Solid vs. cystic predominance in posterior fossa hemangioblastomas: implications for cerebrovascular risks and patient outcome.

BACKGROUND: Hemangioblastomas (HGBs) are highly vascular benign tumors, commonly located in the posterior fossa, and 80% of them are sporadic. Patients usually present with features of raised intracranial pressure and cerebellar symptoms. HGB can be classified as either mostly cystic or solids. Although the solid component is highly vascularized, aneurysm or hemorrhagic presentation is rarely described, having catastrophic results. METHODS: We identified 32 consecutive patients with posterior fossa HBG who underwent surgery from 2008 through 2020 at our medical center. Tumors were classified as predominantly cystic or solid according to radiological features. Resection was defined as gross total (GTR) or subtotal (STR). RESULTS: During the study period, 32 posterior fossa HGBs were resected. There were 26 cerebellar lesions and 4 medullar lesions, and in 2 patients, both structures were affected. Predominant cystic tumors were seen in 15 patients and solids in 17. Preoperative digital subtraction angiography (DSA) was performed in 8 patients with solid tumors, and 4 showed tumor-related aneurysms. Embolization of the tumors was performed in 6 patients, including the four tumor-related aneurysms. GTR was achieved in 29 tumors (91%), and subtotal resection in 3 (9%). Three patients had postoperative lower cranial nerve palsy. Functional status was stable in 5 patients (16%), improved in 24 (75%), and 3 patients (9%) deteriorated. One patient died 2 months after the surgery. Two tumors recurred and underwent a second surgery achieving GTR. The mean follow-up was 42.7 months (SD ± 51.0 months). CONCLUSIONS: Predominant cystic HGB is usually easily treated as the surgery is straightforward. Those with a solid predominance present a more complex challenge sharing features similar to arteriovenous malformations. Given the important vascular association of solid predominance HGB with these added risk factors, the preoperative assessment should include DSA, as in arteriovenous malformations, and endovascular intervention should be considered before surgery.

Superficial Temporal Artery-Middle Cerebral Artery Microvascular Bypass: Its Role in Treatment of Patients with Moyamoya Disease, Cerebral Aneurysms, and Vascular Occlusive Disease.

BACKGROUND: Superficial temporal artery-middle cerebral artery microvascular bypass (STA-MCA MVB) is an important strategy for the management of selected patients OBJECTIVES: To present our 19-year experience with STA-MCA MVB METHODS: Data for consecutive patients who underwent STA-MCA MVB from 2000­2019 due to moyamoya/moyamoya-like disease, complex intracranial aneurysms, or intractable brain ischemia due to internal carotid artery or MCA occlusive disease with repeated ischemic events were retrospectively analyzed under a waiver of informed consent. Key surgical steps and the important role of neuroendovascular interventions are presented. Surgical results and late outcomes were analyzed RESULTS: The study included 32 patients (17 women [53%], 15 men [47%]), mean age 42.94 years (range 16­66). The patients underwent 37 STA-MCA MVB procedures during the study period: 22 with moyamoya/moyamoya-like disease (69%) underwent 27 surgeries (five bilateral); 7 patients with complex aneurysms (22%) and 3 patients with vascular occlusive disease (9%) underwent unilateral bypass. Five of seven aneurysms were treated with coiling or flow-diverter stent implant prior to bypass surgery; two were clipped during the bypass procedure. There were no surgical complications, no perioperative mortality, and no death from complications related to neurovascular disease at late follow-up. Transient neurological deficits following 7/37 surgeries (19%) resolved with no permanent neurologic sequelae. Transient ischemic attacks occurred only in the immediate postoperative period in four patients (11%) CONCLUSIONS: In specific cases, STA-MCA MVB is a feasible and clinically effective procedure. It is important to preserve this technique in the surgical armamentarium

The infratranstentorial subtemporal approach (ITSTA): a valuable skull base approach to deep-seated non-skull base pathology.

