Microsurgical anatomy and approaches to thalamic gliomas. Part 2: Maximal safe resection of thalamic gliomas improves outcomes. A single-center experience.

OBJECTIVE: As presented in Part 1 of this series, thalamic gliomas (TGs) are deep-seated, difficult-to-access tumors surrounded by vital neurovascular structures. Given their high operative morbidity, TGs have historically been considered inoperable lesions. Although maximal safe resection (MSR) has become the treatment standard for lobar and even deep-seated mediobasal temporal and insular gliomas, the eloquent location of TGs has precluded this management strategy, with biopsy and adjuvant treatment being the mainstay. The authors hypothesized that MSR can be achieved with low morbidity and mortality for TGs, thus resulting in improved outcomes. METHODS: A retrospective single-center study was performed on all TG patients from 2006 to 2020. Clinical, imaging, and pathology reports were obtained. Univariate and multivariate analyses were performed to determine prognostic variables. Case examples illustrate various approaches and the rationale for staging resections of more complex TGs. RESULTS: A total of 42 patients (26 males, 16 females), among them 12 pediatric (29%) cases, were included. Their mean age was 36.0 ± 21.4 (median 30, range 3-73) years. The median maximal tumor diameter was 45 (range 19-70) mm. Eighteen patients (43%) had a prior stereotactic needle tumor biopsy, with the ultimate diagnosis changed for 7 patients (39%) following microsurgical resection. The most common surgical approaches were transtemporal (29%), anterior interhemispheric transcallosal (29%), and superior parietal lobule (25%). Overall, the combined subtotal and gross-total resection rate was 95% (n = 40). Low-grade gliomas (LGGs; grades I and II) comprised one-third of the group, whereas half of the patients had glioblastoma multiforme. There were no operative mortalities. Although temporary postoperative motor deficits were observed in 12 patients (28.6%), all improved during the early postoperative period except 1 (2.4%), who had mild residual hemiparesis. Two patients required CSF diversion for hydrocephalus. The 2-year overall survival rate was 90% for LGG patients and 15% for high-grade glioma (HGG) patients. Multivariate analysis revealed that histological grade, age, and extent of resection were independent prognostic factors associated with survival. CONCLUSIONS: Management of TGs is challenging, with resection avoided by many, if not most, neurosurgeons, especially for HGGs. The results reported here demonstrate improved outcomes with resection, particularly in younger LGG patients. The authors therefore advocate for MSR for a select cohort of TG patients using carefully planned surgical approaches, contemporary intraoperative adjuncts, and meticulous microsurgical techniques.

Ovoid Foramen Magnum Shape is Associated with Increased Complications and Decreased Extent of Resection for Anterolateral Foramen Magnum Meningiomas.

Background Antero-laterally located meningiomas of the foramen magnum (FM) pose significant surgical resection challenges. The effect of FM shape on surgical resection of FM meningiomas has not been previously studied. The present study investigates how FM shape effects the extent of tumor resection and complication rates in antero-lateral FM meningiomas. Materials and Methods This retrospective study included 16 consecutive patients with antero-lateral FM meningiomas operated on by a single surgeon. FMs were classified as ovoid ( n = 8) and nonovoid ( n = 8) using radiographic evaluation. Results Sixteen patients were examined: seven males and nine females (mean age of 58.5, and range of 29 to 81 years). Gross total resection was achieved in 81% of patients, with tumor encased vertebral arteries in 44%. Patient characteristics were similar including age, sex, preoperative tumor volume, relationship of vertebral artery with tumor, preoperative Karnofsky performance score (KPS), symptom duration, and presence of lower cranial nerve symptoms. The ovoid FM group had lower volumetric extents of resection without statistical significance (93 ± 10 vs. 100 ± 0%, p = 0.069), more intraoperative blood loss (319 ± 75 vs. 219 ± 75 mL, p = 0.019), more complications per patient (1.9 ± 1.8 vs. 0.3 ± 0.4, p = 0.039), and poorer postoperative KPS (80 ± 21 vs. 96 ± 5, p = 0.007). Hypoglossal nerve palsy was more frequent in the ovoid FM group (38 vs. 13%). Conclusion This is the first study demonstrating that ovoid FMs may pose surgical challenges, poorer operative outcomes, and lower rates of extent of resection. Preoperative radiological investigation including morphometric FM measurement to determine if FMs are ovoid or nonovoid can improve surgical planning and complication avoidance.

Frontal lobe intracerebral schwannoma mimicking metastatic lesion in a patient with papillary thyroid carcinoma.

