Can Ophthalmologic Examination Predict Abducens Nerve Recovery After Endoscopic Skull Base Surgery?

OBJECTIVES: While abducens nerve palsy (ANP) is a known risk in the setting of some endoscopic endonasal skull base surgery (ESBS), frequency and prognosis of post-operative palsy remain unknown. Our goals were to determine the frequency and prognosis of ANP after high-risk ESBS, and identify factors associated with recovery. METHODS: Retrospective case series of all patients with pathology at highest risk for abducens nerve injury (pituitary adenoma, chordoma, meningioma, chondrosarcoma, cholesterol granuloma) generated a list of patients with abducens nerve palsy after ESBS performed from 2011-2016. A validated ophthalmologic clinical grading scale measuring lateral rectus duction from 0 to -5 (full motion to inability to reach midline) was measured at multiple time points to assess recovery of ANP. RESULTS: Of 655 patients who underwent ESBS with increased risk of abducens injury, 40 (6.1%) post-operative palsies were identified and 39 patients with dedicated examination at multiple time points were included in subsequent analysis. Complete resolution was noted in 25 patients (64%) within 12 months. While 19 of 23 (83%) with a partial palsy had complete resolution, only six of 16 (38%) with a complete palsy resolved entirely (P = .005; Fisher's exact test). All six patients with delayed onset of palsy resolved (P = .070; Fisher's exact test). Meningioma and chordoma had higher rates of both temporary and permanent post-operative ANP (P < .0001; Fisher's exact). CONCLUSIONS: The frequency of post-operative ANP following ESBS is low, even in high-risk tumors. While only a minority of complete abducens nerve palsies recover, patients with partial or delayed palsy post-operatively are likely to recover function without intervention. LEVEL OF EVIDENCE: IV Laryngoscope, 131:513-517, 2021.

Anatomical location of the abducens nerves (VI) in the ventral approach of clival tumors.

The aim of this work was to determine reliable anatomical landmarks for locating and preserving the abducens nerves (6th cranial nerves) during trans-facial or trans-nasal endoscopic approaches of skull base tumors involving the clivus and the petrous apex. In order to describe this specific anatomy, we carefully dissected 10 cadaveric heads under optic magnification. Several measurements were taken between the two petro-sphénoidal foramina, from the bottom of the sella and the dorsum sellae. The close relationship between the nerves and the internal carotid artery were taken into account. We defined a trapezoid area that allowed drilling the clivus safely, preserving the 6th cranial nerve while being attentive to the internal carotid artery. The caudal part of this trapezium is, on average, 20 mm long at mi-distance between the two petro-sphenoidal foramina. The cranial part is at the sella level, a line between both paraclival internal carotid arteries. Oblique lateral edges between the cranial and caudal parts completed the trapezium.

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.

[A 4-year-old girl with double vision following trauma]. / Een 4-jarig meisje met dubbelzien na een trauma.

BACKGROUND Due to its long intracranial course, the abducens nerve is vulnerable in case of acceleration injury of the head. In rare cases, this may lead to posttraumatic paralysis of this cranial nerve. CASE DESCRIPTION A 4-year-old girl visited the emergency department after sustaining a head trauma. Neurological examination revealed no focal abnormalities at first. Three days later, she experienced diplopia, the consequence of isolated abducens nerve paralysis. CT and MRI brain imaging revealed no abnormalities. We treated her with an eye patch for a short time. At examination after 1 year, she was no longer experiencing any symptoms and the paralysis had almost completely disappeared. CONCLUSION Isolated paralysis of the abducens nerve may occur until up to 6 days after a trauma, without any visible intracranial abnormalities revealed by imaging. Even though only few children with this condition have been described, prognosis seems to be favourable and symptoms disappear in the majority of patients. Frequent follow-up by the ophthalmologist and the orthoptist is recommended, possibly with symptomatic treatment of the diplopia.

Variations of the 6th cranial nerve (nervus abducens) in the petroclival region: A microsurgical study.

