Kim O. Learned

Radiographic enhancement of the nasoseptal flap does not predict postoperative cerebrospinal fluid leaks in endoscopic skull base reconstruction

Cerebrospinal fluid (CSF) leaks continue to be the most common postoperative complication in expanded endonasal skull base procedures. Currently, a multilayer closure using a vascularized nasoseptal flap is most commonly performed for large ventral skull base defects in an effort to avoid postoperative CSF leaks. We correlated nasoseptal flap enhancement with postoperative CSF leak rates in a group of skull base reconstruction patients. The nasoseptal flap enhancement was determined by immediate postoperative gadolinium‐enhanced magnetic resonance imaging (MRI), which allowed for imaging of the flaps vascular pedicle. Our aim was to identify whether nasoseptal flap enhancement contributed to reduction of postoperative CSF leak rates.

Intraoperative Near-Infrared Optical Imaging Can Localize Gadolinium-Enhancing Gliomas During Surgery

BACKGROUND Although real-time localization of gliomas has improved with intraoperative image guidance systems, these tools are limited by brain shift, surgical cavity deformation, and expense. OBJECTIVE To propose a novel method to perform near-infrared (NIR) imaging during glioma resections based on preclinical and clinical investigations, in order to localize tumors and to potentially identify residual disease. METHODS Fifteen patients were identified and administered a Food and Drug Administration-approved, NIR contrast agent (Second Window indocyanine green [ICG], 5 mg/kg) before surgical resection. An NIR camera was utilized to localize the tumor before resection and to visualize surgical margins following resection. Neuropathology and magnetic resonance imaging data were used to assess the accuracy and precision of NIR fluorescence in identifying tumor tissue. RESULTS NIR visualization of 15 gliomas (10 glioblastoma multiforme, 1 anaplastic astrocytoma, 2 low-grade astrocytoma, 1 juvenile pilocytic astrocytoma, and 1 ganglioglioma) was performed 22.7 hours (mean) after intravenous injection of ICG. During surgery, 12 of 15 tumors were visualized with the NIR camera. The mean signal-to-background ratio was 9.5 ± 0.8 and fluorescence was noted through the dura to a maximum parenchymal depth of 13 mm. The best predictor of positive fluorescence was enhancement on T1-weighted imaging; this correlated with signal-to-background ratio (P = .03). Nonenhancing tumors did not demonstrate NIR fluorescence. Using pathology as the gold standard, the technique demonstrated a sensitivity of 98% and specificity of 45% to identify tumor in gadolinium-enhancing specimens (n = 71). CONCLUSION With the use of Second Window ICG, gadolinium-enhancing tumors can be localized through brain parenchyma intraoperatively. Its utility for margin detection is promising but limited by lower specificity. ABBREVIATIONS 5-ALA, 5-aminolevulinic acidEPR, enhanced permeability and retentionFDA, Food and Drug AdministrationGBM, glioblastomaICG, indocyanine greenNIR, near-infraredNPV, negative predictive valuePPV, positive predictive valueROC, receiver operating characteristicROI, region of interestSBR, signal-to-background ratioWHO, World Health Organization.

Transoral Robotic Surgery in Head and Neck Cancer: What Radiologists Need to Know about the Cutting Edge

The evolution of oncologic surgical technology has moved toward reducing patient morbidity and mortality without compromising oncologic resection or oncologic outcomes. The goals in treating head and neck cancer are to cure patients, as well as to provide quality of life by improving functional and social outcomes through organ-preservation therapies, which may include surgery, chemotherapy, and/or radiation therapy. Transoral robotic surgery (TORS) is an emerging technique that provides several benefits over existing treatment regimens and over open surgery for head and neck cancer, including reductions in operative times, blood loss, intensive care unit stays, and overall duration of patient hospitalization. Transoral robotic techniques allow wide-view, high-resolution, magnified three-dimensional optics for visualization of the mucosal surfaces of the head and neck through an endoscope, while avoiding the extensive external cervical incisions often required for open surgeries. Radiologists play an important role in the successful outcome of these procedures, both before and after TORS. Determining a cancer patients surgical candidacy for TORS requires a thorough preoperative radiologic evaluation, coupled with clinical and intraoperative assessment. Radiologists must pay particular attention to important anatomic landmarks that are clinical blind spots for surgeons. Knowledge of the expected postoperative imaging appearances, so that they can be distinguished from recurrent disease and second primary tumors, is essential for all radiologists involved in the care of these patients.

