Surgery for gliomas and other mass lesions of the brainstem

Upper brainstem pediatric low-grade gliomas: review and neuroendoscopic approach

Pediatric brain tumors, particularly those affecting the brainstem, present a significant challenge due to their intricate anatomical location and diverse classification. This review explores the classification, anatomical considerations, and surgical approaches for pediatric brainstem tumors, focusing on recent updates from the World Health Organization (WHO) classification. Brainstem tumors encompass a spectrum from diffuse gliomas to focal intrinsic and exophytic types, each presenting unique clinical and surgical challenges. Surgical strategies have evolved with advancements in neuroimaging and surgical techniques, emphasizing approaches such as neuroendoscopy and tailored incisions to minimize damage to critical structures. Despite the complexities involved, recent developments offer promising outcomes in tumor resection and patient management, highlighting ongoing advancements in neurosurgical care for pediatric brain tumors.

Axial Sections of Brainstem Safe Entry Zones and Clinical Importance of Intrinsic Structures: A Review

Brainstem surgery is more difficult and riskier than surgeries in other parts of the brain due to the high density of critical tracts and cranial nerves nuclei in this region. For this reason, some safe entry zones into the brainstem have been described. The main purpose of this article is to bring on the agenda the significance of the intrinsic structures of the safe entry zones to the brainstem. Having detailed information about anatomic localization of these sensitive structures is important to predict and avoid possible surgical complications. In order to better understand this complex anatomy, we schematically drew the axial sections of the brainstem showing the intrinsic structures at the level of 9 safe entry zones that we used, taking into account basic neuroanatomy books and atlases. Some illustrations are also supported with intraoperative pictures to provide better surgical orientation. The second purpose is to remind surgeons of clinical syndromes that may occur in case of surgical injury to these delicate structures. Advanced techniques such as tractography, neuronavigation, and neuromonitorization should be used in brainstem surgery, but detailed neuroanatomic knowledge about safe entry zones and a meticulous surgery are more important. The axial brainstem sections we have drawn can help young neurosurgeons better understand this complex anatomy.

Microsurgical management of midbrain gliomas: surgical results and long-term outcome in a large, single-surgeon, consecutive series

OBJECTIVE

The authors report on a large, consecutive, single-surgeon series of patients undergoing microsurgical removal of midbrain gliomas. Emphasis is put on surgical indications, technique, and results as well as long-term oncological follow-up.

METHODS

A retrospective analysis was performed of prospectively collected data from a consecutive series of patients undergoing microneurosurgery for midbrain gliomas from March 2006 through June 2022 at the authors' institution. According to the growth pattern and location of the lesion in the midbrain (tegmentum, central mesencephalic structures, and tectum), one of the following approaches was chosen: transsylvian (TS), extreme anterior interhemispheric transcallosal (eAIT), posterior interhemispheric transtentorial subsplenial (PITS), paramedian supracerebellar transtentorial (PST), perimedian supracerebellar (PeS), perimedian contralateral supracerebellar (PeCS), and transuvulotonsillar fissure (TUTF). Clinical and radiological data were gathered according to a standard protocol and reported according to common descriptive statistics. The main outcomes were rate of gross-total resection; extent of resection; occurrence of any complications; variation in Karnofsky Performance Status score at discharge, 3 months, and last follow-up; progression-free survival (PFS); and overall survival (OS).

RESULTS

Fifty-four patients (28 of them pediatric) met the inclusion criteria (6 with high-grade and 48 with low-grade gliomas [LGGs]). Twenty-two tumors were in the tegmentum, 7 in the central mesencephalic structures, and 25 in the tectum. In no instance did the glioma originate in the cerebral peduncle. TS was performed in 2 patients, eAIT in 6, PITS in 23, PST in 16, PeS in 4, PeCS in 1, and TUTF in 2 patients. Gross-total resection was achieved in 39 patients (72%). The average extent of resection was 98.0% (median 100%, range 82%-100%). There were no deaths due to surgery. Nine patients experienced transient and 2 patients experienced permanent new neurological deficits. At a mean follow-up of 72 months (median 62, range 3-193 months), 49 of the 54 patients were still alive. All patients with LGGs (48/54) were alive with no decrease in their KPS score, whereas 42 showed improvement compared with their preoperative status.

CONCLUSIONS

Microneurosurgical removal of midbrain gliomas is feasible with good surgical results and long-term clinical outcomes, particularly in patients with LGGs. As such, microneurosurgery should be considered as the first therapeutic option. Adequate microsurgical technique and anesthesiological management, along with an accurate preoperative understanding of the tumor's exact topographic origin and growth pattern, is crucial for a good surgical outcome.

Brainstem tumors in children: a monocentric series in the light of genetic and bio-molecular progress in pediatric neuro-oncology

Introduction

Brainstem tumors represent a challenge. Their management and prognosis vary according to anatomopathological findings and genetic and bio-molecular fingerprints. We present our experience with pediatric brainstem tumors.

Material and methods

All patients admitted for a brainstem tumor at the Pediatric Neurosurgical Unit at Hôpital Femme Mère Enfant hospital between January 1997 and December 2019 were considered. Patients data were obtained through a retrospective review of the medical records; follow-up was from the last outpatient consultation.

Results

One hundred and twelve patients were included. Eighty-five patients (75.9%) had open surgery or stereotactic biopsy. Thirty-five patients were treated for hydrocephalus. Sixty-six received an adjuvant treatment. Several protocols were adopted according to the SFOP and SIOP during this time period. The overall survival rate was 45% with a median follow-up of five years (range 1-18 year). However, the survival rate was very different between the diffuse intrinsic pontine gliomas (DIPG) and the others tumor types. If we exclude the DIPG (59 patients), of which only 1 was alive at 3 years, the survival rate was 90.6% (only 5 deaths over 53 patients) with a median follow up of 5 years.

Conclusions

Our series confirms that benign tumors of the brainstem have a good survival when treated with surgical removal ± adjuvant therapy. Diffuse pontine gliomas continue to have a dismal prognosis. Individualized treatment based on molecular fingerprints may help to select the best adjuvant therapy and hence potentially improve survival.

Intraoperative neurophysiology in pediatric neurosurgery: a historical perspective

INTRODUCTION

Intraoperative neurophysiology (ION) has been established over the past three decades as a valuable discipline to improve the safety of neurosurgical procedures with the main goal of reducing neurological morbidity. Neurosurgeons have substantially contributed to the development of this field not only by implementing the use and refinement of ION in the operating room but also by introducing novel techniques for both mapping and monitoring of neural pathways.

METHODS

This review provides a personal perspective on the evolution of ION in a variety of pediatric neurosurgical procedures: from brain tumor to brainstem surgery, from spinal cord tumor to tethered cord surgery.

