Intradural anatomy and mobilization techniques of oculomotor, trochlear and abducens nerve after microsurgical dissection: a cadaveric study.

BACKGROUND: This study investigates the mobilization of cranial nerves in the upper clival region to improve surgical approaches. Cadaveric specimens (n = 20) were dissected to examine the oculomotor, trochlear, and abducens nerves. Dissection techniques focused on the nerves' intradural course and their relationship to surrounding structures. METHODS: Pre-dissection revealed the nerves' entry points into the clival dura and their proximity to each other. Measurements were taken to quantify these distances. Following intradural dissection, measurements were again obtained to assess the degree of nerve mobilization. RESULTS: Dissection showed that the abducens nerve takes three folds during its course: at the dural foramen, towards the posterior cavernous sinus, and lastly within the cavernous sinus. The trochlear nerve enters the dura and makes two bends before entering the cavernous sinus. The oculomotor nerve enters the cavernous sinus directly and runs parallel to the trochlear nerve. Importantly, intradural dissection increased the space between the abducens nerves (by 4.21 mm) and between the oculomotor and trochlear nerves (by 3.09 mm on average). This indicates that nerve mobilization can create wider surgical corridors for approaching lesions in the upper clivus region. CONCLUSIONS: This study provides a detailed anatomical analysis of the oculomotor, trochlear, and abducens nerves in the upper clivus. The cadaveric dissections and measurements demonstrate the feasibility of mobilizing these nerves to achieve wider surgical corridors. This information can be valuable for surgeons planning endoscopic or microscopic approaches to lesions in the upper clivus region.

A Modified Anterior Petrosectomy Approach for Resection of Petroclival Meningioma; with Management of Complications.

Due to deep location and for being adjacent to neurovascular structures, petroclival meningiomas (PCMs) are generally considered to be associated with a high rate of recurrence and cranial nerve deficits.1 This video presents a 49-year-old female patient reporting right trigeminal neuralgia for more than 1 year. The incidence of this symptom with PCMs is about 5%.2 According to the classification system proposed by Kawase et al.3 and Ichimura et al.,4 this is a tentorium type PCM. A modified anterior petrosectomy approach was adopted based on the tumor size and its origin. The case presentation, surgical technique, postoperative outcome are reviewed. The treatments to the intraoperative trochlear nerve injury and temporal bridging vein occlusion are displayed (Video 1). The patient gave verbal consent for participating in the procedure and surgical video.

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Objective: To study the microanatomic structure of the subtemporal transtentorial approach to the lateral side of the brainstem, and to provide anatomical information that will assist clinicians to perform surgeries on the lateral, circumferential, and petroclival regions of the brainstem. Methods: Anatomical investigations were conducted on 8 cadaveric head specimens (16 sides) using the infratemporal transtentorial approach. The heads were tilted to one side, with the zygomatic arch at its highest point. Then, a horseshoe incision was made above the auricle. The incision extended from the midpoint of the zygomatic arch to one third of the mesolateral length of the transverse sinus, with the flap turned towards the temporal part. After removing the bone, the arachnoid and the soft meninges were carefully stripped under the microscope. The exposure range of the surgical approach was observed and the positional relationships of relevant nerves and blood vessels in the approach were clarified. Important structures were photographed and the relevant parameters were measured. Results: The upper edge of the zygomatic arch root could be used to accurately locate the base of the middle cranial fossa. The average distances of the star point to the apex of mastoid, the star point to the superior ridge of external auditory canal, the anterior angle of parietomastoid suture to the superior ridge of external auditory canal, and the anterior angle of parietomastoid suture to the star point of the 10 adult skull specimens were 47.23 mm, 45.27 mm, 26.16 mm, and 23.08 mm, respectively. The subtemporal approach could fully expose the area from as high as the posterior clinoid process to as low as the petrous ridge and the arcuate protuberance after cutting through the cerebellar tentorium. The approach makes it possible to handle lesions on the ventral or lateral sides of the middle clivus, the cistern ambiens, the midbrain, midbrain, and pons. In addition, the approach can significantly expand the exposure area of the upper part of the tentorium cerebelli through cheekbone excision and expand the exposure range of the lower part of the tentorium cerebelli through rock bone grinding technology. The total length of the trochlear nerve, distance of the trochlear nerve to the tentorial edge of cerebellum, length of its shape in the tentorial mezzanine, and its lower part of entering into the tentorium cerebelli to the petrosal ridge were (16.95±4.74) mm, (1.27±0.73) mm, (5.72±1.37) mm, and (4.51±0.39) mm, respectively. The cerebellar tentorium could be safely opened through the posterior clinoid process or arcuate protrusion for localization. The oculomotor nerve could serve as an anatomical landmark to locate the posterior cerebral artery and superior cerebellar artery. Conclusion: Through microanatomic investigation, the exposure range and intraoperative difficulties of the infratemporal transtentorial approach can be clarified, which facilitates clinicians to accurately and safely plan surgical methods and reduce surgical complications.

