Unilateral Mydriasis without Ophthalmoplegia—A Sign of Neurovascular Compression?: Case Report

The Superior Cerebellar Artery: Variability and Clinical Significance

The superior cerebellar artery (SCA) arises from the distal part of the basilar artery and passes by the oculomotor, trochlear, and trigeminal nerves. SCA is known to play a crucial role in the development of trigeminal neuralgia. However, due to its anatomical variability, it may also trigger other neurovascular compression (NVC), including hemifacial spasm, oculomotor nerve palsy, and ocular neuromyotonia. Additionally, it may be associated with ischemic syndromes and aneurysm development, highlighting its clinical significance. The most common anatomical variations of the SCA include duplication, a single vessel origin from the posterior cerebral artery (PCA), and a common trunk with PCA. Rarely observed variants include bifurcation and origin from the internal carotid artery. Certain anatomical variants such as early bifurcation and caudal course of duplicated SCA trunk may increase the risk of NVC. In this narrative review, we aimed to examine the impact of the anatomical variations of SCA on the NVCs based on papers published in Pubmed, Scopus, and Web of Science databases with a snowballing approach. Our review emphasizes the importance of a thorough understanding of the anatomical variability of SCA to optimize the management of patients with NVCs associated with this artery.

Microvascular Decompression for Oculomotor Nerve Palsy due to Nonaneurysmal Vascular Compression

BACKGROUND

Diabetes mellitus and aneurysmal compression are well-known causes of oculomotor nerve palsy (ONP), but nonaneurysmal vascular compression of the oculomotor nerve has rarely been reported.

CASE DESCRIPTION

A 70-year-old nondiabetic man presented with left ONP for the past 2 days. Magnetic resonance imaging revealed the left posterior communicating artery to be compressing the left oculomotor nerve. Microvascular decompression of the offending artery from the nerve via a left frontotemporal craniotomy was performed; the nerve showed a color change suggestive of degenerative alteration. ONP was fully resolved within 1 month of surgery.

CONCLUSIONS

Whether nonaneurysmal vascular compression of the oculomotor nerve is a true cause of ONP is sometimes controversial. However, recent developments in magnetic resonance imaging can clearly demonstrate the spatial relationship between the oculomotor nerve and vessels. Detailed magnetic resonance imaging should be used to diagnose compression of the oculomotor nerve by blood vessels. Microvascular decompression is the treatment of choice in this situation.

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.

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.

Oculomotor nerve palsy secondary to aberrant posterior cerebral artery

The authors report a rare case of an oculomotor nerve palsy attributed to mass effect from an aberrant posterior cerebral artery. The patient presented with complete ptosis, mydriasis and ophthalmoplegia of the affected eye. MRI demonstrated distortion of the oculomotor nerve as it traversed inferior to the non-aneurysmal P1 segment of an aberrant posterior cerebral artery. The oculomotor nerve palsy resolved spontaneously.

[Unilateral isolated partial third nerve palsy and sphenoiditis in a child: A case report]

We report a case of unilateral mydriasis associated with sphenoid sinusitis and mucocele in a child. An 11-year-old girl with a history of unilateral mydriasis was referred for ophthalmologic examination. She complained of a mild headache over the past four days. The right pupil was dilated and nonreactive to light. The left pupil was normal and reactive. There was no ptosis or other focal neurological deficit. She was orthotropic. Visual acuity in both eyes, ocular motility and fundi were normal. Magnetic resonance imaging (MRI) showed a sphenoid sinus mucocele with sphenoiditis. The diagnosis was partial third nerve palsy without ophthalmoplegia. Treatment with antibiotics was initiated and led to complete resolution of the mydriasis. Sphenoid sinus mucoceles are relatively rare. Failure to diagnose and treat can lead to serious neurologic sequellae such as third nerve palsy, compressive optic neuropathy, cavernous sinus thrombosis, meningitis or brain abscess. Head imaging by reconstructed CT and MRI can lead to the diagnosis of mucocele. Isolated unilateral mydriasis as a sign of third nerve palsy may be caused by a slowly enlarging lesion. In a child with isolated unilateral mydriasis, head MRI should be performed to rule out a compressive lesion of the oculomotor nerve.

