Middle Fossa Craniotomy Research Articles

Cochlear FLAIR Signal Changes in Hearing Preservation Vestibular Schwannoma Surgery.

Cochlear fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) signal intensity has been shown to be elevated in patients with vestibular schwannomas (VS). This study evaluated the preoperative and postoperative cochlear signal on FLAIR sequences in patients undergoing hearing preservation surgery. Retrospective chart review. Tertiary referral center. All patients undergoing middle cranial fossa or retrosigmoid craniotomy for VS at a single institution from September 2013 to January 2017 were screened.Hearing was graded according to the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) hearing classification. Inclusion criteria included preoperative AAO-HNS class A or B hearing and available preoperative and postoperative FLAIR sequences. Signal intensity of cochlear FLAIR signal was measured in the affected cochlea and normalized to the contralateral cochlea. Hearing preservation was defined as AAO-HNS class A or B postoperatively. Eighteen patients met all inclusion criteria, and 12/18 experienced hearing preservation. There was no difference in preoperative FLAIR ratio between hearing preserved and nonpreserved groups (2.02 vs 2.32, p = 0.52). Postoperatively, FLAIR ratio was lower in the hearing preserved group compared to the nonpreserved group (1.19 vs 1.87, p = 0.033). The current study is the first to examine postoperative cochlear FLAIR changes in VS patients undergoing hearing preservation surgery. In our study population, abnormal hyperintense FLAIR signal normalized in patients experiencing successful hearing preservation, while those who lost hearing maintained abnormal signal. Future studies may investigate the role of FLAIR in guiding optimal timing of operative intervention in VS patients.

Perilymphatic Fistulas and Superior Semi-Circular Canal Dehiscence Syndrome.

Perilymphatic fistulas (PLF) and superior semi-circular canal dehiscence syndrome (SCDS) are 2 conditions that can present with sound and/or pressure-induced vertigo. PLF should be suspected in cases of trauma or surgery, while a spontaneous PLF is a diagnosis of exclusion. Research is ongoing to identify an ideal biomarker for perilymph. The diagnosis of SCDS continues to evolve with further research into vestibular-evoked myogenic potentials, electrocochleography, and higher resolution CT imaging. Treatment advances include the transmastoid approach, smaller middle fossa craniotomies, and usage of endoscopes. Temporal bone studies have furthered the understanding of pressure dynamics within the ear and how this relates to recommendations for repair versus alternative treatments such as round window plugging.

Preoperative Assessment of Cervical Vestibular Evoked Myogenic Potentials (cVEMPs) Help in Predicting Hearing Preservation After Removal of Vestibular Schwannomas Through a Middle Fossa Craniotomy

To determine whether cervical vestibular evoked myogenic potentials (cVEMPs) are predictive of hearing preservation in patients undergoing vestibular schwannoma removal through middle fossa craniotomy approach. Retrospective case study. Tertiary referral center. Eighteen patients who underwent a middle fossa craniotomy for vestibular schwannoma (stage I or II of Koos classification) with attempted hearing preservation from January 2008 to February 2016 were retrospectively reviewed. Pre-surgical cVEMPs test, videonystagmography (caloric test), and magnetic resonance imaging (MRI) as well as a pre- and post-surgical audiometry test. cVEMPs parameters including amplitude asymmetry ratio (AR), P13, and N23 latencies and peak-to-peak amplitude between P13 and N23 waves were calculated. Hearing data were classified according to the AAO-HNS hearing classes. The nerve of origin of the tumor was specified during surgery and the largest tumor diameter was measure on MRI axial plane on T2-CISS weighed images. Preoperative amplitude asymmetry ratio was lower (n = 15, Mann-Whitney U test, p < 0.001) in the group with postoperative hearing preservation (n = 11) compared with the group with postoperative hearing preservation failure (n = 4). The positive predictive value of an AR less than 24% to assess postoperative hearing preservation is 91.6%. Tumor size and localization were not correlated with cVEMPs, nor with caloric testing in this group of small-sized intracanalicular vestibular schwannomas. Our data suggest that cVEMPs may help predict hearing preservation outcome in vestibular schwannoma surgery via the middle fossa craniotomy approach.