Intracerebral schwannomas are quite rare. Due to their rarity and lack of pathognomonic imaging features, intracerebral schwannoma may be overlooked in the initial differential diagnosis of an intra-axial mass with heterogeneous ring enhancement, such as a high-grade glioma, metastasis or lymphoma. Here, we present a 21-year-old woman with prior diagnosis of papillary thyroid carcinoma and recent history of seizures who had a heterogeneously ring-enhancing left frontal lobe mass. Our presumptive diagnosis was a metastatic tumor since she had a history of thyroid cancer. Because of uncertainty in preoperative differential diagnosis, the decision was made to proceed with excisional biopsy of the tumor via craniotomy. She underwent uneventful gross total resection of the tumor that histopathology revealed as an intracerebral schwannoma.

The Tonsillouvular Fissure Approach: Access to Dorsal and Lateral Aspects of the Fourth Ventricle.

OBJECTIVE: Although approaches to the fourth ventricle (FV) have been studied well, approaches to the lesions located in the dorsal and lateral aspects of the FV have not been shown in anatomic or clinical studies. The aim of this study is to show for the first time in the literature the tonsillouvular fissure approach (TUFA) in anatomic dissections and its use in surgical series. METHODS: For anatomic studies, 4 formalin-fixed human cadaveric heads infused with colored silicone and 10 cerebellar specimens were dissected in a stepwise manner. Records of 12 patients operated on via TUFA were also retrospectively reviewed. RESULTS: Neurosurgical anatomy and critical steps of TUFA were described in detail. Among 12 patients with lesions around the FV (4 cavernous malformation, 2 pilocytic astrocytoma, 2 hemangioblastoma, 1 B-cell lymphoma, 1 metastatic papillary carcinoma, 1 dermoid cyst, and 1 arteriovenous malformation), 11 gross total and 1 subtotal resection were achieved via TUFA without any mortality or morbidity. Comparative analyses of 4 surgical approaches to FV (TUFA, telovelar/cerebellomedullary fissure, supratonsillar/tonsillobiventral lobule fissure, and transvermian approaches) were also presented. CONCLUSIONS: TUFA provides a direct route and excellent surgical view to lesions around the FV, particularly on dorsal and lateral aspects, inferior vermis, and medial part of the dentate nucleus and cerebellar peduncles. It minimizes traversing the normal cerebellar tissue compared with a transvermian approach.

Endoscopic Endonasal Transclival Resection of the Upper Clival Meningioma.

In recent years, endoscope use for the excision of brain stem lesions or those localized to the anterior part of the brain stem has started. In this paper, a case of upper clival meningioma resected through the endoscopic endonasal transclival route has been presented with illustrations, and live surgery videos demonstrating the surgery step-by-step. A 35-year-old male patient presented with dysphagia and impaired consciousness. Magnetic resonance imaging (MRI) showed a mass lesion with a wide base located at the clivus and anterior part of brain stem. Following surgical preparations, the mass was resected through the endoscopic endonasal transclival route. Presigmoid and lateral suboccipital approaches are the most popular methods for petroclival tumors. However, the disadvantages are restricted surgical corridor to reach the anterior lesions of the brain stem, and surgical manipulations that should be performed between the cranial nerves to gain access into the pathological structures. The alternative endoscopic endonasal transclival method, which is preferred to reach these lesions anteriorly, does not have these disadvantages. The endoscopic endonasal transclival route is suitable for meningiomas located in the retroclival area. With advances in endoscopic technology and surgical experience, full endoscopic endonasal transclival approach will be an alternative for the treatment of posterior circulation aneurysms, most of the extradural and intradural lesions of the ventral aspect of brain stem, and neuralgia secondary to vascular compression.

Late Postoperative Rhinological Complications After Microscopic Transnasal Hypophysectomy.

AIM: Major complications of microscopic transnasal hypophyseal surgery (MTHS), such as cerebrospinal fluid rhinorrhea, carotid injury, and optic nerve injury, are very rare. However, late rhinological complications can be ignored because they are a minor cause of morbidity compared with major complications. In this study, we extensively examined postoperative rhinological complications in patients who underwent MTHS for pituitary adenoma. MATERIAL AND METHODS: Thirty-one patients diagnosed with pituitary adenoma, who underwent MTHS and whose preoperative nasal examinations were recorded between January 2007 and January 2014, were included in the study. A detailed rhinological examination of the patients was performed. RESULTS: A total of 12 of 31 patients (38.7%) had a perforated nasal septum, and synechiae were detected in the nasal cavities of 13 patients (42%). Anosmia occurred in three patients, hyposmia in two, and a nasal tip deflection and saddle nose deformity were detected in one patient with a perforated nasal septum. No perinasal loss of sense, oronasal fistula, or purulent secretion in the nasal cavity was found in any patient. CONCLUSION: The nasal structures, particularly the nasal septum mucosa, should be treated gently during MTHS. The nasal stages of the operation should be performed with the help of an otolaryngologist until adequate experience is gained.