Inferior oblique myectomy for postoperative limitation of elevation in abduction.

Antielevation syndrome is commonly described following anteriorization of the inferior oblique muscle. A similar phenomenon may occur following inferior oblique muscle recession, creating a distinct strabismus pattern in the setting of cranial trochlear nerve palsy. We report 3 adult patients, 69-72 years of age, who presented at the Stanford Byers Eye Institute with a similar strabismus pattern-limited elevation in abduction following previous inferior oblique muscle recession for congenital/long-standing trochlear nerve palsy. All 3 patients had a small hypertropia in primary gaze with ipsilateral inferior oblique overaction, limited elevation in abduction, and inferotemporal conjunctival scars. Two patients had a V-pattern strabismus. Following myectomy of the previously recessed inferior oblique muscle, elevation in abduction improved, and symptoms resolved in all 3 patients.

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.

Surgical management of superior oblique palsy with coexisting exotropia.

PURPOSE: To analyze the surgical results of patients treated for superior oblique palsy with coexisting exotropia. METHODS: The medical records of patients with superior oblique palsy and exotropia who underwent inferior oblique weakening and simultaneous lateral rectus recession by a single surgeon from 1996 to 2022 were reviewed retrospectively. Demographics, pre- and postoperative vertical and horizontal deviation, and presence of diplopia were recorded. Surgical success was defined as horizontal deviation <10Δ and vertical deviation ≤4Δ without overcorrection or diplopia. The decision to operate for the horizontal deviation was made based on fusion in free space when the vertical deviation was offset with a prism. RESULTS: A total of 27 patients were included. Mean age was 26.1 ± 22 years (range, 26 months to 78 years). Preoperatively, mean vertical deviation was 15.2Δ ± 7.5Δ (range, 4Δ-30Δ); mean exodeviation, 17Δ ± 5.5Δ (range, 10Δ-35Δ). Of the 27 patients, 25 underwent unilateral and 2 underwent bilateral lateral rectus recession, according to the magnitude of the horizontal deviation. Mean follow-up was 3 ± 3.8 months (range, 2 weeks to 17 months). Postoperative mean vertical alignment was 3.0 ± 5.9, and horizontal alignment was 3.4Δ ± 5.2Δ (esotropia of 7Δ to exotropia of 12Δ; P < 0.0001). Nineteen patients (70%) had a successful result; 2 patients had residual exotropia of >10Δ, 2 had vertical overcorrection (range, 3Δ-4Δ), and 6 had residual vertical deviation ≥4Δ (range, 5Δ-20Δ). None had secondary esotropia >10Δ. Horizontal deviation was corrected successfully with no consecutive esotropia in 25 patients. CONCLUSIONS: In our study cohort, patients with superior oblique palsy and exotropia in whom fusion required both horizontal and vertical prism correction had a high likelihood of successful horizontal alignment after lateral rectus weakening in combination with inferior oblique surgery.

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.

Superior oblique palsy after facial feminization surgery.

Facial feminization surgery (FFS), or gender-affirming facial surgery, is a common procedure for patients with gender dysphoria. One goal of FFS involves extensive contouring of the frontal and nasal bones to reduce supraorbital bossing. Ophthalmic complications after FFS have been rarely reported. We report 2 cases of superior oblique palsy after FFS producing persistent vertical and torsional diplopia. One case was successfully treated with prism spectacles; the other required surgical management. Both cases likely involved surgical trauma to or disinsertion of the trochlea during orbital bony reshaping.

Effect of inferior oblique myectomy on ocular torsion according to the absence of the trochlear nerve in unilateral congenital superior oblique palsy.