The Course of the Trochlear Nerve Presented via a 3-Dimensional Photorealistic Anatomic Model.

OBJECTIVES: Several factors contribute to the anatomical complexity of the trochlear nerve, including small diameter, complex and longest intracranial course, deep location, and numerous neurovascular relationships. A 3-dimensional (3D) photorealistic model of the cranial nerves provides a detailed and immersive representation of the anatomy, enabling one to improve surgical planning, advanced surgical research, and training. The purpose of this work is to present a 3D photogrammetric study for a more intuitive and interactive way to explore and describe the entire course of trochlear nerve. METHODS: Two injected-fixed head human specimens (4 sides) were examined. The dissection protocol was divided into the following steps: 1) brain hemisphere exposure; 2) hemispherectomy dissecting all cranial nerves and partial removal of the free edge of the tentorium; 3) middle fossa and lateral wall of cavernous sinus exposure; and 4) orbital exposure. A detailed 3D photogrammetric model was generated for each dissection step. RESULTS: Four main volumetric models were generated during a step-by-step layered dissection of the entire nerve pathway highlighting its different segments. Finally, a full and integrated model of the entire course of the nerve was created. The models are available for visualization on monoscopic display, virtual, and augmented reality environment. CONCLUSIONS: The present photogrammetric model provides a more comprehensive understanding of the nerve's anatomy in its different segments, allows for customizable views thus simulating different perspectives, and can be a valuable alternative to traditional dissections. It is an advanced tool for surgical planning and surgical simulation as well as virtual reality representation of the anatomy.

Case Report and Literature Review: Isolated Trochlear Nerve Palsy due to Herpes Zoster Infection.

Introduction: Trochlear nerve palsy (TNP) is a common cause of vertical diplopia resulting from superior oblique muscle weakness. While herpes zoster is a well-documented cause of cranial neuropathies, reports of TNP associated with herpes zoster infection remain limited. Case Presentation: We report a case of a 65-year-old patient with typical herpes zoster ophthalmicus on the left side of his face with subsequent corneal endotheliitis and isolated TNP. The MRI revealed a faint enhancement at the cavernous sinus on the same side as the TNP. Cerebrospinal fluid detected human herpesvirus 3, confirming the diagnosis. An intravenous antiviral was administered for 14 days with prolonged maintenance to prevent recurrence. Oral corticosteroids were also used as an adjuvant to reduce inflammation. After treatment, the uveitis subsided, and the vertical diplopia recovered partially. TNP from herpes zoster is a rare presentation. The underlying pathogenic mechanisms, including potential direct viral invasion, inflammatory responses, and possible vasculopathy affecting the trochlear nerve, are explored. Conclusion: TNP can be a rare neuro-ophthalmic complication of herpes zoster infection. Clinicians should maintain a high index of suspicion when assessing patients with cranial neuropathies in the context of herpes zoster. Prompt antiviral therapy and supportive measures can aid in the resolution of symptoms and alleviate potential long-term sequelae.

Compressive lesions of the head and neck: Common and uncommon must-know entities.

There are many lesions that cause compression of nerves and vessels in the head and neck, and they can often be overlooked in the absence of adequate history or if not suspected by the radiologist. Many of these lesions require a high index of suspicion and optimal positioning for imaging. While a multimodality approach is critical in the evaluation of compressive lesions, an MRI utilizing high-resolution (heavily weighted) T2-weighted sequence is extremely useful as a starting point. In this review, we aim to discuss the radiological features of the common and uncommon compressive lesions of the head and neck which are broadly categorized into vascular, osseous, and miscellaneous etiologies.

Postoperative outcomes for unilateral congenital trochlear nerve palsy: A retrospective cohort study.