RESULTS AND DISCUSSION

The contribution of pediatric neurosurgeons is highlighted showing how our discipline has played a crucial role in promoting ION at the turn of the century. Finally, a view on novel ION techniques and their potential implications for pediatric neurosurgery will provide insights into the future of ION, further supporting the view of a functional, rather than merely anatomical, approach to pediatric neurosurgery.

Primary midbrain germinomas: Report of a rare case with an updated review of the literature

Intracranial germinomas are most commonly extra-axial germ cell tumors that are predominantly found in the pineal and suprasellar regions. Primary intra-axial midbrain germinomas are extremely rare, with only eight reported cases. Here we present a 30-year-old man who presented with severe neurological deficits, with an MRI that showed a heterogeneously enhancing mass with ill-defined margins in the midbrain, and with surrounding vasogenic edema extending to the thalamus. The presumptive preoperative differential diagnosis included glial tumors and lymphoma. The patient underwent a right paramedian suboccipital craniotomy and biopsy obtained through the supracerebellar infratentorial transcollicular approach. The histopathological diagnosis was reported as pure germinoma. After patient discharge, he received chemotherapy with carboplatin and etoposide, followed by radiotherapy. Follow-up MRI at up to 26 months showed no contrast-enhancing lesions but a mild T2 FLAIR hyperintensity adjacent to the resection cavity. Differential diagnosis of midbrain lesions can be challenging and should include glial tumors, primary central nervous system lymphoma, germ cell tumors, and metastasis. Accurate diagnosis requires adequate tissue sampling. In this report, we present a very rare case of a primary intra-axial germinoma of the midbrain which is biopsied via a transcollicular approach. This report is also unique as it provides the first surgical video of an open biopsy and the microscopic appearance of an intra-axial primary midbrain germinoma via a transcollicular approach.

Brainstem Surgery: Functional Surgical Anatomy with the Use of an Advanced Modern Intraoperative Neurophysiological Procedure

Intraoperative neurophysiology (ION) in brainstem surgery evolved as brainstem surgery advanced.The original idea of brainstem mapping (BSM) is a neurophysiological procedure to locate cranial nerve motor nuclei (CNMN) on the floor of the fourth ventricle. With the introduction of various skull base approaches to the brainstem, BSM is carried out on any surface of the brainstem to expose the safe entry zone to the intrinsic brainstem lesion. It is the modern concept of BSM, a broader definition of BSM. BSM enables to avoid direct damage to the CNMN when approaching the brainstem through the negative mapping region.The corticobulbar tract (CBT) motor evoked potential (MEP) is another ION procedure in brainstem surgery. It enables monitoring of the functional integrity of the whole cranial motor pathway without interrupting surgical procedures. Combined application of both BSM and CBT-MEP monitoring is indispensable for the functional preservation of the CNMN and their supranuclear innervation during the brainstem surgery.In this paper, the neurophysiological aspect of BSM and the CBT-MEP was fully described. Normal anatomical background of the floor of the fourth ventricle and the detail of the CBT anatomy were demonstrated to better understand their clinical usefulness, limitations, and surgical implications derived from ION procedures. Finally, a future perspective in the role of ION procedures in brainstem surgery was presented. The latest magnetic resonance imaging (MRI) technology can allow surgeons to find an "on the image" safe entry zone to the brainstem. However, the role of BSM and the CBT-MEP monitoring in terms of safe brainstem surgery stays unshakable. Special attention was paid for the recent trend of management in diffuse intrinsic pontine gliomas. A new role of BSM during a stereotactic biopsy was discussed.It is the authors' expectation that the paper enhances the clinical application of a contemporary standard of the ION in brainstem surgery and supports safer brainstem surgery more than ever and in the future.

Perforating Arteries of the Lemniscal Trigone: A Microsurgical Neuroanatomic Description

Background: The perforating arteries in the dorsolateral zone of the midbrain play a crucial role in the functions of the brain stem. Their damage due to herniation, pathological lesions, or surgery, favored by the narrow tentorial incisura, can lead to hemorrhages or ischemia and subsequently to severe consequences for the patient. Objective: In literature, not much attention has been directed to the perforating arteries in the lemniscus; in fact, no reports on the perforators of this anatomical region are available. The present study aims to a detailed analysis of the microanatomy and the clinical implications of these perforators, in relation to the parent vessels. We focused on the small vessels that penetrate the midbrain's dorsolateral surface, known as lemniscal trigone, to understand better their microanatomy and their functional importance in the clinical practice during the microsurgical approach to this area. Methods: Eighty-seven alcohol-fixed cadaveric hemispheres (44 brains) without any pathological lesions provided the material for studying the perforating vessels and their origin around the dorsolateral midbrain using an operating microscope (OPMI 1 FC, Zeiss). Measurements of the perforators' distances, in relation to the parent vessels, were taken using a digital caliper. Results: An origin from the SCA could be found in 70.11% (61) and from the PCA in 27.58% (24) of the hemispheres. In one hemisphere, an origin from the posterior choroidal artery was found (4.54%). No perforating branches were discovered in 8.04% of specimens (7). Conclusion: The perforating arteries of the lemniscal trigone stem not only from the superior cerebellar artery (SCA), as described in the few studies available in literature, but also from the posterior cerebral artery (PCA). Therefore, special attention should be paid during surgery to spare those vessels and associated perforators. A comprehensive understanding of the lemniscal trigone's perforating arteries is vital to avoid infarction of the brainstem when treating midbrain tumors or vascular malformations.

The extreme anterior interhemispheric transcallosal approach for pure aqueduct tumors: surgical technique and case series

Purely aqueductal tumors represent a rare but distinct entity of neoplasms with characteristic morphology and clinical presentation. This study aims to describe the extreme anterior interhemispheric transcallosal approach as a surgical option for purely aqueductal tumors in the upper part of the cerebral aqueduct and present the surgical results. Prospectively collected data of 4 patients undergoing the extreme anterior interhemispheric transcallosal approach for purely aqueductal tumors in the upper cerebral aqueduct was analyzed. The technique is a variation of the anterior interhemispheric transcallosal approach. The callosotomy is placed at the transition between the body and genu of the corpus callosum, allowing an approach steep enough to reach through the foramen of Monro to the upper cerebral aqueduct without opening the choroidal fissure. All patients had preoperative, and intraoperative or immediate postoperative 3-T magnetic resonance imaging, and underwent examination at admission, after surgery, at discharge, and 3 months postoperatively. Patient data are reported according to common descriptive statistics. All patients harbored low-grade gliomas causing hydrocephalus. Complete resection was achieved without mortality or morbidity. All patients recovered and presented neurologically intact at the 3-month postoperative follow-up. None had recurrence or needed adjuvant therapy. The extreme anterior interhemispheric transcallosal approach proved to be effective and safe. This approach does not require manipulation of the choroidal fissure or disrupt healthy brain parenchyma (except for a small callosotomy). We propose it as an option for removing a purely aqueductal tumor in the upper cerebral aqueduct with associated hydrocephalus.

