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.

Transcallosal-Transchoroidal Fissure Approach for Midbrain and Thalamic Cavernous Malformations: 2-Dimensional Operative Video.

INDICATIONS CORRIDOR AND LIMITS OF EXPOSURE: Cavernous malformations of the third ventricle arise from the medial thalamus and/or periaqueductal midbrain. Microsurgical resection is indicated when the lifetime risk of hemorrhage outweighs the surgical risks. ANATOMIC ESSENTIALS NEED FOR PREOPERATIVE PLANNING AND ASSESSMENT: superior sagittal sinus, callosomarginal and pericallosal arteries, corpus callosum, foramen of Monro, choroidal fissure, fornix, thalamostriate veins, internal cerebral veins (ICVs), velum interpositum, and thalamus. ESSENTIAL STEPS OF THE PROCEDURE: The patient consents to the procedure. With the patient supine, the head is turned 90° and laterally flexed 45°. A bifrontal craniotomy positioned two-thirds anterior and one-third posterior to the coronal suture is performed. The interhemispheric fissure is opened, and a 2-cm corpus callosotomy is performed. Choroid plexus cauterization exposes the choroidal fissure. Sharp division of the taenia fornicea opens the velum interpositum, where the thalamostriate vein can be followed around the venous angle to the ICV. The anterior septal vein may be divided to communicate between the foramen of Monro and choroidal fissure. Dissection between the ICVs opens the velum interpositum into the third ventricle. PITFALLS/AVOIDANCE OF COMPLICATIONS: Frontal or deep vein occlusion causes venous infarction, and dissection on the nondominant hemisphere is preferred. Other complications include arterial infarction, fornix injury from choroidal fissure dissection or forniceal retraction, and thalamic or midbrain injury during lesion resection. VARIANTS AND INDICATIONS FOR THEIR USE: The contralateral choroidal fissure is used for low-lying medial thalamic and midbrain lesions. The ipsilateral choroidal fissure is used for high-lying or large lesions extending laterally. Transchoroidal approaches are not needed for superior (transcallosal only) or anterior (contralateral transcallosal-contralateral transforaminal) thalamic lesions. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Infragalenic triangle as a gateway to dorsal midbrain and posteromedial thalamic lesions: descriptive and quantitative analysis of microsurgical anatomy.

OBJECTIVE: Anatomical triangles provide neurosurgeons with the specificity required to access deep targets, supplementing more general instructions, such as craniotomy and approach. The infragalenic triangle (IGT), bordered by the basal vein of Rosenthal (BVR), precentral cerebellar vein (PCV), and the quadrangular lobule of the cerebellum, is one of a system of anatomical triangles recently introduced to guide dissection to brainstem cavernous malformations and has not been described in detail. This study aimed to quantitatively analyze the anatomical parameters of the IGT and present key nuances for its microsurgical use. METHODS: A midline supracerebellar infratentorial (SCIT) approach through a torcular craniotomy was performed on 5 cadaveric heads, and the IGT was identified in each specimen bilaterally. Anatomical measurements were obtained with point coordinates collected using neuronavigation. Three cadaveric brains were used to illustrate relevant brainstem anatomy, and 3D virtual modeling was used to simulate various perspectives of the IGT through different approach angles. In addition, 2 illustrative surgical cases are presented. RESULTS: The longest edge of the IGT was the lateral edge formed by the BVR (mean ± SD length 19.1 ± 2.3 mm), and the shortest edge was the medial edge formed by the PCV (13.9 ± 3.6 mm). The mean surface area of the IGT was 110 ± 34.2 mm2 in the standard exposure. Full expansion of all 3 edges (arachnoid dissection, mobilization, and retraction) resulted in a mean area of 226.0 ± 48.8 mm2 and a 2.5-times increase in surface area exposure of deep structures (e.g., brainstem and thalamus). Thus, almost the entire tectal plate and its relevant safe entry zones can be exposed through an expanded unilateral IGT except for the contralateral inferior colliculus, access to which is usually hindered by PCV tributaries. Exposure of bilateral IGTs may be required to resect larger midline lesions to increase surgical maneuverability or to access the contralateral pulvinar. CONCLUSIONS: The IGT provides a safe access route to the dorsal midbrain and reliable intraoperative guidance in the deep and complex anatomy of the posterior tentorial incisura. Its potential for expansion makes it a versatile anatomical corridor not only for intrinsic brainstem lesions but also for tumors and vascular malformations of the pineal region, dorsal midbrain, and posteromedial thalamus.