PURPOSE: Congenital trochlear nerve palsy is the most common cause of vertical strabismus. The goal of this study was to investigate surgical outcomes after superior oblique tendon plication with or without inferior oblique recession in children and adults with unilateral congenital trochlear nerve palsy. METHODS: Data and outcomes were collected in patients with a diagnosis of unilateral congenital superior oblique palsy during a retrospective single-center study conducted at the University Hospital of Tours. A reproducible, standard ophthalmological and oculomotor examination was performed pre- and postoperatively at 1 year, including presence or absence of diplopia, vertical and horizontal deviations, and compensatory head posture. Surgical success, defined as an endpoint including absence of diplopia in primary position, absence of head tilt, and vertical deviation at distance fixation<5 prism diopters (PD), was analyzed. RESULTS: A total of fifty-seven patients (median [IQR] age of 11 years [5-42]) were analyzed. Patients experienced a significant reduction in vertical distance and near deviations (p<0.001), compensatory head tilt (p < 0.001), and diplopia after surgery (p < 0.001). Surgical success was higher in adults (17/24, 70.8%) than in children (15/33, 45.5%), although this did not reach statistical significance (p=0.0657). CONCLUSION: This study suggests that plication of the superior oblique muscle tendon, with or without recession of the inferior oblique muscle, can be effective in treating unilateral congenital trochlear nerve palsy. Further studies are necessary to compare surgical procedures and investigate their efficacy in adults compared to children in the short and long term.

Comparison of head tilt test between sagging eye syndrome and acquired unilateral trochlear nerve palsy.

PURPOSE: To investigate the distinction between sagging eye syndrome (SES group) and acquired unilateral trochlear nerve palsy (Trochlear group) in the Bielschowsky head tilt test (BHTT). METHODS: Fifteen patients in the SES group (mean age 74.6 ± 5.2 years) and 14 patients in the Trochlear group (55.2 ± 15.9 years) visited the Department of Ophthalmology, Hyogo Medical University Hospital between November 2016 and October 2022 for treatment of their diplopia. Eye position was measured with the alternate prism cover test, and values for fixation of the dominant eye, or unaffected eye, were used. Cyclodeviation was measured with the synoptophore and the Glaucoma Module Premium Edition of the SPECTRALIS optical coherence tomography. In the BHTT, eye position was measured in three head postures: primary position (PP), head tilt to the side with hypertropia (Hyper), and head tilt to the side with hypotropia (Hypo). The differences in vertical deviation between PP and Hyper (Hyper - PP), PP and Hypo (PP - Hypo) and Hyper - Hypo were measured and compared. RESULTS: Vertical deviation in primary position was 7.3 ± 4.5 PD in the SES group and significantly larger (17.1 ± 8.4 PD) in the Trochlear group (p = 0.002). The vertical deviation in Hyper was significantly larger in the Trochlear group with 7.7 ± 4.7 PD and 22.1 ± 9.4 PD, respectively (p < 0.001), whereas the that in Hypo was not significantly different between the two groups with 6.5 ± 3.4 PD and 8.4 ± 6.6 PD, respectively (p = 0.725). The SES group showed no significant difference according to the 3 head postures (p = 0.311), while the Trochlear group showed a significantly different with smaller mean values in vertical deviation in Hypo (p < 0.001). The difference in the vertical deviation for the 3 head postures was the largest in Hyper - Hypo (1.7 ± 2.1 PD and 13.6 ± 7.1 PD, respectively), and the accuracy of SES was at the cutoff value of 6 PD, and it was considered not to be SES if the value was 6PD or higher. The accuracy of SES determination was 100% sensitivity and 100% specificity, and the area under the curve was 1.0. CONCLUSION: The difference in Hyper - Hypo in the BHTT may be the most useful index in differentiating SES from acquired unilateral trochlear nerve palsy; if the difference was more than 6 PD, the probability of SES was very low.

Petroclival Clinoidal Folds and Relationships with Arachnoidal Membranes and Neural Structures of Anterior and Middle Incisural Spaces: Old Neuroanatomical Terms for a New Neurosurgical Speech in Cadaver Labs with Limited Resources Era. Part I: Osteology and Structural Anatomy of Dura Mater.

