Supracerebellar "Flyover" Approach to Dumbbell Falcotentorial Meningioma Encasing the Galenic Venous System.

Falcotentorial meningiomas involve the tentorial apex and straight sinus, posing challenges when encasing the galenic venous system.1 Microneurosurgery is considered the best treatment option for large falcotentorial meningiomas because it provides a definitive cure.2 In contrast, Gamma Knife surgery mainly allows the control of smaller or residual tumors after microsurgical resection.3 Approach selection between interhemispheric supratentorial versa supracerebellar transtentorial is dictated by the displacement of the Galen vein.1,4-8Video 1 describes the critical surgical steps of the supracerebellar "flyover" approach for a Bassiouni type II dumbbell falcotentorial meningiomas encasing the galenic venous system. Preoperative embolization was ruled out due to potential additional morbidity and mortality risks.9,10 A perimedian supracerebellar infratentorial transtentorial approach was performed with the patient in ¾ prone Concorde position. After early devascularization and division of the tentorium, the meningioma was internally debulked while preserving the arachnoid plane. The posterior choroidal arteries, internal cerebral veins, basal veins of Rosenthal, and vein of Galen were carefully dissected, and the tumor was completely resected. The patient was discharged on postoperative day 3 with no deficits. Postoperative magnetic resonance imaging confirmed a Simpson grade 1 resection. Pathology revealed a grade 2 meningioma. The patient remained asymptomatic with no recurrence at a 10-year follow-up. The reported case demonstrates that the most critical factor in the choice of approach to midline dumbbell falcotentorial meningiomas is the relationship of the tumor to the galenic venous system and its tributaries.

The Party Wall: Redefining the Indications of Transcranial Approaches for Giant Pituitary Adenomas in Endoscopic Era.

The evolution of endoscopic trans-sphenoidal surgery raises the question of the role of transcranial surgery for pituitary tumors, particularly with the effectiveness of adjunct irradiation. This narrative review aims to redefine the current indications for the transcranial approaches for giant pituitary adenomas in the endoscopic era. A critical appraisal of the personal series of the senior author (O.A.-M.) was performed to characterize the patient factors and the tumor's pathological anatomy features that endorse a cranial approach. Traditional indications for transcranial approaches include the absent pneumatization of the sphenoid sinus; kissing/ectatic internal carotid arteries; reduced dimensions of the sella; lateral invasion of the cavernous sinus lateral to the carotid artery; dumbbell-shaped tumors caused by severe diaphragm constriction; fibrous/calcified tumor consistency; wide supra-, para-, and retrosellar extension; arterial encasement; brain invasion; coexisting cerebral aneurysms; and separate coexisting pathologies of the sphenoid sinus, especially infections. Residual/recurrent tumors and postoperative pituitary apoplexy after trans-sphenoidal surgery require individualized considerations. Transcranial approaches still have a critical role in giant and complex pituitary adenomas with wide intracranial extension, brain parenchymal involvement, and the encasement of neurovascular structures.

Surgical management of symptomatic hemangioma of the geniculate ganglion: fascicular-sparing resection or grafting?

Geniculate ganglion hemangioma (GGH) is rarely presented in the neurosurgical literature. It extends extradurally on the middle fossa floor and displaces the intratemporal part of the facial nerve. Surgical treatment is advisable at early symptoms. Proposed techniques include fascicular-sparing resection or nerve interruption with grafting. No definitive conclusions exist about the superiority of a certain technique in preserving facial nerve integrity and function. Through the description of a surgically managed symptomatic GGH, we herein discuss literature data about the surgical results of fascicular-sparing resection versus grafting. A PRISMA-based literature search was performed on the PubMed database. Only articles in English and published since 1990 were selected and furtherly filtered based on the best relevance. Statistical comparisons were performed with ANOVA. One hundred sixteen GGHs were collected, 56 were treated by fascicular-sparing resection, and 60 were treated by grafting. The facial function was improved, or unchanged, in 53 patients of the fascicular-sparing group and 30 patients of the grafting one. Sixty-five patients achieved a good (House-Brackmann (HB) grade III) postoperative facial outcome, of which 47 and 18 belonged to the fascicular-sparing and grafting group, respectively. Greater efficacy of the fascicular-sparing technique in the achievement of a better facial outcome was found (p = 0.0014; p = 0.0022). A surgical resection at the earliest symptoms is critical to preserve the facial nerve function in GGHs. Fascicular-sparing resection should be pursued in symptomatic cases with residual facial function (I-III HB). Conversely, grafting has a rationale for higher HB grades (V-VI). Broader studies are required to confirm these findings and turn them into new therapeutic perspectives.

