Pituitary adenoma with oculomotor cistern extension: membranous anatomy and clinical application.

BACKGROUND: The anatomical basis of pituitary adenomas (PAs) with oculomotor cistern (OC) extension as a growth corridor is overlooked in the literature. In this paper, the authors use the technique of epoxy sheet plastination to study the membranous structure of the OC and validate the results by retrospective analysis of patients with OC extension. METHODS: Eighteen specimens were used to study the membranous anatomy surrounding the OC using the epoxy sheet plastination technique. Thirty-four patients with OC extension were retrospectively reviewed. RESULTS: The OC consisted of two thin membranous layers. The inner layer was extended by the arachnoid layer from the posterior fossa, and the lateral layer consisted of the dura mater sinking from the roof of the cavernous sinus. The oculomotor nerve is more likely to displace with a superolateral trajectory due to the weakness of the posterior dura and the relatively large space in the medial and posterior trajectories, which is consistent with the intraoperative observations. Among the anatomical factors that affect the PA by OC extension, we found that the relative position of the internal carotid artery (ICA) and posterior clinoid process may lead to the narrowing of the OC. Of 34 cases, 28 patients achieved total resection. Among 24 preoperative patients with oculomotor nerve palsy, 16 cases were relieved to varying degrees postoperatively. There was no ICA injury or severe intracranial infection found in any of the patients. CONCLUSIONS: Extension into the OC is influenced by two anatomical factors: a weak point in the dura in the posterior OC and a potential space beyond this region of the dura. Meticulous knowledge of the membranous anatomy in endoscopic endonasal surgery is required to safely and effectively resect PA with OC extension.

Malignant nerve sheath tumor of oculomotor nerve in a pediatric patient.

Malignant nerve sheath tumors are extremely rare pathologies. They tend to occur within peripheral nerves and have close association of neurofibromatosis disease. Here, we present the second case of MNST of oculomotor nerve in literature. The patient was a 2-year-old girl with left sided oculomotor nerve palsy. After resection, the patient immediately had chemotherapy and radiotherapy. One year after surgery disease progressed with extensive intracranial seedings, and she passed away.

Surgical anatomy and nuances of the expanded endonasal transdorsum sellae and posterior clinoidectomy approach to the interpeduncular and prepontine cisterns: a stepwise cadaveric dissection of various pituitary gland transpositions.

BACKGROUND: Excelsior knowledge of endoscopic anatomy and techniques to remove the natural barriers preventing full endonasal access to the interpeduncular and prepontine cisterns determines the ease of transposing the pituitary gland (hypophysiopexy) preserving the glandular function without manipulating the optic apparatus and the oculomotor nerves. METHODS: Throughout stepwise cadaveric dissections, we describe the expanded endonasal approach (EEA) to the interpeduncular and prepontine cisterns with special references to the intricate anatomy of the region and techniques for hypophysiopexy and posterior clinoidectomies. CONCLUSION: This article illustrates sellar-diaphragmatic dural incisions and various "pituitary gland transpositions" techniques performed via extradural (lifting the gland still covered by both dural layers), interdural (transcavernous), and intradural (between the medial wall of the cavernous sinus and the pituitary tunica) to access the prepontine and interpeduncular cisterns.

Combined supra-infrasellar approach to pituitary macroadenoma with oculomotor cistern extension: surgical strategy and experience.