BACKGROUND: Surgical access to space-occupying lesions such as tumors and vascular malformations located in the area of the tentorial notch, mediobasal temporal lobe, and para-midbrain is difficult. Lesions in this area are typically resected with supratentorial approaches demanding significant elevation of the temporal lobe or even partial lobectomy, or via a supracerebellar transtentorial approach. We introduce an alternative, the skull base infratranstentorial subtemporal approach (ITSTA), which provides excellent exposure of the incisural area while minimizing risk to the temporal lobe. METHODS: We included consecutive patients with pathology involving the area of the tentorial incisura, para-midbrain, and mediobasal temporal area who underwent surgery via ITSTA from 2012 to 2018. The approach includes partial mastoidectomy, temporal craniotomy, and tentorial section. Space obtained by mastoidectomy provides a sharp high-rising angle-of-attack, significantly diminishing the need for temporal lobe retraction. Surgeries were performed using microsurgical techniques, neuronavigation, and electrophysiological monitoring. Clinical presentation, tumor characteristics, extent of resection, complications, and outcome were retrospectively reviewed under a waiver of informed consent. RESULTS: Nine patients met inclusion criteria (five female, four male; mean age 44 years, range 7-72). They underwent surgery for removal of para-midbrain arteriovenous malformation (AVM, 3/9), medial tentorial meningioma (2/9), mediobasal epidermoid cyst (2/9), oculomotor schwannoma (1/9), or pleomorphic xanthoastrocytoma (PXA) of the fusiform gyrus (1/9). Three AVMs were removed completely; among six patients with tumors, gross total resection was achieved in three and subtotal resection in three. All surgeries were uneventful without complications. There were no new permanent neurological deficits. At late follow-up (mean 42.5 months), eight patients had a Glasgow Outcome Score (GOS) of 5. One 66-year-old female died 18 months after surgery for reasons not related to her disease or surgery. CONCLUSIONS: The ITSTA is a valuable skull base approach for removal of non-skull base pathologies located in the difficult tentorial-incisural parabrainstem area.

Purely endoscopic removal of a parasagittal/falx meningioma.

BACKGROUND: Endoscopic techniques are an integral part of the neurosurgical armamentarium with a growing list of indications. We describe the purely endoscopic removal of an atypical parasagittal meningioma in a patient who could not undergo standard craniotomy due to severe scalp atrophy following childhood irradiation for tinea capitis. METHODS: A 68-year-old man in good general health presented with a parasagittal meningioma that recurred following subtotal removal and adjuvant fractionated stereotactic radiosurgery (FSR). The scalp above the tumor location was very diseased and precluded a regular craniotomy for tumor removal. A 4-cm craniotomy was made in the midline forehead, where the skin was normal. A rigid endoscope was advanced under neuronavigation through the interhemispheric fissure, which provided good access with limited retraction, until the tumor was encountered at a depth of 7-8 cm. Two surgeons performed the surgery using a "four-hands technique". The tumor was removed and the insertion area was resected and coagulated. RESULTS: The surgery was uneventful, with no coagulation or transection of major veins. A subtotal resection was achieved, and the patient recovered with no neurological deficit. CONCLUSIONS: Safe resection of parasagittal meningiomas with a purely endoscopic technique is feasible. This option needs further exploration as an alternative strategy in patients with severely atrophic scalp skin that greatly increases the risk of significant healing complications with calvarian craniotomy.

Physiological Correlates and Predictors of Functional Recovery After Chiasmal Decompression.

BACKGROUND: The intrinsic abilities and limits of the nervous system to repair itself after damage may be assessed using a model of optic chiasmal compression, before and after a corrective surgical procedure. METHODS: Visual fields (VFs), multifocal visual evoked potentials (mfVEP), retinal nerve fiber layer (RNFL) thickness, and diffusion tensor imaging were used to evaluate a patient before and after removal of a meningioma compressing the chiasm. Normally sighted individuals served as controls. The advantage of each modality to document visual function and predict postoperative outcome (2-year follow-up) was evaluated. RESULTS: Postsurgery visual recovery was best explained by critical mass of normally conducting fibers and not associated with average conduction amplitudes. Recovered VF was observed in quadrants in which more than 50% of fibers were identified, characterized by intact mfVEP latencies, but severely reduced amplitudes. Recovery was evident despite additional reduction of RNFL thickness and abnormal optic tract diffusivity. The critical mass of normally conducting fibers was also the best prognostic indicator for functional outcome 2 years later. CONCLUSIONS: Our results highlight the ability of the remaining normally conductive axons to predict visual recovery after decompression of the optic chiasm. The redundancy in anterior visual pathways may be explained, neuroanatomically, by overlapping receptive fields.

