Minimally invasive image-guided access for drainage of petrous apex lesions: a case report

Assessing the feasibility of the transmastoid infralabyrinthine approach without decompression of the jugular bulb to the extradural part of the petrous apex and petroclival junction prior to surgery

BACKGROUND AND OBJECTIVE

This study aims to define specific measurements on cranial high-resolution computed tomography (HRCT) images prior to surgery to prove the feasibility of the navigated transmastoid infralabyrinthine approach (TI-A) without rerouting of the facial nerve (FN) and decompression of the jugular bulb (JB) in accessing the extradural-intrapetrous part of petrous bone lesions located at the petrous apex and petroclival junction.

MATERIALS AND METHODS

Vertical and horizontal distances of the infralabyrinthine space were measured on cranial HRCT images prior to dissection. Subsequently, the area of access was measured on dissected human cadaveric specimens. Infralabyrinthine access to the extradural part of the petrous apex and petroclival junction was evaluated on dissected specimens by two independent raters. Finally, the vertical and horizontal distances were correlated with the area of access.

RESULTS

Fourteen human cadaveric specimens were dissected bilaterally. In 54% of cases, the two independent raters determined appropriate access to the petrous apex and petroclival junction. A highly significant positive correlation (r = 0.99) was observed between the areas of access and the vertical distances. Vertical distances above 5.2 mm were considered to permit suitable infralabyrinthine access to the extradural area of the petrous apex and petroclival junction.

CONCLUSIONS

Prior to surgery, vertical infralabyrinthine distances on HRCT images above 5.2 mm provide suitable infralabyrinthine access to lesions located extradurally at the petrous apex and petroclival junction via the TI-A without rerouting of the FN and without decompression of the JB.

Freehand Stereotactic Image-Guidance Tailored to Neurotologic Surgery

Hypothesis: The use of freehand stereotactic image-guidance with a target registration error (TRE) of μ_TRE + 3σ_TRE < 0.5 mm for navigating surgical instruments during neurotologic surgery is safe and useful. Background: Neurotologic microsurgery requires work at the limits of human visual and tactile capabilities. Anatomy localization comes at the expense of invasiveness caused by exposing structures and using them as orientation landmarks. In the absence of more-precise and less-invasive anatomy localization alternatives, surgery poses considerable risks of iatrogenic injury and sub-optimal treatment. There exists an unmet clinical need for an accurate, precise, and minimally-invasive means for anatomy localization and instrument navigation during neurotologic surgery. Freehand stereotactic image-guidance constitutes a solution to this. While the technology is routinely used in medical fields such as neurosurgery and rhinology, to date, it is not used for neurotologic surgery due to insufficient accuracy of clinically available systems. Materials and Methods: A freehand stereotactic image-guidance system tailored to the needs of neurotologic surgery-most importantly sub-half-millimeter accuracy-was developed. Its TRE was assessed preclinically using a task-specific phantom. A pilot clinical trial targeting N = 20 study participants was conducted (ClinicalTrials.gov ID: NCT03852329) to validate the accuracy and usefulness of the developed system. Clinically, objective assessment of the TRE is impossible because establishing a sufficiently accurate ground-truth is impossible. A method was used to validate accuracy and usefulness based on intersubjectivity assessment of surgeon ratings of corresponding image-pairs from the microscope/endoscope and the image-guidance system. Results: During the preclinical accuracy assessment the TRE was measured as 0.120 ± 0.05 mm (max: 0.27 mm, μ_TRE + 3σ_TRE = 0.27 mm, N = 310). Due to the COVID-19 pandemic, the study was terminated early after N = 3 participants. During an endoscopic cholesteatoma removal, a microscopic facial nerve schwannoma removal, and a microscopic revision cochlear implantation, N = 75 accuracy and usefulness ratings were collected from five surgeons each grading 15 image-pairs. On a scale from 1 (worst rating) to 5 (best rating), the median (interquartile range) accuracy and usefulness ratings were assessed as 5 (4-5) and 4 (4-5) respectively. Conclusion: Navigating surgery in the tympanomastoid compartment and potentially in the lateral skull base with sufficiently accurate freehand stereotactic image-guidance (μ_TRE + 3σ_TRE < 0.5 mm) is feasible, safe, and useful. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03852329.

Cholesterol Granulomas: A Comparative Meta-Analysis of Endonasal Endoscopic versus Open Approaches to the Petrous Apex

Petrous apex cholesterol granulomas (PACG) are rare disorders that can lead to patient morbidity and must, occasionally, be drained by either endoscopic endonasal (EN) or open procedures (OP). The objective of our study was to complete a review of the literature to compare the EN and OP approaches on multiple levels, notably on safety and effectiveness. Ovid MEDLINE and Embase were used to perform a thorough literature review of all cases of PACG treated by either EN or OP dating from January 1948 to August 2017. In total, 49 articles were selected including 23 for EN (n=76) and 26 for OP (n=210). Differences were found in the incidence of preoperative hearing loss (HL) (EN 18.4%, OP 57.3%; p<0.001), headache (EN 48.7%, OP 31.2%; p=0.007), and disequilibrium (EN: 14.5%, OP 26.1%; p=0.04). Differences in lesion proximity to the sphenoid sinus (EN 23.6%, OP: 1.0%; p<0.001), clivus (EN 11.8%, OP 4.7%; p=0.03), otic capsule (EN 0.0%, OP 5.2%; p=0.03), internal auditory canal (EN 2.6%, OP 10.9%; p=0.01), and internal carotid artery (ICA) (EN 9.2%, OP 2.8%; p=0.02) were found on preoperative imaging. The EN procedure had better hearing improvement rates (EN 85.7%, OP 23.4%; p<0.001), lower complication rates (EN 7.9%, OP 17.6%; p=0.04), shorter median follow-up (EN:13.5 months, OP:37.2 months; p<0.001), and shorter time to recurrence (EN 3 months, OP 22.6 months; p=0.002) than the known OP. No differences were found in age, preoperative size, recurrence rate, operative time, stent placement, or improvement of other symptoms. Endoscopic nasal approaches, when feasible, should be favored to open procedures for PACG drainage given their better hearing improvement and less complication rates.