The aim of this study is to present the variations of nervus abducens in localization and number as it pierces the clival dura mater. The calvaria of 16 cadaveric heads were removed by making horizontal incisions from Glabella to Inion in both sides of the head. The dura mater was dissected. Cerebrum and cerebellum were taken out by obtuse dissection. Dissections of cavernous sinus were made under the stereomicroscope and the findings were photographed. Out of 16 specimens, one of them was excluded. Fifteen heads were bilaterally analyzed. Analysis of these nerves presented four different variations. Variation types a classified CN VI as a single trunk and entering a single dural pore with 77% occurrence. Variation type b classified CN VI with two branches running in the petroclival region and entering a single dural pore with 10% occurrence. Variation type c classified CN VI as 2 trunks and entering 2 separate but close dural pores with 10% occurrence. Variation type d classified CN VI with 2 distinct trunks and 2 branches entering 2 separate but close dural pores with 3% occurrence. CN VI plays a major role in the clinic of the eye. Due to its intracranial and extracranial course, injuries to the head and to the nerve may result in malfunctioning of the lateral muscles of the eye. Therefore, the variations of branching, relations and its course were analyzed.

Orbital apex syndrome after trauma in a 6-year-old - a rare occurrence.

Orbital apex syndrome is rare, but can occur as a consequence of trauma from fracture of the medial orbit. This case report highlights the fact that a high index of suspicion is needed when a patient presents with a facial injury, especially in children who cannot give an account of the actual events that transpired. Radiological investigation should be done early when an underlying injury is suspected in a trauma patient. A low threshold for computed tomography should be maintained when proptosis and vision loss are present.

Bilateral traumatic abducens nerve avulsion: A case series and literature review.

Although abducens nerve palsy is an established sequela of head trauma - given the prolonged intracranial course of the nerve - bilateral injury is rare. Here, we present two cases of bilateral traumatic abducens nerve avulsion, in the absence of regional fractures, one of which presented two months following the initial trauma. Additionally, we review the current literature on bilateral abducens nerve palsy secondary to trauma, discussing the anatomy of the nerve's course and potential mechanisms of injury.

Preoperative simulation of the running course of the abducens nerve in a large petroclival meningioma: a case report and literature review.

One of the most important and useful pieces of information in the preoperative evaluation of a large petroclival meningioma is the running course of the abducens nerve. The abducens nerve is small and has a long intracranial course, making it prone to compression by the tumor at various anatomical points. In relatively large tumors, it is difficult to confirm the entire course of the abducens nerve, even by heavy T2-thin slice imaging. We report a case of successful preoperative estimation of the course of the abducens nerve that aided in its complete preservation during the resection of a large petroclival tumor.

Facial reanimation according to the postresection defect during lateral skull base surgery.

The vast majority of benign tumors of the cerebellopontine angle, temporal bone, and parotid gland can be successfully resected without permanent injury to the facial nerve. Malignant tumors or recurrent disease may require facial nerve sacrifice, especially if preoperative facial paresis is present. This article will present case examples of the various methods to reconstruct facial animation after lateral skull base resections that require sacrifice of cranial nerve VII, and the associated mimetic facial musculature. Facial mimetic outcome after reanimation was graded using the House-Brackmann scale. Primary neurorrhaphy or interposition grafting may be performed when both the proximal and distal portions of the facial nerve are available and viable facial musculature is present. If only the distal facial nerve and viable facial musculature are available, a split hypoglossal to facial nerve anastomosis is used. A proximal facial nerve to microvascular free flap is performed when the proximal facial nerve is available without distal nerve or viable musculature. A cross-facial to microvascular free flap is performed when the proximal and distal facial nerve and facial musculature are unavailable. The above methods resulted in a House-Brackmann score of III/VI in all case examples postoperatively. The method of facial reanimation used depends on the availability of viable proximal facial nerve, the location of healthy, tumor-free distal facial nerve, and the presence of functioning facial mimetic musculature.

Abducens Nerve Avulsion and Facial Nerve Palsy After Temporal Bone Fracture: A Rare Concomitance of Injuries.

