Rapid improvement of oculomotor nerve function with ayurvedic treatment in traumatic diplopia - A case report

Diplopia or double vision has many aetiologies and often presents to the ophthalmologist. The causes of diplopia may be ocular or neurogenic in origin. Any trauma to the eyes in the form of blow-out fractures causes diplopia by damaging the third nerve. The management by the practitioners of contemporary science depends upon the extent of the nerve or muscle injury. Entrapment of muscles requires surgical intervention, whereas others are managed conservatively. The recovery rate is the least for diplopia of traumatic origin. A 50-year-old male who sought Ayurvedic treatment for diplopia in the last three months was diagnosed with partial third nerve palsy after a fracture of the left orbit. He underwent Ayurvedic therapy in the form of internal medicines such as Danadanayanadi kashaya, Ksheerabala 101, Vaishwanara churna, and external treatments such as Pratimarsha Nasya, Siro abhyanga, and Tarpana. At the end of 2 months of Ayurvedic treatment, the patient completely recovered from diplopia. Ayurvedic treatment effectively resolved diplopia in a short time. Patients can benefit from the same if treated promptly in the early stage itself. However, more extensive studies with larger samples will yield more data to prove the potential of Ayurveda in such cases.

Oculomotor nerve cavernous malformation: case report and operative video

BACKGROUND

Cavernous malformations (CMs) are clusters of thin-walled sinusoidal vessels without well-defined walls. Though they can occur anywhere in the neuroaxis, cranial nerve (CN) CMs are rare.

METHOD

We report a 47-year-old male with gradual CN III palsy. Initial imaging showed no significant findings, but a follow-up MRI revealed a growing lesion along CN III. Intraoperative findings confirmed a CN III CM. Diagnosing and treating CN III CM are complex. Radiological findings lack specificity, requiring consideration of various diagnoses for patients with isolated CN III palsy and abnormal radiological findings.

CONCLUSION

Surgery is the gold standard, aiming for complete lesion removal while minimizing neurological complications.

Neurocysticercosis presenting with oculomotor nerve palsy: Case report and literature review

Neurocysticercosis (NCC), a central nervous system infection caused by the cystic larvae of Taenia Solium, is endemic in many low-to-middle income countries. NCC is known to have a variety of presentations depending on the size and site of involvement including chronic headaches, seizures, hydrocephalus, and ischemic insults. NCC has also been rarely associated with cranial nerve palsies. We report the case of a 26-year-old Nepalese lady who presented with isolated left-sided oculomotor nerve palsy and was found to have midbrain NCC. She was treated with anthelminthic agents and corticosteroids which led to clinical improvement. NCC can present with a variety of focal neurological syndromes. To the best of our knowledge, this is the first case report of NCC presenting with third cranial nerve palsy in the state of Qatar and the middle east. We also review the literature for other cases of NCC which presented with isolated oculomotor nerve palsy.

Congenital isolated unilateral third nerve palsy in children: the diagnostic contribution of high-resolution MR imaging

PURPOSE

To describe the neuroanatomical correlates of unilateral congenital isolated oculomotor palsy by means of high-resolution MRI.

METHODS

Children with a clinical diagnosis of congenital isolated oculomotr palsy and with a high-resolution MRI acquisition targeted on the orbits and cranial nerves were selected and included in the study. An experienced pediatric neuroradiologist evaluated all the exams, assessing the integrity and morphology of extraocular muscles, oculomotor, trochlear and abducens nerves as well as optic nerves and globes. Clinical data and ophthalmologic evaluations were also collected.

RESULTS

Six children (age range: 1-16 years; males: 3) were selected. All patients showed, on the affected side (left:right = 5:1), anomalies of the III nerve and extraocular muscles innervated by the pathological nerve. One patient had complete nerve agenesis, two patients showed a diffuse thinning of the nerve, from the brainstem to the orbit and 3 patients showed a distal thinning of the oculomotor nerve, starting at the level of the cavernous sinus. In all cases atrophy of corresponding muscles was noticed, but the involvement of the affected muscles varied with the nervous pattern of injury.

CONCLUSIONS

High-resolution MRI represents a valuable tool for the diagnosis of III nerve anomalies in unilateral congenital IOP, showing different patterns of nerve involvement and muscular atrophy.

Meningioma originating from the oculomotor nerve without dural attachment in a child

Meningioma originating from the oculomotor nerve without dural attachment in children has been rarely reported. A 6-year-old patient presented ptosis of the right eye for 5 years. MRI indicated an occupying lesion in the right cavernous sinus. A tumor originating from the oculomotor nerve without dural attachment was found during subsequent surgery and confirmed as meningioma by pathology. Subsequently, the tumor was removed completely, and the oculomotor nerve was reconstructed using the sural nerve. The patient's symptoms were relieved partially after 3 months. The findings of this case suggested that the mechanisms underlying meningioma involve ectopic arachnoid cap cells within the nerve sheath. Thus, the tumor should be removed completely; also, nerve reconstruction is suggested.

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 29^th 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.

The Intersection Between the Oculomotor Nerve and the Internal Carotid Artery to Distinguish Extracavernous and Intracavernous Paraclinoid Aneurysms Using Anatomic Dissections-A New 3T Magnetic Resonance Imaging Protocol Confirmed by Three-Dimensionally Printed Biomodels

OBJECTIVE

To evaluate the relationship between the oculomotor nerve (CNIII) and the internal carotid artery (ICA) as a new anatomic-radiologic landmark for distinguishing the exact location of a paraclinoid intracranial aneurysm (IA).

METHODS

Microanatomic dissections were performed in 20 cavernous sinuses to evaluate the ICA paraclinoid region. Based on anatomic observations, a new magnetic resonance (MRI) protocol to classify paraclinoid aneurysms was proposed. MRI of 42 IAs from 34 patients was independently analyzed and classified as intracavernous, extracavernous, or transitional by 2 neuroradiologists. To validate the proposed MRI protocol, each IA was classified by a three-dimensionally (3D) printed biomodel and agreement with the radiologic classifications was evaluated. Of 42 IAs, 23 undergoing microsurgeries were also classified by direct visualization.

RESULTS

We observed that the true cavernous sinus roof is defined by the carotid-oculomotor membrane, which has an intimate relationship with the intersection between the superior limit of the CNIII and the ICA. Based on this intersection, all 42 IAs were radiologically classified and agreement with the 3D printed biomodels was observed in 95% IAs. Concordance tests showed a statistically significant (P < 0.05) agreement between the classifications. All 23 IAs treated had the radiologic and 3D biomodel classification confirmed.

CONCLUSIONS

The intersection between the ICA and the CNIII, which crosses it transversely in its entire diameter, is a reliable anatomic-radiologic landmark to correctly classify paraclinoid aneurysms. Through a new MRI protocol, it is possible to radiologically identify this intersection and to easily distinguish the intracavernous and extracavernous ICA paraclinoid aneurysms.