Purpose The role of cadaver labs in preparing new generations of effective neurosurgeons is of paramount importance. The Authors describe a personal cadaver lab experience aimed at improving the knowledge of a difficult region of the central skull base. The anterior and middle incisural spaces are regions of remarkable anatomical, and surgical interest due to complex relationships between bony, dural, arachnoidal, and neurovascular structures. The primary purpose of this study is (1) to describe the anatomy of this region with particular emphasis on the relationships between the anterior margin of the free edge of the tentorium and the sphenoid and petrous bone; (2) to identify surgical implications in many different types of neurosurgical procedures dealing with this challenging complex anatomic area.Methods Eight fresh, non-formalin-fixed non-silicon-injected adult cadaver heads and five injected formalin-fixed adult cadaver heads were analyzed in this study.Results The anatomical study was focused on the description of the relationships between bony, dural, arachnoid, and neurovascular structures. Surgical implications are described accordingly.Conclusions Detailed anatomical knowledge of this region finds concrete applications in neurosurgical practice since the anterior and middle incisural spaces are often surgically exposed in neoplastic and vascular diseases.

Petroclival Clinoidal Folds and Relationships with Arachnoidal Membranes of Anterior and Middle Incisural Spaces: Old Neuroanatomical Terms for a New Neurosurgical Speech in Cadaver Labs with Limited Resources Era. Part II: Free Edge of the Tentorium, Petroclinoid Folds, and Incisural Spaces.

BACKGROUND Anatomical dissections play an irreplaceable role in the training of new generations of effective neurosurgeons, especially when addressing skull base lesions is required.The Authors describe an inter-laboratory dissection study aimed at improving the knowledge of a complex region of the skull base. The anterior and middle incisural spaces are of remarkable anatomical and surgical interest due to complex relationships between bony, dural, arachnoidal, and neurovascular structures. The primary purposes of this study are to describe the anatomy of this region with particular emphasis on the relationships between the anterior margin of the free edge of the tentorium and the sphenoid and petrous bone; to identify surgical implications in many different types of neurosurgical procedures dealing with this challenging, complex anatomic area.METHODS Thirteen anatomical specimens, including five injected specimens, were dissected in this study. In the formalin-fixed specimens, vessels were injected with colored silicone.RESULTS The anatomical study was focused on the description of the relationships between bony dural, arachnoid, and neurovascular structures. Surgical implications are described accordingly.CONCLUSIONS Detailed anatomical knowledge of this region finds concrete applications in neurosurgical practice since the anterior and middle incisural spaces are often surgically exposed in neoplastic and vascular diseases. The high-definition pictures reported in this study could represent useful support to understand the anatomy of this complex region.Finally, our study could provide guidance to neurosurgical centers in which resources are limited that are either planning to establish their own cadaver dissection laboratory or failed to do so because of the supposed high-costs.

Petroclival Clinoidal Folds and Relationships with Arachnoidal Membranes of Medial Incisural Space: Old Neuroanatomical Terms for a New Neurosurgical Speech in Cadaver Labs with Limited Resources Era. Part III: Arachnoid Membranes, Cranial Nerves, and Surgical Implications.

BACKGROUND Anatomical dissections play an irreplaceable role in the training of new generations of effective neurosurgeons, especially when addressing skull base lesions is required.The Authors describe an inter-laboratory dissection study aimed at improving the knowledge of a complex region of the skull base. The anterior and middle incisural spaces are of remarkable anatomical and surgical interest due to complex relationships between bony, dural, arachnoidal, and neurovascular structures. The primary purposes of this study are to describe the anatomy of this region with particular emphasis on the relationships between the anterior margin of the free edge of the tentorium and the sphenoid and petrous bone; to identify surgical implications in many different types of neurosurgical procedures dealing with this challenging complex anatomic area.METHODS Thirteen anatomical specimens, including five injected specimens, were dissected in this study. In the formalin-fixed specimens, vessels were injected with colored silicone.RESULTS The anatomical study focused on the description of the relationships between bony dural, arachnoid, and neurovascular structures. Surgical implications are described accordingly.CONCLUSIONS Detailed anatomical knowledge of this region finds concrete applications in neurosurgical practice since the anterior and middle incisural spaces are often surgically exposed in neoplastic and vascular diseases. The high-definition pictures reported in this study could represent useful support to understand the anatomy of this complex region.Finally, our study could provide guidance to neurosurgical centers in which resources are limited that are either planning to establish their own cadaver dissection laboratory or failed to do so because of the supposed high-costs.

Imaging of trochlear nerve schwannomas: a case series and systematic review of the literature.

