Ignazio G. Vetrano

Fusion imaging for intra-operative ultrasound-based navigation in neurosurgery

The major shortcoming of image-guided navigation systems is the use of presurgically acquired image data, which does not account for intra-operative changes such as brain shift, tissue deformation and tissue removal occurring during the surgical procedure. Intra-operative ultrasound (iUS) is becoming widely used in neurosurgery but they lack orientation and panoramic view. In this article, we describe our procedure for US-based real-time neuro-navigation during surgery. We used fusion imaging between preoperative magnetic resonance imaging (MRI) and iUS for brain lesion removal in 67 patients so far. Surgical planning is based on preoperative MRI only. iUS images obtained during surgery are fused with the preoperative MRI. Surgery is performed under intra-operative US control. Relying on US imaging, it is possible to recalibrate navigated MRI imaging, adjusting distortion due to brain shift and tissue resection, continuously updating the two modalities. Ultrasound imaging provides excellent visualization of targets, their margins and surrounding structures. The use of navigated MRI is helpful in better understanding cerebral ultrasound images, providing orientation and panoramic view. Intraoperative US-guided neuro-navigation adjustments are very accurate and helpful in the event of brain shift. The use of this integrated system allows for a true real-time feedback during surgery.SommarioIl principale difetto della neurochirurgia guidata da immagini è il basarsi su immagini acquisite prima dell’intervento, che per ovvie ragioni non possono tenere conto di fenomeni intra-operatori come il brain-shift, la deformazione dei tessuti e l’asportazione di tessuto patologico. L’ecografia intra-operatoria (iUS) sta acquisendo sempre maggior rilevanza in ambito neurochirurgico ma è limitata dalla difficoltosa interpretazione dell’orientamento delle immagini e dalla scarsa panoramicità. In questo articolo descriviamo la nostra tecnica di neuronavigazione real-time basata sull’ecografia intra-operatoria. Fino ad ora abbiamo impiegato la fusione d’immagini tra la risonanza magnetica (MRI) pre-operatoria e l’iUS in 67 pazienti affetti da neoplasie cerebrali. La pianificazione dell’intervento e l’approccio chirurgico è basata sulla (MRI) pre-operatoria mentre l’intervento è guidato dall’iUS. Basandosi sull’iUS è possibile correggere la calibrazione delle immagini (MRI) pre-operatorie correggendo il brain-shift, aggiornando continuamente le due modalità. L’ecografia intra-operatoria permette una eccellente identificazione dei target, dei margini e delle strutture circostanti. L’uso del navigatore basato su (MRI) pre-operatoria è utile nella comprensione delle immagini ecografiche soprattutto per quanto riguarda l’orientazione e la visione panoramica. Le correzione del sistema di neuronavigazione basate sull’iUS sono accurate e utili nel caso di fenomeni intra-operatori come il brain-shift, la deformazione dei tessuti e l’asportazione di tessuto patologico. La neuronavigazione baasata sulla fusione d’immagini tra iUS e (MRI) pre-operatoria permette un vero feeback in real-time durante la chirurgia.

Identification of residual tumor with intraoperative contrast-enhanced ultrasound during glioblastoma resection.

OBJECTIVE The purpose of this study was to assess the capability of contrast-enhanced ultrasound (CEUS) to identify residual tumor mass during glioblastoma multiforme (GBM) surgery, to increase the extent of resection. METHODS The authors prospectively evaluated 10 patients who underwent surgery for GBM removal with navigated ultrasound guidance. Navigated B-mode and CEUS were performed prior to resection, during resection, and after complete tumor resection. Areas suspected for residual tumors on B-mode and CEUS studies were localized within the surgical field with navigated ultrasound and samples were sent separately for histopathological analysis to confirm tumor presence. RESULTS In all cases tumor remnants were visualized as hyperechoic areas on B-mode, highlighted as CEUS-positive areas, and confirmed as tumoral areas on histopathological analysis. In 1 case only, CEUS partially failed to demonstrate residual tumor because the residual hyperechoic area was devascularized prior to ultrasound contrast agent injection. In all cases CEUS enhanced B-mode findings. CONCLUSIONS As has already been shown in other neoplastic lesions in other organs, CEUS is extremely specific in the identification of residual tumor. The ability of CEUS to distinguish between tumor and artifacts or normal brain on B-mode is based on its capacity to show the vascularization degree and not the echogenicity of the tissues. Therefore, CEUS can play a decisive role in the process of maximizing GBM resection.