"Lazy" far-lateral approach to the anterior foramen magnum and lower clivus.

The far-lateral approach (FLA) has become a mainstay for skull base surgeries involving the anterior foramen magnum and lower clivus. The authors present a surgical technique using the FLA for the management of lesions of the anterior/ anterolateral foramen magnum and lower clivus. The authors consider this modification a "lazy" FLA. The vertebral artery (VA) is both a critical anatomical structure and a barrier that limits access to this region. The most important nuance of this FLA technique is the management of this critical vessel. When the lazy FLA is used, the VA is reflected laterally, encased in its periosteal sheath and wrapped in the dura, greatly minimizing the risk for vertebral injury while preserving a wide working space. To accomplish this step, drilling is performed lateral to the point where the VA pierces the dura. The dura is incised medial to the VA entry point by using a slightly curved longitudinal cut. Drilling of the condyle and the C-1 lateral mass is performed in a manner that preserves craniocervical stability. The lazy FLA is a true FLA that is based on manipulation of the VA and lateral bone removal to obtain excellent exposure ventral to the spinal cord and medulla, yet it is among the most conservative FLA techniques for management of the VA and provides a safer window for bone work and lesion management. Among 44 patients for whom this technique was used to resect 42 neoplasms and clip 2 posterior inferior cerebral artery aneurysms, there was no surgical mortality and no injury to the VA.

Safety of drilling for clinoidectomy and optic canal unroofing in anterior skull base surgery.

BACKGROUND: Skull base drilling is a necessary and important element of skull base surgery; however, drilling around vulnerable neurovascular structures has certain risks. We aimed to assess the frequency of complications related to drilling the anterior skull base in the area of the optic nerve (ON) and internal carotid artery (ICA), in a large series of patients. METHODS: We included anterior skull base surgeries performed from 2000 to 2012 that demanded unroofing of the optic canal, with extra- or intradural clinoidectomy and/or drilling of the clinoidal process and lateral aspect of the tuberculum sella. Data was retrieved from a prospective database and supplementary retrospective file review. Our IRB waived the requirement for informed consent. The nature and location of pathology, clinical presentation, surgical techniques, surgical morbidity and mortality, pre- and postoperative vision, and neurological outcomes were reviewed. RESULTS: There were 205 surgeries, including 22 procedures with bilateral optic canal unroofing (227 optic canals unroofed). There was no mortality, drilling-related vascular damage, or brain trauma. Complications possibly related to drilling included CSF leak (6 patients, 2.9 %), new ipsilateral blindness (3 patients, 1.5 %), visual deterioration (3 patients, 1.5 %), and transient oculomotor palsy (5 patients, 2.4 %). In all patients with new neuropathies, the optic and oculomotor nerves were manipulated during tumor removal; thus, new deficits could have resulted from drilling, or tumor dissection, or both. CONCLUSION: Drilling of the clinoid process and tuberculum sella, and optic canal unroofing are important surgical techniques, which may be performed relatively safely by a skilled neurosurgeon.

Very delayed CSF leak in patients after craniotomy for resection of skull base tumors.