OBJECTIVES: To evaluate the effect of inferior oblique (IO) myectomy on ocular torsion according to the absence of the trochlear nerve in unilateral congenital superior oblique palsy (UCSOP). METHODS: We retrospectively reviewed the clinical data of patients who had been diagnosed with UCSOP and underwent ipsilateral IO myectomy (n = 43). Patients were classified into the present and absent groups according to the absence of the trochlear nerve and superior oblique hypoplasia on magnetic resonance imaging (MRI). For quantitative analysis of ocular torsion, disc-fovea angles (DFA) were collected in both eyes using fundus photographs taken within three months before surgery and one month after surgery. RESULTS: DFA of the paretic eye did not differ according to the absence of the trochlear nerve (9.4±5.6° in the present group vs. 11.0±5.4° in the absent group, p = 0.508). However, the present group had a larger DFA in the non-paretic eye than the absent group (14.1±6.7° in the present group vs. 8.0±5.0° in the absent group, p = 0.003). The change of ocular torsion after IO myectomy in the paretic eye was -5.3±3.7° in the present group and -4.8±3.5° in the absent group, respectively (p = 0.801). In the non-paretic eye, the change in DFA was -1.5±3.0° in the present group, which was larger than that in the absent group (0.7±2.6°, p = 0.047). In the multivariate analysis, the change in DFA was correlated with only the preoperative DFA (standardized ß = -0.617, p<0.001 in the paretic eye, and standardized ß = -0.517, p<0.001 in the non-paretic eye). CONCLUSIONS: In the paretic eye, there was no significant difference in the change of ocular torsion between both groups, whereas in the non-paretic eye, the present group had a larger change in DFA after IO myectomy than the absent group. However, in the multivariable analysis, the change in ocular torsion was significantly correlated with preoperative excyclotorsion but not with the presence of the trochlear nerve itself.

Disinsertion-distal myectomy and tucking of inferior oblique combined with superior oblique full tendon advancement in superior oblique palsy.

PURPOSE: To assess the preliminary outcomes of inferior oblique (IO) disinsertion-distal myectomy and tucking combined with superior oblique (SO) full tendon advancement in patients with Knapp II or III superior oblique palsy. METHODS: This single-centered retrospective study included 16 eyes from 13 patients with Knapp Class II or III SO palsy. All patients underwent IO disinsertion-distal myectomy and tucking combined with SO full tendon advancement while under general anesthesia. Pre- and post-operative levels of vertical deviation in the primary position, abnormal head position, IO hyperfunction and SO hypofunction, torsion, as well as the presence of diplopia, were all measured, and the differences were statistically compared. RESULTS: Pre-operatively, 12 patients had abnormal head positions, and two had diplopia. The pre-and post-operative levels of IO hyperfunction and SO hypofunction, as well as a vertical deviation in the primary position and torsion, all differed statistically significantly (p < 0.01). CONCLUSIONS: Inferior oblique disinsertion distal myectomy and tucking combined with SO full tendon advancement surgery appears to be an effective procedure in patients with congenital and acquired Knapp Class II or III SO palsy.

Pseudonystagmus in trochlear nerve palsy.

We present the case report of a patient who presented with intermittent diplopia and left hypertropia associated with an apparent left superior oblique palsy. After dissociation with cover testing, he showed conjugate rhythmic vertical eye movements present in all gazes, thought to represent rapid rhythmically alternating fixation. The vertical rhythmic movement resolved after strabismus surgery.

Clinical features of excyclotorsion in the non-paretic eye of patients with congenital unilateral superior oblique palsy.

BACKGROUND: To investigate preoperative clinical features and postoperative results according to the correspondence between excyclotorsion and the paretic eye in patients with congenital unilateral superior oblique palsy (USOP). METHODS: A retrospective review of medical charts was performed. The patients were divided into the accordance (ocular excyclotorsion in the paretic eye) and disaccordance (ocular excyclotorsion in the non-paretic eye) groups. The degree of excyclotorsion (scale, 0-4) was measured. Age, sex, hypertropia at the primary position, fixation preference, inferior oblique overaction, and degree of excyclotorsion were measured. RESULTS: Ninety-eight patients were included in this study. There were 70 (71.4%) and 28 patients (28.6%) in the accordance and disaccordance groups. Sixteen patients (22.9%) in the accordance group and 12 patients (42.9%) in the disaccordance group were aged under 2 years (p = 0.04). A fixation preference of the paretic eye was observed in 2 (2.9%) and 8 (28.6%) patients in the accordance and disaccordance groups (p < 0.01). The postoperative degree of excyclotorsion in the accordance group (0.14 ± 0.39) was lower than that in the disaccordance group (0.28 ± 0.71) (p = 0.01). The residual postoperative excyclotorsion (> 1) were observed in the disaccordance group (14 patients, 50%) and accordance group (16 patients, 22.9%) (p = 0.01). CONCLUSION: Preoperative disaccordance between excyclotorsion and the paretic eye was observed in patients who were under 2 years of age and preferred fixation of the paretic eye. The postoperative degree of excyclotorsion was lower in the accordance group.