A Cohort Study of Hearing Outcomes Between Middle Fossa Craniotomy and Transmastoid Approach for Surgical Repair of Superior Semicircular Canal Dehiscence Syndrome.

To compare postoperative hearing outcomes between transmastoid and middle fossa craniotomy (MFC) approaches for surgical repair of superior semicircular canal dehiscence syndrome (SCDS) in a tertiary referral center. Historical cohort study. Tertiary referral center. Twelve consecutive SCDS cases who underwent transmastoid plugging of the superior canal; "controls" were 18 audiogram-matched patients who underwent MFC plugging and resurfacing. Differences between preoperative, 7-day postoperative, and long-term (>6 wk) postoperative air and bone conduction, speech discrimination scores (SDS), and pure-tone averages (PTA) in TM cases versus MFC controls. MFC controls were selected by matching preoperative bone conduction (BC) pure-tone thresholds from the TM cases within 10-dBs NHL in ≥80% of recorded frequencies. Wilcoxon signed-rank tests were performed to compare primary outcomes between matches, with a Bonferroni corrected p value of 0.004 (n = 13 variables measured at each time period). No statistically significant differences were found in long-term postoperative air conduction and BC thresholds at any frequency both during the immediate postoperative period as well as at long-term follow-up (p > 0.004). Similarly, there were no differences in long-term SDS or PTA (p > 0.004). In this pilot study, there were no long-term significant differences in hearing outcomes between the two repair techniques for SCDS. We recommend continuing with the established practice for recommending surgical repair based on individual patient characteristics and preferences in managing both vestibular and auditory function.

Pearls for the middle fossa approach in acoustic neuroma surgery.

To discuss the use of the middle fossa craniotomy for resection of vestibular schwannomas; to present pearls of and modifications to the approach. The middle fossa craniotomy allows for hearing preservation in the resection of intracanalicular vestibular schwannomas. Over recent years, the approach has been modified to address larger tumors with a limited cerebellopontine angle component. Positive identification of the superior semicircular canal allows for rapid exposure of the internal auditory canal (IAC). Removal of cerebrospinal fluid from the posterior fossa during exposure of the IAC allows for removal of the middle fossa retractor; reinforced silicone sheeting is used to protect the middle fossa dura during further drilling. The use of the endoscope has allowed for more complete dissection at the fundus of the IAC, including tumors lateral to the transverse crest. Technical modifications to the middle fossa craniotomy have allowed for a shorter duration of temporal lobe retraction intraoperatively and more complete resection of tumors with fundal involvement.

Combined petrosal approach.

The combined petrosal approach to the lateral skull base merges a retrolabyrinthine-presigmoid posterior fossa craniotomy with an adjacent middle fossa craniotomy, which are rendered continuous by division of the tentorium. This is a hearing-preserving approach that affords wide access to the lateral aspect of the clivus, the prepontine space, and the cerebellopontine angle. This article details the historical development of the combined petrosal approach alongside a description. In particular, the critically relevant anatomy is reviewed, including the course of the vein of Labbé, with a view toward avoiding the known complications associated with this approach. Outcomes for application of this approach as applied for various lesions are also reviewed as portrayed by the current literature. The combined petrosal approach affords wide access to the lateral skull base in the middle and posterior fossa. The approach and the lesions addressed by this approach involve delicate and sensitive anatomy. We review the evolution of this approach and highlight advancements that have allowed the combined petrosal approach to be a safe addition to the surgeon's armamentarium.

Novel Method of Measuring Canal Dehiscence and Evaluation of its Potential as a Predictor of Symptom Outcomes After Middle Fossa Craniotomy.