Endoscopic endonasal surgery to treat intrinsic brainstem lesions: correlation between anatomy and surgery

OBJECTIVE

The endoscopic endonasal approach (EEA) has been proposed as an alternative in the surgical removal of ventral brainstem lesions. However, the feasibility and limitations of this approach to treat such pathologies are still poorly understood. This study aimed to report our experience in five consecutive cases of intrinsic brainstem lesions that were managed via an EEA, as well as the specific anatomy of each case.

METHODS

All patients were treated in a single center by a multidisciplinary surgical team between 2015 and 2019. Before surgery, a dedicated anatomical analysis of the brainstem safe entry zone was performed, and proper surgical planning was carried out. Neurophysiological monitoring was used in all cases. Anatomical dissections were performed in three human cadaveric heads using 0° and 30° endoscopes, and specific 3D reconstructions were executed using Amira 3D software.

RESULTS

All lesions were located at the level of the ventral brainstem. Specifically, one mesencephalic cavernoma, two pontine ca- vernomas, one pontine gliomas, and one medullary diffuse midline glioma were reported. Cerebrospinal fluid leak was the major complication that occurred in one case (medullary diffuse midline glioma). From an anatomical standpoint, three main safe entry zones were used, namely the anterior mesencephalic zone (AMZ), the peritrigeminal zone (PTZ, used in two cases), and the olivar zone (OZ). Reviewing the literature, 17 cases of various brainstem lesions treated using an EEA were found.

CONCLUSIONS

To our knowledge, this was the first preliminary clinical series of intrinsic brainstem lesions treated via an EEA presented in the literature. The EEA can be considered a valid surgical alternative to traditional transcranial approaches to treat selected intra-axial brainstem lesions located at the level of the ventral brainstem. To achieve good results, surgery must involve comprehensive anatomical knowledge, meticulous preoperative surgical planning, and intraoperative neurophysiological moni- toring.

The brainstem and its neurosurgical history

Brainstem is one of the most complex structures of the human body, and has the most complex intracranial anatomy, which makes surgery at this level the most difficult. Due to its hidden position, the brainstem became known later by anatomists, and moreover, brainstem surgery cannot be understood without knowing the evolution of ideas in neuroanatomy, neuropathology, and neuroscience. Starting from the first attempts at identifying brainstem anatomy in prehistory and antiquity, the history of brainstem discoveries and approach may be divided into four periods: macroscopic anatomy, microscopic anatomy and neurophysiology, posterior fossa surgery, and brainstem surgery. From the first trepanning of the posterior fossa and later finger surgery, to the occurrence of safe entry zones, this paper aims to review how neuroanatomy and brainstem surgery were understood historically, and how the surgical technique evolved from Galen of Pergamon up to the twenty-first century.

Trans-lamina terminalis suprategmental approach for ventral midbrain lesions: Technical note

Surgical resection of lesions located in the ventral midbrain is challenging. Few approaches and safe entry zones (SEZs) have been proposed and used to remove this type of lesion, and each has its limitations. Using two illustrating cases, the authors describe a trans-lamina terminalis suprategmental approach for removing ventral midbrain lesions. This approach provides a straight surgical trajectory with sparse neurovascular structures and can be performed with a standard pterional or subfrontal craniotomy. It may be the ideal approach for ventromedial midbrain lesions extending towards the third ventricle.

Optimal access route for pontine cavernous malformation resection with preservation of abducens and facial nerve function

OBJECTIVE

The aim of this study was to analyze the differences between posterolateral and posteromedial approaches to pontine cavernous malformations (PCMs) in order to verify the hypothesis that a posterolateral approach is more favorable with regard to preservation of abducens and facial nerve function.

METHODS

The authors conducted a retrospective analysis of 135 consecutive patients who underwent microsurgical resection of a PCM. The vascular lesions were first classified in a blinded fashion into 4 categories according to the possible or only reasonable surgical access route. In a second step, the lesions were assessed according to which approach was performed and different patient groups and subgroups were determined. In a third step, the modified Rankin Scale score and the rates of permanent postoperative abducens and facial nerve palsies were assessed.

RESULTS

The largest group in this series comprised 77 patients. Their pontine lesion was eligible for resection from either a posterolateral or posteromedial approach, in contrast to the remaining 3 patient groups in which the lesion location already had dictated a specific surgical approach. Fifty-four of these 77 individuals underwent surgery via a posterolateral approach and 23 via a posteromedial approach. When comparing these 2 patient subgroups, there was a statistically significant difference between postoperative rates of permanent abducens (3.7% vs 21.7%) and facial (1.9% vs 21.7%) nerve palsies. In the entire patient population, the abducens and facial nerve deficit rates were 5.9% and 5.2%, respectively, and the modified Rankin Scale score significantly decreased from 1.6 ± 1.1 preoperatively to 1.0 ± 1.1 at follow-up.

CONCLUSIONS

The authors' results suggest favoring a posterolateral over a posteromedial access route to PCMs in patients in whom a lesion is encountered that can be removed via either surgical approach. In the present series, the authors have found such a constellation in 57% of all patients. This retrospective analysis confirms their hypothesis in a large patient cohort. Additionally, the authors demonstrated that 4 types of PCMs can be distinguished by preoperatively evaluating whether only one reasonable or two alternative surgical approaches are available to access a specific lesion. The rates of postoperative sixth and seventh nerve palsies in this series are substantially lower than those in the majority of other published reports.

Endoscopic Endonasal Transclival Approach to the Ventral Brainstem: Anatomic Study of the Safe Entry Zones Combining Fiber Dissection Technique with 7 Tesla Magnetic Resonance Guided Neuronavigation

BACKGROUND

Treatment of intrinsic lesions of the ventral brainstem is a surgical challenge that requires complex skull base antero- and posterolateral approaches. More recently, endoscopic endonasal transclival approach (EETA) has been reported in the treatment of selected ventral brainstem lesions.

OBJECTIVE

In this study we explored the endoscopic ventral brainstem anatomy with the aim to describe the degree of exposure of the ventral safe entry zones. In addition, we used a newly developed method combining traditional white matter dissection with high-resolution 7T magnetic resonance imaging (MRI) of the same specimen coregistered using a neuronavigation system.

METHODS

Eight fresh-frozen latex-injected cadaver heads underwent EETA. Additional 8 formalin-fixed brainstems were dissected using Klingler technique guided by ultra-high resolution MRI.