BACKGROUND: Oculomotor cistern extension (OMCE) of pituitary adenoma through the oculomotor triangle may be one of the major characteristics of multi-lobulated adenoma. The OMCE may be hard to remove only through the endonasal approach. METHOD: We applied the simultaneous combined supra-infrasellar approach to remove pituitary adenoma with relatively large OMCE. Four (7.3%) of 55 consecutive patients with initially operated pituitary macroadenoma (> 10 mm) had OMCE. The combined supra-infrasellar approach was adopted in two cases with relatively large OMCE. RESULTS: The simultaneous combined supra-infrasellar approach was performed with the transcranial microscopic transsylvian anterior temporal approach and the nasal endoscopic approach. The medial main mass was removed through the nasal side. The lateral OMCE was also removed through the nasal side by pushing the tumor in the sellar direction from the transcranial side. The oculomotor nerve was confirmed with electrical nerve stimulation. The main medial mass and the OMCE were mostly removed in both cases. Remnant tumor in the cavernous sinus was treated by gamma knife radiosurgery. Endoscopic transsphenoidal removal was performed in the other two cases with relatively small OMCE. CONCLUSIONS: Pituitary macroadenomas with OMCE are a newly recognized form of progression with important implications for surgical strategy. The combined supra-infrasellar approach performed with the transcranial microscopic transsylvian anterior temporal approach using electrical nerve stimulation and the nasal endoscopic approach may be useful for this type of multi-lobulated pituitary adenoma.

Third nerve decompression by anterior petroclinoid ligament opening after clipping of posterior communicating artery aneurysm-How I do it.

BACKGROUND: Posterior communicating artery aneurysms sometimes present with partial or complete oculomotor nerve palsy, due to direct oculomotor nerve compression, irritation by subarachnoid blood, or both. Superiority of surgical clipping over endovascular coiling in terms of postoperative outcome is still controversial. METHOD: Direct oculomotor nerve decompression by opening of the anterior petroclinoid ligament during aneurysm clipping is performed as a simple and feasible surgical maneuver which allows to improve the decompression effect obtained by aneurysm exclusion. CONCLUSION: Anterior petroclinoid ligament opening permits to achieve a better oculomotor nerve decompression. Its efficiency on the recovery of the deficit needs to be proved by larger series.

Usefulness of intraoperative electromyographic monitoring of oculomotor and abducens nerves during skull base surgery.

BACKGROUND: Intraoperative neurophysiologic monitoring of the extraocular cranial nerve (EOCN) is not commonly performed because of technical difficulty and risk, reliability of the result and predictability of the postoperative function of the EOCN. METHODS: We performed oculomotor nerve (CN III) and abducens nerve (CN VI) intraoperative monitoring in patients with skull base surgery by recording the spontaneous muscle activity (SMA) and compound muscle action potential (CMAP). Two types of needle electrodes of different length were percutaneously inserted into the extraocular muscles with the free-hand technique. We studied the relationships between the SMA and CMAP and postoperative function of CN III and CN VI. RESULTS: A total of 23 patients were included. Nineteen oculomotor nerves and 22 abducens nerves were monitored during surgery, respectively. Neurotonic discharge had a positive predictive value of less than 50% and negative predictive value of more than 80% for postoperative CN III and CN VI dysfunction. The latency of patients with postoperative CN III dysfunction was 2.79 ± 0.13 ms, longer than that with intact CN III function (1.73 ± 0.11 ms). One patient had transient CN VI dysfunction, whose CMAP latency (2.54 ms) was longer than that of intact CN VI function (2.11 ± 0.38 ms). There was no statistically significant difference between patients with paresis and with intact function. CONCLUSIONS: The method of intraoperative monitoring of EOCNs described here is safe and useful to record responses of SMA and CMAP. Neurotonic discharge seems to have limited value in predicting the postoperative function of CN III and CN VI. The onset latency of CMAP longer than 2.5 ms after tumor removal is probably relevant to postoperative CN III and CN VI dysfunction. However, a definite quantitative relationship has not been found between the amplitude and stimulation intensity of CMAP and the postoperative outcome of CN III and CN VI.

Microsurgical Anatomy of the Oculomotor Nerve.