Superior semicircular canal dehiscence (SSCD) is an osseous defect of the arcuate eminence of the petrous temporal bone. Strategies for measuring dehiscence size are variable, and the usefulness of such parameters remains in clinical equipoise. To present a novel method of measuring dehiscence volume and to evaluate its potential as a predictor of symptom outcomes after surgical repair of SSCD. High-resolution computed tomographic temporal bone images were imported into a freely available segmentation software. Dehiscence lengths and volumes were ascertained by independent authors. Inter-rater observer reliability was assessed using Cronbach's alpha. Correlation and regression analyses were performed to evaluate for relationships between dehiscence size and symptoms (pre- and post-operative). Thirty-seven dehiscences were segmented using the novel volumetric assessment. Cronbach's alpha for dehiscence lengths and volumes were 0.97 and 0.95, respectively. Dehiscence lengths were more variable as compared to dehiscence volumes (σ2 8.92 vs σ2 0.55, F = 1.74). The mean dehiscence volume was 2.22 mm3 (0.74, 0.64-0.53 mm3). Dehiscence volume and headache at presentation were positively correlated (Rpb = 0.67, P = .03). Dehiscence volume and vertigo improvement after surgery were positively correlated, although this did not reach statistical significance (Rpb = 0.46, P = .21). SSCD volumetry is a novel method of measuring dehiscence size that has excellent inter-rater reliability and is less variable compared to dehiscence length, but its potential as a predictor of symptom outcomes is not substantiated. However, the study is limited by low power.

Incidence of intraoperative hearing loss during middle cranial fossa approach for repair of superior semicircular canal dehiscence

IntroductionSuperior semicircular canal dehiscence is a rare inner ear disorder characterized by an abnormal third opening between the superior semicircular canal and middle fossa. Symptoms include amplification of internal sounds, aural fullness, tinnitus, hearing loss, autophony, sound-induced vertigo (Tullio phenomenon), pressure-induced vertigo (Hennebert sign), disequilibrium, nystagmus, oscillopsia, and headache. While no cure exists for SSCD, surgical treatment has proven to effectively minimize these symptoms. This study reviewed brainstem auditory evoked potentials (BAEPs) that were monitored intraoperatively to better understand hearing loss risks associated with surgical treatment for SSCD. MethodsA retrospective chart review was conducted at the University of California, Los Angeles on adult patients with a confirmed diagnosis of SSCD who had undergone a middle cranial fossa repair from March 2011 to October 2017. A total of 142 cases of SSCD in 118 patients were repaired. ResultsThe majority of patients’ BAEPs remained stable and had no intraoperative hearing changes (n = 135; 95.1%). Seven patients experienced intraoperative changes as determined by a prolongation and reduction of Wave V latency (4.9%). Of these seven cases, five experienced a return to baseline prior to the end of surgery, and had no post-operative changes in hearing (71.4%). Overall, only two of the 142 surgeries (1.4%) resulted in failure to normalize and, as such, these patients experienced permanent changes in hearing. ConclusionThe results of this retrospective review demonstrate a low risk for hearing loss due to SSCD surgery via the middle fossa craniotomy approach.

Middle Cranial Fossa Approach to Repair Tegmen Defects with Autologous or Alloplastic Graft

Temporal bone tegmen defects may be associated with cerebrospinal fluid (CSF) otorrhea. A variety of techniques have been used for repair. We report our experience with skull base reconstruction for tegmen defects using either autologous or alloplastic grafts. A retrospective chart review was performed on patients with tegmen defects treated from 2007 to 2017 at the University Hospital in Columbia, Missouri, USA. Primary outcome measures were analyzed. Twenty-five patients were treated with a middle cranial fossa approach (median age 53, 88% females, median body mass index 34, median follow-up 9 months). Presenting symptoms included CSF leak (92%), hearing loss (44%), imbalance (12%), meningitis (12%), headache (4%), and tinnitus (4%). Most tegmen defects occurred spontaneously (84%) but cholesteatomas (4%), and trauma (12%) also were identified. Pre- and postoperative audiograms were available for 13 patients (52%); 7 (54%) showed objective improvement. Fourteen patients were repaired with autologous bone graft (56%), 7 with alloplastic grafts (28%), and 4 with temporalis fascia only (16%). All patients had resolution of CSF leak. Two patients (8%) suffered wound infections and 3 (12%) had facial and/or petrosal nerve complications. Use of alloplastic graft significantly shortened operative time (allopathic mean 180 minutes vs. autologous mean 208 minutes; P= 0.03). CSF otorrhea due to tegmen defects can be repaired via a middle fossa craniotomy using either an autologous or alloplastic graft with equivalent outcomes and efficacy, although alloplastic graft helps reduce operating time.

Surgical management of spontaneous cerebrospinal fistulas and encephaloceles of the temporal bone.

