacute or chronically progressive. In most cases, the first symptoms are epileptic seizures and mono- or hemiparesis. If these symptoms occur during labor, venous sinus thrombosis is the most likely diagnosis. However, cases of “spontaneous” thrombosis are not uncommon; in such situations, immediate clinical diagnosis is significantly difficult. Erythrocyte pleocytosis may be detected in the cerebrospinal fluid (which, as a rule, gives rise to the erroneous assumption of subarachnoid hemorrhage).
Causes of aseptic thrombosis of large sinuses of the brain: pregnancy and the postpartum period, Behçet’s disease, systemic lupus erythematosus, taking oral contraceptives, polycythemia, antiphospholipid syndrome, deficiency of antithrombin III, protein C, hemolytic anemia, traumatic brain injury, brain tumors, severe dehydration, cerebral arterial occlusions.
Causes of septic thrombosis: general and local infections, diseases of the ear, throat, nose, teeth; facial boils, brain abscesses, osteomyelitis, pneumonia, postpartum endometritis, septic conditions.
Differential diagnosis of dural sinus thrombosis is carried out with impaired arterial circulation of the brain, brain tumor, meningoencephalitis, eclampsia.
Hemorrhagic stroke is often accompanied by a rapid (sometimes instantaneous) development of a coma, but a slow (subacute) deterioration of the condition and an increase in neurological symptoms is possible. Hemisyndromes, bilateral pyramidal signs, meningeal syndrome and lesions of the cranial nerves are detected. Like ischemic strokes, all other cerebrovascular accidents are more common in adulthood and old age and develop against the background of known risk factors.
The diagnosis is based on the results of neuroimaging or angiographic studies, with special attention paid to blood flow velocity and visualization of the sinuses during the late phase of the pulse wave. If the diagnosis of sinus thrombosis is confirmed, a detailed study of the hemostatic system should be mandatory.
The diagnosis is especially aided by neuroimaging methods (“delta sign” on CT: the contrast agent surrounding the thrombosed sinus forms an A shape, reminiscent of the Greek letter delta).
Diffuse cerebral ischemia
Diffuse cerebral ischemia associated with anoxia during atrioventricular block or ventricular fibrillation, or, for example, with carbon monoxide poisoning can lead to progressive darkness. For diagnosis, an anamnesis indicating heart disease, analysis of clinical symptoms, and an ECG are important.
Encephalitis, meningitis
Diagnosis of encephalitis in the acute phase is often difficult. It is important to consider the existence of two variants of encephalitis. Post-infectious encephalitis (encephalomyelitis) usually develops following an unclear viral infection, usually affecting the respiratory tract and is more often observed in children. It manifests itself primarily by general cerebral symptoms, the most striking of which are lethargy, generalized epileptic seizures and diffuse slowing of EEG activity without or with minimal focal changes. Neurological symptoms vary and reflect the location of the predominant lesion. Signs of demyelination predominate.
In contrast to post-infectious encephalitis, in acute viral encephalitis there is focal damage to the brain tissue of one of the hemispheres by a viral agent, which is manifested (in addition to progressive clouding of consciousness) by focal symptoms, for example, aphasia or hemiplegia. We are not considering slow viral infections here.
Any viral encephalitis is characterized by an acute onset and fever. Clinical manifestations of most viral encephalitis include headaches, fever, altered level of consciousness, confusion, speech and behavioral disturbances, and neurological signs such as hemiparesis or epileptic seizures. These symptoms distinguish viral encephalitis from viral meningitis, which usually involves only a stiff neck, headaches, photophobia, and fever. Certain viruses have tropism for certain types of cells in the brain (poliovirus preferentially affects motor neurons; rabies virus affects neurons of the limbic system; damage to cortical neurons leads to epileptic seizures and focal symptoms; herpes symplex affects predominantly the temporal lobes (aphasia, anosmia, temporal lobe seizures, other focal symptoms). The epidemiological situation can help in identifying the nature of the virus. In the cerebrospinal fluid there is usually pleocytosis (mainly mononuclear cells), increased protein content. Sometimes the cerebrospinal fluid can be normal. EEG and MRI reveal focal changes in the brain. Serological studies of cerebrospinal fluid in acute period do not always help the diagnosis.
Diagnosis of meningitis
Diagnosing meningitis is less difficult. The clinical picture of unconsciousness is dominated by meningeal syndrome. CSF analysis solves almost all diagnostic issues.
Wernicke Encephalopathy
Acute or subacute appearance in a patient of such pupillary disorders as uneven dilation of the pupils with impaired photoreactions should facilitate the recognition of Wernicke encephalopathy. The diagnosis is confirmed by the appearance of oculomotor disorders, ataxia, nystagmus, and stupor. These symptoms occur due to damage to the midbrain. At this stage of the disease, there is only a slight disturbance of consciousness, since the activating reticular system has not yet been significantly damaged. Almost all patients have clinical signs of chronic alcohol abuse: mild jaundice, dilated veins, tremor of the fingers, loss of Achilles reflexes. An objective history collected from relatives or friends of the patient is important.
Status epilepticus (simple and complex partial seizures)
With a series of partial epileptic seizures (simple or complex), there may be no progressive confusion of consciousness. This condition is discussed in this chapter because the very moment of a sudden change in the level of consciousness may elude the attention of the doctor and the doctor notes only an increasing deterioration of the condition. Epileptic syndrome extremely rarely debuts with status epilepticus; If the doctor knows that the patient has a history of epileptic seizures, then diagnosing status epilepticus should not cause difficulties. The leading symptoms are characteristic stereotypical convulsions and movements. In the case of status epilepticus with simple partial seizures, these are nystagmoid eye twitches upward with a frequency of about 3 per second and, sometimes, contraction of the facial muscles. In complex partial seizures, the well-known chewing or swallowing movements and/or any stereotypical movements made with both hands, and sometimes vocalizations, are observed. The diagnosis is confirmed by the results of an EEG study: periods of generalized spike-wave activity with a frequency of 3 per second or bilateral sharp wave-slow wave complexes are recorded in the temporal leads. Although this condition develops acutely, if help is not provided for any reason, status epilepticus can lead to progressive cerebral edema and death of the patient.
Metabolic disorders
The clinical manifestations of metabolic disorders are very nonspecific, and their diagnosis is only possible through a wide range of laboratory tests. The most common cause is hyperglycemia (diabetes mellitus), with the hyperosmolar rather than the ketoacidotic form being more common. If diabetes mellitus is excluded, consultation with a physician and screening for other metabolic disorders (uremia, liver failure, etc.) is necessary.
Increased blood viscosity (dehydration)
Often, elderly patients who do not receive adequate care are admitted to the hospital at the stage of progressive confusion, developing as a result of dehydration. This is possible, for example, in patients suffering from dementia – they may simply forget to drink. However, this syndrome can develop not only in a patient at home. A neurologist may encounter such a situation in a surgical hospital, when in the postoperative period a patient on parenteral nutrition does not receive a sufficient amount of fluid. Excessive use of diuretics in an elderly patient, especially one suffering from diabetes mellitus (sometimes undiagnosed), is always fraught with a worsening of the condition.
A progressive deterioration in consciousness may be caused by other somatic diseases (heart failure, pneumonia), which are usually accompanied by a characteristic clinical picture and the corresponding results of paraclinical examination (ECG, chest x-ray, etc.).