REPAIR OF SPONTANEOUS CEREBROSPINAL FLUID OTORRHEA FROM DEFECT OF MIDDLE CRANIAL FOSSA

Sung Hyun Boo1, Chi-Sung Han2

1Department of Otorhinolaryngology-Head and Neck Surgery, Sungkyunkwan University School of Medicine, Samsung Changwon Hospital, Changwon; 2Ulsan Hana ENT Hospital, Ulsan, Korea

Introduction

Cerebrospinal fluid (CSF) otorrhea most commonly occurs as a result of trauma, surgery or congenital anomalies. Although spontaneous CSF otorrhea is a rare condition, it is a life-threatening disease because of the high incidence of subsequent meningitis. Immediate and definitive repair of CSF leak is important to prevent this potential complication. Surgical approaches include a transmastoid approach, middle fossa craniotomy, or a combined approach. We have recently experienced the case of a patient with spontaneous CSF otorrhea occurring through a bony defect in the anterior wall and roof of epitympanum. The defect was successfully repaired using bone chips with fascia via the transmastoid approach.

Case

A 49-year-old woman was referred to our hospital because of right pulsatile otorrhea after myringotomy. Initially, she had experienced right ear fullness and hearing disturbance for two weeks. When a local otolaryn-gologist examined her ear, there was visible fluid through the tympanic membrane. Thus, she was diagnosed as right serous otitis media and treated with antibiotics. However, after the two-week treatment, the fluid in the tympanic cavity was still present. Myringotomy was tried, but profuse pulsatile clear discharge from the myringotomy site was encountered.

Examination of her right ear revealed pulsatile clear discharge through the myringotomy incision site. The pure-tone audiogram showed right conductive hearing loss of 40dB (air-bone gap 32dB). She had no specific past medical history and family history. High-resolution computed tomography (HRCT) scan and magnetic resonance imaging (MRI) of the temporal bone were performed for further evaluation of the otorrhea. On the HRCT scan, anteromedially a large bony defect from the anterior wall to the roof of the right epitympanum was identified (Fig. 1). The right middle-ear cavity and mastoid cavity were filled with soft tissue density. A T2-weighted MRI image demonstrated high signal intensity in the right middle ear and mastoid cavity, which is consistent with CSF (Fig. 2).

Repair of CSF leak through a transmastoid approach was planned. First, after general anesthesia, lumbar drainage was done. Temporalis muscle fascia was harvested. Several pieces of bone chips were taken from the mastoid cortex. A cortical mastoidectomy was performed. On entering the antrum, a profuse clear discharge from the epitympanum was noted. To further evaluate the tegmen tympani, the incus and head of malleus were removed. There was a bony defect of approximately 8 mm from the anterior roof of the epitympanum extending to the anterior wall. Also, there was no identifiable healthy dura or brain tissue herniation at the CSF leak site.

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Fig. 1. Pre-operative HRCT scan of the temporal bone. The axial image (A) demonstrates a large bony defect of the right anterior wall of the epitympanum (arrow). The coronal image (B) shows a bony defect of the right middle cranial fossa. Also, the tympanic and mastoid cavities are filled with soft-tissue density.

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Fig. 2. Pre-operative brain MRI. Gd-enhanced T1-weighted coronal image (A) shows no evidence of brain herniation in the epitym-panum and isosignal intensity (arrow). Unenhanced T2-weighted axial (B) and sagittal (C) images demonstrate high-signal intensity in the right middle ear and mastoid cavity (arrow head).

To repair the defect, fistly, prepared temporalis fascia was inserted in the bony defect. Then a large piece of bone chip was inserted into the defect to cover the fascia. The bony defect, however, was still visible because of its three-dimensional structure. More bone chips were put into the defect, until there was no evidence of the CSF leak left. Surgical glue was applied around the bone chips and gelfoam was inserted in the cavity.

Postoperatively, the CT scan showed a well-sealed defect, but also a pneumocephalus in the right temporal lobe (Fig. 3). But the patient did not complain of a headache or any neurologic deficits. Lumbar drainage was maintained for six days. Two weeks later, the pneumocephalus disappeared and the patient was discharged from hospital. One year later, the CT scan showed a well-healed defect (Fig. 4). There has been no evidence of recurrent CSF leak up to date.