RESULTS

The EETA allows a wide exposure of different safe entry zones located on the ventral brainstem: the exposure of perioculomotor zone requires pituitary transposition and can be hindered by superior cerebellar artery. The peritrigeminal zone was barely visible and its exposure required an extradural anterior petrosectomy. The anterolateral sulcus of the medulla was visible in most of specimens, although its close relationship with the corticospinal tract makes it suboptimal as an entry point for intrinsic lesions. In all cases, the use of 7T-MRI allowed the identification of tiny fiber bundles, improving the quality of the dissection.

CONCLUSION

Exposure of the ventral brainstem with EETA requires mastering surgical maneuvers, including pituitary transposition and extradural petrosectomy. The correlation of fiber dissection with 7T-MRI neuronavigation significantly improves the understanding of the brainstem anatomy.

Important landmarks and distances for posterior fossa surgery measured by temporal MDCT

In this retrospective study, we aimed to present important anatomical structures and distances for posterior fossa surgery by temporal multidetector computed tomography (MDCT). The temporal MDCT images of 317 adult patients (158 males and 159 females) were retrieved from the hospital's picture archiving and communication system (PACS). In the coronal temporal MDCT views, the cochlea-carotid canal and jugular bulb-mastoid bone outer surface were measured. In the axial MDCT views, the carotid canal-jugular bulb and carotid canal-posterior fossa distances were measured; the carotid canal and jugular bulb anterior-posterior (AP) and transverse dimensions were also measured. The bilateral cochlea-carotid canal, jugular bulb-mastoid bone outer surface, and right carotid canal-jugular bulb distances were significantly greater in the males than those in the females (p < 0.05). The carotid canal-posterior fossa distance was not different in both genders (p > 0.05). The carotid canal-jugular bulb and the carotid canal-posterior fossa distances were greater on the left side than those on the right side in both genders (p < 0.05). In males, the outer surface distance was greater on the left jugular bulb-mastoid bone than that on the right side of that bone (p < 0.05). The difference between the carotid canal AP dimensions was not significant between males and females (p > 0.05). However, the carotid canal transverse dimension, jugular bulb AP, and transverse dimensions were significantly greater in the males than those in the females, bilaterally (p < 0.05). In each gender separately, the carotid canal AP and transverse dimensions were greater on the left side and the jugular bulb AP and transverse dimensions were greater on the right side than those on the left side (p < 0.05). Positive correlations were found between the cochlea-carotid canal, the jugular bulb-mastoid bone outer surface, and the carotid canal-jugular bulb distances as well as between the jugular bulb-mastoid bone outer surface and the carotid canal-posterior fossa distances (p < 0.05). In older patients, the carotid canal-posterior fossa distances were shorter on the left side (p < 0.05). Vascular and neural localizations should be well understood in the operative area before applying the surgical approach in the posterior fossa. Computed tomography (CT) has a greater role in the evaluation of bone structures and vascular canals in this area.

Surgical approaches for the lateral mesencephalic sulcus

OBJECTIVE

The brainstem is a compact, delicate structure. The surgeon must have good anatomical knowledge of the safe entry points to safely resect intrinsic lesions. Lesions located at the lateral midbrain surface are better approached through the lateral mesencephalic sulcus (LMS). The goal of this study was to compare the surgical exposure to the LMS provided by the subtemporal (ST) approach and the paramedian and extreme-lateral variants of the supracerebellar infratentorial (SCIT) approach.

METHODS

These 3 approaches were used in 10 cadaveric heads. The authors performed measurements of predetermined points by using a neuronavigation system. Areas of microsurgical exposure and angles of the approaches were determined. Statistical analysis was performed to identify significant differences in the respective exposures.

RESULTS

The surgical exposure was similar for the different approaches-369.8 ± 70.1 mm2 for the ST; 341.2 ± 71.2 mm2 for the SCIT paramedian variant; and 312.0 ± 79.3 mm2 for the SCIT extreme-lateral variant (p = 0.13). However, the vertical angular exposure was 16.3° ± 3.6° for the ST, 19.4° ± 3.4° for the SCIT paramedian variant, and 25.1° ± 3.3° for the SCIT extreme-lateral variant craniotomy (p < 0.001). The horizontal angular exposure was 45.2° ± 6.3° for the ST, 35.6° ± 2.9° for the SCIT paramedian variant, and 45.5° ± 6.6° for the SCIT extreme-lateral variant opening, presenting no difference between the ST and extreme-lateral variant (p = 0.92), but both were superior to the paramedian variant (p < 0.001). Data are expressed as the mean ± SD.

CONCLUSIONS

The extreme-lateral SCIT approach had the smaller area of surgical exposure; however, these differences were not statistically significant. The extreme-lateral SCIT approach presented a wider vertical and horizontal angle to the LMS compared to the other craniotomies. Also, it provides a 90° trajectory to the sulcus that facilitates the intraoperative microsurgical technique.

Utilización de las zonas de entrada seguras para el abordaje de lesiones intrínsecas de tronco cerebral en adultos

Introducción:

Las “zonas de entrada seguras” (ZES) al tronco cerebral describen accesos destinados a preservar estructuras críticas. La mayoría de las publicaciones son descripciones anatómicas; existiendo pocas sobre su aplicación. En este escenario, nuestro trabajo puede sumar información para el manejo quirúrgico en casos seleccionados.

Material y Métodos:

De una serie de 13 pacientes, se presentan 9 que no eran candidatos para biopsia estereotáctica y recibieron microcirugía. Las localizaciones fueron: mesencéfalo (3), tectum (1), protuberancia (2) y bulbo (3). Cinco pacientes tuvieron KPS ≥70; y 4, KPS <70. Diferentes ZES fueron utilizadas según la topografía lesional. El grado de resección se basó en la biopsia intraoperatoria y el monitoreo neurofisiológico.

Resultados:

Los hallazgos patológicos fueron: astrocitoma pilocítico (1), glioma de bajo grado (1), hemangioblastoma (1), subependimoma (1), disgerminoma (1), y lesiones pseudotumorales (3 cavernomas y 1 pseudotumor inflamatorio). El grado de resección fue completo (4), subtotal (3), y biopsia fue considerada suficiente en (2). Un paciente falleció en el postoperatorio.

Discusión:

Las lesiones del tronco cerebral son infrecuentes en adultos. Las controversias surgen cuando se balancean los beneficios de obtener diagnóstico histopatológico y los riesgos potenciales de procedimientos invasivos. La amplia variedad de hallazgos en esta localización exige una precisa definición histopatológica, que no solamente determinará la terapéutica adecuada, sino que advierte sobre las consecuencias potencialmente catastróficas de los tratamientos empíricos. Las ZES ofrecen un acceso posible y seguro, aunque es más realista considerarlas como áreas para abordar lesiones intrínsecas con baja morbilidad más que como zonas completamente seguras.