Fascicular-Sparing Technique for Resection of Cerebellopontine Angle Facial Nerve Schwannoma.

Surgery of cerebellopontine angle (CPA) facial nerve schwannoma (FNS) in patients with good facial nerve function is a challenge.1-10Video 1 highlights the fascicular-sparing technique for resection of a CPA FNS. A 41-year-old male patient symptomatic with persistent headaches and tinnitus underwent a retrosigmoid approach for a right cystic CPA tumor, presumed vestibular schwannoma. Intraoperatively, the facial nerve was identified as fine multiple strands splayed around the perimetry of the tumor, which elicited a motor response at a low threshold stimulation. This finding led to the intraoperative diagnosis of FNS according to the reported criteria.5 Neuromonitoring-assisted fascicular-sparing resection technique was performed. It involved the gradual separation of the uninvolved nerve fibers using a fine-stimulating dissector at a threshold of 0.2 mA. Entry into the tumor was at a stimulation silent cyst. The tumor was debulked with preservation of the endoneurium and pulse irrigation hemostasis. A near-total resection was performed. The patient was discharged on the second postoperative day with a House-Brackman III facial nerve deficit. The deficit remained stable during the following annual follow-up visits. Resection of CPA FNS is indicated at the earliest sign of deficit. However, it might be encountered as masquerading at the surgery of an acoustic tumor. The fascicular-sparing technique is critical in avoiding injuries to the endoneurium during the resection and with the ability to preserve function. The sparing of endoneurium avoids collagenization, fibrosis, and ischemia of the nerve, which are known to be the pathologic substrate of worse functional outcomes.

Intracranial Facial Schwannomas: Multiple Distinct Entities Necessitating Tailored Management.

OBJECTIVE: Facial nerve (FN) schwannomas are extremely rare. According to their origin and involved segment(s), they constitute distinct subtypes. Intact FN function presents a management challenge, particularly in the cerebellopontine angle cisternal subtype that masquerades as a vestibular schwannoma. Fascicular-sparing technique with subtotal resection can maintain a good FN function. This study focuses on management to maintain good FN function. METHODS: A retrospective analysis of a cohort of 13 patients harboring FN schwannoma. Patient demographics, clinical findings, imaging, surgical intervention, and outcomes were analyzed. RESULTS: Five women and 8 men, with an average age of 55.3 years (39-75 years), harbored 6 cisternal, 2 ganglion, and 5 combined tumors. Average tumor size was 28.3 mm (16-50 mm). Eleven patients underwent surgery. Seven patients had fascicle-sparing technique, 5 of whom maintained their preoperative FN function, whereas 2 patients with near-total removal had a deterioration in FN function. Two patients with preoperative complete facial paralysis had gross total removal with interposition nerve graft. CONCLUSIONS: FN schwannomas management is individualized according to the subtype and the FN function at presentation. When FN function is normal, observation can be applied for prolonged period of time. At the early sign of deterioration, sub- or near-total resection with fascicle sparing technique can be performed. The cisternal subtype masquerade as vestibular schwannoma and should be recognized at the initial exposure by the appearance of finely splayed nerve fascicles at the perimetry of the tumor which elicits a motor response at low threshold stimulation.

Preservation of Cranial Nerves Function in Glomus Jugulare Surgery: 2-Dimensional Operative Video.

Owing to their invasive character, extreme vascularity, and critical location, glomus jugulare tumors present a formidable challenge. Techniques have been developed for safe and successful removal of even giant glomus paragangliomas.1-3 Preoperative evaluation including genetic, hormonal, and multiplicity workup4 has enhanced the safety of surgical management, as did modern preoperative embolization by eliminating excessive blood loss.5 Despite these advancements, surgical outcomes of glomus jugulare remain haunted by cranial nerve dysfunction such as facial nerve palsies and hearing loss, with lower cranial nerves dysfunction being the most morbid. These can be avoided by technical maneuvers to preserve the cranial nerves. The external ear canal is not closed to maintain conductive hearing. The facial nerve is not transpositioned and kept inside a bony protective canal. Cranial nerves IX, X, and XI are the most vulnerable because they pass through the jugular foramen ventral to the venous bulb wall. They are preserved by intrabulbar dissection that maintains a protective segment of the venous wall over the nerves. By mastering the anatomy of the upper neck, meticulous dissection is performed to preserve the course of IX, X, XI, and XII.6,7 Ligation of the jugular vein is delayed until the tumor is totally isolated to avoid diffuse bleeding.7 We present the case of a 60-yr-old woman with a glomus jugulare tumor with intradural, extradural, and cervical extension. The technical nuances of cranial nerves preservation are demonstrated. The patient consented to the procedure and publication of her images. Images at 2:12, 2:50, and 3:09 from Al-Mefty and Teixeira,6 with permission from JNSPG.