OBJECTIVE: Cerebrospinal fluid (CSF) leak is a potentially dangerous neurosurgical complication. Delayed CSF leak has already been described after trauma, radiation therapy and endonasal transsphenoidal surgery for Sella turcica pathologies. Still, very few reported cases describe delayed CSF leak after craniotomy for tumors. We present our experience with patients showing delayed CSF leak after skull base tumor resection. METHODS: Data for all tumors resected from the skull base region from January 2004 to December 2018 was retrieved from the surgeon's prospective database and supplemented with a retrospective file review. Patients who presented CSF leak within the first 12 months after surgery and those with a history of trauma or radiation-based treatment to the skull base region were excluded from the study. Epidemiology, clinical presentation, previous surgical approach, pathology, interval between craniotomy and CSF leak and proposed treatment were analyzed. RESULTS: Overall, more than two thousand patients underwent surgery for resection of skull base tumors during the study period. Six patients (two male, four female; mean age 57.5 years, range 30-80) presented with delayed CSF leak, including five (83%) who presented with bacterial meningitis. After skull base tumor resection, CSF leak developed in a mean of 72 months (range 12-132). Three patients underwent retrosigmoid craniotomy, two for resection of cerebellopontine angle epidermoid cyst and one for resection of a petro tentorial meningioma; one had trans petrosal retrolabyrinthine craniotomy for resection of a petroclival epidermoid cyst; one had far lateral craniotomy for resection of a foramen magnum meningioma; and one had pterional craniotomy for resection of a cavernous sinus meningioma. All patients underwent surgical re-exploration and repair. CSF leak was managed with mastoid obliteration in five patients and skull base reconstruction with fat graft in one. CONCLUSION: Recognition of very delayed CSF leak as a potential complication after resection of skull base tumors may be useful tool in long-term patient management. In our experience, these patients usually present with bacterial meningitis. Surgical options should be considered as a definitive treatment.

ICG Flow 800 technology targeted STA-MCA microvascular bypass for exclusion of deep-seated fusiform MCA aneurysm: 2-dimensional operative video.

The authors present the case of an 18-year-old male with a deep-seated left fusiform dissecting M3 aneurysm for which endovascular treatment was not applicable. At the open surgery, they used the less commonly reported FLOW 800 fluorescent indocyanine green (ICG) videoangiography, before and after parental aneurysmal artery temporary clipping, to locate the distal outflow branch of the aneurysm and use it as the recipient artery for a superficial temporal artery-M4 bypass, excluding the aneurysm by clipping the parental artery. Repeated ICG FLOW 800 angiography confirmed bypass patency and adequate blood flow. The aneurysm's exclusion from circulation was confirmed by digital subtraction angiography postoperatively. The video can be found here: https://stream.cadmore.media/r10.3171/2021.10.FOCVID21183.

Cavernous Sinus Epidermoid Cyst Removal through a No-Keyhole Pterional Craniotomy: Operative Video and Technical Nuances.

Intracranial epidermoid cysts are considered benign tumors with good general prognosis. However, their radical removal may be associated with certain morbidity, especially when the capsule is attached to neurovascular structures. Epidermoid cysts located in the cavernous sinus are very rare. We present an operative video of a 22-year-old female patient, who suffered a right-sided headache for 5 years. The video demonstrates main steps and surgical nuances of resection of a right interdural cavernous sinus epidermoid cyst, measuring 22 × 19 × 21 mm (4.3 cc) ( Fig. 1A ). On initial physical examination, the patient had a right partial third nerve palsy (mild ptosis with minimal diplopia), without any other cranial nerve deficit. A right no-keyhole pterional craniotomy was performed, followed by extradural anterior clinoidectomy and peeling of the outer dural layer of the lateral wall of the cavernous sinus. The dura matter was also detached from the distal carotid dural ring, which was exposed by the clinoidectomy ( Fig. 2A ). This maneuver provided excellent exposure of the interdural epidermoid cyst, which severely compressed the oculomotor nerve against the posterior petroclinoid dural fold ( Fig. 2B ). Gross total resection of the epidermoid cyst was achieved ( Fig. 1B and C ). The patient developed a transient worsening of the third nerve palsy, which recovered completely 3 months after the surgery. Postoperative magnetic resonance imaging revealed no signs of residual tumor. The link to the video can be found at: https://youtu.be/pobhYb5ZNig .

Vestibular schwannoma manifesting with hemifacial spasm in a young woman: clinical considerations and tumor removal with hearing preservation. 2-Dimensional operative video.

Hemifacial spasm (HFS) is a rare presentation of vestibular schwannoma. The authors present their experience with a 27-year-old woman who presented with normal hearing and HFS, which was the single neurological manifestation of an 18-mm vestibular schwannoma. In this challenging situation, the treatment goals were maximal tumor removal with preservation of hearing and facial nerve function and cure of the HFS. The authors achieved these goals, performing complete tumor removal via a retrosigmoid approach, assisted with neurophysiological monitoring and a 45°-angle QEVO endoscope. In the video, they explain the clinical, radiological, and surgical considerations and demonstrate the surgical technique. The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID2099.