Oculomotor nerve segment between proximal posterior and superior cerebellar arteries: an MRI study

PURPOSE

No study has documented the oculomotor nerve (OMN) segment lying between the posterior cerebral (PCA) and superior cerebellar (SCA) arteries adjacent to the brainstem. The present study aimed to characterize it.

METHODS

A total of 71 patients underwent thin-sliced, sagittal T2-weighted magnetic resonance imaging for analysis.

RESULTS

The OMN segments lying between the PCA and SCA were identified in all patients. The OMN segment in relation to the PCA and SCA was classified into five types. Of them, the PCA-OMN contact type was the most frequent and found in 35.2% of 71 sides on the right and 39.4% on the left. Also, the PCA-OMN compression type was identified in 12.7% on the right and 15.5% on the left. In these types, the mean distance between the brainstem and contact/compression sites were measured 4.4 ± 2.3 mm on the right and 4.4 ± 1.6 mm on the left. In more than forty percent, the sites were located at the level of the pontomesencephalic junction.

CONCLUSIONS

The OMN may be frequently in contact with the PCA near the brainstem. The site located more distal than the central-peripheral myelin junction of the OMN can attribute to a low frequency of neurovascular compression syndrome of the nerve.

The Development of Indirect Carotid Cavernous Fistulas after Microvascular Ischemic 4th Nerve Palsies

An indirect carotid cavernous fistula (CCF) is an abnormal connection between the cavernous sinus and internal or external carotid artery. Indirect CCFs often occur spontaneously, particularly in the setting of vascular risk factors such as hypertension, diabetes, and atherosclerosis. Microvascular ischemic nerve palsies (NPs) share these vascular risk factors. However, to date, no temporal relationship between microvascular ischemic NP and indirect CCF occurring sequentially has been reported. We describe the cases of 64- and 73-year-old women who developed indirect CCFs within 1-2 weeks after spontaneous resolution of a microvascular ischemic 4th NP. Both patients had complete resolution and an asymptomatic period between the 4th NP and CCF. This case highlights the shared pathophysiology and risk factors between microvascular ischemic NPs and CCFs, and emphasizes that CCFs should be kept in the differential diagnosis for red eye or recurrent diplopia in patients with previous microvascular ischemic NP.

Oculomotor nerve root split: incidental finding on MRI-case report and literature review

BACKGROUND

The oculomotor nerve (OMN) innervates the pupil, ciliary body, upper eyelid, and extraocular muscles through two divisions: a superior division that innervates the levator palpebrae superioris (LPS) and superior rectus (SR), and an inferior division that supplies the medial rectus (MR), inferior rectus (IR), inferior oblique (IO), and parasympathetic fibers to the pupil and ciliary body. We present a case of complete splitting of the cisternal segment of bilateral OMNs that was discovered incidentally on magnetic resonance imaging (MRI) in a patient who had no ocular complaints.

CASE REPORT

A 69-year-old patient was found to have bilateral splitting of the cisternal segments of OMNs during an MRI for trigeminal neuralgia workup. Both nerves sprang from the midbrain as distinct roots. They were symmetric on the right and minimally asymmetric on the left. On both sides, the medial root was slightly inferiorly situated. The patient had no visual problems and continued to function normally. A review of the literature for similar cases identified no such variants; however, it did identify eight examples of OMN fenestrations produced by aneurysms (AN), six of which had no OMN palsy symptoms.

CONCLUSION

An anatomic variant of split bilateral OMN cisternal segments is described. The superior and inferior divisions may have different brainstem origins. Although this variant is an anatomic curiosity, it may have clinical significance and explain the various presentation of compressive OMN palsies.

Microvascular decompression for a patient with oculomotor palsy caused by posterior cerebral artery compression: A case report and literature review

BACKGROUND

Aneurysm compression, diabetes, and traumatic brain injury are well-known causative factors of oculomotor nerve palsy (ONP), while cases of ONP induced by neurovascular conflicts have rarely been reported in the medical community. Here, we report a typical case of ONP caused by right posterior cerebral artery (PCA) compression to increase neurosurgeons’ awareness of the disease and reduce misdiagnosis and recurrence.

CASE SUMMARY

A 54-year-old man without a known medical history presented with right ONP for the past 5 years. The patient presented to the hospital with right ptosis, diplopia, anisocoria (rt 5 mm, lt 2.5 mm), loss of duction in all directions, abduction, and light impaired pupillary reflexes. Magnetic resonance angiography and computed tomography venography examinations showed no phlebangioma, aneurysm, or intracranial lesion. After conducting oral glucose tolerance and prostigmin tests, diabetes and myasthenia gravis were excluded. Cranial nerve magnetic resonance imaging showed that the right PCA loop was in direct contact with the cisternal segment of the right oculomotor nerve (ON). Microvascular decompression (MVD) of the culprit vessel from the ON through a right subtemporal craniotomy was carried out, and the ONP symptoms were significantly relieved after 3 mo.

CONCLUSION

Vascular compression of the ON is a rare pathogeny of ONP that may be refractory to drug therapy and ophthalmic strabismus surgery. MVD is an effective treatment for ONP induced by neurovascular compression.

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.

Tendinous annulus of Zinn for a common origin of the extraocular rectus muscles: a histological study of the orbital apex from donated elderly cadavers

The medial, inferior, lateral, and superior rectus muscles (MR, IR, LR, SR), levator palpebrae superioris (LPS), and superior oblique muscle (SO) seem to originate from the tendinous annulus of Zinn, ring-like fibrous tissue crossing the bony orbital fissure. We observed the histological annulus structure using semi-serial histological sections of the orbital apex from 30 elderly donated cadavers. Nearly frontal sections demonstrated a ring-like fibrous structure (a candidate annulus) connecting or embedding four rectus muscles. The candidate annulus did not contain the LPS and SO, and, in the anterior side, the latter muscles originated from the optic canal opening. Far posterior to the annulus, there was a common tendon of the MR, IR, and LR attached to the infero-medial wall of the bony orbital fissure. At the superior part, the annulus is tightly attached to the optic nerve sheath and the periosteum. Sagittal (or Horizontal) sections clearly exhibited parts of the annulus at the MR (SR) origin. Both sagittal and horizontal sections displayed (1) the common origin of the three rectus muscles near the oculomotor nerve in the bony fissure and (2) an accessory, independent muscle bundle of the MR originating from the superomedial margin of the optic canal near the origins of the LPS or SO. Consequently, the so-called tendinous annulus appeared not to provide origins of all six muscles.