The oculomotor nerve supplies the extraocular muscles. It also supplies the ciliary and sphincter pupillae muscles through the ciliary ganglion. The nerve fibers leave the midbrain through the most medial part of the cerebral peduncle and enter the interpeduncular cistern. After the oculomotor nerve emerges from the interpeduncular fossa, it enters the cavernous sinus slightly lateral and anterior to the dorsum sellae. It enters the orbit through the superior orbital fissure, after exiting the cavernous sinus, to innervate the extraocular muscles. Therefore, knowledge of the detailed anatomy and pathway of the oculomotor nerve is critical for the management of lesions located in the middle cranial fossa and the clival, cavernous, and orbital regions. This review describes the microsurgical anatomy of the oculomotor nerve and presents pictures illustrating this nerve and its surrounding connective and neurovascular structures. Clin. Anat. 30:21-31, 2017. © 2016 Wiley Periodicals, Inc.

Tarsoaponeurectomy as an alternative in difficult blepharoptosis cases.

BACKGROUND: The purpose of this study was to evaluate the results of tarsoaponeurectomy in patients with unsuccessful results after repetitive surgery or who developed post-traumatic blepharoptosis. METHODS: The files of 107 patients (136 eyes) on whom surgery was performed between January 2010 and December 2014 due to blepharoptosis were scanned retrospectively. Among these patients, the files and operational notes of eight patients who underwent surgery through the method of tarsoaponeurectomy were examined in detail. The epidemiological data, indication for surgery, previous ptosis and/or eyelid surgeries and trauma histories, preoperative and postoperative measurement data (palpebral space (PS), margin reflex distance (MRD1, MRD2), levator muscle function (LMF)) of the patients were recorded. The follow-up time of the patients was 7 to 34 months with an average of 16 months. RESULTS: A total of eight patients consisting of three females and five males were included in the study. The age range was 19 to 63 years with an average of 39 ± 16.2 years. Four patients had traumatic ptosis history whereas four patients had previous multiple levator procedure surgery history. Those patients with a history of ptosis had undergone surgery with levator procedure at least two times. Additionally, one patient had upper eyelid entropion, one had anophthalmic socket syndrome, and one had exposure keratopathy and traumatic dilated pupil. Seven patients had ptosis in the left eye whereas one patient had ptosis in the right eye. All patients were given a tarsoaponeurectomy as the basic surgical procedure while the patient with entropion was given a tarsal fracture and ear cartilage grafting as additional surgery. Two patients with vertical notching were also given a vertical blepharotomy through which a strip of tarsus was removed. CONCLUSIONS: Tarsoaponeurectomy is an alternative method for oculoplastic surgeons used to deal with patients on whom sufficient and desired results have not been achieved despite repetitive surgery and in post-traumatic cases where levator muscle and aponeurosis cannot be dissociated peroperatively.

Complete reduction with traction of the infraorbital neurovascular bundle in a delayed patient with white-eyed blow-out fracture.

In case of delayed surgery, if an orbital floor fracture involves the infraorbital canal, adhesions may form between the infraorbital neurovascular bundle and herniated muscle, and manipulations to reduce the fracture may lead to unexpected bleeding due to injury of the infraorbital artery. The author reports a case of a white-eyed blow-out fracture patient, who visited our clinic one-and-a-half months after the injury. Exploration of the fracture confirmed intensive fibrosis of the infraorbital neurovascular bundle and the entrapped inferior rectus muscle at the fracture site. The author was able to reduce the muscle completely with the release of the fibrotic tissue around the nerve bundle by using a vessel loop to safely retract the neurovascular bundle upwards, and obtained good results.

[Detection of oculomotor nerve compression by 3D-FIESTA MRI in a patient with pituitary apoplexy and diabetes mellitus].

We report the usefulness of 3D-FIESTA magnetic resonance imaging(MRI)for the detection of oculomotor nerve palsy in a case of pituitary apoplexy. A 69-year-old man with diabetes mellitus presented with complete left-side blepharoptosis. Computed tomography of the brain showed an intrasellar mass with hemorrhage. MRI demonstrated a pituitary adenoma with a cyst toward the left cavernous sinus, which was diagnosed as pituitary apoplexy. 3D-FIESTA revealed that the left oculomotor nerve was compressed by the cyst. He underwent trans-sphenoid tumor resection at 5 days after his hospitalization. Post-operative 3D-FIESTA MRI revealed decrease in compression of the left oculomotor nerve by the cyst. His left oculomotor palsy recovered completely within a few months. Oculomotor nerve palsy can occur due to various diseases, and 3D-FIESTA MRI is useful for detection of oculomotor nerve compression, especially in the field of parasellar lesions.