Endoscopically assisted presigmoid retrolabyrinthine approach to the lateral mesencephalic sulcus: a cadaveric study with comparison to the variant supracerebellar infratentorial approaches.

The supracerebellar infratentorial (SCIT) approach is commonly used to gain access to the lateral mesencephalic sulcus (LMS), which has been established as a safe entry point into the posterolateral midbrain. This study describes a lateral variant of the SCIT approach, the supreme-lateral SCIT approach, for accessing the LMS through the presigmoid retrolabyrinthine craniectomy and quantitatively compares this approach with the paramedian and extreme-lateral SCIT approaches. Anatomical dissections were performed in four cadaveric heads. In each head, the supreme-lateral SCIT approach was established on one side, following a detailed description of each step, whereas the paramedian and supreme-lateral SCIT approaches were established on the other side. Quantitative measurements of the exposed posterolateral midbrain, the angles of LMS entry, and the depth of surgical corridors were recorded and compared between the three SCIT approach variants. The supreme-lateral (67.70 ± 23.14 mm2) and extreme-lateral (70.83 ± 24.99 mm2) SCIT approaches resulted in larger areas of exposure anterior to the LMS than the paramedian SCIT approach (38.61 ± 9.84 mm2); the supreme-lateral SCIT approach resulted in a significantly smaller area of exposure posterior to the LMS (65.24 ± 6.81 mm2) than the other two variants (paramedian = 162.75 ± 31.98 mm2; extreme-lateral = 143.10 ± 23.26 mm2; both P < .001). Moreover, the supreme-lateral SCIT approach resulted in a surgical corridor with a shallower depth and a smaller angle relative to the horizontal plane than the other two variants. The supreme-lateral SCIT approach is a more lateral approach than the extreme-lateral SCIT approach, providing a subtemporal approach with direct LMS visualization. The supreme-lateral SCIT offers the benefits of both subtemporal and SCIT approaches and represents a suitable option for the management of selected midbrain pathologies.

Resection of Quadrigeminal Midbrain Cavernous Malformation Using the Supracollicular Safe Entry Zone.

Brainstem cavernous malformations (BSCMs) are rare and challenging neurosurgical lesions that demand a sophisticated and nuanced strategy for resection. A key element of surgical planning for BSCM resection is brainstem safe entry zones, a set of neuroanatomically defined locations where a pial resection can be executed with minimal risk to the adjacent central nervous system tracts and nuclei.1-5 Quadrigeminal BSCMs are particularly unusual and can be accessed via the supra-, inter-, or infracollicular safe entry zones.2,4,5 We report a unique demonstration of the supracollicular safe entry zone for the resection of a symptomatic hemorrhagic quadrigeminal plate BSCM. A man in his early 60s presented with transient hearing loss and visual dysfunction. A right quadrigeminal midbrain cavernous malformation was identified on magnetic resonance imaging. Surgical resection was performed with the patient in the sitting position. A bipedicular suboccipital flap, torcular craniotomy, and midline supracerebellar infratentorial approach were used. The lesion itself was accessed via the supracollicular safe entry zone, where pial hemosiderin staining was also encountered, using a linear transverse incision just above the right superior colliculus. Gross total resection was achieved, and the patient recovered from surgery with no new neurologic deficits (Video 1).

A system of anatomical triangles defining dissection routes to brainstem cavernous malformations: definitions and application to a cohort of 183 patients.