Predictors of visual function after resection of skull base meningiomas with extradural anterior clinoidectomy

Skull base meningiomas threatening the optic nerves may require performing an extradural anterior clinoidectomy (EAC) to optimally decompress the optic pathways. The present study evaluated the functional results and morbidity after surgical resection of skull base meningiomas including EAC, focusing on visual acuity (VA) and oculomotricity. Eighty-seven consecutive patients harboring skull base meningiomas who underwent surgical resection that included an EAC between 2003 and 2020 were retrospectively analyzed (86% women, median age 53 years). Decreased visual acuity (DVA) was graded as functional (VA ≥ 5/10) and nonfunctional (VA < 5/10). Statistical analyses were performed on VA and oculomotor nerve (OcN) dysfunction. Ninety surgical procedures were performed. Meningiomas were located at the anterior clinoid process (39%), cavernous sinus (31%), and spheno-orbital (30%) levels. Patients with a preoperative functional vision (normal or functional DVA) had a 90.9% (IC95% = [84.0; 97.8]) probability of preserving it at 6 months and an 84.8% (IC95% = [76.2; 93.5]) probability at last follow-up. Patients with preoperative nonfunctional vision (nonfunctional DVA or blindness) had a 19.0% (IC95% = [2.3; 35.8]) probability of recovery of functional vision at 6 months and a 23.8% (IC95% = [5.6; 42.0]) probability at last follow-up. Preoperative DVA was significantly associated with early postoperative DVA in univariate analyses (p = 0.04). Concerning the OcN, 65% of the patients experienced a postoperative dysfunction, and 78% of those cases recovered. Our study confirms EAC as a useful technical option for skull base meningiomas threatening the optic nerve, especially relevant for patients with preoperative functional vision, and supports early surgical management for these meningiomas.

Pathological evidence of demyelination in the recurrent laryngeal, phrenic, and oculomotor nerves in Charcot-Marie-Tooth disease 4F

We present pathology of the peripheral nerves of a patient with Adult-onset Charcot-Marie-Tooth disease 4F caused by periaxin gene mutation p.D651N. The patient was a 72-year-old woman. She had hoarseness and underwent continuous positive airway pressure therapy at night due to sleep apnea. The patient died abruptly. Remarkable demyelination with tomacula formation was found in the phrenic nerve, vagal nerve, recurrent laryngeal nerve, and oculomotor nerves. The cause of death could have been insufficient reactivity to the aspiration or sudden onset of bilateral vocal cord palsy. We must pay attention to respiratory function and cranial nerve palsies in hereditary demyelinating neuropathies.

Hakuba's triangle: a cadaveric study detailing its anatomy and neurovascular contents with vascular and skull base implications

Hakuba's triangle is a superior cavernous sinus triangle that allows for wide and relatively safe exposure of vascular and neoplastic lesions. This study provides cadaveric measurements of the borders of Hakuba's triangle and describes its neurovascular contents in order to enrich the available literature. The anatomical borders of the Hakuba's triangle (lateral, medial, and posterior borders) were defined based on Hakuba's description and identified. Then the triangle was dissected to reveal its morphology and relationship with adjacent neurovascular structures in Embalmed Caucasian cadaveric specimens. The oculomotor nerve occupied roughly one-third of the area of the triangle and the nerve was more or less parallel to its medial border. The mean lengths of the lateral border, posterior border, and medial border were 17 mm ± 0.5 mm, 12.2 mm ± 0.4 mm, and 10.6 mm ± 0.4 mm, respectively. The mean area of Hakuba's triangle was 63.9 mm² ± 4.4 mm². In this study, we provided cadaveric measurements of the borders of Hakuba's triangle along with descriptions of its neurovascular contents.

Pediatric intracranial neurenteric cyst of the oculomotor nerve: a case-based review

BACKGROUND

Neurenteric cysts (NECs) of the central nervous system (CNS) are uncommon congenital entities arising from embryonal elements. Intracranial NECs in the pediatric population are rare.

METHODS

The authors describe the presentation, radiographic imaging, and pathologic findings of an 11-year-old boy with a right oculomotor nerve NEC. A literature review was performed to identify additional cases of pediatric intracranial NECs published in the English language, over the past 30 years (1990-2020). The authors discuss the presentation, investigations, management, and prognosis of this interesting entity.

RESULTS

We describe an 11-year-old boy who presented to neurosurgical attention with disconjugate gaze, anisocoria, and ptosis. Magnetic resonance imaging (MRI) demonstrated a lobulated, cystic, and peripherally enhancing mass involving the right oculomotor nerve. The patient underwent pterional craniotomy for drainage of the cyst and subtotal resection of the cyst wall. The tan-colored mass was displacing the basilar artery, compressing the cerebral peduncle, and adherent to the inferior surface of the tentorium. The lesion was within the oculomotor nerve and splitting the fibers, and the cystic contents were thick and mucinous. Histopathological examination of the specimen demonstrated a thin fibrous cyst wall with scattered inflammatory cells and lined by simple columnar epithelium containing mucin. The lining cells were immunoreactive with epithelial membrane antigen (EMA) and pan-keratin AE1/AE3. The diagnosis of a NEC was rendered. A comprehensive literature review of pediatric intracranial NECs yielded 46 additional lesions published in the literature, involving the skull base, posterior fossa, cerebral convexity, and cranial nerves. NECs present with local mass effect and less commonly, with aseptic meningitis or intracystic hemorrhage. Maximal safe GTR remains the mainstay management, although cyst drainage and marsupialization, cyst shunting, and fenestration of cystic contents into the ventricle or basal cisterns have been reported with variable success.

CONCLUSION

CNS NECs are rare congenital entities; although they occur less frequently in the intracranial components compared to the spine, their diagnosis and management should be considered for intracranial cystic lesions. Maximal safe GTR is the mainstay treatment and frequently yields favorable outcomes.

Oculomotor nerve schwannoma: case series and literature review

Oculomotor nerve schwannomas are rare benign cranial nerve tumors. There are only a limited number of reports on this pathology in the literature, and there are currently no established management guidelines that aid providers in deciding on surgical versus nonsurgical management. We assess the published literature on the topic to identify indications for treatment as well as outcome measures (e.g., local control rates, survival rates, and complication rates) that have been reported as associated with the various treatment modalities. We attempt to develop an algorithm for evaluation and treatment of oculomotor nerve schwannomas in order to establish consensus on how these tumors should be treated.