Intrinsic Well-Demarcated Midline Brainstem Lesion Successfully Resected through a Midline Pontine Splitting Approach

INTRODUCTION

Surgical approaches to intrinsic pontine lesions are technically difficult and prone to complications. The surgical approach to the brainstem through midline pontine splitting is regarded as safe since there are no crossing vital fibers in the midline between the abducens nuclei at the facial colliculi in the pons and the oculomotor nucleus in the midbrain, although its actual utilization has not been reported previously.

CASE PRESENTATION

A 6-year-old boy presented with a large intrinsic cystic lesion in the pons. We successfully achieved gross total removal via the median sulcus of the fourth ventricle. The fixation in adduction and limitation of abduction were newly observed in the left eye after surgery.

DISCUSSION

The advantage of the surgical approach through the median sulcus is the longer line of dissection in an axial direction and the gain of a wider operative view. On the other hand, the disadvantage of this approach is the limited orientation and view toward lateral side and a possible impairment of the medial longitudinal fasciculi and paramedian pontine reticular formation, which are located lateral to the midline sulcus bilaterally and are easily affected via the median sulcus of the fourth ventricular floor. Ongoing developments in intraoperative neuro-monitoring and navigation systems are expected to enhance this promising approach, resulting in a safer and less complicated procedure in the future.

CONCLUSION

The surgical approach through midline pontine splitting is suitable for midline and deep locations of relatively large pontine lesions that necessitate a wider surgical window.

The pretemporal approach to anterolateral midbrain cavernous malformations

Operating on the anterolateral midbrain is challenging due to limited surgical freedom provided by classic approaches and restraints imposed by the basilar artery apex and branches, their perforators, and the oculomotor nerve (Abla et al., 2011; Bricolo and Turazzi, 1995; Cavalcanti et al., 2016).

This video demonstrates the benefits provided by the pretemporal approach for resection of an anterolateral mesencephalic cavernous malformation (Chaddad-Neto et al., 2014; de Oliveira et al., 1995). Four steps are well demonstrated in the video: 1) section of temporal pole veins to the sphenoparietal sinus; 2) division of arachnoid attaching the oculomotor nerve to the tentorial edge and uncus; 3) releasing the arachnoid between the anterior choroidal artery and uncus; and 4) following the oculomotor nerve to its origin.

The video can be found here: https://youtu.be/7ZuK-ewNo6w.

Analysis of safe entry zones into the brainstem

Intra-axial brainstem surgeries are challenging. Many experience-based "safe entry zones (SEZs)" into brainstem lesions have been proposed in the existing literature. The evidence for each one seems limited. English-language publications were retrieved using PubMed/MEDLINE. Studies that focused only on cadaveric anatomy were also included, but the clinical case number was treated as zero. The clinical evidence level was defined as "case report" when the surgical case number was ≤ 5, "limited evidence" when there were more than 5 but less than 25 cases, and "credible evidence" when a publication presented more than 25 cases. Twenty-five out of 32 publications were included, and 21 different SEZs were found for the brainstem: six SEZs were located in the midbrain, 9 SEZs in the pons, and 6 SEZs in the medulla. Case report evidence was found for 10 SEZs, and limited evidence for 7 SEZs. Four SEZs were determined to be backed by credible evidence. The proposed SEZs came from initial cadaveric anatomy studies, followed by some published clinical experience. Only a few SEZs have elevated clinical evidence. The choice of the right approach into the brainstem remains a challenge in each case.

Supracerebellar Infratentorial Variant Approaches to the Intercollicular Safe Entry Zone

OBJECTIVE

To describe and compare surgical exposure through microsurgical cadaveric dissection of the intercollicular region afforded by the median, paramedian, and extreme-lateral supracerebellar infratentorial (SCIT) approaches.

METHODS

Ten cadaveric heads were dissected using SCIT variant approaches. A neuronavigation system was used to determine tridimensional coordinates for the intercollicular zone in each route. The areas of surgical and angular exposure were evaluated and determined by software analysis for each specimen.

RESULTS

The median surgical exposure was similar for the different craniotomies: 282.9 ± 72.4 mm² for the median, 341.2 ± 71.2 mm² for the paramedian, and 312.0 ± 79.3 mm² for the extreme-lateral (P = 0.33). The vertical angular exposure to the center of the intercollicular safe entry zone was also similar between the approaches (P = 0.92). On the other hand, the horizontal angular exposure was significantly wider for the median approach (P < 0.001).

CONCLUSIONS

All the SCIT approaches warrant a safe route to the quadrigeminal plate. Among the different variants, the median approach had the smallest median surgical area exposure but presented superior results to access the intercollicular safe entry zone.

Surgical treatment and prognosis of adult patients with brainstem gliomas

The paper presents 47 adult patients who were surgically treated due to brainstem gliomas. Thirteen patients presented with contrast-enhancing Grades III and IV gliomas, according to the WHO classification, 13 patients with contrast-enhancing tumours originating from the glial cells (Grade I; WHO classification), 9 patients with diffuse gliomas, 5 patients with tectal brainstem gliomas and 7 patients with exophytic brainstem gliomas. During the surgical procedure, neuronavigation and the diffusion tensor tractography (DTI) of the corticospinal tract were used with the examination of motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs) with direct stimulation of the fundus of the fourth brain ventricle in order to define the localization of the nuclei of nerves VII, IX, X and XII. Cerebellar dysfunction, damage to cranial nerves and dysphagia were the most frequent postoperative sequelae which were also the most difficult to resolve. The Karnofsky score established preoperatively and the extent of tumour resection were the factors affecting the prognosis. The mean time of progression-free survival (14 months) and the mean survival time after surgery (20 months) were the shortest for malignant brainstem gliomas. In the group with tectal brainstem gliomas, no cases of progression were found and none of the patients died during the follow-up. Some patients were professionally active. Partial resection of diffuse brainstem gliomas did not prolong the mean survival above 5 years. However, some patients survived over 5 years in good condition.

Human Connectome-Based Tractographic Atlas of the Brainstem Connections and Surgical Approaches

BACKGROUND

The brainstem is one of the most challenging areas for the neurosurgeon because of the limited space between gray matter nuclei and white matter pathways. Diffusion tensor imaging-based tractography has been used to study the brainstem structure, but the angular and spatial resolution could be improved further with advanced diffusion magnetic resonance imaging (MRI).

OBJECTIVE

To construct a high-angular/spatial resolution, wide-population-based, comprehensive tractography atlas that presents an anatomical review of the surgical approaches to the brainstem.

