OVERVIEW
Intracranial abscess refers to the purulent inflammation and limited abscess caused by the invasion of pyogenic bacteria into the skull. Generally single, but there are also multiple, and can occur in any part of the skull, according to the different parts of the occurrence of intracranial abscess can be divided into brain abscess, epidural abscess, subdural abscess and so on. If the abscess is located in the brain tissue, it is called brain abscess; if it is located outside the dura mater, it is called epidural abscess; if it is located under the dura mater, it is called subdural abscess; if two or more types of abscesses exist at the same time, it is called mixed intracranial abscess.
Causes
Primary infections and susceptibility factors of intracranial abscess include otitis media, sinusitis, brain penetrating injury and post-surgery, lung infection (lung abscess, pyothorax, bronchiectasis), congenital heart disease, acute or subacute bacterial endocarditis, ulcerative colitis, immunocompromised state (e.g., after chemotherapy for tumors of various parts of the body, long-term use of immunosuppressed organ transplantation patients, patients with AIDS, etc.); cranial brain injury (especially); craniocerebral injury (especially); craniocerebral injury (especially); craniocaudal injury (especially); craniocaudal injury (especially). craniocerebral injury (especially skull penetrating injury, intracranial foreign body, craniocerebral firearm injury, etc.), brain surgery infection, pterygoid sinusitis, cranial or pterygoid sinus osteomyelitis, cavernous sinus thrombophlebitis, and so on.
The common causative organisms are mainly staphylococcus, streptococcus, metaplasmosis, Escherichia coli and so on. In recent years, the proportion of abscesses caused by anaerobic bacteria has gradually increased, and mixed infections of various bacteria are also common, in which special attention should be paid to the mixed infection of aerobic bacteria and anaerobic bacteria.
Symptoms
1. Brain abscess
Clinical manifestations of brain abscess may vary according to the speed of abscess formation, size, location and stage of pathological development.
(1) Symptoms of increased intracranial pressure
It may appear in the stage of acute encephalitis. With the formation and gradual enlargement of abscess, the symptoms are further aggravated, and the symptoms of increased intracranial pressure, such as headache, vomiting, and optic papillae edema, are the three main symptoms.
(2) Neurological focal signs
According to the location, size and nature of the abscess lesion, corresponding neurological localization signs may appear. If the main hemisphere (usually the left side) is involved, various kinds of aphasia may appear. If the motor and sensory centers and conduction tracts are involved, central hemiparesis and hemisensory deficits of varying degrees on the contralateral side may occur, and seizures may occur due to stimulation of the motor areas. The optic nerve may be affected, resulting in different degrees of ipsilateral hemianopsia in both eyes. Involvement of the frontal lobe often results in personality changes, mood and memory disorders. Horizontal nystagmus, ataxia, forced head position, positive Romberg’s sign and other limited signs often appear in cerebellar abscess.
(3) Systemic poisoning symptoms
Generally the onset is rapid, with fever, chills, headache, nausea, vomiting, malaise, drowsiness or agitation, and muscle aches and pains. There are signs of meningeal irritation such as resistance in the neck, positive Kirschner’s sign and Briggs’ sign on examination. If the abscess breaks into the ventricle of the brain, the patient’s condition often worsens suddenly, and coma occurs, even life-threatening in a short time.
2. Subdural abscess
(1) Symptoms of primary infection.
(2) Symptoms of systemic infection and poisoning are often manifested as headache, chills, fever, nausea, vomiting, restlessness, drowsiness, and even coma. Examination of the patient may have symptoms of meningeal irritation such as cervical rigidity and positive Kirschner’s sign; the fundus of the eye can be seen as optic papilla edema, and intracranial pressure increase symptoms such as hemorrhage and exudation can sometimes be seen in the retina.
(3) Focal localization signs, which may cause hemiparesis, aphasia, limited seizures or epileptic status. If the abscess occurs on both sides, the neurological signs on both sides may appear or the fixed side signs are not obvious. In patients with subdural abscesses adjacent to the falx cerebri, hemiparesis of the lower extremities occurs earlier and there are limited seizures. In severe cases, brain herniation may occur.
3. Epidural abscesses
(1) Acute stage
Patients mostly have systemic symptoms of infection, such as headache, chills, fever, malaise, malaise, limited headache. Severe infection may present high fever, chills, delirium and meningeal irritation.
(2) Chronic phase
A few weeks after the onset of the disease, abscesses are formed and the symptoms are instead reduced. Secondary to cranial osteomyelitis, when the local formation of abscess or sinus tract and pus discharge, the symptoms can be improved; secondary to frontal sinusitis, otitis media and mastoiditis, most of the local skin edema and tenderness; otitis media caused by the destruction of the tip of the rocky bone can lead to the ipsilateral damage to the trigeminal nerve and the abducens nerve is called Grodenigo syndrome.
Examination
1. Cerebrospinal fluid examination
The pressure of cerebrospinal fluid is mostly increased, the number of cells in the cerebrospinal fluid is obviously increased in the acute stage, the sugar and chloride are normal or low, and the protein content is mostly increased.
2. Blood test
The white blood cell count and classification count are increased, and the blood sedimentation rate is increased.
3. X-ray cephalometric film
Most of them are normal. Occasionally, cranial osteomyelitis, intracranial metal foreign body, middle ear mastoiditis (especially cholesteatoma), sinusitis, etc. can be found to help diagnosis.