MR imaging evaluation of endoscopic cranial base reconstruction with pedicled nasoseptal flap following endoscopic endonasal skull base surgery

INTRODUCTION Postoperative CSF leak is the most common complication of endoscopic endonasal approach (EEA) to skull base lesions. Endoscopic multilayer closure of skull base defect using pedicled nasoseptal flaps (NSF) based off the sphenopalatine artery reduces CSF leaks. EEA robustly expands in surgical arena, yet postoperative imaging evaluation remains poorly studied. This work illustrates normal MR imaging appearance of skull base reconstruction utilizing NSFs during immediate postoperative period. METHODS We retrospectively identified patients who had skull base reconstructions utilizing NSFs following EEAs and immediate postoperative-enhanced brain MRI. NSFs and free grafts were evaluated for signal intensity, thickness, configuration, enhancement, vascular pedicle of NSF, relationship in multilayer reconstruction, and defect coverage. Imaging findings were correlated with surgical technique and CSF leaks. RESULTS Twenty-eight patients had 26 multilayer reconstructions and 34 NSFs. Twenty-nine NSFs showed enhancing C-shaped arc at the skull base. Of those, 26 flaps (90%) were confidently identified by visualization of their vascular pedicles, 3 were not distinguishable from adjacent mucosa and pedicles were not identified. Five NSFs showed no enhancement (1 CSF leak). Twenty-seven enhancing NSFs approximated defects with close abutment to free grafts. One flap was displaced; one incompletely covered the defect (2 CSF leaks). Fisher exact test demonstrated an association between incomplete defect coverage and displacement of NSFs with CSF leak (P=0.05). CONCLUSION Endoscopic skull base reconstruction utilizing NSF has characteristic MR imaging appearance. Non-enhancing mucosal gap or displacement of NSF may indicate incomplete defect coverage, identifying patients at risk for CSF leak.

Cranial Nerve Schwannomas: Diagnostic Imaging Approach

Schwannomas are benign nerve sheath tumors that may arise along the complex course of the cranial nerves (CNs), anywhere in the head and neck. Sound knowledge of the CN anatomy and imaging features of schwannomas is paramount for making the correct diagnosis. In this article, we review approaches to diagnosing CN schwannomas by describing their imaging characteristics and the associated clinical presentations. Relevant anatomic considerations are highlighted by using illustrative examples and key differential diagnoses categorized according to regions, which include the anterior skull base, orbit, cavernous sinus, basal cisterns, and neck. The clinical presentations associated with CN schwannomas vary and range from no symptoms to symptoms caused by mass effect or CN deficits. Individuals with the inherited disorder neurofibromatosis type 2 are predisposed to multiple schwannomas. When a lesion follows the course of a CN, the radiologists roles are to confirm the imaging features of schwannoma and exclude appropriate differential considerations. The characteristic imaging features of CN schwannomas reflect their slow growth as benign neoplasms and include circumscribed margins, displacement of local structures, and smooth expansion of osseous foramina. These neoplasms exhibit various degrees of solid enhancement, often with internal cystic spaces on magnetic resonance (MR) and computed tomographic (CT) images and heterogeneous high signal intensity specifically on T2-weighted MR images. Clinical and/or imaging evidence of end-organ compromise of the involved CN may exist and aid in the identification of the nerve of origin. With a detailed understanding of the course of the CNs, the diagnostic features of CN schwannomas, and the correlation between these data and the associated clinical presentations of these tumors, the radiologist can have a key role in the diagnosis of CN schwannomas and the treatment planning for affected patients. (©)RSNA, 2016.

Myocutaneous Flaps and Other Vascularized Grafts in Head and Neck Reconstruction for Cancer Treatment

This article addresses the clinical evaluation and some of the more common flaps and grafts used to reconstruct the surgical bed after excision of primary head and neck cancers and nodal metastases. This focused summary is intended to enhance the readers understanding and improve the interpretation of posttreatment MR imaging. A practical approach to MR imaging evaluation of the postoperative reconstructed neck is presented. Readers of this article will become familiar with the normal appearances of commonly used flaps, recognize common complications, be able to delineate residual and recurrent neoplasm, and learn to avoid interpretative pitfalls.

Hypoglossal nerve palsy missed and misinterpreted: the hidden skull base.

Objective Dysarthria and tongue swelling may be seen with hypoglossal nerve palsy, and on cross-sectional imaging studies, tongue denervation can be misinterpreted as a primary base-of-tongue mass. Understanding radiological patterns of tongue denervation is important to prevent misinterpretation. Close evaluation of the skull base is critical as hypoglossal palsies resulting from pathology here are often overlooked. Methods Neck and brain magnetic resonance imaging studies obtained in 7 adult patients referred to our institution with clinically and/or radiologically suspected tongue base masses were retrospectively reviewed. Outside imaging evaluations were misinterpreted as base-of-tongue tumors in 3 patients, incorrectly read as normal in 2, and skull base pathologies were missed in 5. Results All 7 patients showed magnetic resonance imaging findings typical of tongue denervation: T2-weighted hyperintensity of involved hemitongue, protrusion of the tongue into oropharynx, variable fatty infiltration. All 5 skull base masses involved hypoglossal canal (4 metastases, 1 multiple myeloma; 4 newly diagnosed cancers). Two patients had internal carotid artery dissections at the skull base. Conclusions To avoid misinterpretation of tongue denervation for tongue base mass, understanding of tongue innervations and classic imaging findings of hypoglossal denervation are essential. Careful inspection of skull base is paramount to avoid overlooking these hidden pathologies.