Resection of Clival Chordoma Through the Anterior Clivectomy: 2-Dimensional Operative Video.

Clival chordomas are rare malignant behaving tumors that grow, locally invade, metastasize, and seed, and they have a high recurrence rate.1,2 The longest disease control is achieved by radical resection followed by high doses of radiation therapy, commonly proton beam.3 To achieve radical tumor removal, multiple surgical procedures through different approaches might be required.4 Since the chordoma's origin is, and remains, extradural, an extradural approach is preferred, and can lead to intradural extension. Anterior approach is frequently utilized to remove the midline-located tumor and the eroded clivus.5 Several midline approaches were utilized, including the transbasal, transfacial, transcervical, open door, and Lefort's maxillotomies1; however, the same tumor removal can be achieved with a simple extension of the trans-sphenoidal approach, by resecting the anterior maxillary wall, of the contralateral to the lesion preponderant side.5 This approach coupled with the use of neuronavigation on mobile head and endoscopic-assisted technique allowed to achieve a wide and direct exposure, with the ability to resect extra- and intradural tumors.2,5 Lately, the endonasal endoscopic technique became popular as an alternative4; however, we found a great advantage in the ability to combine the stereoscopic microsurgical technique with the endoscopic dissection, in addition to avoiding the extensive nasal dissection and its complications. We present a case of a 63-yr old woman with an upper clivus chordoma compressing the brainstem who underwent a gross total resection by endoscopic-assisted microscopic techniques through an anterior clivectomy approach. Patient consented to the procedure and publication of her images.

Cortical and Subcortical Anatomy of the Orbitofrontal Cortex: A White Matter Microfiberdissection Study and Case Series.

BACKGROUND: The literature on white matter anatomy underlying the human orbitofrontal cortex (OFC) is scarce in spite of its relevance for glioma surgery. OBJECTIVE: To describe the anatomy of the OFC and of the underlying white matter fiber anatomy, with a particular focus on the surgical structures relevant for a safe and efficient orbitofrontal glioma resection. Based on anatomical and radiological data, the secondary objective was to describe the growth pattern of OFC gliomas. METHODS: The study was performed on 10 brain specimens prepared according to Klingler's protocol and dissected using the fiber microdissection technique modified according to U.T., under the microscope at high magnification. RESULTS: A detailed stratigraphy of the OFC was performed, from the cortex up to the frontal horn of the lateral ventricle. The interposed neural structures are described together with relevant neighboring topographic areas and nuclei. Combining anatomical and radiological data, it appears that the anatomical boundaries delimiting and guiding the macroscopical growth of OFC gliomas are as follows: the corpus callosum superiorly, the external capsule laterally, the basal forebrain and lentiform nucleus posteriorly, and the gyrus rectus medially. Thus, OFC gliomas seem to grow ventriculopetally, avoiding the laterally located neocortex. CONCLUSION: The findings in our study supplement available anatomical knowledge of the OFC, providing reliable landmarks for a precise topographical diagnosis of OFC lesions and for perioperative orientation. The relationships between deep anatomic structures and glioma formations described in this study are relevant for surgery in this highly interconnected area.

Integration of Microanatomy, Neuronavigation, Dynamic Neurophysiologic Monitoring, and Intraoperative Multimodality Imaging for the Safe Removal of an Insular Glioma: 2-Dimensional Operative Video.