Purpose Trochlear nerve schwannomas are rare tumors. So far, only 121 cases have been published. We present four new cases, discuss the imaging characteristics and summarize all previously published cases through a systematic review.Methods Four cases, all treated in AZ Sint-Jan Hospital Brugge-Oostende (Belgium), were collected, including their demographic, clinical and radiological data. All MR imaging was performed with the three-dimensional fluid-attenuated inversion recovery (3D-FLAIR), turbo spin echo T1 high-resolution (TSE T1 HR), three-dimensional balanced fast-field echo (3D b-FFE) and three-dimensional T1 black blood (3D T1 black blood) sequence. We compared our findings with the present literature through a systematic literature review in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.Results Screening with routine unenhanced 3D-FLAIR imaging could identify all schwannomas as hyperintense lesions on the course of the trochlear nerve. The use of 3D T1 black blood sequences was superior in depicting the lesions, while high-resolution 3D b-FFE images enabled us to visualize the anatomic boundaries of the lesions in detail. Most trochlear schwannomas are located in the ambient cistern, at or just below the free edge of the tentorium.Conclusion The majority of trochlear nerve schwannomas are located cisternal and display variable enhancement on contrast administration. 3D-FLAIR imaging is superior in detecting these lesions. Comparison with data collected from previous cases demonstrates the importance of early diagnosis and treatment. Generally, patients with trochlear nerve schwannomas have a good prognosis.

COVID-19 and sudden-onset ocular neurogenic palsy in prior healthy patients: a systematic review.

BACKGROUND: The aim of this systematic review is to identify cases of neurogenic ocular palsy in the presence of COVID-19 and to document patient characteristics, type of palsy and possible aetiologies. METHODS: A systematic search of PubMed, Medline and CINAHL databases was conducted on the 6th of January 2023 to identify cases of neurogenic ocular palsy in patients with current or previous COVID-19 infection. Data were pooled to summarise the neurogenic palsy, patient clinical characteristics and proposed palsy mechanisms. RESULTS: The combined database search yielded 1197 articles. Of these, 23 publications consisting of 25 patients met the inclusion criteria. Most patients were male (68%) and ranged in age from 2 to 71 years (median=32.7, SD=21.4). Seven patients (28%) were children aged 2 to 10 years old. Abducens palsies were most common (68%) and the most common ocular presentation was diplopia (76%) with an average time of onset 15 days from testing positive to COVID-19 or having symptoms of the virus. Proposed mechanism of development of a neurogenic palsy secondary to COVID-19 infection was classified into one of three categories: vascular/thrombotic, a viral neuro-invasive or inflammatory virus-mediated immune response. DISCUSSION: This study suggests that COVID-19 infection may be linked to oculomotor, trochlear and abducens nerve palsies and the underlying mechanisms may vary but are difficult to definitively establish. Further studies investigating the onset of neurogenic palsy secondary to COVID-19 infection is required.

Microsurgical Resection of a Giant Trochlear Nerve Schwannoma: 2-Dimensional Operative Video.

We present the case of a 17-year-old male, who complained of a 1-year onset of pulsatile headache, dysphagia, speech changes, and emotional lability. Neuroimaging revealed a large left-sided contrast-enhancing tumor located at the infratentorial space consistent with a large trochlear nerve schwannoma. The tumor was compressing the brainstem, obstructing the outflow of the third and lateral ventricles causing hydrocephalus, and disturbing the cortico-bulbar pathways bilaterally leading to the diagnosis of pseudobulbar palsy. After the patient consented the surgical procedure, he was operated through a subtemporal transtentorial approach placed in the lateral position. A lumbar drain was used for brain relaxation during the procedure and image guidance to define the limits of surgical exposure. A microsurgical technique was used, aiming to preserve the cranial nerves and the vascular structures running through the perimesencephalic cisterns. Gross total resection was achieved and clinical course remained uneventful aside from a transient third nerve palsy. Symptoms improved and the three-month follow-up revealed an almost complete function of the oculomotor nerve (Video 1). Trochlear nerve schwannomas are the rarest variety of the cranial nerve schwannomas. Depending on tumor size, clinical and neuroimaging signs of mass effect and brainstem compression, treatment can be observation, microsurgical resection through cranial base approaches or radiosurgery.1-5.

Case report: isolated trochlear nerve palsy associated with posterior cerebral artery aneurysm.