OBJECTIVE: Anatomical triangles defined by intersecting neurovascular structures delineate surgical routes to pathological targets and guide neurosurgeons during dissection steps. Collections or systems of anatomical triangles have been integrated into skull base surgery to help surgeons navigate complex regions such as the cavernous sinus. The authors present a system of triangles specifically intended for resection of brainstem cavernous malformations (BSCMs). This system of triangles is complementary to the authors' BSCM taxonomy that defines dissection routes to these lesions. METHODS: The anatomical triangle through which a BSCM was resected microsurgically was determined for the patients treated during a 23-year period who had both brain MRI and intraoperative photographs or videos available for review. RESULTS: Of 183 patients who met the inclusion criteria, 50 had midbrain lesions (27%), 102 had pontine lesions (56%), and 31 had medullary lesions (17%). The craniotomies used to resect these BSCMs included the extended retrosigmoid (66 [36.1%]), midline suboccipital (46 [25.1%]), far lateral (30 [16.4%]), pterional/orbitozygomatic (17 [9.3%]), torcular (8 [4.4%]), and lateral suboccipital (8 [4.4%]) approaches. The anatomical triangles through which the BSCMs were most frequently resected were the interlobular (37 [20.2%]), vallecular (32 [17.5%]), vagoaccessory (30 [16.4%]), supracerebellar-infratrochlear (16 [8.7%]), subtonsillar (14 [7.7%]), oculomotor-tentorial (11 [6.0%]), infragalenic (8 [4.4%]), and supracerebellar-supratrochlear (8 [4.4%]) triangles. New but infrequently used triangles included the vertebrobasilar junctional (1 [0.5%]), supratrigeminal (3 [1.6%]), and infratrigeminal (5 [2.7%]) triangles. Overall, 15 BSCM subtypes were exposed through 6 craniotomies, and the approach was redirected to the BSCM by one of the 14 triangles paired with the BSCM subtype. CONCLUSIONS: A system of BSCM triangles, including 9 newly defined triangles, was introduced to guide dissection to these lesions. The use of an anatomical triangle better defines the pathway taken through the craniotomy to the lesion and refines the conceptualization of surgical approaches. The triangle concept and the BSCM triangle system increase the precision of dissection through subarachnoid corridors, enhance microsurgical execution, and potentially improve patient outcomes.

Therapeutic functions of astrocytes to treat α-synuclein pathology in Parkinson's disease.

Intraneuronal inclusions of misfolded α-synuclein (α-syn) and prion-like spread of the pathologic α-syn contribute to progressive neuronal death in Parkinson's disease (PD). Despite the pathologic significance, no efficient therapeutic intervention targeting α-synucleinopathy has been developed. In this study, we provide evidence that astrocytes, especially those cultured from the ventral midbrain (VM), show therapeutic potential to alleviate α-syn pathology in multiple in vitro and in vivo α-synucleinopathic models. Regulation of neuronal α-syn proteostasis underlies the therapeutic function of astrocytes. Specifically, VM-derived astrocytes inhibited neuronal α-syn aggregation and transmission in a paracrine manner by correcting not only intraneuronal oxidative and mitochondrial stresses but also extracellular inflammatory environments, in which α-syn proteins are prone to pathologic misfolding. The astrocyte-derived paracrine factors also promoted disassembly of extracellular α-syn aggregates. In addition to the aggregated form of α-syn, VM astrocytes reduced total α-syn protein loads both by actively scavenging extracellular α-syn fibrils and by a paracrine stimulation of neuronal autophagic clearance of α-syn. Transplantation of VM astrocytes into the midbrain of PD model mice alleviated α-syn pathology and protected the midbrain dopamine neurons from neurodegeneration. We further showed that cografting of VM astrocytes could be exploited in stem cell-based therapy for PD, in which host-to-graft transmission of α-syn pathology remains a critical concern for long-term cell therapeutic effects.

Lateral Supracerebellar Infratentorial Approach for Superior Oblique Myokymia: A Case Series.

