Extracranial transport of brain lymphatics via cranial nerve in human.

Extracranial waste transport from the brain interstitial fluid to the deep cervical lymph node (dCLN) is not extensively understood. The present study aims to show the cranial nerves that have a role in the transport of brain lymphatics vessels (LVs), their localization, diameter, and number using podoplanin (PDPN) and CD31 immunohistochemistry (IHC) and Western blotting. Cranial nerve samples from 6 human cases (3 cadavers, and 3 autopsies) were evaluated for IHC and 3 autopsies for Western blotting. The IHC staining showed LVs along the optic, olfactory, oculomotor, trigeminal, facial, glossopharyngeal, accessory, and vagus nerves. However, no LVs present along the trochlear, abducens, vestibulocochlear, and hypoglossal nerves. The LVs were predominantly localized at the endoneurium of the cranial nerve that has motor components, and LVs in the cranial nerves that had sensory components were present in all 3 layers. The number of LVs accompanying the olfactory, optic, and trigeminal nerves was classified as numerous; oculomotor, glossopharyngeal, vagus, and accessory was moderate; and facial nerves was few. The largest diameter of LVs was in the epineurium and the smallest one was in the endoneurium. The majority of Western blotting results correlated with the IHC. The present findings suggest that specific cranial nerves with variable quantities provide a pathway for the transport of wastes from the brain to dCLN. Thus, the knowledge of the transport of brain lymphatics along cranial nerves may help understand the pathophysiology of various neurological diseases.

Evolution and development of extraocular motor neurons, nerves and muscles in vertebrates.

The purpose of this review is to analyze the origin of ocular motor neurons, define the pattern of innervation of nerve fibers that project to the extraocular eye muscles (EOMs), describe congenital disorders that alter the development of ocular motor neurons, and provide an overview of vestibular pathway inputs to ocular motor nuclei. Six eye muscles are innervated by axons of three ocular motor neurons, the oculomotor (CNIII), trochlear (CNIV), and abducens (CNVI) neurons. Ocular motor neurons (CNIII) originate in the midbrain and innervate the ipsilateral orbit, except for the superior rectus and the levator palpebrae, which are contralaterally innervated. Trochlear motor neurons (CNIV) originate at the midbrain-hindbrain junction and innervate the contralateral superior oblique muscle. Abducens motor neurons (CNVI) originate variously in the hindbrain of rhombomeres r4-6 that innervate the posterior (or lateral) rectus muscle and innervate the retractor bulbi. Genes allow a distinction between special somatic (CNIII, IV) and somatic (CNVI) ocular motor neurons. Development of ocular motor neurons and their axonal projections to the EOMs may be derailed by various genetic causes, resulting in the congenital cranial dysinnervation disorders. The ocular motor neurons innervate EOMs while the vestibular nuclei connect with the midbrain-brainstem motor neurons.

Two cases of Duane retraction syndrome with abnormal orbital structures.

Duane retraction syndrome (DRS) is a rare congenital nonprogressive restrictive strabismus. The absence/hypoplasia of the abducens nerve and the aberrant innervation of the lateral rectus muscle by the oculomotor nerve have been hypothesized as causes of DRS, although the phenomenon of globe retraction can also occur in the setting of mechanical factors, such as congenital abnormal orbital structures or orbital trauma. We present the cases of 2 DRS patients with absent abducens nerve and abnormal muscular bands connecting the superior rectus and inferior rectus muscles on the temporal side of the optic nerve.

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.

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.

Clinical Reasoning: A 74-Year-Old Woman Presenting With Monocular Ptosis and Binocular Diplopia.

A 74-year-old woman presented with acute-onset right ptosis and binocular diplopia. CT scan showed low-density lesions in the bilateral basal ganglia and adjacent to lateral ventricles. Intracranial aneurysm was not detected. This case highlights the importance of neurologic localization of ophthalmoplegia based on physical examination and the microanatomy of the oculomotor nerve.

An unexpected case report of epidermoid cyst at the oculomotor nerve: mimicking a common cyst on MRI.

