Middle Cranial Fossa Encephalocele and Cerebrospinal Fluid Leakage: Etiology, Approach, Outcomes

摘要

Objective?To compare outcome data for surgical approaches in the management of a middle cranial fossa encephalocele or cerebrospinal fluid (CSF) leak and, secondarily, to evaluate the role of obesity and the etiology of the defect.Design?RetrospectiveSetting?Quaternary referral centerParticipants?The study included 73 patients who underwent surgical repair of middle cranial fossa tegmen defects, two of which underwent bilateral repair.Outcome Measures?Demographic characteristics, clinical presentation, etiology, imaging, audiometry, surgical findings, method and material for repair, and postoperative course.Results?Fifty cases were spontaneous in origin, 2 were iatrogenic, and 23 were because of chronic otitis media. Of the 50, 18 underwent middle fossa craniotomy, 29 underwent a transmastoid approach, and 28 underwent a combined approach for repair. A postoperative CSF leak was seen in five patients: one who had undergone a transmastoid approach and four after a combined approach. There was no significant difference between the three approaches and risk of postoperative CSF fistulae. Two of the CSF fistulae resolved after a lumbar drain, and the remaining three patients required revision surgery.Conclusions?Middle cranial fossa tegmen defects are most commonly seen in obese females and are spontaneous in origin. The most common location was the tegmen mastoideum, and these defects were most commonly repaired through the transmastoid approach, with no greater risk of recurrence. Keywords: encephalocele, cerebrospinal fluid leakage, middle cranial fossa, obesityIntroductionIn the past, bony defects of the temporal bone were most likely to occur as a result of chronic otitis media, trauma, or an iatrogenic injury. Spontaneous defects were less common, reported in approximately 20% of postmortem temporal bones studied.~(1)~(2)However, recent reports confirm that the incidence of spontaneous defects is increasing.~(3)These are typically observed in middle-aged adults, who are more likely to be overweight and suffer from obstructive sleep apnea (OSA).~(4)The presentation may include aural fullness, hearing loss, pulsatile tinnitus, and a unilateral middle ear effusion on examination.~(5)These patients are at a risk of life-threatening complications such as meningitis, brain abscesses, and temporal lobe seizures. There are three standard approaches for repair: middle cranial fossa (MCF), transmastoid (TM), and combined MCF/TM.The middle fossa craniotomy approach has been the standard surgical approach for the repair of middle fossa cranial defects. This approach provides exposure of the entire tegmen and petrous apex but is associated with the morbidity of a craniotomy, subjects the patient to temporal lobe retraction, and warrants a postoperative intensive care unit admission.~(6)According to Nelson et al, the national rate of craniotomy for spontaneous cerebrospinal fluid (CSF) leak repair is rising.~(4)The TM approach may be used alone or in combination with a middle fossa craniotomy.~(5)~(7)~(8)When used alone, the TM approach may provide less exposure and therefore a greater risk of failure.~(9)~(10)~(11)There also exists the concern for injury to the ossicular chain with subsequent hearing loss. Recent literature suggests that the TM approach can provide sufficient exposure with a resolution of the preoperative air-bone gap.~(5)Others argue that the combined approach is the optimal technique, allowing for a more precise identification of the defect(s) and more reliable repair, as the surgeon is able to inspect the integrity of the repair from below. There are little data in the literature comparing the safety and efficacy of the three approaches.Traditional materials for repair included autologous temporalis fascia, muscle, and/or adipose tissue combined with postoperative lumbar drainage.~(2)We continue to use autologous material but have also incorporated the use of synthetic materials with great success. This study illustrates our surgical technique and postoperative outcomes using a multilayer repair without a lumbar drain.MethodsData CollectionApproval was obtained from the St. John Providence Health System's Institutional Review Board. A retrospective chart review was conducted of cases involving middle fossa tegmen defects, encephaloceles, and CSF effusions presenting to the Michigan Ear Institute between January 2009 and July 2015. Exclusion criteria included patients under the age of 18 and those who had undergone repair at an outside institution. The following data were collected: demographic characteristics, clinical presentation, etiology, imaging, audiometry, surgical findings, method and material for repair, and postoperative course.The main outcome variables included etiology, location and size of the defect, method of repair, operating time, postoperative hearing, complications, need for additional surgeries, and length of follow-up. Descriptive statistics were used to characterize the pati