Insular gliomas are located amongst myriad critical neurovascular structures, including lenticulostriate vessels, long insular perforators, putamen, internal capsule, frontal and temporal opercula, and key fasciculi.1-6 Each of these critical structures engenders key function of the brain, which must be preserved. Although anatomic knowledge remains the cornerstone of insular glioma surgery, novel tools have been developed to aid the surgeon in identifying and preserving these essential structures. Modern surgery of the insular glioma calls for seamless integration of these techniques to maximize the safety and totality of insular glioma resection, which has been shown to improve length of survival and seizure control, while reducing risk of tumor transformation.7-10 Neuronavigation can be used to help plan the craniotomy to achieve adequate exposure and assist during tumor resection. Brain "shift" can be corrected by re-registration following intraoperative magnetic resonance imaging (MRI). Interval ultrasound imaging reflects real-time progressive tumor resection. Dynamic neurophysiologic monitoring using thresholding techniques guides the surgeon as he resects tumor at its depth and posterior pole-close to the internal capsule. Intraoperative magnetic resonance imaging depicts residual infiltrative tumor that may require additional resection. The patient is a 33-yr-old woman with progressive growth of a right insular tumor and has consented to surgery, photography, and video recording. Figure at 1:57, © Ossama Al-Mefty, used with permission.

Resection of Pontine Cavernoma Through the Anterior Transpetrosal Approach: 2-Dimensional Operative Video.

The pons is the most frequent local for brain stem cavernoma.1 Repeated hemorrhage of brainstem cavernoma is associated with significant and accumulative neurological deficits and thus requires treatment. According to the Swedish Karolinska's group of radiosurgery, "it could not be concluded whether GKRS affects the natural course of a CM. The incidence of radiation-induced complications was approximately seven times higher than that expected."2 Thus, microsurgical removal has become the mainstay of treatment. In our experience, the following details assist in obtaining favorable outcomes and avoiding postoperative complications3,4: (a) the entry into the cavernoma based on thorough knowledge of the microanatomy; (b) the detailed study of the images and the presentation of the cavernoma on or near the brain stem surface; (c) the resection of the live cavernous hemangioma and not the mere removal of the multiple aged organized hematomas; (d) the preservation of the associated venous angioma; (e) the direct and shortest access to the lesion provided by a skull base approach; and (f) the use of the available technology, such as intraoperative neuromonitoring and neuroimaging. We present the case of a 54-yr-old male with recent deterioration in year 2001, past repetitive episodes of gait imbalance, and speech difficulty over a 7-yr period from known pontine cavernoma. The anterior petrosal approach provided superb and direct exposure to the entry at the lateral pons and the cavernoma was totally removed with preservation of the venous angioma. His preoperative neurological deficit rapidly recovered. Patient consented to the procedure and photography. Images at 3:15 from Kadri et al, The anatomical basis for surgical presercation of temporal muscle. J Neurosurg. 2004;100:517-522, used with permission from JNSPG. Image at 3:27 from Al-Mefty O, Operative Atlas of Meningiomas, © LWW, 1997, with permission.

The Resection of a Thalamic Pilocytic Astrocytoma Through the Transchoroidal Fissure, Transcallosal Approach: 2-Dimensional Operative Video.

Surgical resection is the primary treatment of pilocytic astrocytomas and total removal can be curative. However, these lesions occur in critical areas, such as the thalamus, being surrounded by critical life neurovascular structures, which imposes a surgical challenge.1-5 Exhaustive acquisition and meticulous interpretation of preoperative radiological exams; reliable surgical orientation based on profound microneurosurgical anatomic knowledge and judicious discernment of the neuroanatomic distortions on the surface and deep-seated structures inflicted by the neuropathological entity; embracing and comprehensive application of the vast scope of available intraoperative guidance imaging and neurophysiological monitoring; in alliance with the mastered carefully microsurgical technique supported by endoscopic visualization are the keystones to the pursed duet "cure with quality of life" in the treatment of these lesions. We present the case of a 17-yr-old young lady with a progressive motor deficit in her right hemibody for over 2 yr. Her radiological investigation demonstrated a left thalamic lesion displacing the projection fibers (corticospinal tract) within the internal capsule laterally. The patient consented to the surgical procedure. The surgical strategy, intraoperative findings, and microsurgical and endoscopic technique, as well as the postoperative radiological and clinical evaluation are presented. The patient gave her informed consent for the publication of the case.

Fiber Microdissection Technique for Demonstrating the Deep Cerebellar Nuclei and Cerebellar Peduncles.