BACKGROUND: Avulsion of the abducens nerve in the setting of geniculate ganglion injury after temporal bone fracture is unreported previously. We discuss clinical assessment and management of a patient with traumatic avulsion of cranial nerve (CN) VI in the setting of an ipsilateral CN VII injury after temporal bone fracture and call attention to this unusual injury. CASE DESCRIPTION: A 26-year-old man suffered a temporal bone fracture after a motor vehicle accident and developed diplopia and right-sided facial droop. Six weeks after the accident, the patient was readmitted with worsening diplopia and ipsilateral facial weakness. He demonstrated absent lateral gaze on the right suggestive of either restrictive movement or right. CN VI DEFICIT: In addition, he had right-sided facial palsy graded as 6/6 House-Brackmann. High-resolution computed tomography demonstrated a right-sided longitudinal otic capsule-sparing temporal bone fracture that propagated into the facial nerve canal and geniculate fossa. Magnetic resonance imaging revealed discontinuity of the right CN VI between the pons and the Dorello canal, as well as injury to the ipsilateral geniculate ganglion. CN VII was intact proximally, from the pons through the internal auditory canal. Consensus was reached to proceed with conservative management. At 13 months after injury, the patient reported 1/6 House-Brackmann with no improvement in CN VI function. CONCLUSIONS: This case illustrates 2 subtle findings on imaging with potential therapeutic implications, notably the role of surgical intervention for facial nerve palsy.

Usefulness of flat detector CT (FD-CT) with biplane fluoroscopy for complication avoidance during radiofrequency thermal rhizotomy for trigeminal neuralgia.

INTRODUCTION: Trigeminal neuralgia (TN) is characterized by episodes of shooting pain in the areas innervated by one or more divisions of the trigeminal nerve. The initial treatment of TN is with drugs but the increased frequency and intensity of the neuralgic episodes often force the patient to seek alternative therapies. Microvascular decompression (MVD) and radiofrequency thermal lesioning of trigeminal rootlets (RFTR) offer close to the best results for TN. MVD has the disadvantage of being an open surgical procedure with its attendant risks and longer hospital stay, whereas RFTR is a short, 'day-care' procedure. However this latter procedure involves positioning of the RF needle in the area behind the trigeminal ganglion through the foramen ovale, which can pose significant challenges. OBJECTIVE: To use the fluoroscopic support of a biplane catheter laboratory to access the foramen, and flat detector CT to confirm the location of the tip of the RF needle in the optimal position. METHODS: Fifty-three patients with TN underwent RFTR under local anesthesia with conscious sedation. RESULTS: All patients reported pain relief with hypesthesia over the offending trigeminal division. In seven patients the needle tip required repositioning according to the CT images. Two patients each had loss of corneal reflex and abducens nerve palsy after the procedure. No other complications were seen. CONCLUSIONS: The superior view in two planes coupled with the anatomical confirmation of the position of the needle tip in the Meckel's cave during the rhizotomy reduces the need for multiple passages of the needle to access the foramen ovale and achieves accurate needle tip positioning. The technique increases the safety and precision of such treatments and helps to manage potential complications.

Delayed Superior Orbital Fissure Syndrome After Reconstruction of Blowout Fracture.

The superior orbital fissure syndrome (SOFS) has been known to be a condition caused by impairment of the nerves that cross the superior orbital fissure. Traumatic SOFS is an uncommon complication which occurs usually within 48 hours after a facial injury. A 25-year-old male sustained facial trauma following an altercation. Clinical findings on presentation included swelling, ecchymosis, hyphema, subretinal hemorrhage, and mild extraocular movement limitation upon lateral gaze on his right eyelids. Facial computed tomography scan confirmed fractures of the medial walls of the right orbit and herniation of orbital soft tissue without the incarceration of medial rectus muscle. Ten days after the trauma, the operation was performed. On postoperative day 16, the patient showed ptosis of the right upper eyelid with a fixed pupil, and there was a hypoesthesia over the distribution of the right supraorbital and supratrochlear nerves. The authors diagnosed as a delayed SOFS and prescribed 4 mg of methylprednisolone q.i.d. for 30 days. After steroid therapy, extraocular movement limitations improved progressively. After 8 months, movement was completely restored. The authors experienced delayed SOFS on posttrauma day 27, and it was treated by steroid therapy. Surgical intervention is required when there is an evident etiology such as underlying hematoma or plate migration. If the reason is not clear like our case, steroid therapy can be considered as one of the options. Particularly, the authors should give special attention to the patient who has congenitally narrow superior orbital fissure, like Fujiwara et al suggested.