METHODS

We applied advanced diffusion MRI fiber tractography to a population-based atlas constructed with data from a total of 488 subjects from the Human Connectome Project-488. Five formalin-fixed brains were studied for surgical landmarks. Luxol Fast Blue-stained histological sections were used to validate the results of tractography.

RESULTS

We acquired the tractography of the major brainstem pathways and validated them with histological analysis. The pathways included the cerebellar peduncles, corticospinal tract, corticopontine tracts, medial lemniscus, lateral lemniscus, spinothalamic tract, rubrospinal tract, central tegmental tract, medial longitudinal fasciculus, and dorsal longitudinal fasciculus. Then, the reconstructed 3-dimensional brainstem structure was sectioned at the level of classic surgical approaches, namely supracollicular, infracollicular, lateral mesencephalic, perioculomotor, peritrigeminal, anterolateral (to the medulla), and retro-olivary approaches.

CONCLUSION

The advanced diffusion MRI fiber tracking is a powerful tool to explore the brainstem neuroanatomy and to achieve a better understanding of surgical approaches.

ABBREVIATIONS

CN, cranial nerveCPT, corticopontine tractCST, corticospinal tractCTT, central tegmental tractDLF, dorsal longitudinal fasciculusHCP, Human Connectome ProjectML, medial lemniscusMLF, medial longitudinal fasciculusRST, rubrospinal tractSTT, spinothalamic tract.

Potential New Therapies for Pediatric Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is an extensively invasive malignancy with infiltration into other regions of the brainstem. Although large numbers of specific targeted therapies have been tested, no significant progress has been made in treating these high-grade gliomas. Therefore, the identification of new therapeutic approaches is of great importance for the development of more effective treatments. This article reviews the conventional therapies and new potential therapeutic approaches for DIPG, including epigenetic therapy, immunotherapy, and the combination of stem cells with nanoparticle delivery systems.

Mapping the Internal Anatomy of the Lateral Brainstem: Anatomical Study with Application to Far Lateral Approaches to Intrinsic Brainstem Tumors

INTRODUCTION

Intramedullary brainstem tumors present a special challenge to the neurosurgeon. Unfortunately, there is no ideal part of the brainstem to incise for approaches to such pathology. Therefore, the present study was performed to identify what incisions on the lateral brainstem would result in the least amount of damage to eloquent tracts and nuclei. Case illustrations are also discussed.

MATERIALS AND METHODS

Eight human brainstems were evaluated. Based on dissections and the use of standard atlases of brainstem anatomy, the most important deeper brainstem structures were mapped to the surface of the lateral brainstem.

RESULTS

With these data, we defined superior acute and inferior obtuse corridors for surgical entrance into the lateral brainstem that would minimize injury to deeper tracts and nuclei, the damage to which would result in significant morbidity.

CONCLUSIONS

To our knowledge, a superficial map of the lateral brainstem for identifying deeper lying and clinically significant nuclei and tracts has not previously been available. Such data might decrease patient morbidity following biopsy or tumor removal or aspiration of brainstem hemorrhage. Additionally, this information can be coupled with the previous literature on approaches into the fourth ventricular floor for more complex, multidimensional lesions.

The superior fovea triangle approach: a novel safe entry zone to the brainstem

The authors describe a safe entry zone, the superior fovea triangle, on the floor of the fourth ventricle for resection of deep dorsal pontine lesions at the level of the facial colliculus. Clinical data from a patient undergoing a suboccipital telovelar transsuperior fovea triangle approach to a deep pontine cavernous malformation were reviewed and supplemented with 6 formalin-fixed adult human brainstem and 2 silicone-injected adult human cadaveric heads using the fiber dissection technique to illustrate the utility of this novel safe entry zone. The superior fovea has a triangular shape that is an important landmark for the motor nucleus of the trigeminal, abducens, and facial nerves. The inferior half of the superior fovea triangle may be incised to remove deep dorsal pontine lesions through the floor of the fourth ventricle. The superior fovea triangle may be used as a safe entry zone for dorsally located lesions at the level of the facial colliculus.

Microsurgical anatomy of safe entry zones to the brainstem

OBJECT

The aim of this study was to enhance the planning and use of microsurgical resection techniques for intrinsic brainstem lesions by better defining anatomical safe entry zones.

METHODS

Five cadaveric heads were dissected using 10 surgical approaches per head. Stepwise dissections focused on the actual areas of brainstem surface that were exposed through each approach and an analysis of the structures found, as well as which safe entry zones were accessible via each of the 10 surgical windows.

RESULTS

Thirteen safe entry zones have been reported and validated for approaching lesions in the brainstem, including the anterior mesencephalic zone, lateral mesencephalic sulcus, intercollicular region, peritrigeminal zone, supratrigeminal zone, lateral pontine zone, supracollicularzone, infracollicularzone, median sulcus of the fourth ventricle, anterolateral and posterior median sulci of the medulla, olivary zone, and lateral medullary zone. A discussion of the approaches, anatomy, and limitations of these entry zones is included.

CONCLUSIONS

A detailed understanding of the anatomy, area of exposure, and safe entry zones for each major approach allows for improved surgical planning and dissemination of the techniques required to successfully resect intrinsic brainstem lesions.

Surgical Application of the Suboccipital Subtonsillar Approach to Reach the Inferior Half of Medulla Oblongata Tumors in Adult Patients

Medulla oblongata (MO) tumors are uncommon in adults. Controversies about their treatment arise regarding the need for histological diagnosis in this eloquent area of the brain, weighing benefits of a reliable diagnosis, and the potential disadvantages of invasive procedures. As a broader variety of pathological findings could be found in this localization, the accurate histopathological definition could not only allow an adequate therapy but also can prevent the disastrous consequences of empiric treatments. There are few publications about their surgical management and all belongs to small retrospective cohorts. In this scenario, we are reporting two patients with exophytic or focal lesions in the inferior half of the medulla, who underwent surgery by suboccipital midline subtonsillar approach. This approach was not specifically described to reach MO before, and we found that the lesions produced a mild elevation of the tonsils providing a wide surgical view from the medulla to the foramen of Luchska laterally, and up to the middle cerebellar peduncle, offering a wide and safe access.