The Oculomotor Cistern and Its Role in the Management of Pituitary Lesions: An Anatomical, Radiographic, and Clinical Scoping Review.

BACKGROUND: The oculomotor cistern (OMC) is a cerebrospinal fluid space bound by meningeal layers that surrounds the oculomotor nerve as it crosses the oculomotor triangle to reach the lateral wall of the cavernous sinus at the level of the anterior clinoid process. Although several anatomical and radiological studies are available, its anatomy and relationship with pituitary adenomas (PAs) are still matter of discussion. OBJECTIVE: The aim of the study is to provide an updated and focused overview of the OMC, highlighting the different perspectives and descriptions from anatomical, radiological, and clinical points of view. METHODS: A scoping review was conducted up to 29th October 2022, according to PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) criteria. PubMed, Web of Science, Scopus databases, and correlated citations were investigated. RESULTS: Of the 562 records identified, 22 were included in the present analysis. There were 13, 5, and 4 anatomo-surgical, radiological, and clinical studies, respectively. Though there is general consensus on its definition, data are variable on different features of OMC. Defects or absence of dural layers adjacent to the oculomotor nerve were described in only 4 papers. The transition from meningeal to neural layers is still unclear. PAs with OMC involvement are poorly studied and have unique clinical characteristics. To date, 21 patients have been described; the reported prevalence of OMC involvement by PAs ranges from 4.1% to 14.6%. CONCLUSIONS: Clarifying the OMC features with further systematic studies may not only broaden theoretical knowledge but also have implications on endoscopic transnasal pituitary surgery.

Neuromuscular hamartoma is a possible primary pathology of oculomotor ophthalmoplegic migraine.

BACKGROUND: Oculomotor ophthalmoplegic migraine (O-OPM) occurs in many children, and in some cases MRI shows a small mass in the root exit zone (REZ) of the oculomotor nerve. This mass is considered to result from nerve hypertrophy caused by repeated demyelination. CASE RESULTS: A 51-year-old man has been on oral medication for O-OPM, which he had from 6 years of age. However, the frequency and intensity of his migraine attacks have gradually increased. Brain magnetic resonance imaging (MRI) revealed a small nodular mass in the REZ of the oculomotor nerve. The mass was initially diagnosed as oculomotor schwannoma and tumor resection was attempted. However, as the mass was tightly adhered to the oculomotor nerve and hemorrhagic, biopsy was performed. The pathological diagnosis was neuromuscular hamartoma. CONCLUSION: The small nodular mass in the REZ of the oculomotor nerve may be a hamartoma associated with congenital factors and may possibly be the primary pathology of O-OPM in this case.

The oculomotor nerve: anatomic relationship with the floor of the third ventricle.

PURPOSE: Endoscopic third ventriculostomy (ETV) has become first-line treatment for obstructive hydrocephalus. Many complications have been described, but the literature about oculomotor palsy after ETV is scarce. Therefore we undertook an anatomical study of the relationship of the oculomotor nerve to the floor of the third ventricle. METHODS: Distances and angles between the third nerve and the bottom of the third ventricle were studied both in two cadaver heads and in high-definition CISS images in 16 MRI scans. The angles of the trajectories putting the nerve at risk or not were compared. Finally, in a retrospective analysis of intraoperative images the appearance of the membranous portion of the floor was defined and if visible, the distance of the third nerve to the midline was estimated by comparing with the 8-mm balloon catheter. RESULTS: The course of the third nerve is approximately 8 mm laterally and approximately 17 mm caudally distant from the midpoint of the floor of the third ventricle. The angle of the trajectory to damage the third nerve is at least 12° greater than any safe angle of ETV trajectory through a normal burr hole. CONCLUSIONS: The third nerve is not always visible during ETV procedures, but the angular and linear measurements imply that the risk to damage the nerve should be relatively small. Confirmation of these data in hydrocephalic patients with distorted anatomy is needed.

