Successful treatment with ultrasound-guided aspiration of otogenic brain abscess with transmastoid approach.

To the Editor: Otogenic brain abscesses are one of the most severe complications of the suppurative otitis media. Although extensive use of antibiotics has significantly reduced the mortality and morbidity of otogenic brain abscesses over the past years, there are still substantial patient deaths due to cerebral hernia or brain abscess rupture. In these lethal cases, proper time and means to drain the abscess are very important for good outcomes. Herein, we describe the successful management of a young male patient with otogenic brain abscess and cerebral hernia using transmastoid middle skull base craniectomy and ultrasound-guided abscess aspiration.

A 22-year-old man was presented to our hospital complaining of severe headache and neck pain on the right side, as well as nausea. He had intermittent right ear otalgia and hearing loss in the past month. Physical examination showed signs of acute mastoiditis and meningeal irritation sign. An urgent computed tomography (CT) revealed a soft-tissue density filling the middle ear cavity and mastoid, and the bone defect of the tegmen tympani. Magnetic resonance imaging (MRI) scan demonstrated inflammation of the right temporal lobe and immature abscess formation [Figure 1A]. Intravenous antibiotics (ceftriaxone and vancomycin) and mannitol were prescribed immediately under close observation.

Figure 1

(A) The 3.2 cm × 2.8 cm × 3.2 cm-sized, immature abscess on T2-weighted magnetic resonance imaging. (B) ALOKA Prosound α7 ultrasonic apparatus, with broadband fan brush pen type probe. The center frequency is 5.0 MHz. (C) A 1.0 cm × 0.7 cm low anechoic area with thick and coarse wall and sample clip figure echo inside, and mild compression displacement of surrounding tissue.

Symptom worsened after 1 day as the patient suddenly got convulsion for 2 min and lost his consciousness thereafter. Physical examination showed mydriasis of the right eye. Contract-enhance CT revealed enlargement of the intracranial lesion locating in the inferior part of the temporal lobe near the skull base, measuring 3.2 cm × 2.8 cm × 3.2 cm. A small pus cavity had already formed and sign of cerebral hernia had also appeared. An urgent radical mastoidectomy of the right side was performed. During the operation, only granulation tissue was found in the mastoid with no cholesteatoma. The tegmen was eroded with about 8 mm × 5 mm bone defect, and the inflammatory dura bulged. After removal of the adherent granulation tissues, an area of 6 cm × 7 cm bony plate was drilled at middle skull base through the mastoid cavity until the normal dura was exposed, and the intracranial pressure was decreased.

Considering the pus cavity was too small to locate, we introduced ultrasound for guidance. We used ALOKA Prosound α7 ultrasonic apparatus with a multi-frequency burr-hole transducer (UST-5268P-5) dedicated in the brain scan. Using saline in the mastoid cavity acting as the medium, gray-scale ultrasonography was used first to identify a 1.0 cm × 0.7 cm anechoic area with echogenic foci inside [Figure 1B and 1C]. Then color Doppler mode was used to identify the optimal puncture path without damaging the blood vessels. An ultrasound-guided aspiration needle was advanced into the abscess cavity freehand through the middle cranial fossa dura, and only 1 mL of pus was able to be aspirated. Then the brain tissue retracted and the pulse was visible. After this operation, the patient recovered consciousness and gained isocoria with normal light reflex.

After 2 weeks’ of anti-infective therapy during which the cerebral abscess had matured, a second surgery was performed by a neurosurgeon to drain the pus and a catheter was indwelled. All symptoms disappeared after another 5-weeks’ course of intravenous antibiotics. The patient was discharged home. Two months later his muscle strength grade of left side was V–. No other complications of brain abscess were left during the 3-year follow-up.

Cerebral abscesses remain one of the most severe complications of the otitis media. Although the mortality rates dropped in general, complications still occur. When intracranial complications become life-threatening, surgical intervention is often required immediately. The most important problem related to the operation technique was the precise location and puncture of the abscess.

Cerebral abscess aspiration is a rapid and safe procedure, especially with stereotactic techniques, such as intraoperative ultrasound, or CT scan guidance. Compared to craniotomy, imaging-guided stereotactic aspiration is considered a better choice in the management of brain abscesses. CT-guided stereotaxy[ should be considered the choice for all but the most superficial and large cerebral abscesses. However, it requires a long time for preparation and a prohibitively high cost, which make it not readily available in many hospitals. A needle puncture is often used from the transmastoid approach, but it needs experienced surgeon to recognize and judge the location of the abscess according to the preoperative CT or MRI scans.[

In 1986, Nagle et al[ reported a case of a 1000 g neonate who developed a frontal brain abscess, and it was then successfully aspirated in the intensive care nursery with ultrasound guidance. Then the method of ultrasound guidance is applied in a single burr hole approach for real-time imaging of the whole procedure.[ However, a burr hole must be made first because of the transdural attenuation.

In our case, the patient who had otogenic brain abscesses due to acute middle ear infection was treated with radical mastoidectomy immediately when he presented the symptom of cerebral hernia. During the mastoidectomy, a 6 cm × 7 cm bone plate of the middle cranial fossa was opened, and the intracranial pressure was effectively decompressed. To improve the effect of the surgery without increasing the trauma of the surgery and prolonging the operating time, we introduced ultrasound to guide the aspiration of the immature abscess, which turned out to be successful as most of single-stage trans-mastoid drainage of otogenic brain abscess.[

Just like most of the otogenic brain abscesses, it mainly located within the inferior temporal lobe. If punctured from other approach, the puncture pathway would be too far away from the target, and might have caused damages in the cortex or even iatrogenic spread of infection into the ventricles. Through the transmastoid approach, the puncture path was short, easier to locate and monitor, and therefore associated with much lower surgical risk.

The body of the probe was Z type, which was convenient to be hand held. With grooves on both sides, it can easily be installed into the puncture frame. After the probe was attached to the dura, the site of the pus cavity was visualized clearly. The pus cavity volume shrank significantly immediately after the aspiration. Although the residual inflammation continued to grow and the second aspiration had to be performed through a burred hole 2 weeks later, we thought that the first single stage mastoidectomy with ultrasound-guided aspiration by trans-mastoid approach was very important for good outcomes.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.

Funding

This work was supported by grants from the Peking University Third Hospital Clinical Project Fund (No. BYSY2017025) and The China Capital Health Development Project (No. 2016-2-4094).

Conflicts of interest

None.