Microsurgical anatomy and internal architecture of the brainstem in 3D images: surgical considerations

OBJECT Brainstem surgery remains a challenge for the neurosurgeon despite recent improvements in neuroimaging, microsurgical techniques, and electrophysiological monitoring. A detailed knowledge of the microsurgical anatomy of the brainstem surface and its internal architecture is mandatory to plan appropriate approaches to the brainstem, to choose the safest point of entry, and to avoid potential surgical complications. METHODS An extensive review of the literature was performed regarding the brainstem surgical approaches, and their correlations with the pertinent anatomy were studied and illustrated through dissection of human brainstems properly fixed with 10% formalin. The specimens were dissected using the fiber dissection technique, under ×6 to ×40 magnification. 3D stereoscopic photographs were obtained (anaglyphic 3D) for better illustration of this study. RESULTS The main surgical landmarks and their relationship with the cerebellum and vascular structures were identified on the surface of the brainstem. The arrangements of the white matter (ascending and descending pathways as well as the cerebellar peduncles) were demonstrated on each part of the brainstem (midbrain, pons, and medulla oblongata), with emphasis on their relationships with the surface. The gray matter, constituted mainly by nuclei of the cranial nerves, was also studied and illustrated. CONCLUSIONS The objective of this article is to review the microsurgical anatomy and the surgical approaches pertinent to the brainstem, providing a framework of its external and internal architecture to guide the neurosurgeon during its related surgical procedures.

Surgical approaches to IV ventricle--anatomical study

PURPOSE

Knowledge of anatomy of the IV ventricle is basic to surgical approach of any kind of lesion in its compartment as well as for those located in its neighborhood. The purpose of this study is to demonstrate the surgical approach options for the IV ventricle, based on the step by step dissection of anatomical specimens.

METHODS

Fifty formalin-fixed specimens provided were the material for this study. The dissections were performed in the microsurgical laboratory in Gainesville, Florida, USA.

RESULTS

The IV ventricle in a midline sagittal cut shows a tent-shaped cavity with its roofs pointing posteriorly and the floor formed by the pons and the medulla. The superior roof is formed by the superior cerebellar peduncles laterally and the superior medullary velum on the midline. The inferior roof is formed by the tela choroidea, the velum medullary inferior, and the nodule. The floor of the IV ventricle has a rhomboid shape. The rostral two thirds are related to the pons, and the caudal one third is posterior to the medulla. The median sulcus divides the floor in symmetrical halves. The sulcus limitans runs laterally to the median sulcus, and the area between the two sulci is called the median eminence. The median eminence contains rounded prominence related to the cranial nucleus of facial, hypoglossal, and vagal nerves. The lateral recesses are extensions of the IV ventricle that opens into the cerebellopontine cistern. The cerebellomedullary fissure is a space between the cerebellum and the medulla and can be used as a surgical corridor to the IV ventricle.

CONCLUSIONS

We obtained in this study a didactic dissection of the different anatomical structures, whose recognition is important for addressing the IV ventricle lesions.

Anatomy and approaches along the cerebellar-brainstem fissures

OBJECT Fissure dissection is routinely used in the supratentorial region to access deeply situated pathology while minimizing division of neural tissue. Use of fissure dissection is also practical in the posterior fossa. In this study, the microsurgical anatomy of the 3 cerebellar-brainstem fissures (cerebellomesencephalic, cerebellopontine, and cerebellomedullary) and the various procedures exposing these fissures in brainstem surgery were examined. METHODS Seven cadaveric heads were examined with a microsurgical technique and 3 with fiber dissection to clarify the anatomy of the cerebellar-brainstem and adjacent cerebellar fissures, in which the major vessels and neural structures are located. Several approaches directed along the cerebellar surfaces and fissures, including the supracerebellar infratentorial, occipital transtentorial, retrosigmoid, and midline suboccipital approaches, were examined. The 3 heads examined using fiber dissection defined the anatomy of the cerebellar peduncles coursing in the depths of these fissures. RESULTS Dissections directed along the cerebellar-brainstem and cerebellar fissures provided access to the posterior and posterolateral midbrain and upper pons, lateral pons, floor and lateral wall of the fourth ventricle, and dorsal and lateral medulla. CONCLUSIONS Opening the cerebellar-brainstem and adjacent cerebellar fissures provided access to the brainstem surface hidden by the cerebellum, while minimizing division of neural tissue. Most of the major cerebellar arteries, veins, and vital neural structures are located in or near these fissures and can be accessed through them.

Three-dimensional microsurgical anatomy and the safe entry zones of the brainstem

BACKGROUND

There have been no studies of the structure and safe surgical entry zones of the brainstem based on fiber dissection studies combined with 3-dimensional (3-D) photography.

OBJECTIVE

To examine the 3-D internal architecture and relationships of the proposed safe entry zones into the midbrain, pons, and medulla.

METHODS

Fifteen formalin and alcohol-fixed human brainstems were dissected by using fiber dissection techniques, ×6 to ×40 magnification, and 3-D photography to define the anatomy and the safe entry zones. The entry zones evaluated were the perioculomotor, lateral mesencephalic sulcus, and supra- and infracollicular areas in the midbrain; the peritrigeminal zone, supra- and infrafacial approaches, acoustic area, and median sulcus above the facial colliculus in the pons; and the anterolateral, postolivary, and dorsal medullary sulci in the medulla.

RESULTS

The safest approach for lesions located below the surface is usually the shortest and most direct route. Previous studies have often focused on surface structures. In this study, the deeper structures that may be at risk in each of the proposed safe entry zones plus the borders of each entry zone were defined. This study includes an examination of the relationships of the cerebellar peduncles, long tracts, intra-axial segments of the cranial nerves, and important nuclei of the brainstem to the proposed safe entry zones.

CONCLUSION

Fiber dissection technique in combination with the 3-D photography is a useful addition to the goal of making entry into the brainstem more accurate and safe.

Focal brainstem gliomas. Advances in intra-operative management

Improved neuronavigation guidance as well as intraoperative imaging and neurophysiologic monitoring technologies have enhanced the ability of neurosurgeons to resect focal brainstem gliomas. In contrast, diffuse brainstem gliomas are considered to be inoperable lesions. This article is a continuation of an article that discussed brainstem glioma diagnostics, imaging, and classification. Here, we address open surgical treatment of and approaches to focal, dorsally exophytic, and cervicomedullary brainstem gliomas. Intraoperative neuronavigation, intraoperative neurophysiologic monitoring, as well as intraoperative imaging are discussed as adjunctive measures to help render these procedures safer, more acute, and closer to achieving surgical goals.

The lateral infratrigeminal transpontine window to deep pontine lesions

OBJECT

Surgery of brainstem lesions is increasingly performed despite the fact that surgical indications and techniques continue to be debated. The deep pons, in particular, continues to be a critical area in which the specific risks related to different surgical strategies continue to be examined. With the intention of bringing new knowledge into this important arena, the authors systematically examined the results of brainstem surgeries that have been performed through the lateral infratrigeminal transpontine window.

METHODS

Between 1990 and 2013, 29 consecutive patients underwent surgery through this window for either biopsy sampling or for removal of a deep pontine lesion. All of this work was performed at the Department of Neurosurgery of the Istituto Nazionale Neurologico "Carlo Besta", in Milan, Italy. A retrospective analysis of the findings was conducted with the intention of bringing further clarity to this important surgical strategy.