Surgical Technique and Nuances of Resection of a Trochlear Schwannoma: Operative Video.

Cranial nerve schwannomas accounts for around 8% of all benign intracranial tumors, arising most commonly from the vestibular nerve, followed by the trigeminal nerve and other lower cranial nerves. However, trochlear schwannoma in a patient without neurofibromatosis-2 are extremely rare and to date, fewer than 100 cases have been reported in the literature. They are either asymptomatic or present with ophthalmologic or neurologic symptoms. Diplopia is the most common initial symptom. As the tumor grows, it can compress the surrounding brainstem and other cranial nerves, causing neurologic symptoms. Asymptomatic lesions are detected incidentally following imaging for some other reason. There are no clear guidelines for the management of these tumors. In general, small asymptomatic tumors are closely observed by serial imaging and symptomatic or larger tumors are managed by surgical excision and/or stereotactic radiosurgery.1-7 Here we present a 41-year-old female patient with incidentally detected left trochlear schwannoma during the follow-up magnetic resonance imaging (MRI) scans. She was followed up regularly with multiple repeat MRI. Recently she started complaining of occasional headaches, and MRI showed a left peimesencephalic cistern tumor causing mass effect on the ipsilateral midbrain. There was also significant brainstem edema. Hence she underwent left retromastoid suboccipital craniectomy, lateral supracerbellar approach, and complete excision of the tumor. Postoperatively the patient had an uneventful recovery without any new neurologic deficits. At 6 months' follow-up the patient is doing well.

Lateral Supracerebellar Infratentorial Approach for Superior Oblique Myokymia: A Case Series.

BACKGROUND: Few reports have shown that superior oblique myokymia (SOM) may result from vascular compression of the trochlear nerve and may be curable using microvascular decompression (MVD). OBJECTIVE: To report the clinical characteristics and surgical treatment of 2 cases of SOM and provide a review of the related literature. METHODS: Two patients with SOM were treated using MVD with the lateral supracerebellar infratentorial approach. The patients underwent diagnostic magnetic resonance imaging and three-dimensional fusion imaging preoperatively. A lateral suboccipital craniotomy was performed in the park-bench position. The trochlear nerve and branches of the superior cerebellar artery were confirmed after opening the cerebellomesencephalic fissure over the tentorial surface of the cerebellum. The vessel, which compressed the root exit zone of the trochlear nerve, was transposed far from the nerve and attached to the surface of the midbrain using Teflon felt and fibrin glue. RESULTS: The first case showed compression on both the ventral and rostral sides of the trochlear nerve root exit zone, and the second showed compression only on the ventral side. Large bridging veins on the tentorial surface of the cerebellum complicated the approach in the second case. Postoperatively, both patients had immediate and complete resolution of symptoms without recurrence at the 24-mo and 17-mo follow-ups, respectively. Five previous reports described the complete resolution of SOM after MVD. CONCLUSION: A presentation of an intermittent fluttering ocular sensation should prompt magnetic resonance imaging for ipsilateral trochlear nerve compression. The lateral supracerebellar infratentorial approach allows safe and efficacious MVD for SOM.

Anomalous insertion of the superior oblique tendon onto the superior rectus muscle causing congenital superior oblique palsy.

Congenital superior oblique (SO) palsy is often associated with anomalies of its tendon, increased tendon laxity being the most common. Rarely, the tendon lies in an abnormal location nasal to the superior rectus (SR) muscle, either attaching to the sclera or to Tenon's capsule. We describe a case of a child who presented with abnormal head posture and exotropia. The orthoptic evaluation revealed a left hypertropia and V-pattern exotropia. The motility pattern and the Parks three-step test were suggestive of left-sided SO palsy. Intraoperatively, the left SO tendon was very lax and was absent from its usual insertion. Further exploration revealed it to be inserted entirely to the nasal border of the SR muscle, with no scleral attachment. This tendon was advanced to its normal attachment to the sclera, and 11 mm inferior oblique recession was also performed. Postoperative alignment was satisfactory.