BACKGROUND: The cerebellum is one of the most primitive and complex parts of the human brain. The fiber microdissection technique can be extremely useful for neurosurgeons to understand the topographical organization of the cerebellum's important contents, such as the deep cerebellar nuclei and the cerebellar peduncles, and their relationship with the brain stem. OBJECTIVE: To dissect the deep cerebellar nuclei and the cerebellar peduncles using the fiber microdissection technique. METHODS: Under the operating microscope, 5 previously frozen, formalin-fixed human cerebellums and brain stems were dissected from the superior surface, and 5 were dissected from the inferior surface. Each stage of the process is described. The primary dissection tools were handmade, thin, wooden spatulas with tips of various sizes, toothpicks, and a fine regulated suction. RESULTS: In 15 simplified dissection steps (6 for the superior surface and 9 for the inferior surface), the deep cerebellar nuclei (dentate, interpositus, and fastigial) and the cerebellar peduncles (inferior, middle, and superior) are delineated. Their anatomical relationships with each other and other neighboring structures are demonstrated. CONCLUSION: The anatomy of the deep cerebellar nuclei and the cerebellar peduncles are clearly defined and understood through the use of the fiber microdissection technique. These stepwise dissections will guide the neurosurgeon in acquiring a topographical understanding of these complex and deep structures of the cerebellum. This knowledge, along with radiological information, can help in planning the most appropriate surgical strategy for various lesions of the cerebellum.

Safe Zones for Temporal Muscle Hook Retraction: A Technical Note.

BACKGROUND: The temporal muscle (TM) needs to be dissected and reflected downward in some anterolateral cranial approaches, and failing to preserve its integrity could have severe functional and cosmetic consequences. Most articles focus on techniques to prevent vascular injury during retrograde dissection or techniques to preserve the facial nerve; however, information on how to take care of the muscle during hook retraction is limited. We presented an anatomic study of vascularization of the TM, and we established safe areas for muscular hook retraction. METHODS: We dissected 16 TMs in 8 cadaveric heads. The TM was reflected downward, and we measured the distance between the anterior branch of the posterior deep temporal artery (PDTA) and the frontozygomatic suture and the distance between the posterior branch of the PDTA and the external auditory meatus projection. RESULTS: The average distance between the anterior branch of the PDTA and the frontozygomatic suture was 19.5 mm (range, 14-26 mm). The average distance between the posterior branch of the PDTA and the external auditory canal was 37.1 mm (range, 31-43 mm). We established 2 safe zones for hook placement: an anterior safe zone 14 mm posterior to the frontozygomatic suture and a posterior safe zone 30 mm anterior to the external auditory meatus. CONCLUSIONS: We delimited 2 safe zones for hook placement during TM retraction aiming to avoid direct vascular damage in anterolateral cranial approaches.

Surgical Approaches to the Temporal Horn: An Anatomic Analysis of White Matter Tract Interruption.

BACKGROUND: Surgical access to the temporal horn is necessary to treat tumors and vascular lesions, but is used mainly in patients with mediobasal temporal epilepsy. The surgical approaches to this cavity fall into 3 primary categories: lateral, inferior, and transsylvian. The current neurosurgical literature has underestimated the interruption of involved fiber bundles and the correlated clinical manifestations. OBJECTIVE: To delineate the interruption of fiber bundles during the different approaches to the temporal horn. METHODS: We simulated the lateral (trans-middle temporal gyrus), inferior (transparahippocampal gyrus), and transsylvian approaches in 20 previously frozen, formalin-fixed human brains (40 hemispheres). Fiber dissection was then done along the lateral and inferior aspects under the operating microscope. Each stage of dissection and its respective fiber tract interruption were defined. RESULTS: The lateral (trans-middle temporal gyrus) approach interrupted "U" fibers, the superior longitudinal fasciculus (inferior arm), occipitofrontal fasciculus (ventral segment), uncinate fasciculus (dorsolateral segment), anterior commissure (posterior segment), temporopontine, inferior thalamic peduncle (posterior fibers), posterior thalamic peduncle (anterior portion), and tapetum fibers. The inferior (transparahippocampal gyrus) approach interrupted "U" fibers, the cingulum (inferior arm), and fimbria, and transected the hippocampal formation. The transsylvian approach interrupted "U" fibers (anterobasal region of the extreme capsule), the uncinate fasciculus (ventromedial segment), and anterior commissure (anterior segment), and transected the anterosuperior aspect of the amygdala. CONCLUSION: White matter dissection improves our knowledge of the complex anatomy surrounding the temporal horn. Identifying the fiber bundles at risk during each surgical approach adds important information for choosing the appropriate surgical strategy.