Anatomical features of the cisternal segment of the oculomotor nerve: neurovascular relationships and abnormal compression on magnetic resonance imaging

OBJECT

The object of this study was to assess the detailed anatomical features and vascular relationships of the cisternal segment of the oculomotor nerve, and to assess the utility of MR imaging in oculomotor nerve palsy caused by abnormal compression related to arteries and tumors.

METHODS

The anatomy of the oculomotor nerve was depicted using 3D Fourier transformation constructive interference in steady-state (CISS) MR imaging in 196 volunteers (392 total nerves), in 9 patients with paralysis of the oculomotor nerve, and in 1 preoperative patient with cholesteatoma in the pontine cistern. The vessels adjacent to the oculomotor nerve were detected and compared using 3D time-of-flight MR imaging. The 3D CISS multiplanar reconstruction (MPR) images of the oculomotor nerve in cadavers and in specimens from the cadavers were used to verify the oculomotor nerve shown in the 196 patients. The images were assessed with respect to the demonstration of the oculomotor nerve, the optimal display angles on MPR images, the visualized length of the nerve, neurovascular relationships, and abnormal compression caused by arteries and tumors.

RESULTS

Three-dimensional CISS MR imaging depicted the cisternal segment of the oculomotor nerve with certainty in 100% of the patients in the transverse, sagittal, and coronal planes. Three-dimensional CISS imaging of the oculomotor nerve in 196 volunteers revealed similar results corresponding to 3D CISS MPR images of cadavers and cadaver specimens. The maximum visualized length of the oculomotor nerve was 14.61 +/- 2.33 mm. The angle between the oculomotor nerve and the median sagittal plane was 24.48 +/- 4.57 degrees on the left and 24.48 +/- 5.07 degrees on the right. The posterior cerebral artery was observed to contact the oculomotor nerve in 216 (55.1%) of 392 nerves, and the superior cerebellar artery was observed to contact the oculomotor nerve in 231 (58.9%) of 392 nerves. The abnormal nerve compression in 9 patients with paralysis of the oculomotor nerve was displayed well in all patients. The adjacent relationship of the oculomotor nerve in 1 preoperative patient with cholesteatoma in the pontine cistern was also demonstrated clearly.

CONCLUSIONS

Use of 3D CISS sequences and 3D time-of-flight sequences enables accurate identification of the cisternal segment of the oculomotor nerve, neurovascular relationships, and abnormal compression caused by arteries and tumors.

Isolated unilateral ptosis and mydriasis from ventral midbrain infarction

We report a patient who has a tremor and unilateral ptosis and mydriasis without extraocular muscle paresis from an intra-axial lesion demonstrated on neuroimaging. Previously extraocular muscles sparing partial third nerve palsy has been thought to be due to extra-axial lesion such as vascular compression. Compared to proposed models for arrangement of oculomotor fascicle, this case demonstrates that it is possible to damage the fibers destined for levator and pupillomotor function without affecting the extra-ocular muscles.

The dilated pupil: an update

The dilated pupil can present a significant challenge to the clinician. Although in most cases a complete history and physical examination is sufficient to make an accurate diagnosis, selected patients will require further investigation, including pharmacologic testing and neuroimaging. This review outlines the physiology, clinical features, and diagnostic approach to the most important causes of the dilated pupil. Particular attention is given to recent publications on this topic.

Diagnosis and management of third nerve palsy

PURPOSE OF REVIEW

To provide clinically relevant information regarding the diagnosis, etiology, work-up and treatment of third cranial nerve palsies, while incorporating information from current publications and providing our opinions on these studies.

RECENT FINDINGS

In the past year, an important study focused on the confirmation of current neuro-imaging guidelines for third cranial nerve palsies. Recent case reports have highlighted etiologies such as giant cell arteritis, trauma, neuro-syphilis and demyelination secondary to infliximab and multiple sclerosis. Surgically, newer studies have focused on globe-tethering procedures for correcting strabismus and the use of frontalis suspension for correcting ptosis. Improved imaging technology with high-resolution magnetic resonance imaging (hr-MRI) allows for direct visualization of the entire nerve path and the affected muscles.

SUMMARY

Management of a third nerve palsy depends upon localization of the causative lesion and determination of the underlying etiology. Once these issues are addressed, strabismus surgery can be both challenging and rewarding in these complex patients.