Oculomotor nerve guidance and terminal branching requires interactions with differentiating extraocular muscles

Muscle function is dependent on innervation by the correct motor nerves. Motor nerves are composed of motor axons which extend through peripheral tissues as a compact bundle, then diverge to create terminal nerve branches to specific muscle targets. As motor nerves approach their targets, they undergo a transition where the fasciculated nerve halts further growth then after a pause, the nerve later initiates branching to muscles. This transition point is potentially an intermediate target or guidepost to present specific cellular and molecular signals for navigation. Here we describe the navigation of the oculomotor nerve and its association with developing muscles in mouse embryos. We found that the oculomotor nerve initially grew to the eye three days prior to the appearance of any extraocular muscles. The oculomotor axons spread to form a plexus within a mass of cells, which included precursors of extraocular muscles and other orbital tissues and expressed the transcription factor Pitx2. The nerve growth paused in the plexus for more than two days, persisting during primary extraocular myogenesis, with a subsequent phase in which the nerve branched out to specific muscles. To test the functional significance of the nerve contact with Pitx2+ cells in the plexus, we used two strategies to genetically ablate Pitx2+ cells or muscle precursors early in nerve development. The first strategy used Myf5-Cre-mediated expression of diphtheria toxin A to ablate muscle precursors, leading to loss of extraocular muscles. The oculomotor axons navigated to the eye to form the main nerve, but subsequently largely failed to initiate terminal branches. The second strategy studied Pitx2 homozygous mutants, which have early apoptosis of Pitx2-expressing precursor cells, including precursors for extraocular muscles and other orbital tissues. Oculomotor nerve fibers also grew to the eye, but failed to stop to form the plexus, instead grew long ectopic projections. These results show that neither Pitx2 function nor Myf5-expressing cells are required for oculomotor nerve navigation to the eye. However, Pitx2 function is required for oculomotor axons to pause growth in the plexus, while Myf5-expressing cells are required for terminal branch initiation.

Resection of Oculomotor Nerve Lesions Using Continuous Stimulation of the Oculomotor Nerve Proximal to the Lesion: A Technical Report

BACKGROUND

We describe a continuous monitoring method aimed at preserving nerve function during biopsy of lesions on the oculomotor nerve using stimulation of the oculomotor nerve proximal to the lesion.

CASE DESCRIPTION

A 5-year-old girl with a recurrent left oculomotor nerve palsy and contrast-enhancing left oculomotor nerve mass on magnetic resonance imaging underwent a biopsy of the lesion to aid in its diagnosis. At the time of surgery, needle electrodes were inserted into the superior and inferior rectus muscles percutaneously, and cotton-covered electrodes were implanted into the oculomotor nerve proximal to the lesion. Compound muscle action potentials of the oculomotor nerve were measured continuously by monopolar stimulation. The lesion was mapped by direct stimulation, and the unresponsive area was excised. The amplitude of the compound muscle action potentials decreased during the resection but recovered postoperatively. After resection of the lesion, the compound muscle action potentials remained the same as they were preoperatively. No obvious postoperative oculomotor nerve palsy was observed.

CONCLUSIONS

This method of continuous monitoring of the function of the oculomotor nerve is simple to use and is suitable for lesions in close proximity to the oculomotor nerve.

Delayed oculomotor nerve palsy associated with a ruptured anterior communicating aneurysm: Case report

BACKGROUND AND IMPORTANCE

Oculomotor nerve palsy (ONP) is usually associated with posterior communicating (PCOM) aneurysms. ONP in patients with anterior circulation aneurysms are extremely rare, with only a handful of such published cases to date. There is currently no accepted mechanism to explain this clinical finding.

CLINICAL PRESENTATION

We describe a case of a 60-year-old female that benefitted from endovascular coiling of a ruptured anterior communicating (ACOM) aneurysm. In the following days, she clinically deteriorated and benefitted from another digital subtraction angiography (DSA) with intravascular verapamil for suspected vasospasm, and subsequently developed a right ONP.

CONCLUSION

Although classically related to PCOM aneurysm, ONP may be associated with ACOM aneurysms. The causative mechanism is unclear, but vasospasm may alter the microvascularisation of the oculomotor nerve, leading to ischemia.

Oculomotor nerve palsy in pituitary apoplexy associated with pituitary adenoma: a radiological analysis with fast imaging employing with steady-state acquisition

PURPOSE

Oculomotor nerve palsy (ONP) occasionally occurs in cases of pituitary apoplexy (PA) associated with pituitary adenoma, but its mechanism remains unclear. Intracranial nerves are clearly visualized by fast-imaging employing with steady-state acquisition (FIESTA). Here, we assessed the oculomotor nerve compression in patients with PA associated with pituitary adenoma using FIESTA.

METHODS

Twenty-eight cases of PA, with or without ONP, were retrospectively reviewed. All patients had undergone preoperative FIESTA. Two neuroradiologists, unaware of the patient's clinical symptoms, evaluated the presence and location of oculomotor nerve compression due to the tumor.

RESULTS

Thirteen of the twenty-eight PA cases were associated with ONP. Tumor size and degree of cavernous sinus invasion were not significantly different between the ONP and non-ONP groups. Even in the ONP group, 8/13 (62%) tumors did not show cavernous sinus invasion. Via FIESTA, the presence of oculomotor nerve compression was confirmed in 11/13 (85%) and 5/15 (33%) cases in the ONP and non-ONP groups, respectively (p = 0.008). The radiologists' diagnoses of laterality of nerve compression (right or left) were consistent with the patient's affected eye. In the ONP group, the location of the nerve compression was located at the entry point to the cavernous sinus, the so-called oculomotor triangle, in 9/11 (82%) cases and intra cavernous sinus in 2/11 (18%) cases.

CONCLUSION

Compression at the oculomotor triangle is considered the main cause of ONP with PA in pituitary adenomas.

High-resolution MRI demonstrates signal abnormalities of the 3rd cranial nerve in giant cell arteritis patients with 3rd cranial nerve impairment

OBJECTIVE

To determine the sensitivity and specificity of high-resolution (HR) MRI for detecting signal abnormalities of cranial nerves (CN) in giant cell arteritis (GCA) patients presenting with diplopia.

METHODS

This IRB-approved retrospective single-center study included GCA patients who underwent 3-T HR MRI from December 2014 to January 2020. Two radiologists, blinded to all data, individually assessed for the presence of enhancement of the 3rd, 4th, and/or 6th CN on post-contrast HR imaging and high signal intensity on HR T2-WI, for signal abnormalities of extraocular muscles and the brainstem, and for inflammatory changes of the ophthalmic and extracranial arteries. A Fisher's exact test was used to compare patients with or without diplopia.

RESULTS

In total, 64 patients (42/64 (66%) women and 22/64 (34%) men, mean age 76.3 ± 8 years) were included. Of the 64 patients, 14 (21.9%) presented with diplopia. Third CN enhancement was detected in 7/8 (87.5%) patients with 3rd CN impairment, as compared to no patients with 4th or 6th CN impairment or to patients without diplopia (p < 0.001). Third CN abnormal high signal intensity on HR T2-WI was detected in 4/5 patients (80%) with 3rd CN impairment versus none of other patients (p < 0.001). Sensitivity, specificity, positive predictive value, and negative predictive value for detecting 3rd CN signal abnormalities were of 0.88, 1, 1, and 0.99 and 0.8, 1, 1, and 0.98 for post-contrast HR imaging and HR T2-WI, respectively.