4.CT examination
CT scan helps to understand the size, number and shape of the abscess, and helps to choose the timing of surgery and determine the treatment. In the acute encephalitis stage when the abscess has not yet formed, the brain abscess is characterized by a low-density lesion with blurred edges and occupying effect, which is not enhanced in the enhanced scan. After the formation of brain abscess, the enhancement scan can see a complete, thick and homogeneous obvious ring-shaped enhancement shadow with a low-density necrotic area in the center, and there is obvious irregular edema around the enhancement foci, and there is a significant occupying effect. Most of them are single, but they can also be multicompartmental.
Epidural abscess can be seen as epidural trapezoidal irregular mixed density or hyperdense shadow.
CT of subdural abscess can be seen as crescent-shaped low-density shadow of subdural cavity inside and outside the brain, with compression of brain tissues and displacement of midline structures, sometimes accompanied by edema of adjacent brain tissues, cerebral infarction or brain abscess. Enhancement scan can see the enhancement of the peritoneum, especially the enhancement of the lateral peritoneum of the brain tissue is obvious.
5.MRI
MRI examination is more sensitive and accurate than CT in the diagnosis of various types of brain abscess.
For the diagnosis of brain abscess, the necrotic area of brain abscess on T1WI shows low signal intensity, which is surrounded by a thin ring of equal or high signal, which is the peritoneum of the abscess. The low-signal area outside the peritoneum is the edema area. Enhanced scanning clearly shows an enhanced ring of peritoneum, a central area of necrotic abscess, and a surrounding area of edema.
The pus of subdural abscess is low signal in T1WI and high signal in T2WI, and the wall of abscess can be strengthened in the enhanced scan, which can clearly show the adjacent brain tissue, brain tissue edema, cerebral infarction, or cerebral abscess, and can effectively distinguish epidural abscess, subdural pus, and chronic subdural hematoma.
Epidural abscess is similar to subdural abscess on MRI, and the enhancement scan shows that the abscess is located outside the dura.
5. Electroencephalography
Focal slow waves can be seen at the abscess, which is mainly of localization significance for cerebral hemisphere abscess.
Diagnosis
1. Relevant medical history: some of them may have an infectious origin, such as otogenic, hematogenic, open craniocerebral trauma, etc.
2. Systemic manifestations: most patients have systemic symptoms of infection, fever, signs of meningeal irritation, and increased leukocyte counts and neutrophil ratios can be seen in routine blood tests. Patients with abscesses in the chronic stage do not have systemic infections.
3. patients with neurological symptoms, examination can be seen related to neurological localization signs. ct primary screening can be seen intracranial occupational lesions.
4. It is almost impossible to distinguish brain abscess from pyogenic meningitis in the early stage, and CT and MRI can see ring-shaped enhancement of the abscess wall or sheet-like mixed or high-density shadow after abscess formation, which can help to distinguish.
Treatment
(I) Brain abscess
The general principle of treatment is that when the abscess has not yet formed, internal medicine should be the main comprehensive treatment. Once the abscess is formed, surgical treatment should be carried out on the basis of medical treatment. However, if the patient’s cranial pressure is very high and signs of brain herniation have already appeared, emergency surgery should be performed regardless of whether or not an abscess has formed, in order to save lives.
The choice of antibiotics should be based on the type of pathogenic bacteria, the sensitivity of bacteria and the permeability of the drug to the blood-brain barrier, in principle, the drug that is sensitive to the pathogenic bacteria and can easily pass the blood-brain barrier should be used. In principle, the drug should be sensitive to the pathogenic bacteria and easily pass the blood-brain barrier. Before the bacteria are detected, broad-spectrum antibiotics that can easily pass the blood-brain barrier can be used according to the condition of the patient, and the results of bacterial culture and drug sensitivity test should be adjusted appropriately. Generally, the drugs can be given intravenously, and if necessary, intrathecal, ventricular and intrapulmonary injections can also be used.
(2) Dehydration drugs
Mainly used to reduce intracranial pressure, relieve the symptoms of increased intracranial pressure, and prevent cerebral hernia. Commonly used dehydration drugs are mannitol, glycerol solution, furosemide, sodium diuretic acid, etc. When using drugs, attention should be paid to renal function, acid-base and water-electrolyte balance.
3.Symptomatic supportive treatment
Pay attention to water, electrolyte and acid-base balance. If there is high fever, physical cooling can be used; for those with epilepsy, antiepileptic drugs should be given.
(II) Subdural abscess
Since the disease is very easy to spread and can penetrate the arachnoid membrane, causing purulent meningitis and ventriculitis, it is very important to treat and drain the abscess in time through surgical cranial drilling and drainage or craniotomy to remove the abscess. Preoperative and postoperative antibiotics should be applied, and the duration of antibiotics should not be less than 4 weeks. In addition, the primary focus should be actively treated. Patients with seizures should be treated with antiepileptic drugs for 12-18 months.
(iii) Epidural abscesses
Different surgical methods are used to deal with different sources of infection, but regardless of the type of surgery, a sufficient amount of antibiotics should be used before and after surgery until a few days after the symptoms have disappeared, and antibiotics are usually required for more than 6 weeks.
1. Cranial drilling and drainage
For epidural abscesses without cranial osteomyelitis. If necessary, it is necessary to open the interspace between the abscesses through neuroendoscopy and provide adequate drainage.
2. Removal of infected foci
It is suitable for extradural abscesses secondary to cranial osteomyelitis, and should be performed on the basis of adequate drainage to completely remove lifeless dead bone and granulation tissue.
3. Treatment of primary foci
Abscesses caused by frontal sinusitis, apophysitis, and retrobulbar infections should be removed together with the primary foci and other radical treatments.