BACKGROUND: Few reports have shown that superior oblique myokymia (SOM) may result from vascular compression of the trochlear nerve and may be curable using microvascular decompression (MVD). OBJECTIVE: To report the clinical characteristics and surgical treatment of 2 cases of SOM and provide a review of the related literature. METHODS: Two patients with SOM were treated using MVD with the lateral supracerebellar infratentorial approach. The patients underwent diagnostic magnetic resonance imaging and three-dimensional fusion imaging preoperatively. A lateral suboccipital craniotomy was performed in the park-bench position. The trochlear nerve and branches of the superior cerebellar artery were confirmed after opening the cerebellomesencephalic fissure over the tentorial surface of the cerebellum. The vessel, which compressed the root exit zone of the trochlear nerve, was transposed far from the nerve and attached to the surface of the midbrain using Teflon felt and fibrin glue. RESULTS: The first case showed compression on both the ventral and rostral sides of the trochlear nerve root exit zone, and the second showed compression only on the ventral side. Large bridging veins on the tentorial surface of the cerebellum complicated the approach in the second case. Postoperatively, both patients had immediate and complete resolution of symptoms without recurrence at the 24-mo and 17-mo follow-ups, respectively. Five previous reports described the complete resolution of SOM after MVD. CONCLUSION: A presentation of an intermittent fluttering ocular sensation should prompt magnetic resonance imaging for ipsilateral trochlear nerve compression. The lateral supracerebellar infratentorial approach allows safe and efficacious MVD for SOM.

Microsurgical management of midbrain cavernous malformations: does lesion depth influence the outcome?

BACKGROUND: The purpose of this study was to clarify whether the intrinsic depth of midbrain cavernous malformations (MCMs) influenced the surgical outcome. METHODS: The authors conducted a retrospective study of 76 consecutive patients who underwent microsurgical resection of a MCM. The vascular lesions were categorized into 4 distinct groups based on how these lesions had altered the brainstem surface. Additionally, it was verified whether the actual aspect of the brainstem surface could be predicted only by evaluating the pertinent preoperative MRI slices. Clinical outcome was assessed by determining the modified Rankin Scale Score (mRS) before and after surgery. RESULTS: Twenty-three MCMs (30.3%) were located deeply within the midbrain. The overlying midbrain surface appeared to be normal (group nl). In 33 patients (43.4%), the midbrain surface showed only a yellowish discoloration (group yw). In another 14 individuals (18.4%), the midbrain surface was distorted by the underlying MCM and bulging out while the vascular lesion still remained covered by a thin parenchymal layer (group bg). In the smallest group comprising 6 patients (7.9%), the exophytic MCM had disrupted the midbrain surface and was clearly visible at microsurgical exposure (group ex). The mean mRS decreased in the group nl from 1.43 preoperatively to 0.61 at follow-up. CONCLUSION: This study demonstrates in a large patient population that a deep intrinsic MCM location is not necessarily associated with an unfavorable clinical outcome after microsurgical lesionectomy. Predicting the aspect of the midbrain surface by evaluating preoperative MR images alone was not sufficiently reliable.

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.

The Paramedian Supracerebellar Approach: A Less Disruptive and More Flexible Operative Corridor to the Pineal and Posterior Upper Brainstem Regions.

The paramedian supracerebellar craniotomy is an underrecognized route to the midline and paramedian regions of the upper posterior brainstem. As compared with its midline supracerebellar counterpart, this less disruptive approach preserves the majority of the midline bridging veins, requires less cerebellar retraction, and is significantly more efficient. In this offering, I will emphasize the realities of this flexible route and its remarkable advantages in reaching deep-seated lesions.

Endoscopic Endonasal Transclival Approach to Spontaneous Hypertensive Brainstem Hemorrhage.

Surgical management of spontaneous hypertensive brainstem hemorrhage remains a challenge for neurosurgeons, especially when the hemorrhage is located the ventral brainstem. Recently endoscopic endonasal approach has been applied for resection of ventral brainstem lesions, though no published literature has explored its utility in treating brainstem hemorrhage. Here we reported a successful evacuation of severe hypertensive brainstem hemorrhage through endoscopic endonasal transclival approach. A 37 years-old male with a 5-year history of uncontrolled hypertension was brought to the Emergency Department with sudden vomiting, limb convulsions, and loss of consciousness for 2 hours. Computed tomography demonstrated a hemorrhage measuring 2.5 × 2.2 cm in the ventral midbrain and pontine. He presented with a Glasgow coma scale (GCS) score of 3 and disrupted vitals, and was intubated in the Emergency Department. Considering the ventral location of the hemorrhage and the need for emergent surgical decompression, an endoscopic endonasal approach was applied. Evacuation of the brainstem hemorrhage was achieved and his spontaneous respiration improved immediately after surgery. He was weaned off the ventilator and extubated on postoperative day 1, along with an improved GCS score of 5 (E2V1M2). At 1 month postoperatively his GCS score improved to 11 (E4V2M5) and he is currently under rehabilitation. Endoscopic endonasal approach is a feasible alternative for emergent surgery of ventrally located brainstem hemorrhage in carefully selected cases by providing direct visualization of the area and a good working angle, which facilitate evacuation of the hemorrhage with minimal damage to the brainstem.