The Natural History and Management of Petrous Apex Cholesterol Granulomas

OBJECTIVE

To evaluate the clinical and radiographic characteristics of cholesterol granulomas of the petrous apex, as well as the outcomes of operative and conservative management.

STUDY DESIGN

Retrospective chart review.

SETTING

Two independent tertiary academic referral centers.

PATIENTS

Adult and pediatric patients with cholesterol granulomas of the petrous apex were identified from the experience of two separate centers. Patients were included after radiographic diagnosis and clinical evaluation. All patients with less than 6 months of follow-up and those with iatrogenic postoperative cholesterol granulomas were excluded.

INTERVENTION

Demographic information, presenting symptoms, imaging characteristics, treatment strategies, and outcomes were recorded.

MAIN OUTCOME MEASURES

Patients were evaluated on the basis of symptom and radiographic evolution during time, with or without operative intervention.

RESULTS

Ninety petrous apex cholesterol granulomas were analyzed (57.8% females, 55.6% right-sided). The average age at presentation was 43.1 years (median 42.0, range 8.0-77.0 years). The most common presenting symptom was headache (56.7%), and the average lesion size in the greatest dimension was 2.1 cm (median 1.7, range 0.7-5.0 cm). During a mean follow-up of 46.0 months, no cases of spontaneous rupture or carotid injury occurred. Twenty-three patients (25.6%) ultimately underwent surgical management, most commonly for intractable headache, and only 47.8% of these patients experienced durable symptom improvement by their last postoperative follow-up.

CONCLUSION

Many cholesterol granulomas of the petrous apex remain stable during time and can be safely managed with primary observation. Surgery should be reserved for lesions that are causing, or threatening, neurologic dysfunction because of mass effect or erosion of critical structures such as the otic capsule. Cranial neuropathy associated with cholesterol granuloma may improve after operative management; however, symptoms such as headache and dizziness are less likely to benefit from surgery. As a general guideline, in the presence of a radiologically stable cholesterol granuloma in the petrous apex, alternative etiologies for headache and dizziness should be considered and treated before offering surgical intervention.

Decompression of the Jugular Bulb for Enhanced Infralabyrinthine Access to the Petroclival Region: A Quantitative Analysis

Objectives To describe an enhanced infralabyrinthine approach to petroclival lesions with jugular bulb decompression, and to quantify surgical access using a flat-panel computed tomography image protocol. Design Retrospective case series and paired comparison of pre- versus post-dissection anatomy. Setting Tertiary academic medical center. Participants Four patients presenting with petroclival lesions. Six fresh cadaveric specimens were used for temporal bone dissection. Main Outcome Measures Axial and coronal dimensions, and access angles of the infralabyrinthine surgical corridor. Results Decompression of the jugular bulb increased the craniocaudal width of the infralabyrinthine corridor from 0.9 to 7.9 mm to 6.5 to 11.6 mm. The mean increase of 4 mm was statistically significant (t = 3.7; p < .05). There was also a significant widening of the infralabyrinthine window along the axial dimension by 0.9 to 4.5 mm or a mean of 2 mm (t = 3.7; p < .05). Angles of access to the petroclival region were wider following jugular bulb decompression, particularly in the coronal plane (mean difference 7.9 degrees; t = 5.0; p < .005) but less so in the axial plane (mean difference 4.7 degrees; t = 2.5; p = .05). Conclusions Jugular bulb decompression enhances infralabyrinthine access to petroclival lesions, permitting the removal of tissue for diagnoses or partial resection, without significant additional morbidity.

Cholesterol Granuloma Development following Temporal Bone Surgery

OBJECTIVE

To describe the clinical presentation and management of patients with cholesterol granulomas (CGs) that develop following temporal bone surgery.

STUDY DESIGN

Case series with chart review.

SETTING

Two independent tertiary academic referral centers.

SUBJECTS AND METHODS

A multicenter retrospective review was performed to identify all patients between 2001 and 2014 who were diagnosed with a CG that developed following temporal bone surgery. Patients with a history of idiopathic petrous apex CGs were excluded, as were those with <6 months of follow-up after diagnosis. Demographic and clinical data were recorded at presentation, and the main outcome measure was symptom evolution over time.

RESULTS

A total of 20 patients met inclusion criteria (median age, 55.0 years; 70.0% female), and their cases were analyzed. Diagnosis was made, on average, 149.5 months (median, 94.5; range, 13.0-480.0) following a temporal bone operation, which was for chronic ear disease in 75.0% of cases. The most common presenting symptoms were otalgia (55.0%) and otorrhea (40.0%). In patients initially managed with observation, 71.4% required no surgical intervention through a mean of 56.8 months (median, 30; range, 12.0-178.0) of follow-up. For those who initially underwent surgical excision, durable symptom relief was achieved in 66.7% of cases.

CONCLUSION

Postoperative CG formation in the temporal bone is a rare occurrence that can be encountered years following surgery. The present study suggests that conservative management can be appropriate for many cases in which patients are relatively asymptomatic.