To describe the presentation, surgical findings, and outcomes in patients with spontaneous temporal bone cerebrospinal fluid (CSF) fistulas and encephaloceles. Retrospective chart review. A retrospective chart review of patients treated for a spontaneous temporal bone CSF fistula and/or encephalocele over a 10-year period was performed. Data recorded included demographic information, presenting signs and symptoms, radiographic and laboratory studies, surgical approach, materials used for repair, surgical complications, and successful closure of the CSF fistula. Fifty patients were identified. Five patients underwent bilateral procedures, for a total of 55 surgical repairs. Thirty-seven of the patients were female, with a mean age of 57.2 years. Seventy percent of patients were obese, with a mean body mass index of 35.0 kg/m2 . The most common presentation was tympanostomy tube otorrhea (68%). Seven patients (14%) presented with meningitis. The middle fossa craniotomy approach was used in 87.3% of cases. Hydroxyapatite bone cement was used in 82.4% of cases. There were four surgical complications: seizure, mastoid infection, tympanic membrane retraction, and a delayed subdural hematoma. There were five persistent or recurrent CSF fistulas that underwent successful revision surgery. Spontaneous CSF fistulas are most common in obese females and should be suspected with a chronic middle ear effusion, persistent otorrhea after tympanostomy tube placement, or in patients with a history of meningitis. The middle fossa craniotomy approach with the use of hydroxyapatite bone cement has a high success rate with a low incidence of postoperative complications. 4 Laryngoscope, 128:2170-2177, 2018.

Bone Metabolic Markers in the Clinical Assessment of Patients with Superior Semicircular Canal Dehiscence

Superior semicircular canal dehiscence (SSCD) is a bony defect in the osseous shell of the petrous temporal bone. The pathophysiological association between osteoporosis and SSCD remains poorly understood. We investigated the relationship between bone metabolic markers and symptoms in patients with SSCD. We collected patient demographics and clinical parameters for adult patients diagnosed with SSCD on high-resolution computed tomography scans. We used point-biserial correlation analysis to investigate the relationship between bone metabolic markers and symptoms in patients with SSCD. We compared clinical symptoms before and after surgical repair of SSCD through a middle fossa craniotomy using McNemar's test for paired comparisons of binary measures. We included a total of 99 patients (64 females and 35 males; average age 52 years; 118 surgeries). The level of serum calcium correlated with the need for a second surgery (rpb=-0.35, P= 0.001). Postoperative calcium supplementation negatively correlated with improvement in dizziness (rpb=-0.36, P= 0.01). The level of 25-hydroxyvitamin D correlated with preoperative hyperacusis (rpb=-0.98, P= 0.02) and postoperative autophony (rpb= 0.96, P= 0.04). Postoperative vitamin D supplementation positively correlated with hearing decline (rpb= 0.04, P= 0.04) The level of thyroid stimulating hormone correlated withpreoperative autophony, amplification, and tinnitus (rpb=-0.71, rpb=-0.75, rpb=-0.70, all P < 0.001). Bone metabolic markers could be important in the clinical assessment of SSCD patients and could be potential targets for symptom management.

Bone Metabolic Markers in the Clinical Assessment of Patients with Superior Semicircular Canal Dehiscence Treated with Middle Fossa Craniotomy

Bone Metabolic Markers in the Clinical Assessment of Patients with Superior Semicircular Canal Dehiscence Treated with Middle Fossa Craniotomy

Temporal bone fracture requiring facial nerve decompression or repair

Facial nerve paralysis is one of the complications with temporal bone fractures. Although most are treated medically with observation and steroids, we review the indications and surgical approaches to the facial nerve along its course within the temporal bone. It is important to get an examination as early as possible to determine immediate vs delayed, and complete vs incomplete paralysis. Patients with immediate onset, complete facial nerve paralysis should receive electrodiagnostic testing 3-7 days after onset, to allow for Wallerian degeneration. If there is >90% electroneuronography degeneration within 6 days or >95% degeneration within 14 days, surgical exploration is recommended. Exact surgical timing for decompression is controversial and definitive data is lacking but some authors have had success even beyond 2 months postinjury and the risks and benefits should always be discussed with each patient. The approach for surgical decompression of the facial nerve should be based on the site of injury, if discernible, but most commonly involves transmastoid, middle fossa craniotomy, or a combination of these approaches. The perigeniculate region is the most commonly injured portion of the facial nerve with temporal bone fractures. If a transection is encountered, the nerve should be repaired by either primary nerve repair if tension free, otherwise a secondary repair with a cable graft should be performed.