Flow-diverter stents in the early management of acutely ruptured brain aneurysms: effective rebleeding protection with low thromboembolic complications.

OBJECTIVE: Flow-diverter stents (FDSs) are not generally used for the management of acutely ruptured aneurysms with associated subarachnoid hemorrhage (SAH). Herein, the authors present their experience with FDSs in this scenario, focusing on the antiplatelet regimen, perioperative management, and outcome. METHODS: The authors retrospectively reviewed their institutional database for the treatment and outcomes of all patients with acutely ruptured aneurysms and associated SAH from July 2010 to September 2018 who had received an FDS implant as stand-alone treatment within 4 days after diagnosis. The protocol with the use of flow diversion in these patients includes a low threshold for placement of external ventricular drains before stenting, followed by the administration of aspirin and clopidogrel with platelet testing before stent implantation. With this approach, the risk of hemorrhage and stent-related thrombus formation is limited. Demographic, clinical, technical, and imaging data were analyzed. RESULTS: Overall, 76 patients (61% females, mean age 42.8 ± 11.3 years) met the inclusion criteria. FDS implantation was performed a median of 2 days after diagnosis. On average, 1.05 devices were used per procedure. There was no procedural mortality directly attributed to the endovascular intervention. Procedural device-related clinical complications were recorded in a total of 6 cases (7.9%) and resulted in permanent neurological morbidity in 2 cases (2.6%). There was complete immediate aneurysm occlusion in 11 patients (14.5%), and persistent aneurysm filling was seen in 65 patients (85.5%). Despite this, no patient presented with rebleeding from the target aneurysm. There was an excellent clinical outcome in 62 patients (81.6%), who had a 90-day modified Rankin Scale score of 0-2. Among the 71 survivors, total or near-total occlusion was observed in 64/67 patients (95.5%) with a 3- to 6-month angiographic follow-up and in all cases evaluated at 12 months. Five patients (6.6%) died during follow-up for reasons unrelated to the procedure or new hemorrhage. CONCLUSIONS: Flow diversion is an effective therapeutic strategy for the management of select acutely ruptured aneurysms. Despite low rates of immediate aneurysm occlusion after FDS implantation, the device exerts an important protective effect. The authors' experience confirmed no aneurysm rerupture, high rates of delayed complete occlusion, and complication rates that compare favorably with the rates obtained using other techniques.

Acquisition of Basic Microsurgical Skills Using Low-Cost, Readily Available Models: The Orange Model.

BACKGROUND: Attainment of basic microsurgical skills in neurosurgery presents a departmental challenge worldwide. Models for teaching are either not readily available or expensive and are incompatible with a resident's busy schedule, requiring lengthy and proper setup. We present a model and a set of measurable tasks, based on a fruit (orange) that is cheap, easy to set up instantly when desired, and useful for training of basic microsurgical skills. METHODS: Basic microsurgical skills were identified, necessitating hand-eye coordination working with the microscope. The goal was to dissect an orange segment while preserving adjacent segments. Assessment was based on the number of side tears and task completion duration. The task was repeated in a sequential manner (n = 10), for validation purposes, for 3 operators at different seniority levels. RESULTS: An improvement in the number of side tears (mean of 12.66 ± 9.01 in the first trial vs. 4 ± 4.35 in the 10th trial, P < 0.01), as well as duration of time required for task completion (mean initial duration of 28:16 ± 19:00 minutes to a duration of 16:33 ± 10:50 minutes in the last attempt, P < 0.01), was observed. Daily practice scores and time gradually improved, and the seniority level of operators was correlated with scoring between individuals. CONCLUSIONS: The orange model is an easily accessible, cheap model that enables the acquisition of basic microneurosurgical skills. In this work, we validated and defined reproducible tasks that can be scored and tracked, correlated with operator's proficiency and experience. This model can be incorporated into a resident's workflow environment and provides a platform for attainment of elementary microsurgical skills for neurosurgical residents.

The oblique occipital sinus - implications in posterior fossa approaches.

