Subdural abscess

Introduction to subdural abscess Subdural abscess refers to the accumulation of pus in the subdural space between the dura mater and the arachnoid membrane after purulent infection in the brain. Because of the lack of any anatomical features of the subdural space, once a subdural abscess occurs, The spread of abscess is often extensive. The pus not only spreads along one side of the brain surface, but sometimes spreads to the opposite side through the lower edge of the brain, and even invades the underside of the brain, which has serious consequences, so it deserves great attention. basic knowledge The proportion of the disease: in the systemic infectious diseases, the incidence of the disease is about 0.5% -1% Susceptible people: no special people Mode of infection: non-infectious Complications: meningitis, brain abscess, epilepsy, hydrocephalus

Subdural abscess

Disease factors (45%):

Adjacent to purulent lesions, such as otitis media, mastoiditis, sinusitis (especially frontal sinus), skull osteomyelitis and other direct spread. The pathological changes of subdural abscess are mainly inflammatory changes in the inner layer of the dura mater, so in the past it was often called dural meningitis.

Infection factor (30%):

Venous retrograde infection of the facial triangle and scalp infection through retrograde infections such as the cranial vein and the guiding vein. Trauma or craniotomy Open cranial trauma and craniotomy, secondary infections, such as subdural hematoma, brain abscess ruptured into the subdural space.

Blood infection (25%):

It is caused by the spread of sepsis or bacteremia, which is less common. The pathogens of subdural abscess are often streptococcus and staphylococci, and infants and young children are mostly influenza or pneumococcal.

Pathogenesis

In the early stage, there is a fibrous purulent exudate on the inner surface of the dura mater. The exudate is mostly located in the convex surface of the brain, first in the frontal lobe, then inwardly to the top and down to the lateral cerebral palsy. Invasion of the frontal lobe, but such purulent exudate is not easy to find in the frontal lobe, because the frontal lobe and the dome are closely attached, and the purulent exudate can also extend along the lateral fissure to the optic chiasm. The cerebral palsy extends to the medial side of the frontal lobes, even to the contralateral cerebral convex surface. When the purulent effusion accumulates to a considerable amount, it not only causes the brain to be compressed, but also causes an increase in intracranial pressure when the inflammation extends below it. The pia mater and brain tissue are more clinically significant, entering the chronic phase, between the dura mater and the arachnoid, forming an adhesion between the arachnoid and the brain, and the subdural abscess has a thicker envelope. It is difficult for antibiotics to enter the abscess capsule.

Subdural abscess prevention

Treatment of adjacent suppurative lesions, prevention of retrograde infection of the facial triangle and scalp, aseptic operation during trauma or craniotomy, can help prevent subdural abscess.

Subdural abscess complications Complications meningitis brain abscess epilepsy hydrocephalus

Common complications of subdural abscess are cerebral thrombophlebitis and sinusitis, sometimes wearing arachnoid and causing purulent meningitis or brain abscess. The sequelae include epilepsy, aphasia, hemiplegia and hydrocephalus.

Subdural abscess symptoms Common symptoms Increased intracranial pressure Meningeal irritation Symptoms Deep headache Sleepiness Meningitis Irritability edema nausea Systemic infection Poisoning symptoms

1. Primary infection symptoms

More obvious, even in chronic lesions, there are many manifestations of acute attacks.

2. Systemic infection symptoms

Coexisting with symptoms of increased intracranial pressure and meningeal irritation, patients often present with headache, chills, fever, nausea, vomiting, stiff neck, irritability, lethargy, and even coma. The patient may have neck resistance and positive Klinefelter sign. The optic disc edema can be seen in the fundus, and the retina sometimes shows bleeding and exudation.

3. Focal location sign

Due to the involvement of the abscess and the cerebral cortex and the thrombophlebitis of the cerebral vein, it may cause localized seizures or epileptic seizures, hemiplegia, aphasia and other symptoms. In severe cases, cerebral palsy may occur, and a small number of patients may suffer from physical resistance. Strong, low bacterial virulence, clinically subacute performance, infants and young children are mostly children under 2 years old, usually occur 1 to 2 weeks after the onset of meningitis, when the sick child is treated with antibiotics, check the cerebrospinal fluid gradually Normal, but the nerve and meningeal irritation symptoms did not improve, but increased vomiting, seizures, anterior hernia, and the gradual enlargement of the skull, indicating the possibility of complicated subdural abscess or effusion.

Examination of subdural abscess

Lumbar puncture can be found in increased intracranial pressure, cerebrospinal fluid examination, leukocytosis, increased protein, slightly lower or normal sugar and chloride.

1. Brain CT scan

The typical manifestation is the convex surface of the brain. A wide range of crescent-shaped low-density areas can be seen under the inner skull. The CT value is generally 0~16Hu in the early stage. A wide range of edema can be seen in the adjacent brain tissue. The occupancy effect is significant, and the midline structure shifts, involving both sides. The displacement of the midline structure can be inconspicuous. CT enhanced scan, visible fine band with clear boundary and uniform thickness, the brain surface of the opposite brain is strengthened, the density of the inner band of the abscess is uneven, the thickness is irregular, and the longitudinal crack For the main range of subdural abscess, mostly fusiform.

2. Brain MRI scan

The abscess on the T1 image is lower than the brain parenchyma and higher than the cerebrospinal fluid. The T2 image is the opposite. The signal is higher than the brain parenchyma and slightly lower than the cerebrospinal fluid. It is crescent-shaped, even fusiform, and there is no low signal on the inner edge. The curved band, the coronal image can be used to understand whether the bottom of the brain is empyema, and the lesion adjacent to the brain tissue can show signs of cerebral edema.

3. Drilling or anterior puncture

Infants and young children with anterior sacral subdural puncture or adult transcranial exploration of the subdural pus can be clearly diagnosed.

Diagnosis and diagnosis of subdural abscess

In addition to the primary lesions, medical history and clinical manifestations, the disease can also be diagnosed by various auxiliary examinations, especially CT and MRI.

Subdural abscess should be differentiated from other intracranial infectious diseases. It should also be differentiated from epidural abscess. In general, the symptoms of extra-abdominal abscess are mild, CT scan lesions are limited, fusiform, enhanced scanning abscess The inner edge of the enhancement zone is significant. The inner edge of the abscess is a low-signal curved annulus on the MRI T1 or T2 image, while the subdural abscess is severe. The CT scan has a wide range of lesions covering the surface of the cerebral hemisphere. The longitudinal extension of the cerebral stenosis enhances the enhancement of the inner edge of the abscess. It is crescent-shaped and has a crescent shape. The MRI image does not show a low-signal annulus. The identification is not difficult, but when the epidural abscess is located on one side of the cerebral hemisphere and the dura mater When the lower empyema is more limited, the identification will be difficult.

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