Subtemporal, Transapical, and Transcavernous Approach to Clip Low-Lying Basilar Tip Aneurysm: 2-Dimensional Operative Video

Basilar tip aneurysm clipping is technically challenging because of the depth of operative corridor, rarity in presentation, and important perforators supplying deep, critical structures. Two major approaches to basilar tip aneurysms include (1) a frontotemporal (transorbital) trans-sylvian approach for most aneurysms and (2) a modified subtemporal approach for aneurysms with low-lying necks. A 53-yr-old woman presented to our institution with a large unruptured basilar tip aneurysm notable for a low, broad neck (6.4 mm). After discussion of risks and benefits of endovascular vs surgical options, the patient consented to operative intervention. She underwent a right frontotemporal craniotomy with zygomatic osteotomy, intradural petrous apicectomy, elective sectioning of the fourth cranial nerve (CN IV), and intracavernous removal of the dorsum sellae and posterior clinoid process to provide more space for aneurysm dissection. After temporary clipping of the basilar artery, the perforating arteries were dissected free from the aneurysm and the aneurysm occluded with 2 fenestrated clips. Important technical nuances of the approach include (1) achieving ample working room for temporary occlusion aneurysm dissection, (2) careful dissection of the perforators and contralateral P1, and (3) utilization of 2 fenestrated clips to accommodate and preserve the ipsilateral P1 segment. Postoperative angiogram showed complete aneur-ysmal occlusion. Postoperatively, the patient demonstrated mild cognitive impairment and a right CN IV palsy. At 6-wk follow-up, cognition recovered to normalcy. More recently, at 12-mo follow-up, the patient noted intermittent diplopia. Formal neuro-ophthalmologic assessment confirmed persistence of a CN IV palsy treated with prism lenses but no other neurological deficits.

Calcifying pseudoneoplasm of the neuraxis: A rare case involving the oculomotor nerve

Background: Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare entity which can occur at intracranial and spinal locations. Clinical presentation is due to local mass effect rather than tissue infiltration. Lesions causing significant symptoms or are showing radiological progression require surgical resection. Maximal surgical resection is considered curative for this non-neoplastic entity with only two cases of recurrence reported in the literature. Cranial nerve involvement is extremely rare and the presenting neurological deficit is unlikely to improve even with surgical intervention. Case Description: We describe a case of CAPNON at the right posterior clinoid process with involvement of the right oculomotor nerve in a 38-year-old male. Computed tomography demonstrated an amorphous mass which had intermediate to low T1 and T2 signal on magnetic resonance imaging. The oculomotor nerve was compressed with sign of atrophy. The patient underwent maximal surgical debulking for progressive symptoms of worsening pain and ophthalmoplegia. Postoperatively, the patient’s symptoms were stable but did not improve. Conclusion: Preoperative diagnosis of CAPNON is difficult due to its rarity and nonspecific clinical and radiological findings. Surgical resection is considered in cases with worsening symptoms, progression on serial imaging, or uncertain diagnosis. Relatively inaccessible lesions with little or no clinical symptoms can be observed.

Surgical implementation and efficacy of endoscopic endonasal extradural posterior clinoidectomy

OBJECTIVEThe endoscopic endonasal approach (EEA) for skull base tumors has become an important topic in recent years, but its use, merits, and demerits are still being debated. Herein, the authors describe the nuances and efficacy of the endoscopic endonasal extradural posterior clinoidectomy for maximal tumor exposure.METHODSThe surgical technique included extradural posterior clinoidectomy following lateral retraction of the paraclival internal carotid artery and extradural pituitary transposition. In cases with prominent posterior clinoid process, a midline sellar dura cut was added to facilitate extradural exposure. Forty-four consecutive patients, in whom this technique was performed between 2016 and 2018 at Osaka City University Hospital, were reviewed. The pathology included 19 craniopharyngiomas, 7 chordomas, 6 meningiomas, 6 pituitary adenomas, 4 chondrosarcomas, and 2 miscellaneous. Utilization and effectiveness of this approach were further demonstrated with neuroimaging.RESULTSExtradural posterior clinoidectomies were successfully applied in all patients without permanent neurovascular injury and with better maneuverability and greater resection rate of the tumors. Four patients experienced transient postoperative abducens nerve paresis, and 1 patient experienced transient postoperative oculomotor nerve paresis; however, the patients with deficits recovered within 3 months. On radiological examination, the surgical field was 2.2 times wider in cases with bilateral posterior clinoidectomy than in cases without posterior clinoidectomy.CONCLUSIONSThe extended EEA with extradural posterior clinoidectomy creates an extra working space and allows adequate accessibility with safe surgical maneuverability to remove tumors that extend behind the posterior clinoid and dorsum sellae.

Endonasal interdural pituitary transposition for resection of a posterior clinoid process enchondroma in a patient with Maffucci syndrome

Maffucci syndrome is an extremely rare disorder characterized by benign enchondromas, skeletal deformities, and cutaneous lesions composed of abnormal blood vessels. Enchondromas rarely arise in the cranial bones. Interdural pituitary transposition is an effective way to gain access to the posterior clinoid, without affecting the function of the pituitary gland. Here, the authors present a case of a posterior clinoid process enchondroma in a patient with Maffucci syndrome. The tumor was resected via an interdural pituitary transposition fashion. Four months postoperatively, the patient’s oculomotor function had recovered to normal and the function of the pituitary gland was preserved intact.The video can be found here: https://youtu.be/EYgVwVZuC4g.