CONCLUSIONS

HR MRI had excellent diagnostic sensitivity and specificity when detecting signal abnormalities of the 3rd CN in GCA patients presenting with 3rd CN impairment.

KEY POINTS

• Third cranial nerve enhancement was detected in all patients with 3rd cranial nerve impairment except for one with transient diplopia. • The "check mark sign" might be useful to identify 3rd cranial nerve signal abnormalities in the orbital apex. • No signal abnormalities of the 4th or 6th cranial nerves could be detected on high-resolution MRI.

Triggered Electrooculography for Identification of Oculomotor and Abducens Nerves during Skull Base Surgery

OBJECTIVE

Electrooculography (EOG) records eyeball movements as changes in the potential difference between the negatively charged retina and the positively charged cornea. We aimed to investigate whether reliable EOG waveforms can be evoked by electrical stimulation of the oculomotor and abducens nerves during skull base surgery.

METHODS

We retrospectively reviewed the records of 18 patients who had undergone a skull base tumor surgery using EOG (11 craniotomies and seven endonasal endoscopic surgeries). Stimulation was performed at 5 Hz with a stimulus duration of 200 μs and an intensity of 0.1-5 mA using a concentric bipolar probe. Recording electrodes were placed on the upper (active) and lower (reference) eyelids, and on the outer corners of both eyes; the active electrode was placed on the contralateral side.

RESULTS

Reproducibly triggered EOG waveforms were observed in all cases. Electrical stimulation of cranial nerves (CNs) III and VI elicited positive waveforms and negative waveforms, respectively, in the horizontal recording. The median latencies were 3.1 and 0.5 ms for craniotomies and endonasal endoscopic surgeries, respectively (p=0.007). Additionally, the median amplitudes were 33.7 and 46.4 μV for craniotomies and endonasal endoscopic surgeries, respectively (p=0.40).

CONCLUSION

This study showed reliably triggered EOG waveforms with stimulation of CNs III and VI during skull base surgery. The latency was different according to the point of stimulation and thus predictable. As EOG is noninvasive and relatively easy to perform, it can be used to identify the ocular motor nerves during surgeries as an alternative of electromyography.

Morphometric Comparison of the Pterional Trans-Sylvian and the Pretemporal Trans-Clinoidal Approaches to the Posterior Communicating Artery

BACKGROUND

Posterior communicating (Pcom) aneurysms in the modern era have tended toward increased complexity and technical difficulties. The pretemporal approach is a valuable extension to the pterional approach for basilar apex aneurysms, but its advantages for Pcom aneurysms have not been previously elucidated.

OBJECTIVE

To quantify characteristics of the pretemporal approach to the Pcom.

METHODS

We dissected 6 cadaveric heads (12 sides) with a pretemporal transclinoidal approach and measured the following variables: (1) exposed length of internal carotid artery (ICA) proximal to the Pcom artery; (2) exposed circumference of ICA at the origin of Pcom; (3) deep working area between the optic nerve and tentorium/oculomotor nerve; (4) superficial working area; (5) exposure depth; and (6) the frontotemporal (superior posterolateral) and (7) orbito-sphenoidal (inferior anterolateral) angles of exposure.

RESULTS

Compared with pterional craniotomy, the pretemporal transclinoidal approach increased the exposed length of the proximal ICA from 3.3 to 11.7 mm (P = .0001) and its circumference from 5.1 to 7.8 mm (P = .0003), allowing a 210° view of the ICA (vs 137.9°). The deep and superficial working areas also significantly widened from 53.7 to 92.4 mm2 (P = .0048) and 252.8 to 418.2 mm2 (P = .0001), respectively; the depth of the exposure was equivalent. The frontotemporal and spheno-Sylvian angles increased by 17° (P = .0006) and 10° (P = .0037), respectively.

CONCLUSION

The pretemporal approach can be useful for complex Pcom aneurysms by providing easier proximal control, wider working space, improved aneurysm visualization, and more versatile clipping angles. Enhanced exposure results in a potentially higher rate of complete aneurysm obliteration and complication avoidance.

High-resolution magnetic resonance imaging in isolated, traumatic oculomotor nerve palsy: A case report

Traumatic, isolated oculomotor nerve palsy is a rare clinical finding and only few reports demonstrate associated magnetic resonance imaging (MRI) findings. Here, we present the case of a 70-year-old woman with left-sided oculomotor nerve palsy following a mild head trauma due to an e-bike accident. Post-traumatic cerebral computed tomography revealed punctiform hemorrhage in the left interpeduncular cistern and the following MRI confirmed an intraneural hemorrhage of the left oculomotor nerve. Nine weeks later, the follow-up MRI showed progressive atrophy and contrast-enhancement of the left oculomotor nerve. To support functional recovery, a treatment with intravenous corticosteroids was started. Six months later, the patient presented with improved oculomotor nerve function and partial recovery of ptosis and diplopia. In accordance, MRI demonstrated recurrent contrast-enhancement of the atrophic nerve. In conclusion, high-resolution MRI allows the reliable delineation of the oculomotor nerve and can support diagnosis in trauma patients with isolated oculomotor nerve palsy.

Unruptured internal carotid-posterior communicating artery aneurysm splitting the oculomotor nerve: A case report and literature review

Background:

Although it is well known that internal carotid-posterior communicating artery (ICA-PcomA) aneurysms compress the oculomotor nerve and cause nerve palsy, cases of ICA-PcomA aneurysms splitting the oculomotor nerve are extremely rare.

Case Description:

We present the rare case of an asymptomatic, growing, left-sided ICA-PcomA aneurysm that was confirmed to split the oculomotor nerve. We report the clinical course and discuss the underlying mechanism. The oculomotor nerve, which is an aggregate of multiple fibers, exhibits age-related loss of compactness in the arrangement of its nerve fibers.

Conclusion:

We speculate that injury to the nerve fibers by aneurysmal compression was avoided because of the rare phenomenon of splitting of the oculomotor nerve.

Signal intensity pattern of the normal oculomotor nerve on contrast-enhanced 3D FLAIR at 3.0 T MRI

PURPOSE

The aim of this study was to depict the signal intensity pattern of the normal oculomotor nerve demonstrated on contrast-enhanced three-dimensional fluid-attenuated inversion recovery images.

MATERIALS AND METHODS

Eighty-one patients were included in the study. Contrast-enhanced three-dimensional fluid-attenuated inversion recovery images with magnetisation-prepared rapid acquisition were reconstructed and evaluated in the coronal plane. The signal intensity of the cisternal segment of the oculomotor nerve was graded into a visual scale of 1 to 5 as compared to the white matter, grey matter and the pituitary stalk. The signal intensity ratio of the oculomotor nerve was consequently measured.