Intracranial epidermoid cysts are benign lesions and are rarely seen in clinical practice. Owing to similarities in imaging findings to those of common cystic lesions, the preoperative diagnosis is rendered challenging. Here, we present a case report of an epidermoid cyst at the right oculomotor nerve, which was initially misdiagnosed as a common cyst. A 14-year-old female child was admitted to our department due to a previous magnetic resonance imaging scan of a cystic lesion on the right side of the saddle that was suspected to be an oculomotor nerve cyst. In our department, this patient underwent a complete surgical resection of the tumor, and the pathology results revealed an epidermoid cyst. This is the first study that reported an epidermoid cyst at the right oculomotor nerve entering the orbit, mimicking a common cyst in imaging. We hope that this study would allow clinicians to consider this type of lesion as a differential diagnosis. Moreover, we suggest that specific diffusion-weighted imaging scan should be performed to aid in the diagnosis.

Third cranial nerve palsy due to COVID-19 infection.

We report a case of a previously healthy man in his 40s who presented with mild SARS-CoV-2 infection (COVID-19) concomitant with acute onset of left third cranial nerve palsy with restricted supraduction, adduction and infraduction. Our patient did not present any history of hypertension, hyperlipidaemia, diabetes mellitus or smoking. The patient recovered spontaneously without any antiviral treatment. To our knowledge, this is the second report of third cranial nerve palsy spontaneously resolved without any risk factors of vascular disease, specific image findings, nor any possible causes other than COVID-19. In addition, we reviewed 10 other cases of third cranial nerve palsy associated with COVID-19, which suggested that the aetiology varies greatly. As a clinician, it is important to recognise COVID-19 as a differential diagnosis for third cranial nerve palsy. Finally, we aimed to encapsulate the aetiologies and the prognosis of the third cranial nerve palsy associated with COVID-19.

Oculomotor nerve palsy as an extraintestinal manifestation of Crohn's disease.

Patients with inflammatory bowel disease (IBD) may present with extraintestinal manifestations. Neurological symptoms associated with IBD are infrequent. Thus, any unexplained neurological symptom that occurs in patients with IBD should raise the suspicion of a link between the two disorders. We report a case of a man in his 60s, who was diagnosed with Crohn's disease and developed ptosis and diplopia. Neurological examination revealed oculomotor nerve palsy, sparing the pupil. MRI and magnetic resonance angiography of the brain were insignificant and no other cause was determined. He was treated with oral corticosteroids and symptoms gradually subsided. Cranial nerve palsies associated with IBD have been rarely reported. They usually involve the optic and acoustic nerve and are attributed to a common dysimmune base. This is the first reported case of oculomotor nerve palsy (III cranial nerve) associated with IBD. Clinicians treating patients with IBD should be alert for unusual neurological complications and treat them appropriately.

Fenestrated P1 segment of posterior cerebral artery, partly duplicated posterior communicating artery.

PURPOSE: Anatomic variations at the junction of primitive internal carotid and basilar arteries are exceedingly rare. We aimed at reporting such rare variants involving the posterior communicating artery (PComA) and the P1 segment of posterior cerebral artery (PCA). METHODS: The circle of Willis was dissected in an adult cadaver after removal of the cranial vault and cerebral hemispheres. RESULTS: The basilar end was rotated axially to the right. The P1 segment of the right PCA was fenestrated and occupied the interpeduncular fossa. The right PComA passed over the oculomotor nerve to join the anterior arm of the P1 fenestration. On the opposite side, the PComA coursed supero-medially to the oculomotor nerve and it had a partly duplicated posterior end, with two arms, medial, larger, and lateral, thinner, inserting successively into the left PCA. CONCLUSION: Extremely rare anatomic variations of the circle of Willis should not be ignored when endovascular or microneurosurgical specific approaches are intended.

Morphometry and anatomical variations of the inferior oblique muscle as relevant to the strabismus surgeries.