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Fig. 3. HRCT of the temporal bone one week post-operative. Axial (A) and coronal (B) images show bone chip graft covering the defect of the right middle cranial fossa (white arrow). Pneumocephalus was noted in the right temporal lobe (black arrow).

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Fig. 4. HRCT scan of temporal bone one year post-operative. Axial (A) and coronal (B) images demonstrate a well-sustained anterior wall and roof of epitympanum (arrow). There is no evidence of CSF leak in the tympanic cavity.

Discussion

Spontaneous CSF otorrhea is defined when there are no identifiable causes such as past history of trauma, surgery, infection or tumor.1 The origin of the CSF leak is most commonly a defect in the tegmen of the middle cranial fossa, less commonly in the posterior fossa.

The pathophysiology of spontaneous CSF otorrhea is not entirely clear but there are two main theories concerning the etiology of bony defect. The first is the congenital defect theory, where a tiny defect within the tegmen, caused by aberrant embryologic development, enlarges over time due to constant CSF pressure. This enlargement leads to eventual dural herniation and subsequent bony and dural thinning, resulting in CSF otorrhea.2 The second theory, the arachnoid granulation theory postulated by Gacek, suggests that arachnoid granulations that do not find a venous termination during embryonic development come to lie in a blind end against the inner bony surface of the skull.3 These granulations enlarge with age and may eventually erode bone. Aberrant arachnoid granulations located in the dural surface of the temporal bone are thought to be responsible for communication between the CSF space and the mastoid air-cell system. Gacek3 identified an 8.5% incidence of arachnoid granulations in the posterior fossa of the temporal bone, while Ferguson4 observed an incidence of 22% of pit holes created by arachnoid granulations in the middle fossa surface.

Bone defects of the cranial fossa can be closed using many autologous materials such as fascia, fat, muscle, cartilage and bone or synthetic materials such as silicone, silastic, Marlex, hydroxyapatite cement and titanium plate.5 Each material must be strong enough to withstand intracranial pressure and be compliant enough to form a seal.

There are three surgical approaches for the repair of the CSF otorrhea: the transmastoid approach, middle fossa craniotomy, and a combined approach.3,5,6 Surgeons can choose one of them by location and size of defect, their experience or preference, and better surgical view. The favored technique is a combined transmastoid-middle fossa approach, which gives a whole visualization of the tegmen and definite closure of the entire region. But this approach has a great potential for complications and should only be performed by experienced surgeons. Whereas the transmastoid approach is technically easier to perform, and includes fewer risks and complications, an anterior defect in the tegmen tymapni may require the removal of ossicles to ensure better exposure of the lesion. This causes hearing disturbance which can be restored with ossicular reconstruction in the same stage or the second stage. In our case, the lesion was located at the antero-medial side of the middle cranial fossa, so the combined approach could be suitable. However, we could also use the transmastoid approach with removal of ossicles only to obtain clear view of lesion and successfully manage the defect.

References

1.Jahrsdoerfer RA, Richtsmeier WJ, Cantrell RW. Spontaneous CSF otorrhea. Arch Otolaryngol Head Neck Surg 107:257–261, 1999

2.Pappas DG Jr, Hoffman RA, Cohen NL, Pappas DG Sr. Spontaneous temporal bone cerebrospinal fluid leak. Am J Otol 16: 765–771, 1992

3.Gacek RR. Arachnoid granulation cerebrospinal fluid otorrhea. Ann Otol Rhinol Laryngol 99:854–862, 1990

4.Ferguson BJ, Wilkins RH, Hudson W, Farmer J Jr. Spontaneous CSF otorrhea from tegmen and posterior fossa defects. Laryngoscope 96:635–644, 1986

5.Kutz JW Jr, Husain IA, Isaacson B, Roland PS. Management of spontaneous cerebrospinal fluid otorrhea. Laryngoscope 118: 2195–2199, 2008

6.Bento FR, Padua FG. Tegmen tympani cerebrospinal fluid leak repair. Acta Otolaryngol 124:443–448, 2004

Address for correspondence: Sung Hyun Boo, Samsung Changwon Hospital, Sungkyunkwan University, Hapsung 2dong Changwon, Korea. descent@skku.edu

Cholesteatoma and Ear Surgery – An Update, pp. 463–466

Edited by Haruo Takahashi

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