US-guided Biopsy of Neck Lesions: The Head and Neck Neuroradiologist’s Perspective

Ultrasonographically (US) guided percutaneous biopsy of a neck lesion is a cost-effective, safe, and diagnostically effective procedure without radiation exposure. The benefit of real-time visualization of the needle location allows for instantaneous maneuvering of the needle trajectory for safe and accurate tissue sampling with short procedural time. Effective US-guided biopsy requires technical experience, strong clinical acumen, and skillful biopsy technique. A neuroradiologists knowledge of head and neck anatomy and pathology allows correlation with cross-sectional imaging and enhances the understanding of US imaging evaluation. Familiarity with a spectrum of neck surgeries and reconstructions and expertise in imaging evaluation of the treated neck are invaluable in accurate identification of the target for biopsy in patients with treatment-related altered anatomy using US guidance. After thyroid nodules, the common adult neck masses are lymphadenopathy, head and neck cancer, salivary neoplasms, nerve sheath tumors, and inflammatory and infectious pseudomasses. Diagnostic expertise in the imaging characteristics of these individual pathologic conditions and their differential diagnoses also play an important role in choosing the biopsy technique and in procuring an adequate sample for diagnosis, including material for ancillary laboratory testing. Using an anatomic zone approach, this article illustrates the practical considerations in patient selection, the methodical analysis of preprocedure cross-sectional imaging and its correlation with real-time US evaluation, general principles for optimizing US instrumentation, and biopsy technique. In skillful hands, the versatility and portability of US make it the valuable modality for histologic sampling of superficial head and neck lesions. Online supplemental material is available for this article.

Pediatric nasoseptal flap reconstruction for suprasellar approaches

To determine the pediatric age groups viable for nasoseptal flap (NSF) reconstruction of endoscopic endonasal approaches (EEA) to intracranial pathology of suprasella neoplasms.

Folate receptor overexpression can be visualized in real time during pituitary adenoma endoscopic transsphenoidal surgery with near-infrared imaging

OBJECTIVE Pituitary adenomas account for approximately 10% of intracranial tumors and have an estimated prevalence of 15%-20% in the general US population. Resection is the primary treatment for pituitary adenomas, and the transsphenoidal approach remains the most common. The greatest challenge with pituitary adenomas is that 20% of patients develop tumor recurrence. Current approaches to reduce recurrence, such as intraoperative MRI, are costly, associated with high false-positive rates, and not recommended. Pituitary adenomas are known to overexpress folate receptor alpha (FRα), and it was hypothesized that OTL38, a folate analog conjugated to a near-infrared (NIR) fluorescent dye, could provide real-time intraoperative visual contrast of the tumor versus the surrounding nonneoplastic tissues. The preliminary results of this novel clinical trial are presented. METHODS Nineteen adult patients who presented with pituitary adenoma were enrolled. Patients were infused with OTL38 2-4 hours prior to surgery. A 4-mm endoscope with both visible and NIR light capabilities was used to visualize the pituitary adenoma and its margins in real time during surgery. The signal-to-background ratio (SBR) was recorded for each tumor and surrounding tissues at various endoscope-to-sella distances. Immunohistochemical analysis was performed to assess the FRα expression levels in all specimens and classify patients as having either high or low FRα expression. RESULTS Data from 15 patients (4 with null cell adenomas, 1 clinically silent gonadotroph, 1 totally silent somatotroph, 5 with a corticotroph, 3 with somatotrophs, and 1 somatocorticotroph) were analyzed in this preliminary analysis. Four patients were excluded for technical considerations. Intraoperative NIR imaging delineated the main tumors in all 15 patients with an average SBR of 1.9 ± 0.70. The FRα expression level of the adenomas and endoscope-to-sella distance had statistically significant impacts on the fluorescent SBRs. Additional considerations included adenoma functional status and time from OTL38 injection. SBRs were 3.0 ± 0.29 for tumors with high FRα expression (n = 3) and 1.6 ± 0.43 for tumors with low FRα expression (n = 12; p < 0.05). In 3 patients with immunohistochemistry-confirmed FRα overexpression (2 patients with null cell adenoma and 1 patient with clinically silent gonadotroph), intraoperative NIR imaging demonstrated perfect classification of the tumor margins with 100% sensitivity and 100% specificity. In addition, for these 3 patients, intraoperative residual fluorescence predicted postoperative MRI results with perfect concordance. CONCLUSIONS Pituitary adenomas and their margins can be intraoperatively visualized with the preoperative injection of OTL38, a folate analog conjugated to NIR dye. Tumor-to-background contrast is most pronounced in adenomas that overexpress FRα. Intraoperative SBR at the appropriate endoscope-to-sella distance can predict adenoma FRα expression status in real time. This work suggests that for adenomas with high FRα expression, it may be possible to identify margins and to predict postoperative MRI findings.