Effective outcome of inferior oblique (IO) corrective surgeries demands a detailed knowledge of morphometry and variations of IO. Our aim was to study and morphometrically define the surgical anatomy of the IO muscle and its variations. Also to provide easily identifiable surgical coordinates to locate, the IO origin and the oculomotor nerve entry point into the IO. Dissection was performed on 16 cadaveric orbits. IO anatomy, variations, morphometry and relevant surgical distances were measured using digital caliper. IO with multiple bellies was found in five specimens. The IO mean length was 33.1 ± 3.3 mm, width at origin was 3.1 ± 0.6 mm, and width at insertion was 8.8 ± 1.5 mm. For easy localization of origin, its distance from the palpable landmarks, Zygomatico-maxillary suture and fronto-maxillary suture was measured. The mean distance between IO and the optic nerve was 10 mm. Distance of the nerve to inferior oblique entry point to the origin and insertion of the inferior oblique was measured. The nerve to IO was 28 mm long. The mean distance of the nerve entry point to IO origin was 15.5 ± 2.3 mm and distance to IO insertion was 15.2 ± 2.8 mm. A muscular bridge between the Inferior rectus (IR) & IO was found in one case, affecting ~» of the IO length; the distal end of the bridge was 5 mm from the IO insertion. Origin of the IO can be localized on the orbital surface of maxilla, 1-2 cm from the point where zygomatico-maxillary suture cuts the inferior orbital margin and 1-2 cm from the fronto-maxillary suture. In 19% of the orbits, the IO length was less than 30 mm, which may cause traction injury in muscle transposition procedures. The width at insertion is useful as most corrective surgeries are performed at the insertion site. The nerve to IO consistently entered at the center of medial border. The nerve entry point is important surgically as myectomy is performed between it and the insertion point. The safe distance available from the optic nerve was 7 mm. Detailed morphometry of IO may aid surgeons in better surgical planning and execution.

COVID-19 and isolated oculomotor nerve palsy: Clinical features and outcomes.

AIM: This study aims to describe the clinical characteristics of patients with isolated oculomotor nerve palsy from COVID-19 infection, and provide guidance on their treatment and management. METHODS: We performed a systematic review and retrospective analysis on the clinical features and outcomes of patients with isolated oculomotor nerve palsy from COVID-19 reported in literature over the past three years. RESULTS: We analyzed a total of 11 cases; 9 identified in literature from January 2020 to September 2022, together with our two patients. Their median age was 46 years (range 2-65), and three were children. More than half (6/11, 55 %) were without medical history. Oculomotor nerve palsies tended to occur early (longest interval of 16 days), but they can also occur concurrently (2/11, 18 %) or before the appearance of COVID-19 symptoms (1/11, 9 %). COVID-19 symptoms tended to be mild (8/11, 73 %). Oculomotor nerve palsies, however, displayed neither a clear gender predilection, nor consistent clinical features in terms of the severity of extraocular weakness and the involvement of pupillary light responses. Nearly two-thirds (7/11, 64 %) received no pharmacological treatment. Regardless, recovery was complete in nearly all (9/10, 90 %), with most occurring within a month (8/9, 89 %) CONCLUSION: Isolated oculomotor nerve palsies are early but uncommon complications of COVID-19. They affect patients with mild infections, and can be the first symptom. Prognosis is excellent, with recovery being often complete and early. Early discharge and outpatient clinical review, with or without short courses of oral steroids, are reasonable treatment measures.

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.

A Newly Discovered Dural Venous Sinus of the Skull Base: The Anterior Petroclinoid Sinus.

INTRODUCTION: Neurosurgeons must master microanatomy and its variants that occur at the skull base. To the best of our knowledge, we describe a previously unreported dural venous sinus (DVS) within the anterior petroclinoid fold and discuss its potential surgical relevance. METHODS: Fifteen latex-injected human cadaveric heads (30 sides) underwent skull base dissection using a surgical microscope. The anterior petroclinoid fold was opened in search of evidence of an embedded DVS. When identified, this sinus was documented, photographed, and measured with microcalipers. RESULTS: An anterior petroclinoid sinus (APCS) was identified in 67% of sides. These DVSs had a mean diameter of 0.65 mm and a length ranging from 8 to 15 mm (mean: 12.5 mm). The APCS ran from the anterior aspect of the cavernous sinus, arising just lateral (60%), posterior (20%), or medial (20%) to the anterior clinoid process, to the superior petrosal sinus (65%) or the posterior aspect of the cavernous sinus (35%), at the level of the posterior clinoid process. Along the course of the APCS, the oculomotor nerve was located medially at the oculomotor porus. Although slightly more common and larger on the right side, there was no statistically significant side difference. CONCLUSIONS: An improved knowledge of variant DVSs can lower the risk of intraoperative complications and increase our understanding of the venous outflow from the cavernous sinus. Future neuroimaging techniques might also seek to identify the APCS. This is the first description of a DVS contained within the anterior petroclinoid fold.