Morphological Variation of Anterior Clinoid Process in Dry Human Skulls

Introduction: The anatomical relationship of the Anterior Clinoid Process (ACP) with its neighboring structures in the base of the skull is complex with different variations. Thus, study of its morphology is essential in defining and directing surgery. Objective: This study aims to investigate the anatomy of the anterior clinoid process and prevalence of Caroticoclinoid foramen (CCF) to highlight its variations. Methodology: The measurements were performed in 31 dry human skulls to define the structure of ACP, the presence of CCF and other relevant landmarks using digital Vernier Calipers. Results: The mean length, basal width and thickness of the right ACP was 9.88+/- 1.36 mm, 8.72+/-1.50 mm, and 5.21+/-1.83 mm respectively and that of the left was 10.30+/-1.47, 8.73+/-1.71, and 5.33+/-1.60 mm respectively. Paired t-test was used to compare the mean of these sides. Type III was the most common form of ACP for both the sides. Out of 31 skulls, CCF was observed in 12 (38.7%) skulls with 7 (22.6%) in right and 5 (16.13%) in left side. Distances between neighboring ACP’s, between Posterior Clinoid process (PCP), between ACP to Crista Galli (CG) and ACP to PCP were 24.41+/-2.32, 20.01+/-3.23, 31.6+/-2.20, and 8.30+/-3.10 mm respectively. Conclusion: This article highlights the detailed morphology of ACP. There is variation in relation to its dimensions across other studies. This study also explores the prevalence of CCF and parasellar landmarks in relation to ACP giving an idea of the exposure achievable during surgical approach of the region.

Surgical Nuances of Endoscopic Endonasal Upper Clivectomy for Radical Resection of Central Skull Base Tumors: Two-Dimensional Operative Videos

INTRODUCTION With routine endoscopic endonasal approach (EEA) for resection of skull base tumors, it is difficult to remove tumors that extend behind the posterior clinoid process (PCP) and dorsum sellae due to the limited exposure. Critical neurovascular structures (internal carotid artery, cavernous sinus, pituitary gland), PCP and dorsum sellae obstruct tumor visualization. Posterior clinoidectomy gives an excellent wider operative view and allows radical resection of tumors in the retrosellar area, prepontine and interpeduncular cisterns. We modified the endoscopic posterior clinoidectomy for safer endonasal extradural posterior clinoidectomy and applied it in 44 patients with parasellar and retrosellar tumors. This is the largest clinical series of endonasal extradural posterior clinoidectomy in which the clinical outcomes were evaluated. METHODS An extradural upper clivectomy (with complete posterior clinoidectomies) following lateral retraction of the paraclival internal carotid artery and extradural pituitary transposition were applied while preserving the blood supply and venous drainage of the pituitary gland. No violation to the cavernous sinuses. In cases with prominent posterior clinoid process, a midline sellar dura cut was added to facilitate its extradural exposure. Forty-four consecutive patients, in whom this technique was performed, between 2016 and 2018 at Osaka City University Hospital, were reviewed. The pathology included 19 craniopharyngiomas, 7 chordomas, 6 meningiomas, 6 pituitary adenomas, 4 chondrosarcomas, and 2 miscellaneous. Utilization and effectiveness of this approach were further demonstrated with neuroimaging. RESULTS On radiological examination, the surgical field was 2.2 times wider in cases with bilateral posterior clinoidectomies than in cases without posterior clinoidectomy. Upper clivectomies were successfully applied in all patients without permanent neurovascular injury, with better maneuverability and greater resection rate of the tumors. Four patients experienced transient postoperative abducens nerve paresis, and one patient experienced transient postoperative oculomotor nerve paresis; nevertheless, the deficits recovered within 3 mo. CONCLUSION The extended EEA with extradural upper clivectomy creates an extra-working space and allows adequate accessibility with safe surgical maneuverability to remove tumors that extend behind the posterior clinoid and dorsum sellae.

The Petroclinoid Ligament: Its Morphometrics, Relationships, Variations, and Suggestion for New Terminology

The anatomy and definition of the petroclinoid ligament (PCL) and its relationship with the abducens nerve are variably described. The goal of this study was to clarify the anatomy of the PCL and better elucidate its relationship with the abducens nerve. Thirty-six sides from 18 fresh-frozen adult cadaveric heads were used in this study. Specimens were all Caucasian and derived from 10 males and 8 females. The mean age at death was 79 years. Dissection of the PCL and abducens nerve was performed using a surgical microscope. The anterior and posterior attachments of the PCL, and position of the abducens nerve were noted. Subsequently, the width, thickness, and length of the ligament, and diameter of the abducens nerve were measured. Thirty-one sides (86.1%) were found to have a PCL, on two sides (5.6%), the PCL was ossified, and on three sides (8.3%), the PCL was absent. The width, thickness, and length of the PCL ranged from 0.54 to 3.39, 0.07 to 0.49, and 3.27 to 17.85 mm, respectively. No PCL had an anterior attachment onto the posterior clinoid process but rather, the clivus. Therefore, based on our findings, the PCL would be better described as the petroclival ligament.