Cranial nerve palsies after shunting of an isolated fourth ventricle.

An isolated fourth ventricle is characterised by cerebrospinal fluid (CSF) trapping in the fourth ventricle. Although there is no consensus regarding treatment, ventriculoperitoneal (VP) shunting of the fourth ventricle is an option. Complications include infection, mechanical irritation of the brainstem, malfunction and overdrainage. Cranial nerve palsy is a rare complication and has been mostly described in children. We present two adult cases of abducens and facial nerve palsies occurring secondary to this procedure. Placement of a higher resistance valve brought about complete recovery in one patient while withdrawal of the catheter by a few millimetres led to complete recovery in the second patient.

Delayed-onset bilateral abducens paresis after head trauma.

Bilateral sixth nerve paresis following closed head injury, though rare, is a known entity. However, delayed-onset post-traumatic bilateral abducens paresis is extremely rare. We present two cases. The first patient had onset of bilateral abducens paresis 2 weeks after closed head injury and the second patient after 3 days. The cause in the former was detected to be chronic subdural hematoma and in the latter is speculated to be edema/ischemia due to injury to soft tissue structures housing these nerves. The delayed onset of bilateral abducens paresis following head injury may vary according to the cause. There may be another mechanism of injury apart from direct trauma. Though rare, it needs to be evaluated and may have a treatable cause like elevated intracranial pressure.

Dorello canal revisited: an observation that potentially explains the frequency of abducens nerve injury after head injury.

OBJECTIVE: The abducens nerve is frequently injured after head trauma and some investigators have attributed this to its long intracranial course. The present study aimed to elucidate an additional mechanism to explain this phenomenon. METHODS: Twelve fresh adult cadavers underwent dissection of Dorello canal using standard microsurgical techniques. In addition, traction was applied to the nerve at its entrance into this canal before and after transection of Gruber ligament to observe for movement. RESULTS: In all specimens, a secondary tunnel (i.e., tube within a tube) was found within Dorello canal that exclusively contained the abducens nerve. This structure rigidly fixated the abducens nerve as it traversed Dorello canal, thereby not allowing any movement. Transection of Gruber ligament did not detach the nerve, but after release of the inner tube, the nerve was easily mobilized. CONCLUSIONS: Rigid tethering of the abducens nerve with a second tube within Dorello canal affords this nerve no ability for movement with motion of the brainstem. We hypothesize that this finding is a main factor in the high incidence of abducens nerve injury after head trauma.

Cranial nerve injury after Le Fort I osteotomy.

A Le Fort I osteotomy is widely used to correct dentofacial deformity because it is a safe and reliable surgical method. Although rare, various complications have been reported in relation to pterygomaxillary separation. Cranial nerve damage is one of the serious complications that can occur after Le Fort I osteotomy. In this report, a 19-year-old man with unilateral cleft lip and palate underwent surgery to correct maxillary hypoplasia, asymmetry and mandibular prognathism. After the Le Fort I maxillary osteotomy, the patient showed multiple cranial nerve damage; an impairment of outward movement of the eye (abducens nerve), decreased vision (optic nerve), and paraesthesia of the frontal and upper cheek area (ophthalmic and maxillary nerve). The damage to the cranial nerve was related to an unexpected sphenoid bone fracture and subsequent trauma in the cavernous sinus during the pterygomaxillary osteotomy.