From Grey Scale B-Mode to Elastosonography: Multimodal Ultrasound Imaging in Meningioma Surgery—Pictorial Essay and Literature Review

The main goal in meningioma surgery is to achieve complete tumor removal, when possible, while improving or preserving patient neurological functions. Intraoperative imaging guidance is one fundamental tool for such achievement. In this regard, intra-operative ultrasound (ioUS) is a reliable solution to obtain real-time information during surgery and it has been applied in many different aspect of neurosurgery. In the last years, different ioUS modalities have been described: B-mode, Fusion Imaging with pre-operative acquired MRI, Doppler, contrast enhanced ultrasound (CEUS), and elastosonography. In this paper, we present our US based multimodal approach in meningioma surgery. We describe all the most relevant ioUS modalities and their intraoperative application to obtain precise and specific information regarding the lesion for a tailored approach in meningioma surgery. For each modality, we perform a review of the literature accompanied by a pictorial essay based on our routinely use of ioUS for meningioma resection.

Intraoperative Navigated Angiosonography for Skull Base Tumor Surgery.

BACKGROUND One of the main challenges during skull base tumor surgery is identifying the relationships between the lesion and the principal intracranial vessels. To this end, neuronavigation systems based on preoperative imaging lack accuracy because of brain shift and brain deformation. Intraoperative navigated B-mode ultrasonography is useful in defining the extent of brain tumor. Doppler imaging adds information regarding flow entity in neighboring vessels. Second-generation ultrasound contrast agents improve the signal-to-noise ratio of B-mode imaging and permit the study of the vessels course, blood flow, and perfusion characteristics of focal lesions. We report our experience using intraoperative navigated contrast-enhanced ultrasound to perform a navigated angiosonography (N-ASG) for the visualization of vessels in a series of 18 skull base tumors. METHODS We performed N-ASG in a series of 18 skull base tumors (10 meningiomas, 3 craniopharyngiomas, 2 giant pituitary adenomas, 1 posterior fossa epidermoid, 2 dermoid cysts). N-ASG was obtained after craniotomy before resecting each lesion and during tumor removal, after intravenous injection of ultrasound contrast agent. RESULTS In all 18 cases, major vessels and their branches were simultaneously identified (both high and low flow) using N-ASG, which allowed to visualize the whole length of each vessels. N-ASG was also useful in highlighting the lesion, compared with standard B-mode imaging, and showing its perfusion patterns. CONCLUSIONS N-ASG can be applied to skull base tumor surgery, providing helpful information about the relationship between principal intracranial vessels and tumors. This technique could be of assistance in approaching the tumor and avoiding vascular damages.

Discrete or diffuse intramedullary tumor? Contrast-enhanced intraoperative ultrasound in a case of intramedullary cervicothoracic hemangioblastomas mimicking a diffuse infiltrative glioma: Technical note and case report

Hemangioblastomas are benign, highly vascularized intramedullary lesions that may also extend into the intradural space. Surgery represents the standard therapy, with the goal of obtaining complete resection even at the risk of neurological morbidity. MRI is the gold standard for diagnosis and assessment of intramedullary tumors. Nevertheless, sometimes MRI may not accurately differentiate between different types of intramedullary tumors, in particular if they are associated with syringes or intra- and peritumoral cysts. This could subsequently affect surgical strategies. Intraoperative ultrasound (ioUS) has become in the last few years a very useful tool for use during neurosurgical procedures. Various ioUS modalities such as B-mode and Doppler have been applied during neurosurgical procedures. On the other hand, the use of contrast-enhanced ultrasound (CEUS) is not yet well defined and standardized in this field. We report a case of a young patient harboring a cervicothoracic intramedullary tumor, for which the preoperative neuroradiologi-cal diagnosis was in favor of a diffuse astrocytoma with nodular components whereas ioUS demonstrated 3 distinct intramedullary nodules. CEUS showed highly vascularized lesions, compatible with hemangioblastomas. These findings, particularly those obtained with CEUS, allowed better definition of the lesions for diagnosis, enhanced understanding of the physiopathological aspects, and permitted the localization of all 3 nodules, thus limiting spinal cord manipulation and allowing complete resection of the lesions, with an uneventful postoperative neurological course. To the best of our knowledge, this is the first report of the use of intraoperative CEUS in a case of intramedullary hemangioblastoma.

Chiari malformation-related headache: outcome after surgical treatment

The outcome of headache in a series of 135 operated CM1 is presented. Favorable results were obtained in 85% of atypical and 93% typical headache with the support of a multidisciplinary approach that restricted the indications for surgery.

The importance of predicting factors in the surgical outcome of peripheral nerve sheath tumors.

OBJECTIVE Peripheral nerve sheath tumors (PNSTs) are tumors arising from the neural sheath cells. Surgery plays a central role in the management of this disease, with the purpose of obtaining radical tumors resection and at the same time providing the best outcome. We retrospectively analyzed 53 PNSTs in 42 patients in an attempt to identify some factors that may improve surgical outcome. MATERIAL AND METHODS Clinical, histologic, and imaging data of 42 patients with PNSTs treated at our Institute between 2001 and 2012 were collected and analyzed. We evaluated the outcome 1 month and 6 month after surgery using three clinical parameters (pain, motor deficits, and sensory deficits) in relation to different histotypes, the presence of neurofibromatosis type 1, tumor location, and duration of symptoms before treatment. RESULTS The best functional results were observed in patients having neurofibromas; the worst outcomes were observed in patients with malignant PNSTs. The other factors were not associated with outcome. CONCLUSION The timing of surgery is the most important predictive factor of surgical outcome, being the only factor that allows to improve the outcome. With the current study, we want to stress the importance of treating PNSTs as soon as possible to provide the best outcome possible.