Endoscope-assisted repair of CSF otorrhea and temporal lobe encephaloceles via keyhole craniotomy.

OBJECTIVE Temporal lobe encephaloceles and cerebrospinal fluid otorrhea from temporal bone defects that involve the tegmen tympani and mastoideum are generally repaired using middle fossa craniotomy, mastoidectomy, or combined approaches. Standard middle fossa craniotomy exposes patients to dural retraction, which can lead to postoperative neurological complications. Endoscopic and minimally invasive techniques have been used in other surgeries to minimize brain retraction, and so these methods were applied to repair the lateral skull base. The goal of this study was to determine if the use of endoscopic visualization through a middle fossa keyhole craniotomy could effectively repair tegmen defects. METHODS The authors conducted a retrospective review of 6 cases of endoscope-assisted middle fossa repairs of tegmen dehiscences at a tertiary care medical center within an 18-month period. RESULTS All cases were successfully treated using a keyhole craniotomy with endoscopic visualization and minimal retraction. Surgical times did not increase. There were no major postoperative complications, recurrences of encephaloceles, or cerebrospinal fluid otorrhea in these patients. CONCLUSIONS Endoscopic visualization allows for smaller incisions and craniotomies and less risk of brain retraction injury without compromising repair integrity during temporal encephalocele and tegmen repairs.

Outcomes of middle fossa craniotomy for the repair of superior semicircular canal dehiscence

Superior semicircular canal dehiscence (SSCD) is a rare defect of the arcuate eminence that causes an abnormal connection between the superior semicircular canal and middle cranial fossa. Patients often present with a variety of auditory and vestibular symptoms. Trigger avoidance is the initial strategy, but surgery may be necessary in debilitating cases. We retrospectively reviewed SSCD patients undergoing repair via a middle fossa craniotomy between March 2011 and September 2015. Forty-nine patients undergoing 58 surgeries were identified. Autophony was the most common symptom at presentation (n=44; 90%). Mean follow-up was 10.9months, with 100% of patients reporting resolution of at least one symptom. Aural fullness was the most commonly resolved symptom following surgical repair (n=19/22; 86%). Hearing loss (n=11/25; 44%) and tinnitus (n=11/38; 29%) were the most common symptoms to persist following surgery. The most common symptom to develop after surgery was disequilibrium (n=4/18; 22%). Upon comparing the overall pre-operative and post-operative groups, the number of patients with autophony (p<0.0001), aural fullness (p=0.0006), hearing loss (p=0.0119), disequilibrium (p=0.0002), sound- and pressure-induced vertigo (p<0.0001), and tinnitus (p<0.0001) were significantly different. Improved clinical outcomes were demonstrated in patients undergoing SSCD repair through a middle cranial fossa approach. The most common presenting symptom (autophony) was also most likely to resolve after surgery. Hearing loss is less amenable to surgical correction. Disequilibrium developed in a small number of patients after repair.

Minimally Invasive Middle Fossa Keyhole Craniectomy for Repair of Superior Semicircular Canal Dehiscence.

Superior semicircular canal dehiscence (SSCD) presents with varying degrees of auditory and vestibular dysfunction. The condition is confirmed on high-resolution computed tomography (CT) imaging, and symptoms are often improved by surgical repair. Although a classic middle fossa craniotomy has been used with good results, recent advances in technique have allowed for modification of the traditional approach into a smaller skin incision and a minimally invasive middle fossa keyhole craniectomy roughly 1.7 cm in diameter. To delineate this novel approach and describe the technique for accurate localization of the dehiscence using preoperative measurements and intraoperative image guidance, thereby minimizing the need for a larger skin incision and craniotomy. Patients were independently diagnosed with SSCD by the senior authors. Once relevant imaging was acquired, the novel keyhole technique was performed. Patients' vestibular and auditory symptoms before and after the procedure were assessed. Outcomes from a series of patients treated with this keyhole approach were tabulated and reported. Twelve cases from 11 patients were included in this series. Auditory symptoms had high rates of resolution with pulsatile tinnitus, internal amplification of sounds, and autophony being resolved in a majority of cases. Only 2 cases reported hearing decline. Sound/pressure induced vertigo and disequilibrium also demonstrated high rates of resolution. No complications were reported. The minimally invasive middle fossa keyhole craniectomy is a novel approach for the repair of SSCD. This approach may contribute to resolved auditory and vestibular symptoms with low morbidity and quick recovery.