Interrupção das fibras brancas nos acessos cirúrgicos ao corno temporal do ventrículo lateral: estudo anatômico / White matter interruption in the surgical approaches to the temporal horn of the lateral ventricle

Introdução: A exploração cirúrgica do como temporal do ventrículo lateral (CTVL) é realizada para o tratamento de lesões neoplásica, vasculares e, principalmente, para o tratamento cirúrgico da epilepsia do lobo temporal. As abordagens cirúrgicas a esta cavidade são realizadas, a partir da superficie cortical e através de suas paredes, pelos acessos laterais, transsilvianos e inferiores. A escolha do acesso cirúrgico se baseia na exposição adequada e nas alterações neurológicas que possam advir do trauma ao parênquima cerebral. A secção dos diferentes feixes de fibras brancas pode resultar em déficits neurológicos mais duradouros do que a lesão ao córtex cerebral. Os déficits visuais oriundos da interrupção das fibras da radiação óptica são os mais estudados. A identificação das interrupções dos demais conjuntos de fibras e as correlações dos déficits neurológicos originados têm sido subestimadas na literatura Objetivo: Avaliar a interrupção dos feixes de fibras brancas nos diferentes acessos cirúrgicos ao como temporal do ventrículo lateral, utilizando a técnica de dissecção de fibras brancas de Klinger. Métodos: Para o estudo, foram utilizados 40 hemisférios cerebrais cadavéricos adultos (20 encéfalos) preparados no Laboratório de Anatomia da UFMS de acordo com a descrição do método de preparação de Klinger. As aberturas da cavidade ventricular, mimetizando os acessos cirúrgicos lateral (através do giro temporal médio), inferior (através do giro parahipocampal), transsilviano e transuncal foram realizados por meio de incisões de l5 mm a partir das superficies corticais. Resultados: A introdução dos instrumentos de dissecção, de 15 mm de largura por 2 mm de espessura, garantiu a uniformidade das transecções das fibras da superficie cortical à cavidade ventricular. Como resultado obteve­se o acesso que causou menor comprometimento de fibras brancas foi o acesso transucal, esse que atingiu apenas 8,3% das fibras analisadas, sendo as fibras em "U" situadas no...

Introduction: Surgical access to the temporal hom of lateral ventric1e is performed to treat tumoral and vascular lesions, but mainly to the surgi cal treatment of temporal epilepsy. The surgi cal exploration of this cavity is realized from the cortical surface towards the ventricular walls, through the lateral, transsylvian and inferior approaches, based on the adequate exposure of the cavity and on the postoperative deficits that might be originated from the brain parenchymal trauma. Lesions to the fibers bundles often result in more severe and prolonged deficits than corticallesions. The most common recognized deficits are the visual fields defects secondary to injuries to the optic radiation. Identification of the interruption of other fibers bundles involved and their correlated c1inical manifestation have been underestimated on the literature. Objective: To identify the interruption of the fiber bundles originated from the different approaches to the temporal hom utilizing the Klinger's fiber dissection technique. Methods: We studied 40 cerebral hemispheres of 20 brains, prepared according to Klingers method, at the UFMS Laboratory of Anatomy. The surgical access of the temporal hom was performed simulating the lateral (middle temporal gyrus), inferior (parahippocampal gyrus), transsylvian and transuncal approaches, through 15 mm cortical incisions, followed by stepwise dissection of the fibers. Results: Introduction ofthe dissector (15 mm width, 2 mm height) warranted an uniform transection of the fibers from the cortical surface to the ventricular cavity. The least destructive access encountered was the transuncal access, interrupting 8,3% of the studied fibers. Following it, the inferior and the transsylvian approaches interrupted 25% of the fibers. The most destructive, interrupting 75% of the studied fibers was the lateral approach. Conclusion: The lateral approach through the middle temporal gyrus caused interruptions on...

Medial acoustic neuromas: clinical and surgical implications.

