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12 Meningoencephalic Herniation
Meningoencephalic herniation is the herniation of meningeal and/or encephalic tissue in the middle ear or mastoid. It occurs in connection with infection, previous surgery, head trauma, or congenital tegmental defects. A patient with meningoencephalic herniation has a high risk of developing meningitis and epilepsy due to epileptogenic focus in the herniating tissues. The patient may present with a pulsatile retrotympanic mass, cerebrospinal fluid (CSF) leakage, and aphasia. However, the most common manifestation is that of a conductive or mixed hearing loss with a draining ear or serous otitis media.
Figure 12.1 Left meningoencephalic herniation in a patient who had previously undergone open tympanoplasty. The hernia protrudes into the attic through a small tegmental defect and appears otoscopically as a pulsatile retrotympanic mass.
Figure 12.2 CT scan of the case described in Figure 12.1, coronal view. The osseous defect with the herniating tissue can be clearly visualized.
Figure 12.3 MRI of the previous case. The protrusion of the cerebral tissue into the middle ear is visible.
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Figure 12.4 Postoperative CT scan. The hernia was managed using a middle fossa approach. The bony defect was repaired using cartilage. The temporal craniotomy (arrow) and the cartilage (arrowhead) are clearly visible.
Figure 12.5 Left meningoencephalic hernia. The superior wall of the external auditory canal is dehiscent. A soft, reducible, nonpulsating mass is observed. The patient had a history of head trauma with transverse fracture of the temporal bone that occurred 3 years before presentation. He complained of left hearing loss and the sensation of ear fullness.
Figure 12.6 Preoperative CT scan of the case in Figure 12.5 demonstrating the herniation of cerebral tissue into the middle ear.
Figure 12.7 CT scan of the previous case 1 year postoperatively. The hernia was managed using a middle fossa approach, placing a cartilaginous plate to reconstruct the bony defect after having sectioned the neck of the herniating tissue. The cerebral tissue, which is left in the ear during the operation, is resorbed with time as seen in the CT scan
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Figure 12.8 Left meningoencephalic herniation in a patient |
Figure 12.9 CT scan of the case presented in Figure 12.8. |
who had previously undergone multiple ear surgeries. The |
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only manifestation was conductive hearing loss. |
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Figure 12.10 Another example of a right meningoencephalic herniation in a patient who had undergone open tympanoplasty. Otoscopically, a large pulsatile mass is visible in the attic.
Figure 12.11 CT scan of the case presented in Figure 12.10, coronal view. The tegmen antri is absent and the herniation of the temporal lobe in the mastoid cavity and external auditory canal is demonstrated.
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Figure 12.12 A patient with a history of left open tympanoplasty presenting with conductive hearing loss. Otoscopy demonstrates a badly performed cavity with high facial ridge, secretions, granulations in the posterior wall of the cavity and an attic defect through which a soft-tissue mass protrudes into the middle ear. A CT scan was performed that confirmed the presence of a meningoencephalic hernia (see following figures).
Figure 12.13 CT scan, coronal view, soft-tissue window of the case presented in Figure 12.12 demonstrating the herniating cerebral tissue into the cavity.
Figure 12.14 CT scan, axial view. Arrows show the herniat- |
Figure 12.15 CT scan, coronal view, bone window. |
ing cerebral tissue. |
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Figure 12.16 CT scan of a patient with a congenital tegmental defect. This patient has a higher risk of meningitis following an episode of otitis.
Figure 12.17 Right ear. Meningoencephalic herniation in a plurioperated patient. The otoscopy shows a new tympanic membrane lateralized by a retrotympanic whitish mass. The patient complained of right ear anacusis and H.B. grade III facial nerve palsy of 1 year duration.
Figure 12.18 CT scan revealed the presence of a mass occupying the surgical cavity with erosion of the cochlea and absence of the tegmen.
Figure 12.19 MRI also demonstrated the presence of meningoencephalic herniation (arrows). During surgery, the cholesteatoma was confirmed together with a large encephalic herniation.
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Summary
Herniation of the meningeal and/or encephalic tissue into the middle ear space is a rare condition occurring most frequently postsurgically, spontaneously due to congenital defects, post infection, and post trauma. For herniation to occur, a bony defect should be present. Through this dehiscence, a meningocele, an encephalocele, or both can occur. The most appropriate term seems to be meningoencephalic herniation.
The condition can lead to serious sequelae such as CSF leak, meningitis, epilepsy, and aphasia. Therefore, once diagnosed, surgical correction should be performed. The herniated tissue is usually resected and the defect is reconstructed. The surgical approach is determined by the size of the defect. Small defects are managed using a transmastoid approach. In hernias with middle-sized defects, the transmastoid approach is combined with a minicraniotomy, which allows the placement of a larger piece of septal cartilage for reconstruction of the defect. In large defects, however, a middle cranial fossa approach is adopted. In this approach, the dura of the temporal lobe is carefully elevated until the neck of the hernia is identified and bipolarly coagulated. The herniated part is left inside the middle ear or mastoid where it acts as a barrier against infection of the intracranial spaces. The defect is reconstructed by placing a piece of temporalis fascia between the cerebral tissue and the dura; another piece of fascia is placed extradurally. Next, a piece of cartilage is placed between the bony defect and the dura to reinforce the sealing. In other cases, a piece of muscle can also be placed between the bony defect and the cartilage for further reinforcement.