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  • A Review of Middle Fossa Defects: A Case Series Examination of Risk Factors and Surgical Procedures

    Final Number:

    Christine Tschoe MD; Emily Anderson; Carlos A. David MD

    Study Design:

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2018 Annual Meeting

    Introduction: Middle fossa defects are increasingly common. Two variants are commonly seen: spontaneous temporal encephaloceles (TEs) and semicircular canal dehiscences (SCCDs). While the underlying cause of these conditions remains unknown, a common factor associated with both defects is obesity. Our investigation analyzes the correlation between obesity and the development of TEs and SSCDs. Our technique for repair of the middle fossa is presented.

    Methods: The study is a retrospective review of those patients undergoing middle fossa repair of either TEs or SSCDs at our institution between January 2010 and December 2017. Age, gender, middle fossa defect diagnosis, past medical history, and surgical procedure with 30 day follow up were recorded for each patient. In categorizing weight, overweight was considered BMI 25.0-29.9 and obese was considered > 30.0. All patients presenting with the diagnosis of a middle fossa defect underwent a middle fossa exposure with repair employing bone cement.

    Results: Sixteen patients met criteria to be included in the retrospective review (fig 1). Ten patients presented with TEs and seven presented with SSCDs. In both clinical entities, there was a predominance of men presenting with these defects. 12/16 (75%) of patients were categorized as either overweight or obese. Of these patients, 50% of obese patients also had a diagnosis of hypertension and hyperlipidemia (fig 2).

    Conclusions: This is the first report that reviews the possibility of metabolic syndrome as a risk factor for developing middle fossa defects. Although a small review, there appears to be a correlation between the presentation of this clinical triad and the presence of TEs or SSCDs. We also report a surgical technique in the repair that provides durable results.

    Patient Care: Our research aims to evaluate for modifiable risk factors leading to the development of middle fossa defects so that preventative health measures can be enacted prior to symptomatic presentation. We also describe a potentially more durable repair of these defects that lead to decreased return to OR for persistent CSF leaks in these settings.

    Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the different entities of middle fossa defects; 2) Recognize the risk factors for middle fossa defects; 3) Understand the technical repair details.

    References: 1. Carlson ML, et al. Temporal bone encephalocele and cerebrospinal fluid fistula repair utilizing the middle cranial fossa or combined mastoid-middle cranial fossa approach. J Neurosurg. 2013 Nov;119(5):1314-22. 2. Chung LK, et al. Clinical outcomes of middle fossa craniotomy for superior semicircular canal dehiscence repair. J Neurosurg. 2016 Nov;125(5):1187-1193. 3. Kenning TJ, et al. Surgical management of temporal meningoencephaloceles, cerebrospinal fluid leaks, and intracranial hypertension: treatment paradigm and outcomes. Neurosurg Focus 32 (6):E6, 2012. 4. Lundy LB, Graham MD, Kartush JM, LaRouere MJ. Temporal bone encephalocele and cerebrospinal fluid leaks. Am J Otol. 1996 May;17(3):461-9. 5. Mollan SP, et al. Evolving evidence in adult idiopathic intracranial hypertension: pathophysiology and management. J Neurol Neurosurg Psychiatry. 2016 Sep;87(9):982-92. doi: 10.1136/jnnp-2015-311302. 6. Wind JJ, Caputy AJ, Roberti F. Spontaneous encephaloceles of the temporal lobe. Neurosurg Focus. 2008;25(6):E11.

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