A Novel Minimally Invasive Approach to the Middle Cranial Fossa: Surgical Technique and Clinical Outcomes

Background: Middle fossa craniotomy is an established surgical approach to manage lateral skull base pathology, such as superior canal dehiscence (SCD) or tegmen defects resulting in encephalocele and/or cerebrospinal fluid (CSF) leak. Traditionally described surgical incisions for MFC consist of a straight or curved pre-tragal vertical incision, or a large “C-shaped” incision, designed to facilitate a craniotomy of ~5x5cm (25cm2). Such an approach maximizes surgical exposure at the cost of a large incision and potential cosmetic deformity. In an attempt to optimize cosmetic outcomes in non-tumor MFC surgery, we have designed a minimally invasive approach characterized by a horizontally oriented S-shaped incision placed entirely within the hair-bearing skin, an anteroinferiorly based temporalis muscle flap, and small craniotomy. We hypothesize that our minimally invasive approach provides adequate exposure for management of non-tumor lateral skull base pathology with minimal postoperative morbidity.

Superior Semicircular Canal Dehiscence Repair through Middle Cranial Fossa Craniotomy with 5 Layers Reconstruction: Our Experience and Surgical Technique

Superior Semicircular Canal Dehiscence Repair through Middle Cranial Fossa Craniotomy with 5 Layers Reconstruction: Our Experience and Surgical Technique

Minimally invasive middle fossa craniotomy approach with endoscopic repair of superior canal dehiscence

Superior canal dehiscence (SCD) is a bony defect of the superior semicircular canal. SCD syndrome occurs when vestibular or auditory dysfunction accompanies SCD. Although not all patients with SCD are symptomatic, surgical repair is an option in patients with incapacitating symptoms and are unresponsive to conservative treatment. Traditionally, repair of SCD when involving the arcuate eminence can be achieved using a middle fossa craniotomy approach. However, approximately 30% of SCD cases have a medial arcuate eminence defect along a downsloping tegmen, making the defect difficult to visualize with the binocular microscope without a large craniotomy, extensive temporal lobe retraction, and drilling of the skull base. As complete visualization of an arcuate eminence defect is essential for successful repair, we describe an operative approach to visualize the SCD that combines a small middle fossa craniotomy and rigid endoscopy. The wide-field view and superior transillumination with skull base endoscopy can be achieved with a minimal access skin incision, small bony window, less dural dissection, and reduced brain retraction, resulting in unequivocal identification of the entire arcuate eminence defect.

Cadaveric Study of an Endoscopic Keyhole Middle Fossa Craniotomy Approach to the Superior Semicircular Canal.

Demonstrate that an endoscopic keyhole approach to the middle cranial fossa is technically feasible for repair of semicircular canal dehiscence. Cadaveric technical feasibility/methods development study. Tertiary care military medical center. Three fresh cadaveric heads (six sides). Endoscopic minimally invasive approach to the middle cranial fossa using the Medtronic Fusion Guidance system. Ability to identify the surgical landmarks of the middle cranial fossa and successfully identify and instrument the superior semicircular canal. In every attempt, the arcuate eminence was successfully identified under endoscopic visualization and with the assistance of surgical navigation. The superior semicircular canal was unroofed, and its location confirmed visually and with the navigation system. The opened canal was then plugged with bone wax, bone pate, and covered with fascia. The 15-mm burr hole craniotomy provided ample room for one working instrument and a 4-mm 0-degree endoscope. The endoscopic keyhole approach to superior semicircular canal dehiscence is technically feasible in a human cadaveric model. Further studies will determine 1) if this approach is possible and safe in vivo, 2) is associated with improved surgical outcomes, and 3) if surgical navigation aids in this approach.