The retrosigmoid craniotomy is the standard approach to resect pathologies in the cerebellopontine angle (CPA). Following the craniotomy, the dura mater is opened in the inferolateral direction and the basal cistern arachnoid is dissected in order to release pressure by the outflow of cerebrospinal fluid (CSF) from the foramen magnum, so that the CPA compartment can be approached with minimal retraction of the cerebellum. We report two patients, both with vestibular schwannoma, in whom preoperative magnetic resonance imaging (MRI) revealed unusual large oblique occipital sinus (OOS) draining laterally into the sigmoid sinus - jugular bulb junction. The sinuses were preserved intact while dura mater was opened for CSF release. Careful preoperative imaging is essential prior to posterior fossa lesions approaches in order to evaluate the persistency of an OOS, especially in a retrosigmoid approach. Inadvertent OOS damage might result in, not only significant bleeding during dural opening, but also air embolism or venous hypertension, if the contralateral sigmoid sinus is small or absent.

Spontaneous symptomatic orbital meningoencephalocele in an adult patient. Case report and review of the literature.

Symptomatic spontaneous meningoencephalocele (MEC) is a very rare entity in adults and there have been no reported cases of spontaneous MEC through the orbital roof in an adult. We report a 41-year-old woman who presented with a left eyelid swelling for several weeks without any history of trauma. Brain magnetic resonance imaging (MRI) showed a MEC through the orbital roof causing a significant blepharocele in this young patient. Supraorbital craniotomy was performed to repair the bone defect. The symptoms resolved immediately after surgery. Even though blepharocele is a rare manifestation of spontaneous orbital MEC it should be considered in the differential diagnosis for appropriate surgical management.

CPA Epidermoid Cyst with Rare Anatomic Variant: Anterior Inferior Cerebellar Artery Embedded in the Subarcuate Fossa: Operative Video and Technical Nuances.

Intracranial epidermoid cysts are considered benign tumors with a good general prognosis; however, their radical removal, including tumor capsule, is associated with significant morbidity, especially when the capsule is attached to neurovascular structures. We show an operative video describing main steps and surgical nuances in the resection of a large right cerebellopontine angle (CPA) epidermoid cyst in a 42-year-old male patient who presented with intractable trigeminal neuralgia. Craniectomy was performed to exposure the transverse-sigmoid sinus junction. A mold for a polymethylmethacrylate (PMMA) bone flap was built before opening the dura to avoid potentially neurotoxic effects on the cerebellum. The video illustrates the management of the rare anatomical variant of the anterior inferior cerebellar artery (AICA). Its loop was embedded in the dura, covering the subarcuate fossa where it gives off the subarcuate artery. Near total removal of the epidermoid cyst was achieved, leaving only a tiny capsule remnant adhering to the abducens nerve. Postoperatively the patient's trigeminal neuralgia was fully relieved and medications were discontinued. The patient's hearing was preserved per audiometry at the preoperative level (Gardner-Robertson II). Postoperative magnetic resonance imaging (MRI) revealed no signs of residual tumor. In this case, it was not possible to obtain optimal surgical exposure of the CPA without handling a rare anatomical anomaly of the AICA in the dura of the subarcuate fossa, which demanded coagulation and transection of the subarcuate artery and transposition of AICA with the dural cuff. This manipulation enabled optimal surgical removal of the epidermoid and didn't cause any neurological deficit. The link to the video can be found at: https://youtu.be/lLZqBHlu-uA .

Medulla oblongata cavernoma removal through a lazy far lateral approach: operative video and technical nuances.

Removal of brainstem cavernous malformation remains a surgical challenge. We present a case of a 63-year-old female who was diagnosed with a large cavernoma located in the medulla oblongata. The patient suffered three episodes of brainstem bleeding resulting in significant neurological deficits (hemiparesis, dysphagia, and dysarthria). It was decided to remove the cavernoma through a left-sided modified far lateral approach.3 The operative video demonstrates the surgical steps and nuances of a complete removal of this complex medulla oblongata cavernous malformation. Total resection was achieved without complications. Postoperative MRI revealed no signs of residual cavernoma with clinical improvement. The video can be found here: https://youtu.be/BTtMvvLMOFM.