RESULTS

By using the visual scale, more than half of the oculomotor nerves showed higher signal intensity than the grey matter signal on contrast-enhanced three-dimensional fluid-attenuated inversion recovery images (59.3-80.2%). It can demonstrate a signal intensity similar to the pituitary stalk (14.8%) by visualisation. None of them showed signal intensity equal to the normal white matter signal. By signal intensity measurement, the mean signal intensity ratio of oculomotor nerves to white matter equals 1.54±0.20 (95% confidence interval (CI) 1.51-1.57); mean signal intensity ratio to grey matter equals 1.16±0.15 (95% CI 1.14-1.18); mean signal intensity ratio to the pituitary stalk equals 0.68±0.10 (95% CI 0.64-0.70).

CONCLUSIONS

The normal oculomotor nerve visualised on contrast-enhanced three-dimensional fluid-attenuated inversion recovery images has a higher signal intensity than the white matter and may have a signal intensity similar to the grey matter or the pituitary stalk. The high signal intensity of the oculomotor nerve in contrast-enhanced three-dimensional fluid-attenuated inversion recovery should not be misinterpreted as a pathology.

Meningothelial meningioma of the oculomotor nerve: A case report and review of the literature

Background:

The origin of meningioma tumors is known as the meningothelial or arachnoid cap cells. The arachnoid granulations or villi are concentrated along with the dural venous sinuses in the cerebral convexity, parasagittally, and sphenoid wing regions. The majority of meningiomas are found in these locations with dural attachment. Infrequently, meningiomas develop without dural attachment but in dural adjacent. There are numerous reports of patients with cranial nerve involvement as a result of the compressive effect of the sinus cavernous or adjacent structures meningioma tumor on the cranial nerve.

Case Description:

In this study, we reviewed all reports of patients with third nerve involvement as a result of meningioma tumors in addition to the introduction of a new case. We present a 47-year-old woman presented with headache, diplopia, and ptosis. A gadolinium-enhanced mass on anterolateral of the left cerebral peduncle with no dural attachment was suggesting for Schwannoma at preoperative imaging. An adhesive 10 × 5 × 4 mm meningothelial meningioma arising from the oculomotor nerve was resected.

Conclusion:

The findings of this review suggest that there may be other mechanisms as the origin of meningiomas tumors. It is crucial to take into account origination mechanisms of meningioma using ectopic meningiomas due to the increasing prevalence of meningioma.

A Case of Meningioma Originating from the Oculomotor Nerve

BACKGROUND

Schwannoma originating from the oculomotor nerve has been reported. However, meningioma originating from this nerve was unknown.

CASE DESCRIPTION

A 22-year-old woman presented with a unique case of meningioma originating from the oculomotor nerve manifesting as periorbital pain and diplopia beginning 4 months previously. Oculomotor nerve schwannoma was suggested by several pretreatment examinations. Tumor resection was considered risky for preservation of the oculomotor nerve function; therefore, gamma knife surgery (GKS) was performed. Six months later, she suffered right complete ptosis and worsened blurry vision. Corticosteroid was administered, but her symptoms did not improve. Magnetic resonance imaging showed the tumor lesion had grown larger. We decided to resect the tumor lesion because of her uncontrolled periorbital pain. The tumor had occupied the oculomotor cistern and was gross totally removed. Histologic diagnosis was surprisingly transitional meningioma. The tumor lesion occupied the oculomotor cistern and was refractory to GKS, with a progressive clinical course, which is more suggestive of meningioma than schwannoma, although extremely rare. Her periorbital pain and blurry vision gradually regressed, whereas complete oculomotor nerve palsy persisted.

CONCLUSIONS

In such a case, tumor resection after GKS should be considered.

Microvascular decompression of the posterior cerebral artery for treatment of oculomotor nerve palsy

Oculomotor nerve palsy resulting from non-aneurysmal vascular compression is extremely rare. Microvascular decompression (MVD) has been previously shown to improve oculomotor nerve palsy (ONP) secondary to arterial compression. A 71-year-old female, with a history of Cushing's disease previously treated with two transsphenoidal resections and Gamma Knife radiosurgery, presented with one year of progressive left eye diplopia and was diagnosed with a partial left oculomotor nerve palsy. We performed an orbitozygomatic craniotomy for MVD of the left posterior cerebral artery, which was found to be compressing the oculomotor nerve against the tentorium. Unfortunately, the patient's partial ONP remained unchanged at one year follow-up. The present case suggests inconsistent outcomes of MVD for ONP. Patients with prior sellar or parasellar irradiation may be less likely to benefit from this treatment approach.

A clinical study of ocular motor nerve functions after petroclival meningioma resection

BACKGROUND

Ocular motor dysfunction is one of the most common postoperative complications of petroclival meningioma. However, its incidence, recovery rate, and independent risk factors remain poorly explored.

METHODS

A prospective analysis of 31 petroclival meningiomas was performed. Operative approaches were selected by utilizing a new 6-region classification of petroclival meningiomas we proposed. Two scores were used to evaluate the functions of the oculomotor and abducens nerves. Pearson correlation analysis and binary logistic regression analysis were used to identify independent risk factors for intraoperative oculomotor and abducens nerve injury.

RESULTS

Postoperative new-onset dysfunctions in the pupillary light reflex and eye/eyelid movements as well as abducens paralysis were detected in eight (25.8%), ten (32.3%) and twelve (38.7%) cases, respectively. Their corresponding recovery rates after 6 months of follow-up were 75% (6/8), 80% (8/10), and 83.3% (10/12), respectively, and their mean times to start recovery were 4.03, 2.43, and 2.5 months, respectively. Tumor invasion into the suprasellar region/sphenoid sinus was the only risk factor for dysfunctions in both the pupillary light reflex (p = 0.001) and eye/eyelid movements (p = 0.002). Intraoperative utilization of the infratrigeminal interspace was the only risk factor for dysfunction in eyeball abduction movement (p = 0.004).

CONCLUSIONS

Dysfunctions of the oculomotor and abducens nerves recovered within 6 months postoperatively. Tumor extension into the suprasellar region/sphenoid sinus was the only risk factor for oculomotor nerve paralysis. Eye/eyelid movements were more sensitive than the pupillary light reflex in reflecting nerve dysfunctions. Intraoperative utilization of the infratrigeminal interspace was the only risk factor for abducens nerve paralysis.

The oculomotor neurovascular conflict: Literature review and proposal of management

BACKGROUND

The Oculomotor nerve (OCN) lies in a close relationship with large arteries inside the basal cisterns. Therefore, it may be compressed by vascular malformations or aneurysms. Nevertheless, the compression is not always related to pathologic conditions. Indeed, some cases of neurovascular conflicts of the OCN have been described in the literature.