Endoscopic Paramedian Sitting Craniotomy for Resection of a Dorsal Midbrain Cavernous Malformation: 2-Dimensional Operative Video.

This case video demonstrates the surgical technique for resection of a cavernous malformation in the right dorsal midbrain. This video was deemed exempt by the University of Pennsylvania Institutional Review Board (IRB), as it is considered a case report, which does not require IRB approval or patient consent. The patient was a 57-yr-old male with cerebral cavernous malformation syndrome with multiple intracranial cavernomas. He was noticed to have progressively slowed speech with worsening confusion and drowsiness. On exam, the patient exhibited worsening in swallowing and upward gaze paresis, secondary to Parinaud phenomena. The patient was treated with microsurgical resection, utilizing stereotactic navigation and intraoperative neurophysiologic monitoring. Intraoperative view provided in the video was captured using a Karl Storz Endoscope (Karl Storz SE & Co KG, Tuttlingen, Germany). Postoperatively, the patient had worsening double vision, which improved on follow-up, in addition to improvement in sensorium and swallowing.

Subtemporal Transtentorial Approach in Mesencephalic and Perimesencephalic Lesions in Children-A Series of 20 Patients.

BACKGROUND: Midbrain and surrounding areas are among the most difficult regions to surgically approach in neurosurgery. The subtemporal approach is a well-known neurosurgical approach that is rarely described in children. OBJECTIVE: To assess the feasibility, advantages, and disadvantages of subtemporal approach in children. METHODS: A total of 20 pediatric patients with intra-axial tumors involving the lateral midbrain or superior cerebellar peduncle or with extra-axial tumors in the middle incisural space/Meckel cave underwent subtemporal transtentorial approaches with the aim to remove (16 cases) or biopsy (4 cases) their lesions. These cases were retrospectively reviewed and the surgical approach described. RESULTS: Total resection was achieved in 11 patients. In the 4 patients who underwent biopsies, a diagnosis was obtained. A total of 5 patients presented non-neoplastic lesions (dermoid tumors or cavernomas). A total of 9 patients harbored low-grade tumors and 6 high-grade tumors. Patients with low-grade tumors and non-neoplastic lesions are all alive with no evidence of disease or stable residue. Four patients affected by high grade tumors died. No patient suffered permanent neurological deficits related to the surgical approach. Three patients presented temporary neurological deficits following the procedure: one case of strabismus, one case of aphasia and hemiparesis, secondary to delayed, transient thrombosis of the Labbé vein, and 1 case of trigeminal neuralgia. CONCLUSION: The subtemporal approach represents a feasible approach for mesencephalic and perimesencephalic lesions in children. It provides an ample and direct access, with excellent outcomes and acceptable postoperative morbidity.

Supracerebellar-Infratrochlear Approach for Midbrain Cavernoma: 3-Dimensional Operative Video.

Gravity retraction is an underutilized adjunct in neurosurgery. Gravity is gentler than retractor blades; it does not cause brain edema or injury, and it tends to open natural subarachnoidal plans to deep lesions.1-3 A good example of this is the supracerebellar infratrochlear approach4-7 in semisitting position for resection to a midbrain cavernous malformation. This approach was selected because the cavernous malformation was 1 mm under the lateral mesencephalic sulcus. The procedure was developed with the use of transesophageal ultrasound and physiological neuromonitoring. We present a 3-dimensional video of this surgery with all the tricks and details used in the procedure. The patient consented to the procedure and to publication of the photos and surgical video.