Subdural empyema is an infectious lesion of the central nervous system, characterized by the accumulation of purulent exudate in a limited space between the hard and soft cerebral membranes. It appears with headache, vomiting, progressive disorder of consciousness, focal neurological deficit (hemiparesis, cranial nerve dysfunction, aphasia), epiprimes. Subdural empyema is diagnosed mainly with the help of MRI and CT with contrast. Emergency treatment — surgical drainage or removal of empyema against the background of intensive antibacterial therapy. The prognosis is serious.
General information
Subdural empyema is an accumulation of purulent discharge (exudate) in a certain area between the membranes covering the brain. In this case, the pus occupies the space between the more superficially hard (dural) shell and the soft cerebral membrane located under it, directly adjacent to the brain. In neurology, epidural empyema is also distinguished, in which the purulent discharge is located above the dural membrane, between it and the bones of the skull.
Subdural empyema accounts for about 1/5 of all limited intracranial infectious processes. The reason for the formation of purulent discharge is the penetration of a purulent infection into the intervertebral space. In 75% of cases, subdural empyema is one-sided. The volume of purulent exudate can range from 2-3 to 200 ml. With a minimum volume of pus, symptoms of irritation of the cerebral membranes and the cerebral cortex may prevail. As a rule, a rapid increase in the amount of exudate leads to the progressive development of symptoms of compression of the brain.
Causes
The etiological factor is pyogenic microorganisms. More often it is a mixed streptococcal infection (about 35% of aerobas and 10% of anaerobes). Subdural empyema caused by staphylococci, clostridium, gram-negative rods is less common. In patients with compromised immune systems (for example, those suffering from HIV or undergoing cytostatic therapy), Salmonella, associations of microorganisms, Candida fungi may be the etiofactor.
The penetration of infection between the membranes can occur in several ways. Subdural empyema is most often caused by the spread of the infectious process from the paranasal sinuses (with sinusitis) and the mastoid process (with otitis and mastoiditis). Moreover, the “entry” of microorganisms into the cerebral membranes from the focus of purulent inflammation can be carried out both by contact and by hematogenic means. There may be an outpouring of pus into the intervertebral space with a breakthrough of a brain abscess or a suppurated cerebral cyst. Purulent meningitis sometimes serves as a source of purulent discharge in young children.
The penetration of infectious agents is facilitated by traumatic brain injuries with fractures of the skull bones. According to statistics, subdural empyema is a complication of 2-4% of gunshot wounds to the head. Infection is possible with osteomyelitis of the skull bones. Suppurated subdural hematoma can also lead to subdural empyema. In some cases, the ingress of pyogenic microorganisms into the hematoma occurs during its neurosurgical drainage.
Symptoms
Usually subdural empyema has a severe rapidly progressive course. It starts with a headache and a temperature increased to 39-40 ° C. Nausea and vomiting are noted, indicating a sharp intracranial hypertension. 75-80% of patients have meningeal syndrome, a symptom complex that occurs when the cerebral membranes are irritated (occipital rigidity, symptoms of Kernig and Brudzinsky). Certain disorders of consciousness are characteristic, which in about 50% of cases occur already at the beginning of the clinical manifestation of empyema.
According to various data, in 60-80% of patients, the above symptoms appear against the background of the presence of a primary purulent focus (more often chronic purulent otitis or sinusitis). In such cases, the localization of headache initially, as a rule, corresponds to the primary focus. Then the pain becomes widespread. Rapidly increasing intracranial pressure and cerebral edema aggravate the disturbance of consciousness up to coma. In infants, the bulging of the still unclosed large fontanel occurs.
In most cases, focal neurological deficiency is detected already in the first 1-2 days after the onset of the disease. Most often, this is central hemiparesis — weakness and impaired sensitivity of the arm and leg from the opposite localization of the empyema side of the body. Depending on the location of the subdural empyema, there may be: aphasia, bilateral loss of half of the visual field (homonymous hemianopsia), cerebellar ataxia, oculomotor disorders. In half of the patients, subdural empyema occurs with epileptic seizures. Both paroxysms of focal epilepsy and generalized epi-seizures are possible.
Separately, there is a lightning-fast variant of subdural empyema, in which cerebral edema progresses in a matter of hours, which is accompanied by rapid depression of consciousness with the development of coma. Even against the background of treatment, this form often ends fatally.
Diagnostics
To diagnose a subdural hematoma in the absence of the possibility of CT or MRI is a difficult task for a neurologist. A general blood test indicates an inflammatory process (leukocytosis, elevation of ESR). It is important to identify a history of purulent otitis or sinusitis, as well as to diagnose them according to radiography. The study of cerebrospinal fluid is uninformative, since it detects changes that are nonspecific for the empyema. In addition, lumbar puncture in conditions of increasing cerebral edema is dangerous by inserting the brain stem into the large occipital foramen, and therefore, if subdural empyema is suspected, it is usually not performed.
CT scans of the brain with contrast and MRI are the most informative. On CT, the subdural empyema is visible as a crescent-shaped band under the arch of the skull, over which, after contrast is introduced, a narrow band of increased signal appears. However, with a small empyema size, CT can give a false negative result. MRI of the brain allows not only to identify subdural empyema, even of small size, but also to assess its size and prevalence. By the intensity of the MR signal, the radiologist can differentiate empyema from serous exudate, chronic subdural hematoma and epidural abscess.
If tomographic methods of examination are unavailable or their urgent execution is impossible, cerebral angiography can be performed. She visualizes the subdural empyema as a volumetric formation located in the shells without vessels.
Treatment
Timely surgical treatment against the background of massive antimicrobial therapy allows to save the patient. The latter is prescribed empirically until the results of a bacteriological examination of the purulent discharge are obtained. As a rule, broad-spectrum antibiotics (ceftriaxone, cefotaxime) are used, which are administered intravenously after an allergy test. In parallel, drugs are prescribed for the relief of cerebral edema and epi-paroxysms, glucocorticosteroids, according to indications, artificial ventilation of the lungs is carried out.
Operations with empyema are reduced to 2 methods: drainage through a milling hole and removal of empyema by trepanation of the skull. The first method is more often used by neurosurgeons in weakened patients with a high operational risk of trepanation. Several drainage holes may be superimposed in the skull above the subdural empyema zone. However, this does not always allow you to create a good outflow of thick purulent exudate. Trepanation is performed by cutting out the bone-aponeurotic flap and opening the dural shell. It is more traumatic, but it gives a good overview, the opportunity to “clean out” all purulent congestion, and then carry out active drainage.
The purulent discharge obtained during the operation is sent for bacteriological examination, according to the results of which the correction of the antibiotic therapy is performed. On average, antibacterial treatment is continued for up to a month. During the period of convalescence, a rehabilitation course is started, aimed at a more complete restoration of neurological deficit. Under the supervision of a rehabilitologist, the patient undergoes massage and reflexotherapy, is engaged in physical therapy, learns self-service skills in the conditions of persistent neurological abnormalities (paresis, sensitivity disorder, aphasia).
Forecast
On average, mortality among patients with subdural empyema is about 20%. The most unfavorable prognosis is in the lightning form. Prognostically, the beginning of treatment at the stage of severe disorders of consciousness and severe neurological deficit is considered less favorable. Up to a quarter of the surviving patients have gross residual disorders in the form of paresis or paralysis, speech disorders, etc. The development of epilepsy is possible.