METHODS

A case of neurovascular conflict of the OCN resolved after steroid treatment is reported. Additionally, a systematic literature review of those cases was performed.

RESULTS

OCN palsy due to a neurovascular conflict has been described as acute or chronic persistent palsy, or with an intermittent presentation. Symptoms result from compression, although asymptomatic compression is not uncommon. Surgical treatment, pharmacological treatment, and observation have been reported as options in the literature. Microvascular decompression was employed effectively in some cases of OCN neurovascular conflict. Nevertheless, other cases were treated successfully with steroids (persistent presentation) and carbamazepine (intermittent presentation). A management algorithm based on the results of the literature review is proposed.

CONCLUSIONS

Treatment options for OCN neurovascular conflicts and their results are heterogeneous. Based on the literature review, the pharmacological treatment seems to be the most appropriate first-line approach, reserving surgery for refractory cases. Collecting clinical information about new cases will allow defining treatment standards for this rare condition.

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.

Resection of Cavernous Sinus Meningioma via Lateral Orbitotomy Approach: 2-Dimensional Operative Video

Cavernous sinus meningiomas are rare benign tumors arising from the dural wall of the cavernous sinus. These complex lesions are difficult to access surgically but can lead to cranial nerve palsies if left untreated. The case described in this video involved a 14-yr-old girl who presented initially with right ocular pain at 9 yr old. Strabismus of the right eye developed when she was 10 yr old; it was treated surgically without improvement. She developed ptosis and worsening strabismus at age 13 yr, at which time magnetic resonance imaging revealed a lesion in the anterior cavernous sinus and superior orbital fissure. Given the progressively worsening oculomotor palsy and potential for future tumor growth because of her young age, the patient's family wished to pursue surgical rather than radiation treatment. The patient underwent a right lateral orbitotomy for exploration and resection of the lesion. She tolerated the procedure well. Postoperatively, she experienced improvement in her ocular pain and persistent oculomotor nerve palsy without any new neurologic deficits. Her cosmetic results from this incision were satisfactory. Postoperative computed tomography demonstrated thinning of the right lateral orbital wall and removal of the tumor. The pathological analysis of the tissue was consistent with a grade 1 meningioma. This video demonstrates the opportunity to resect a lesion from the cavernous sinus that prevents progressive cranial neuropathies. Some cavernous meningiomas are well circumscribed and can be resected totally. The patient's parents provided consent for publication.

Comparison of lateral and medial rectus muscle in human: an anatomical study with particular emphasis on morphology, intramuscular innervation pattern variations and discussion on clinical significance

This paper aims to present various aspects of the anatomy of horizontal (i.e., lateral and medial) rectus muscles. It mainly compares morphology and detailed patterns of intramuscular innervation of those muscles. It is also one of the first reports that uses the Sihler's stain to examine human extraocular muscles. The study was conducted on 80 isolated cadaveric hemi-heads. Sihler technique of nerves staining served to expose the course of intramuscular branches of the oculomotor and abducens nerves. The lateral rectus was longer (48 mm versus 46.5 mm) and more distant from the limbus (6.8 mm versus 5.7 mm) than the medial rectus muscle. Three variants of the abducens nerve primary division were observed in the lateral rectus muscle. In the medial rectus muscle, the motor branch from the oculomotor nerve was more evenly divided into sub-branches. In both examined horizontal rectus muscles, primary muscular branches split into secondary sub-branches, which undergo numerous further divisions. The most numerous terminal sub-branches formed the terminal plexus. The distance between the insertion and the anterior-most end of the terminal plexus referenced to the total length of the muscle ranged from 35.4 to 48.5% for the lateral rectus muscle and from 36.3 to 50.5% for medial rectus muscle. Both horizontal rectus muscles share similar general pattern of distribution of intramuscular nerves, with characteristic root-like arborizations of sub-branches. The terminal nerve plexus was observed near half of both muscles' length. Knowledge of variations and innervation pattern of the extraocular muscles may be relevant during ophthalmology surgeries.

Gone in the blink of an eye - A Tolosa-Hunt syndrome variant

Tolosa-Hunt syndrome is a rare disorder characterized by severe peri-orbital headache and ophthalmoplegia resulting from pseudotumour in the cavernous sinus compressing structures within it, namely cranial nerves III, IV, and VI and the superior divisions of cranial nerve V. We report the case of a 47 year old female who presented with painless left unilateral ptosis and complete external ophthalmoplegia. Magnetic Resonance Imaging (MRI) identified an enhancing heterogeneous mass filling the left cavernous sinus, following the course of the oculomotor nerve. After 2 weeks symptoms and signs resolved and there was a parallel resolution of the MRI findings, without the administration of corticosteroids. As far as we are aware this is one of the first reports of Tolosa-Hunt syndrome variant, with painless neurological involvement confined solely to the oculomotor nerve, and with complete resolution without pharmacological intervention.

Persistent Bilateral Mydriasis Associated With a Pituitary Adenoma in a Horse

Severe bilateral mydriasis and bilaterally decreased vision were observed in a 23-year-old crossbred warmblood gelding with a history of pituitary pars intermedia dysfunction. Ten years after the onset of clinical signs, it was killed humanely because of worsening of clinical signs and loss of therapeutic responsiveness. Postmortem examination of the head was performed to confirm the suspected pituitary neoplasm and to investigate secondary oculomotor lesions. Pathomorphologic examination revealed an expansile space-occupying pituitary adenoma and degenerative changes in the preganglionic oculomotor nerve, ciliary ganglion, and optic chiasm. The ocular clinical findings share features of a cavernous sinus syndrome.

Anatomical variations of the levator palpebrae superioris, including observations on its innervation and intramuscular nerves' distribution pattern

BACKGROUND

The levator palpebrae superioris muscle (LPS) acts as the upper eyelid's major elevator and retractor and is innervated by the oculomotor nerve. The muscle's paralysis is manifested by ptosis.

MATERIAL AND METHODS

70 orbits were dissected. After removing the orbital roof, the LPS' shape and anatomical variations (i.e., the presence of accessory muscular bands or atypical formation of the muscle) were assessed. To visualize the distribution of the oculomotor nerve's intramuscular sub-branches, the isolated levator palpebrae superioris muscles were stained using Sihler's staining technique.