The neurovascular relationships of the oculomotor nerve.

In this study, the arterial supply of the cisternal (initial) and the subcavernous parts of the oculomotor nerve (ON) and the relation between the nerve and adjacent vascular structures like posterior cerebral artery (PCA) and superior cerebellar artery (SCA) were investigated. A total of 140 formalin fixed hemispheres from 70 human cadaveric brains were examined. The nutrient branches reaching the cisternal and subcavernous parts of the ON were investigated, along with branches of adjacent vascular structures penetrating the nerve and passing through it. In the material examined, the ON, after arising from the midbrain, mostly continues laterally between PCA and SCA or between PCA and the rostral SCA trunk. However, in three hemispheres of our specimens, the ON run between the rostral and caudal SCA trunks. We observed that the branches of PCA-P1 segment supplied the cisternal part of the ON in all specimens. In one specimen, the cisternal part of the ON was supplied by a branch arising from the rostral SCA trunk which was also originating from PCA. Differently, in four hemispheres, branches arising from PCA or SCA perforated the cisternal part of the ON and passed through it. We also observed a tortuous caudal trunk of duplicated SCA in one of our specimens and considered it as a rare variation. The anatomy of the ON and its vascular relations is significant in terms of not only understanding the compression syndromes and its vascular dysfunctions, but the exact diagnosis and treatment as well.

"Interdural" oculomotor neurinoma: report of two surgically treated cases.

BACKGROUND: Dural relationships and their possible implications on surgical treatment of oculomotor nerve neurinomas are discussed on the basis of surgical experience with two cases. MATERIALS AND METHODS: We describe two cases with large oculomotor neurinomas that probably arose from the precavernous sinus segment of the nerve. Both tumors were located entirely within the confines of dura or were "interdural." Operating within the limits set and protection afforded by the dura, the tumors could be excised relatively easily and safely. While the third nerve function recovered completely in one patient, the other continued to have complete third nerve palsy. The duration of follow-up in two cases was 52 and 24 months. RESULTS AND CONCLUSIONS: Even the intracranial component of large oculomotor neurinoma can be covered entirely by dura. Understanding of the dural relationship can assist in planning and conduct of surgery.

Endodermal Cyst Arising from the Oculomotor Nerve: A Case Report Outlining the Novel Insertion of Cysto-subarachnoid Shunt for Refractory Disease.

BACKGROUND: Endodermal cysts of the oculomotor nerve are rare presentations. Only case reports are available to help guide clinicians with managing this rare entity. CASE DESCRIPTION: A 3-year-old boy presented with an acute on chronic left oculomotor nerve palsy due to a left interpeduncular cistern cyst found on magnetic resonance imaging. He underwent a left pterional craniotomy and fenestration of the histologically proven endodermal cyst and had initial improvement at the 2-month review. He subsequently developed clinical and radiologic evidence of recurrence and was treated surgically with a refenestration and insertion of a cysto-subarachnoid shunt through a trans-sylvian approach. At 6-month follow-up, there was complete resolution of the oculomotor nerve palsy with interval development of oculomotor synkinesis. CONCLUSIONS: Magnetic resonance imaging is an essential modality in the follow-up of these patients postoperatively in the setting of unchanged or deteriorated neurology. Fenestration of the cyst is appropriate first-line surgical management; however, a cysto-subarachnoid shunt is a safe consideration in recurrent, symptomatic cysts and provides sustained symptom resolution.

Do we have to dissect infraorbital nerve from periorbita in orbital floor fracture?