OBJECT: Medial acoustic neuroma is a rare entity that confers a distinct clinical syndrome. It is scarcely discussed in the literature and is associated with adverse features. This study evaluates the clinical and imaging features, pertinent surgical challenges, and treatment outcome in a large series of this variant. The authors postulate that the particular pathological anatomy with its arachnoidal rearrangement has a profound implication on the surgical technique and outcome. METHODS: The authors conducted a retrospective analysis of 52 cases involving 33 women and 19 men who underwent resection of medial acoustic neuromas performed by the senior author (O.A.) over a 20-year period (1993-2013). Clinical, radiological, and operative records were reviewed, with a specific focus on the neurological outcomes and facial nerve function and hearing preservation. Intraoperative findings were analyzed with respect to the effect of arachnoidal arrangement on the surgeon's ability to resect the lesion and the impact on postoperative function. RESULTS: The average tumor size was 34.5 mm (maximum diameter), with over 90% of tumors being 25 mm or larger and 71% being cystic. Cerebellar, trigeminal nerve, and facial nerve dysfunction were common preoperative findings. Hydrocephalus was present in 11 patients. Distinguishing intraoperative findings included marked tumor adherence to the brainstem and frequent hypervascularity, which prompted intracapsular dissection resulting in enhancement on postoperative MRI in 18 cases, with only 3 demonstrating growth on follow-up. There was no mortality or major postoperative neurological deficit. Cerebrospinal fluid leak was encountered in 7 patients, with 4 requiring surgical repair. Among 45 patients who had intact preoperative facial function, only 1 had permanent facial nerve paralysis on extended follow-up. Of the patients with preoperative Grade I-II facial function, 87% continued to have Grade I-II function on follow-up. Of 10 patients who had Class A hearing preoperatively, 5 continued to have Class A or B hearing after surgery. CONCLUSIONS: Medial acoustic neuromas represent a rare subgroup whose site of origin and growth patterns produce a distinct clinical presentation and present specific operative challenges. They reach giant size and are frequently cystic and hypervascular. Their origin and growth pattern lead to arachnoidal rearrangement with marked adherence against the brainstem, which is critical in the surgical management. Excellent surgical outcome is achievable with a high rate of facial nerve function and attainable hearing preservation. These results suggest that similar or better results may be achieved in less complex tumors.

Anterior clivectomy: surgical technique and clinical applications.

OBJECT: Midline clival lesions, whether involving the clivus or simply situated anterior to the brainstem, present a technical challenge for adequate exposure and safe resection. The authors describe, as a minimally invasive technique, an anterior clivectomy performed via an expanded transsphenoidal approach coupled with the use of a neuronavigation on mobile head and endoscopic-assisted technique. Wide and direct exposure, with the ability to resect extra- and intradural tumors, was achieved without mortality and with a low rate of complications. METHODS: Cadaveric dissections were performed to outline the landmarks and measure the window that is created by resecting the clivus anteriorly. The technique was used in 43 patients to resect tumors located at or invading the clivus. The initial exposure of the clivus was obtained via the sublabial transsphenoidal approach. The wall of the anterior maxilla, often on 1 side, was removed to allow a wide side-to-side opening of the nasal speculum. Using neuronavigation, the authors made clivectomy windows by drilling the clivus between anatomical landmarks. Bilateral intraoperative neurophysiological monitoring was used (somatosensory evoked potentials, brainstem auditory evoked responses, and cranial nerves VI-XII). RESULTS: Of the 43 patients, 26 were female and 17 were male, and they ranged in age from 3.5 to 76 years (mean 41.5 years). Thirty-eight patients harbored a chordoma and 5 a giant invasive pituitary adenoma. Gross-total resection of the tumor was achieved in 34 cases (79%). Nine patients (21%) had residual tumor unreachable through the anterior clivectomy, and this required a second-stage resection. Four patients developed new transient extraocular movement deficits. One patient developed a permanent cranial nerve VI palsy. Twenty-seven patients with chordoma underwent postoperative proton-beam radiotherapy. Tumor recurred in 19% of these cases. In 3 patients a cerebrospinal fluid leak developed during hospitalization and was treated successfully. Two other patients presented with a delayed cerebrospinal fluid leak after radiotherapy. Only 1 patient, who had previously undergone Gamma Knife surgery, experienced postoperative hemiparesis. CONCLUSIONS: A complete anterior clivectomy via a simple extension of the transsphenoidal approach allows the surgeon access to different lesions involving the clivus or situated anterior to the brainstem. The exposure is similar to that provided by more extensive transfacial approaches. Instrument manipulation is easy. Neuronavigation, endoscopy, and intraoperative monitoring are easily incorporated and enhance the capability and safety of this approach.