RESULTS

Several LPS anatomical variations were observed in the specimens examined, in seven of which (7/70; 10%) additional delicate muscular slips arose from the LPS' lateral border and reached the lacrimal gland. Histological examination confirmed the presence of striated skeletal muscle fibers in all those cases. In three other specimens (3/70; 4.28%), supernumerary muscular bands ("tensor trochleae") were found that linked the levator with the superior oblique muscle's trochlea. In the next case, the LPS' origin was double and the muscle was bipartite on its proximal half. In most cases (55/70; 78.6%), muscular branches formed a single bundle that wrapped around the superior rectus muscle's medial border to reach the levator's inferior surface. Intramuscular sub-branches were distributed largely within the proximal two-thirds of the LPS and formed an irregular, tree-like pattern. However, thin sub-branches and small retrograde sub-branches extended as far as the muscle's insertion.

CONCLUSIONS

Plastic surgeons and ophthalmologists should be aware of the levator palpebrae superioris muscle's anatomic variations both in planning and conducting surgeries on the upper eyelid.

Prognosis Factor in Oculomotor Schwannoma: A Case of Endoscopic Endonasal Approach and Systematic Review of the Literature

BACKGROUND

We report the first case of oculomotor nerve (ON) schwannoma treatment through an endonasal endoscopic approach. We also review the literature to determine prognosis factors of ON function after treatment.

METHODS

A complete MEDLINE search was undertaken for all articles reporting data for oculomotor schwannoma. We divided the patient population into 2 groups; Group I: patients who conserved or recovered good ON function and Group II: patients with either new, worsening, or unchanged third-nerve palsy at the last available follow-up. We conducted a comparative statistical analysis of data between the 2 groups.

RESULTS

We identified 55 reported cases of ON schwannoma, all of whom were treated with open transcranial surgery, stereotactic radiosurgery, or observation. There were 22 patients in group I and 33 in group II. At admission, 29 patients had complete oculomotor nerve palsy (34.7% in group I and 67.7% in group II; P = 0.02). Surgical treatment was performed in 36 cases. Radiosurgery was performed in 3 cases. Among patients with good preoperative ON function, 34.6% worsened at last follow-up (26.6% after surgery and 50% with observation; P = 0.03). In total, 31% of patients with total or near-total palsy at admission had an improvement of their ON function (all after surgical resection; P = 0.05).

CONCLUSIONS

ON function at admission and surgical resection of schwannoma appears to be a predictive factor of favorable prognosis regardless of location and tumor size. The endonasal endoscopic approach can be used to biopsy tumors in cases in which open surgery is considered too risky, such as cavernous sinus schwannomas.

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.

Isolate unilateral oculomotor palsy after mild traumatic brain injury

Isolated traumatic oculomotor nerve (ON) palsy is an uncommon clinical presentation of mild traumatic brain injury (TBI). There are very few cases in which it has been possible to demonstrate the isolated damage of the ON by avulsion of the roots, accompanied with traumatic axonal injury and intraneural microhemorrhage. We present a 23-year-old female who, after mild TBI, began to experience right ptosis, binocular diplopia, and photophobia. Clinical examination showed a complete ophthalmoparesis of the right ON, without other neurological deficits. Neuroimaging studies demonstrated no structural compressive damage of the right ON. Magnetic resonance imaging (MRI) with Gradient-echo and T1 weighted post-gadolinium was made, demonstrating signs of intraneural hemorrhage of the right ON, in addition to traumatic axonal injury extending from the right cerebral peduncle to the orbital fissure. Specific MRI protocols contribute as evidence of an isolated lesion to the ON.

Comparative Analysis of Orbitozygomatic and Subtemporal Approaches to the Basilar Apex: A Cadaveric Study

BACKGROUND

The subtemporal and orbitozygomatic approaches are the most commonly used surgical approaches for the treatment of basilar artery apex (BAX) aneurysms. Relative advantages and disadvantages are generally reported based on surgeons' experience. This study was performed to provide a detailed comparison between the subtemporal and orbitozygomatic approaches based on cadaveric dissection analysis for the treatment of BAX aneurysms.

METHODS

Subtemporal and orbitozygomatic approaches were performed on 5 cadaveric heads (10 sides), and the following variables were assessed and compared between the 2 approaches: 1) number of exposed perforators on P₁-posterior cerebral arteries (PCA); 2) lengths of exposure and clipping for bilateral PCA, superior cerebellar arteries (SCA), and basilar trunk; 3) surgical area of exposure; and 4) surgical freedom at the BAX.

RESULTS

Number of perforators exposed on P₁-PCA was not different between the subtemporal and orbitozygomatic approaches. Exposure and clipping of ipsilateral SCA and PCA were superior using the subtemporal approach, and better for contralateral SCA and PCA using the orbitozygomatic approach, all reaching statistical significance. The orbitozygomatic approach provided greater exposure and clipping length for the proximal basilar trunk. Although the surgical area of exposure was similar between the 2 approaches, the overall surgical freedom was greater in the orbitozygomatic approach.

CONCLUSIONS

The orbitozygomatic approach provides a greater number of surgical corridors to the BAX and is superior regarding multiple surgically relevant anatomic parameters. Importantly, control over the basilar trunk and over the contralateral SCA and PCA (blind spots) is superior with the orbitozygomatic approach.

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.

Frontalis sling surgery: A treatment modality for cyclic oculomotor nerve palsy

Cyclic oculomotor nerve paresis and spasm are a rare disorder characterized by alternating spastic and paretic phase of the muscles supplied by the oculomotor nerve. A 26-year-old male presented with abnormal right eyelid movements since early childhood. Examination findings were consistent with diagnosis of right eye cyclic oculomotor nerve palsy. A paretic phase with complete upper eyelid ptosis, exotropia, hypotropia and dilatation of the pupil was followed by a phase of orthotropia, the absence of ptosis and normal pupil size. The whole cycle was of about 100 s duration with patient having no voluntary control over the eyelid movements and ocular alignment. Systemic evaluation and neuroimaging were normal. A tarsofrontal silicone sling surgery done for the ptosis correction decreased the eyelid movements during different phases of the cycle.

Massive Oculomotor Nerve Enlargement: A Case of Presumed Schwannomatosis

A 45-year-old man presented with a slowly progressive pupil-involving third nerve palsy. Magnetic resonance imaging (MRI) revealed a tubular lesion extending from the interpeduncular cistern through the cavernous sinus and into the left orbit where it branched into a superior and an inferior division, clearly outlining the anatomy of the third cranial nerve. Multiple other, less pronounced, enlarged cranial nerves were noted. The differential diagnosis included chronic inflammatory demyelinating polyneuropathy (CIDP), hereditary motor and sensory neuropathy (HMSN), neurofibromatosis (NF), and schwannomatosis. The absence of other muscle weakness and of sensory symptoms combined with normal peripheral nerve conduction studies effectively ruled out the hypertrophic polyneuropathies and pointed to a syndromic cause of multiple benign peripheral nerve sheath tumours (PNSTs). The authors are treating this case as presumed schwannomatosis, a syndrome similar to NF2 with much lower frequency of acoustic neuromas.