The aim if this study was to see whether we have to dissect the infraorbital nerve from periorbita in orbital floor fractures.Orbital floors were reconstructed in 174 patients. Among them, 31 patients were treated with horseshoe-shaped synthetic sheets. Preoperative and postoperative findings including hypesthesia, diplopia, Hertel exophthalmometry, and occurrence of complications were checked.After the subciliary incision through skin and orbicularis oculi muscle, the skin-muscle flap was elevated just superficial to the orbital septum to the arcus marginalis. The periosteum was incised and elevated to expose the fracture site. The orbital branch of the infraorbital artery was identified. The periorbita was not separated from the infraorbital nerve, and the orbital branch of the infraorbital artery was preserved. The sheet was trimmed in horseshoe shape as the cleft fits to the infraorbital groove.On physical examination before surgery, diplopia was the most common (58.1%) associated complication, followed by hypesthesia (35.5%), limited ocular movement (9.7%), enophthalmos (3.2%), and hematoma (3.2%).Even if the fracture site is the posterior half, the periorbita does not have to be separated from the infraorbital nerve to avoid injury of the orbital branch of the infraorbital artery. Instead, the fracture site might be covered by a horseshoe-shaped sheet.

Study on surgical approaches and electrode implantation of oculomotor nerve and inferior obliquus in beagle dogs.

OBJECTIVES: To study the surgical anatomy and approaches of intracranial oculomotor nerve (OMN) and inferior obliquus (IO), and the methods of their electrode implantation in dogs. METHODS: The research was performed on 30 adult beagle dogs at Shanghai Jiaotong University Medical College, Shanghai, China from November 2007 to August 2008. All animals were subjected to a right transfrontotemperal approach to intracranial OMN, a transconjunctival route to IO, and the neuro-stimulating and recording electrode implantation under general anaesthesia. The OMN was stimulated and the electromyography of IO recorded and analyzed with the Powerlab System. The security and reliability of the implanted electrodes were investigated. RESULTS: The surgical anatomy and approaches of both the OMN from its exit from midbrain to the entrance into cavernous sinus and the IO were described. Moreover, the implantation methods of OMN stimulating electrode and the electromyographic recording electrode of IO were displayed. The implanted electrodes were safe and reliable. Some electrophysiologic data of IO were obtained in the healthy dogs. Also, some perioperative precautions for intracranial and ophthalmic surgical procedures in dog were exhibited. The mortality rate of the dogs was 0%, and no operative complications were observed. CONCLUSION: With the data provided, these surgical approaches and the methods of electrode implantation offer a choice to construct an animal model for studying various aspects of OMN regeneration.

Cerebral Aneurysm Arising from Variant Posterior Communicating Artery Lying Lateral to Oculomotor Nerve.

BACKGROUND: In most cases, the posterior communicating artery (PCoA) lies medial to the oculomotor nerve. In this report, a rare case of a ruptured cerebral aneurysm arising from a variant PCoA lying lateral to the oculomotor nerve is described. CASE DESCRIPTION: A 41-year-old woman who had a history of surgical clipping of a right PCoA aneurysm 13 years earlier developed a subarachnoid hemorrhage due to a ruptured left true PCoA aneurysm. Three-dimensional computed tomography angiography showed a small saccular aneurysm arising from the PCoA itself. She underwent surgical clipping via a left frontotemporal craniotomy. Interestingly, the PCoA lay lateral to the oculomotor nerve, and the aneurysm dome projected medially and compressed the oculomotor nerve medially. A slightly angled fenestrated miniclip was applied across the PCoA, followed by reconstruction of the PCoA medial wall and simultaneous obliteration of the aneurysm. Complete aneurysm obliteration and good patency of both the PCoA and perforating arteries were confirmed intraoperatively by indocyanine green videoangiography. The patient's postoperative course was uneventful, and the patient was discharged with no neurologic deficits. CONCLUSIONS: Recognizing this anatomic variant is helpful in minimizing the potential complications in microsurgical management around the PCoA and oculomotor nerve. Lateral localization of the P1-2 junction might affect this rare anatomic variant.