Chiari malformation type 1-related headache: the importance of a multidisciplinary study.

Chiari type 1 Malformation (CM 1) is a structural defect consisting of a displacement of the cerebellar tonsils through the foramen magnum causing obstruction of cerebrospinal fluid (CSF) outflow. CM 1 has a variety of presentation with headache being the most common symptom. The evaluation and treatment of headache related to CM 1 are often difficult, because the pain in the occipital-suboccipital region or headache that is of cough-type suggests symptomatic CM 1, but patients suffering from CM 1 can also report migraine or tension-type headache. In 2015 we started a collaborative project in which our group of neurologists, neurosurgeons and neuroradiologists contribute to create a Chiari Special Outpatient Service; this was set up to provide a multidisciplinary evaluation, treatment and follow-up of patient suffering from CM 1. 201 patients (58 males, 143 females) suffering from CM 1 were multidisciplinary evaluated. Headache characteristics, clinical features, and treatment of patients are discussed. Further progress in multidisciplinary care of headache and CM 1 should be performed to define guidelines.

Contrast-enhanced ultrasound (CEUS) in spinal tumor surgery

Dear Editor, We read with great interest the technical note by Della Pepa GM, Mattogno LL et al. entitled BReal-time intraoperative contrastenhanced ultrasound (CEUS) in vascularized spinal tumors: a technical note^ which appeared recently as BOnline First Articles^ inActaNeurochirurgica [3], describingCEUS findings in a case of spinal tumor. CEUS is indeed an imaging modality that is gaining popularity: the use of contrast agents, as for computed tomography (CT) and magnetic resonance imaging (MRI), is becoming well established for ultrasound (US). The European Federation for Ultrasound in Medicine and Biology (EFSUMB) published the first BGuidelines for the use of contrast agents in ultrasound^ in 2004 [1]. Since then, many updates, mainly on liver applications, have been published [2, 6]. Recently, our group in Milan had the opportunity to contribute to the new EFSUMB update BGuidelines and Recommendations for the Clinical Practice of Contrast-Enhanced Ultrasound (CEUS) in Non-Hepatic Applications^ which deal with the use of UCA outside the liver in many established and emerging applications, including for the first time neurosurgery for both cranial and spinal diseases [10]. We praise Della Pepa, Mattogno et al. for their effort in implementing their intraoperative imaging tools using CEUS, adding valuable contributions to the growing body of evidence supporting the use of CEUS during neurosurgical procedures, as they already showed in a case of spinal dural artero-venous fistula [4]. In their article, the Authors describe in convincing detail the application of this intraoperative image technique on a highly vascularized tumor diagnosed as a thoracic hemangiopericytoma (HCP). However, it is important to point out for completeness that, different from what was stated in one paragraph of their paper, there were already some previously published papers and book chapters on the use of intraoperative ultrasound (IoUS), and specifically CEUS, for neoplastic and non-neoplastic medullary lesions [7–9, 11–13]. In August 2015, we reported a case of a dorsal schwannoma in which the preoperativeMRI showed findings compatible with an intramedullary lesion with an exophitic component. However, intraoperative ultrasonography with the adjunct of contrastenhanced ultrasound helped us to understand, prior dural opening, that the lesion was completely extramedullary [12]. That report was the first description of CEUS application during spinal tumor surgery in an intradural extramedullary tumor. Again in 2015, in another paper, we showed the case of an intramedullary cervico-dorsal multinodular tumor [13]. The lesion was highly vascularized and constituted by three different nodules. B-mode examination, Doppler, and CEUS permitted us to accurately localize all three nodules, thus limiting spinal cord manipulation, and allowing complete surgical resection of the lesions, with an uneventful post-operative neurological course. The final histopathological diagnosis was that of a hemangioblastoma. The use of CEUS in surgery involving the spinal cord was also described in 2017 in a case of a spinal dural artero-venous fistula (FAVD), in which microbubbles were able to show the abnormal shunt and its pathological medullary venous drainage, both in axial and sagittal scans, prior dural opening, and the normalization of the pathological findings after interruption of the shunt [7]. The synergistic use of imaging with fluorescent agents along with the tomographic sections offered by ioUS combines a direct view of the surface with indirect sectional views. Furthermore, in the recently released updated EFSUMB guidelines for the clinical use of CEUS in non-hepatic applications [10], the use of intraoperative CEUS for the evaluation of This article is part of the Topical Collection on Tumor Other

Intraoperative Findings in Spinal Lesions

Ultrasonographic appearance of spinal tumors has been described in few studies until now, and the role of intraoperative ultrasound is not yet well standardized in spinal tumor surgery.