Otogenic cerebellar abscess: causes, symptoms, diagnosis, treatment

According to summary statistics from the second half of the 20th century, 98% of purulent diseases of the cerebellum are due to otogenic cerebellar abscess.

In the pathogenesis of the disease, the following routes of infection are distinguished:

1. the labyrinthine pathway (60%) is the most common, caused by a focus of purulent infection in the posterior semicircular canal; less often, the infection spreads through the vestibular aqueduct and through the endolymphatic sac, and even less often through the posterior semicircular canal and facial canal;
2. the hematogenous route is the second most common route of infection in the development of otogenic cerebellar abscess; most often, the infection spreads through the veins related to the sigmoid and petrosal sinuses; the arterial route of infection is extremely rare;
3. along the length (per continuitatem); this path is formed during the exacerbation of a chronic purulent process in the middle ear, developing in the cells of the mastoid process, deep intersinofacial and retrolabyrinthine cells, with the involvement of the meninges of the posterior cranial fossa in the pathological process.

Pathological anatomy. An otogenic cerebellar abscess may be located inside the cerebellum without damaging its cortex; with a superficial localization of the abscess, it is located in the gray and partially in the white matter of the cerebellum, and, as a rule, communicates with the primary focus of infection by means of a "peduncle fistula". An otogenic cerebellar abscess may be solitary or multiple, ranging in size from a hazelnut to a walnut. The density of its capsule is determined by the duration of the disease - from poorly differentiated and fragile in fresh cases to sharply thickened and strong in old abscesses.

Symptoms of otogenic cerebellar abscess. The initial period of otogenic cerebellar abscess is masked by the clinical picture of the underlying disease and lasts approximately between the end of the first week of exacerbation of the purulent process in the middle ear and can last up to 8 weeks, manifesting only by general signs of the infectious process. During this period, it is not easy to suspect the occurrence of otogenic cerebellar abscess, and only in the second half of the period does this become possible with a thorough examination of the patient by an experienced neurologist.

The period of the "light" interval creates the illusion of recovery, it can last for several weeks. During this time, the patient's condition is satisfactory, only some movement disorders on the side of the abscess may be noted.

The peak period is characterized by general toxic, hydrocephalic and focal syndromes. The earliest and most pronounced signs are those of increased intracranial pressure. Headache is localized in the occipital region, vomiting, dizziness, and loss of consciousness often occur; bradycardia and congestion of the optic nerve are observed in 20-25% of cases. Focal symptoms are characterized by impaired swallowing, dysarthria, the appearance of pathological reflexes, hemiplegia, cranial nerve paralysis, and spontaneous cerebellar nystagmus. Cerebellar symptoms are often accompanied by:

1. signs of gait disorder (“drunk gait” - disorderly staggering with a tendency to fall backwards and towards the affected area);
2. disorders of voluntary movements (intentional tremors during pointing tests, hypermetria, adiadochokinesia, scanned speech, etc.);
3. Vestibular disorders can manifest as peripheral and central symptoms.

Peripheral symptoms occur when the primary focus of infection is located in the ear labyrinth (posterior semicircular canal), then they precede the otogenic abscess of the cerebellum and are manifested by spontaneous vertical nystagmus upwards in the initial stage of serous labyrinthitis, with purulent labyrinthitis - downwards or diagonal or horizontal-rotatory (circular) spontaneous nystagmus towards the healthy labyrinth. When the labyrinth is switched off, the caloric test (bithermal caloric test) on it does not cause any changes in spontaneous nystagmus, while the same test, if it is cold, leads to a decrease in the intensity of spontaneous nystagmus, with a heat test it increases. These changes in spontaneous nystagmus indicate its peripheral, i.e. labyrinthine genesis. At the same time, harmonic disturbances of movement coordination tests, systemic dizziness consistent with the direction and components of spontaneous nystagmus, and vestibulo-vegetative reactions occur. Central vestibular disturbances (absence of labyrinthitis!) occur with compression of the brainstem in the area where the vestibular nuclei are located, i.e., due to increased pressure in the posterior cranial fossa, which may be caused by occlusion of the cerebrospinal fluid pathways and pressure of the cerebellum on the medulla oblongata. In this case, spontaneous nystagmus is central in nature and changes when the ear labyrinth is irrigated only with cold or heat caloric stimuli (changes in spontaneous nystagmus in direction).