We describe a case of isolated trochlear nerve palsy caused by an unruptured posterior cerebral artery (PCA) aneurysm in an 82-year-old male who consulted an ophthalmologist after developing diplopia. Magnetic resonance angiography showed a left PCA aneurysm in the ambient cistern, and T2WI showed an aneurysm compressing the left trochlear nerve to the cerebellar tentorium. Digital subtraction angiography revealed that the lesion was located between the left P2a segment. We attributed this isolated trochlear palsy to left PCA unruptured aneurysm pressure. Thus, we performed stent-assisted coil embolization. The aneurysm was obliterated, and trochlear nerve palsy improved completely.

Oculomotor and trochlear nerve neuritis following botulinum toxin injection for masseter hypertrophy - a case report with literature review.

OBJECTIVE: To report a rare complication of oculomotor and trochlear nerve neuritis following botulinum toxin injection for masseter hypertrophy. CASE PRESENTATION: A previously healthy 31-year-old man presented with a two-week history of left eye (OS) ptosis and diplopia, following botulinum toxin injection over the masseter area for masseter hypertrophy at an aesthetic centre. He had no proptosis or facial asymmetry. Visual acuity was 6/6 in the right eye (OD) and 6/9 in the OS. There was anisocoria, with pupils measuring 3 mm in the OD and 5 mm in the OS but no relative afferent pupillary defect. OS appeared hypertropic in primary gaze with impaired intorsion. Extraocular movement of the OS was restricted in all gazes, except for laevoversion; that of the OD was normal. This was associated with diplopia in all gazes except on laevoversion. Both eyes' anterior and posterior segment examinations were otherwise unremarkable. Besides the oculomotor and trochlear nerve, the other cranial nerves and neurological examinations were normal. Investigations including blood and cerebrospinal fluid, magnetic resonance imaging and angiography of the brain, were normal. Our impression was left oculomotor and trochlear nerve neuritis secondary to botulinum toxin injection. He was started on oral prednisolone 1 mg/kg daily and tapered by 5 mg per week. His condition improved gradually with no residual ptosis or anisocoria after three months. Extraocular movements normalised except for minimal residual restriction on depression. CONCLUSION: Oculomotor and trochlear nerve neuritis can occur following botulinum toxin injection over the masseter area. Healthcare professionals should be aware of this potential complication before offering the injection.

Isolated Sudden-Onset Trochlear Nerve Palsy Associated with Mild Novel Coronavirus Disease (COVID-19) Infection.

PURPOSE: To present a case of sudden isolated unilateral trochlear nerve palsy of new onset associated with a COVID-19 infection without a severe course. METHODS: A 49-year-old previously healthy man suddenly noticed seeing double while going down the stairs to go out for the first time the day after the completion of medical treatment and home isolation for COVID-19. There was no systemic disease or history of trauma. RESULTS: Magnetic resonance imaging of the brain and orbits was normal and the neurology examination revealed no pathology. The acute onset of the diplopia, the small vertical fusion amplitude, and the lack of facial asymmetry supported acquired trochlear nerve palsy. CONCLUSIONS: Trochlear nerve palsy has rarely been reported in association with the various types of viral infections. To the best of our knowledge, this is the first case of isolated unilateral trochlear nerve palsy with no additional neurological finding or any radiological finding that is possibly associated with mild SARS-CoV-2 infection.

Cranial Polyneuropathy Secondary to Remote Iophendylate Myelography.

A 68-year-old woman with controlled hypertension, and degenerative joint disease of the spine for which she had undergone several myelograms and three surgeries 30-32 years earlier, presented with a 2 year history of painless, oblique, binocular diplopia. Her prior ophthalmic evaluations were consistent with an isolated left trochlear nerve paresis. She had magnetic resonance imaging (MRI) showing multiple foci of T1-weighted hyperintensities around the midbrain and brainstem thought to represent subarachnoid fat from a ruptured dermoid cyst. An extensive evaluation revealed a left trochlear nerve paresis as well as diminished sensation in the distributions of the first and second divisions of the left trigeminal nerve. Review of her MRI and history of myelograms raised the possibility of focal inflammation from intrathecal iophendylate (Pantopaque®). Repeat MRI was obtained that showed T1-weighted hyperintensities similar to her previous MRI, but in this study, T1-weighted fat suppression imaging also was performed and revealed these foci to be of low signal intensity, consistent with retained iophendylate.