RESULTS

The lateral infratrigeminal transpontine window was exposed through 4 different approaches: 1) classic retrosigmoid (15 cases), 2) minimally invasive keyhole retrosigmoid (10 cases), 3) translabyrinthine (1 case), and 4) combined petrosal (3 cases). No deaths occurred during the entire clinical study. The surgical complications that were observed included hydrocephalus (2 cases) and CSF leakage (1 case). In 6 (20.7%) of 29 patients the authors encountered new neurological deficits during the immediate postoperative period. All 6 of these patients had undergone lesion removal. In only 2 of these 6 patients were permanent sequelae observed at 3 months follow-up. These findings show that 93% of the patients studied did not report any permanent worsening of their neurological condition after this surgical intervention.

CONCLUSIONS

This retrospective study supports the idea that the lateral infratrigeminal transpontine window is both a low-risk and safe corridor for either biopsy sampling or for removal of deep pontine lesions.

Surgical approaches for brainstem tumors in pediatric patients

PURPOSE

To analyze the pathways to brainstem tumors in childhood, as well as safe entry zones.

METHOD

We conducted a retrospective study of 207 patients less than 18 years old who underwent brainstem tumor resection by the first author (Cavalheiro, S.) at the Neurosurgical Service and Pediatric Oncology Institute of the São Paulo Federal University from 1991 to 2011.

RESULTS

Brainstem tumors corresponded to 9.1 % of all pediatric tumors operated in that same period. Eleven previously described "safe entry zones" were used. We describe a new safe zone located in the superior ventral pons, which we named supratrigeminal approach. The operative mortality seen in the first 2 months after surgery was 1.9 % (four patients), and the morbidity rate was 21.2 %.

CONCLUSIONS

Anatomic knowledge of intrinsic and extrinsic brainstem structures, in association with a refined neurosurgical technique assisted by intraoperative monitoring, and surgical planning based on magnetic resonance imaging (MRI) and tractography have allowed for wide resection of brainstem lesions with low mortality and acceptable morbidity rates.

Surgical management of brainstem cavernous malformations

Bleeding from brainstem cavernomas may cause severe deficits due to the absence of non-eloquent nervous tissue and the presence of several ascending and descending white matter tracts and nerve nuclei. Surgical removal of these lesions presents a challenge to the most surgeons. The authors present their experience with the surgical treatment of 43 patients with brainstem cavernomas. Important aspects of microsurgical anatomy are reviewed. The surgical management, with special focus on new intraoperative technologies as well as controversies on indications and timing of surgery are presented. According to several published studies the outcome of brainstem cavernomas treated conservatively is poor. In our experience, surgical resection remains the treatment of choice if there was previous hemorrhage and the lesion reaches the surface of brainstem. These procedures should be performed by experienced neurosurgeons in referral centers employing all the currently available technology.

Brainstem cavernous malformations: anatomical, clinical, and surgical considerations

Symptomatic brainstem cavernous malformations carry a high risk of permanent neurological deficit related to recurrent hemorrhage, which justifies aggressive management. Detailed knowledge of the microscopic and surface anatomy is important for understanding the clinical presentation, predicting possible surgical complications, and formulating an adequate surgical plan. In this article the authors review and illustrate the surgical and microscopic anatomy of the brainstem, provide anatomoclinical correlations, and illustrate a few clinical cases of cavernous malformations in the most common brainstem areas.

Intraoperative neurophysiology for surgery in and around the brainstem: role of brainstem mapping and corticobulbar tract motor-evoked potential monitoring

INTRODUCTION

New advancements of intraoperative neurophysiology for surgery in and around the brainstem have been described. NEUROPHYSIOLOGICAL TECHNIQUES: Brainstem mapping (BSM) is applied to locate cranial nerves and their motor nuclei (CMN) on the floor of the fourth ventricle. Corticobulbar tract (CBT) motor-evoked potential (MEP) monitoring is used to achieve on-line monitoring of the cranial motor nerves' functional integrity.

DISCUSSION

Each of these procedures bears a specific role: BSM can help avoid direct damage to CMNs on the fourth ventricular floor; CBT-MEP can provide simultaneous feedback on the functional integrity of the CBT and CMN during surgery, eventually leading to "tailored" modifications of the surgical procedure, based upon neurophysiological responses.

CONCLUSIONS

CBT-MEP monitoring has less restriction in terms of clinical indications, but a combination of both procedures is essential for functional preservation of CMNs during surgery in and around the brainstem.

Clinical and surgical features of lower brain stem hemangioblastomas in von Hippel-Lindau disease

BACKGROUND

In the context of von Hippel-Lindau disease (VHL), the medulla oblongata is a relatively frequent site of growth of hemangioblastomas, posing related clinical and surgical difficulties. Their management requires a close correlation between clinical evolution and morphological surveillance. In order to describe their clinical and surgical features, we reviewed our experience in the treatment of these lesions.

METHODS

Between 2001 and 2009, 14 patients (9 female and 5 male, mean age 34 years) underwent removal of 15 lower brain stem hemangioblastomas. Based on the review of the clinical records and outpatient long-term follow-up visits, their clinical course was analyzed. Functional evaluation was measured with the Karnofsky Performance Scale (KPS) on admission, at discharge and at the last follow-up. The mean follow-up period was 30.8 months (range 4-99).

RESULTS

All the operated hemangioblastomas were located in the dorsal medulla oblongata, in the context of multiple lesions, cerebellar and/or spinal. In ten patients hemangioblastomas were located in a median position at the obex area; in four cases a lateral location was observed. Cystic component was absent in two cases. Clinical onset preceded surgery by a mean of 8.5 months. Preoperatively three patients showed a KPS lower than 80, ten patients between 80 and 90, and one patient scored 100 (asymptomatic). There was no surgical mortality. Nine out of 14 patients showed a temporary surgical morbidity. One patient required a tracheostomy. At follow-up ten patients scored a KPS better than before the operation, while the other four patients remained stable. Permanent morbidity was observed in three patients.

CONCLUSIONS

Lower brain stem hemangioblastomas in the context of VHL show an often gradual onset of signs and symptoms except for patients who develop an obstructive hydrocephalus. Although transient surgical complications are possible, surgery provides favorable long-term results.

Cystic hemangioblastoma of the brainstem

Hemangioblastomas are very highly vascular neoplasm with benign characteristics and; in comparison to cerebellar hemangioblastoma; cases of cystic hemangioblastoma of the brain stem are rare with only a few case reports available in the literature. We report the case of a 43-year-old-female with cystic hemagioblastoma of the brainstem managed successfully and review the relevant literature.