In the terminal period, bulbar symptoms increase, manifested by disturbances of cardiac and respiratory activity, dysphagia, dysarthria, lesions of the caudal group nerves and the MMU nerves, including facial nerve paralysis, facial hyperesthesia, disappearance of corneal and pupillary reflexes on the affected side. Death occurs from paralysis of the vasomotor and respiratory centers, caused by cerebral edema and herniation of the medulla oblongata into the foramen magnum.

The prognosis is determined by the same criteria as for otogenic abscess of the temporoparietal region, but it is more serious due to the fact that otogenic abscess of the cerebellum forms near the vital centers of the brainstem and, if not recognized in a timely manner, can cause sudden occlusion of the medulla oblongata and sudden death from respiratory arrest and cardiac cessation.

Diagnosis of otogenic cerebellar abscess is difficult at the initial stage, when cerebellar symptoms are not expressed, and the general condition of the patient and local inflammatory phenomena in the temporal bone mask the signs of the beginning of otogenic cerebellar abscess. As a rule, the diagnosis of otogenic cerebellar abscess is established in the period of its peak based on the presence of a triad - dizziness, spontaneous nystagmus, strabismus in combination with characteristic cerebellar symptoms.

Currently, the main instrumental methods for diagnosing brain abscess are MRI and CT, which have a high resolution in determining the location, size, and structure of the abscess, such as the density of its capsule or the contents of its cavity. In the absence of these methods, survey and tomographic X-ray examination of the skull and brain, radiography of the temporal bones according to Schuller, Mayer, and Stenvers, as well as some axial projections that allow assessing the condition of the basal parts of the skull and brain are used. It is possible to use other methods for examining the brain, such as EEG, ultrasound diagnostics, rheoencephalography, angiography, ventriculography, but with the introduction of MRI and CT into practice, these methods have retained only auxiliary functions.

Differential diagnosis is made between abscess of the temporal lobe, labyrinthitis, empyema of the endolymphatic sac (the so-called retrolabyrinthine abscess and otogenic hydrocephalus:

• with labyrinthitis, there are no signs of increased intracranial pressure and changes in the cerebrospinal fluid, but there are clear signs of peripheral damage to the vestibular apparatus (spontaneous nystagmus, harmonic disturbance of pointing tests, lateropulsion, etc.) and the cochlea (pronounced perceptual hearing loss or deafness);
• retrolabyrinthine abscess is, in essence, an intermediate stage between labyrinthitis and otogenic cerebellar abscess, therefore, it may contain signs of labyrinthitis and the initial stage of otogenic cerebellar abscess;
• Otogenic hydrocephalus is characterized by a combination of chronic purulent inflammation of the middle ear, usually complicated by cholesteatoma and bone caries, with paroxysmal or constant severe headaches, accompanied by pronounced congestion in the fundus; Otogenic hydrocephalus differs from cerebellar abscess by the absence of a forced position of the head (throwing back the head), meningeal symptoms, impaired consciousness, and characteristic cerebellar symptoms; with otogenic hydrocephalus, high cerebrospinal fluid pressure is observed (up to 600 mm H2O), the protein content in the cerebrospinal fluid is normal or slightly reduced (0.33-0.44 g / l), the number of cells is normal.

Treatment of otogenic cerebellar abscess. If symptoms of otogenic cerebellar abscess are observed, but there is no sufficiently convincing evidence of its presence obtained by CT or MRI, then first a one-stage extended RO is performed with the removal of the entire affected bone and mastoid cells, perisinus and perilabyrinthine cells, the posterior cranial fossa is opened and the sigmoid sinus is exposed, its condition and the condition of the dura mater are assessed. If it is detected in this area of the posterior cranial fossa, it is removed and a wait-and-see tactic is used for 24-48 hours. During this time, the ear wound is treated openly with massive antibiotic therapy, and measures are taken to stabilize intracranial pressure and the functions of vital organs. If during this time there is no improvement in the patient's general condition, and general cerebral and cerebellar symptoms increase, then they begin to search for an otogenic cerebellar abscess and, if found, to remove it. If an abscess is found using CT or MRI, a wait-and-see approach is not used and after general cavity RO, they begin to search for the abscess and remove it. The postoperative cavity of the otogenic cerebellar abscess and middle ear is constantly washed with antibiotic solutions for 48 hours and drained with gauze turundas.

In case of sigmoid sinus thrombosis, its pathologically altered part is removed and the otogenic cerebellar abscess is opened through the space remaining after removal of part of the sinus. In case of labyrinth damage, it is removed.

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