Spontaneous Recovery of Traumatic Unilateral Superior Oblique Palsy and Ocular Factors for Predicting Prognosis.

PURPOSE: This study evaluated the prognosis of patients with traumatic unilateral superior oblique palsy (SOP) and clinical factors associated with spontaneous resolution. METHODS: Medical records of patients with traumatic unilateral SOP who visited two hospitals (Yeungnam University Hospital and Daegu Catholic University Medical Center) between January 2015 and June 2020 were reviewed retrospectively. When traumatic unilateral SOP did not recover within at least 1 year of follow-up, no spontaneous resolution was considered. Both traumatic and ocular factors were evaluated to evaluate their association with spontaneous recovery. RESULTS: Fifty-nine patients (mean age, 52.6 years; 48 male patients) were enrolled in this study. The mean interval from trauma to initial presentation was 3.9 months. The mean vertical deviation at initial presentation was 6.34 ± 5.22 prism diopters (PD) (range, 0-25 PD). During the mean 24.1-month follow-up period, 28 patients (47.5%) achieved spontaneous resolution of SOP. Thirteen patients underwent surgical treatment for SOP. Vertical deviation <6 PD at the initial visit and low fundus torsion in the nonparetic eye and both eyes were significantly associated with spontaneous recovery (p < 0.05, logistic regression analysis). Traumatic factors, including the trauma type, presence of intracranial lesion, loss of consciousness, and Glasgow Coma Scale score, were not associated with spontaneous recovery. CONCLUSIONS: In this multicenter study, spontaneously recovery was achieved in 47.5% patients with traumatic unilateral SOP. Even mild head trauma can lead to permanent SOP. Ocular factors, including the angle of deviation and fundus torsion, may better predict spontaneous resolution than traumatic factors in patients with traumatic unilateral SOP.

Types of Surgery Performed and Reoperation Rate for Congenital Superior Oblique Palsy: a Claims Database Study.

PURPOSE: To investigate types of surgeries performed to treat a presumed congenital superior oblique palsy (SOP) and the reoperation rate. METHODS: This was a population-based retrospective cohort study using claims data from the United States. Patients who underwent strabismus surgery for a presumed congenital SOP with ≥ 3 months of continuous enrolment after the initial surgery were included. We investigated age, surgical methods and the time interval between the initial surgery and reoperation. The hazard ratios for reoperation were estimated according to the surgical methods using Cox regression analysis. RESULTS: A total of 3,998 patients underwent surgery for presumed congenital SOP; 2,981 (74.6%) on only one vertical muscle (excluding superior oblique). Reoperation was performed on 427 patients (10.7%). Compared to patients who underwent unilateral surgery on one vertical muscle (excluding superior oblique muscle), patients who underwent surgery that included the superior oblique muscle (unilateral 2.08; 95% CI, 1.61-2.67, p < 0.001; bilateral 2.44; 95% CI, 1.40-4.28, p = 0.002) and two or more vertical muscles (excluding the superior oblique muscle) (unilateral 2.99; 95% CI, 2.00-4.49, p < 0.001; bilateral 1.68; 95% CI, 1.23-2.28, p = 0.001) had increased hazard ratios for reoperation. The median period between the initial surgery and reoperation was 168.0 [Q1-Q3 84.0-407.8] days and negatively correlated with patient age at initial surgery (r = -0.199, p < 0.001). CONCLUSION: The reoperation rate for presumed congenital SOP was 10.7%. Patients who underwent surgery on two or more vertical muscles or the superior oblique muscle had an increased risk of reoperation.

Inferior oblique recession associated to partial temporal inferior rectus recession in unilateral congenital superior oblique palsy.

PURPOSE: To evaluate the effectiveness of inferior oblique recession with contralateral partial temporal inferior rectus recession in patients with decompensated congenital unilateral superior oblique palsy (SOP) in correcting moderate vertical deviations in primary position. METHODS: The medical records of patients with SOP who underwent inferior oblique recession with contralateral partial temporal inferior rectus recession were reviewed retrospectively. Vertical deviation in primary position, subjective torsion, diplopia, residual deviation, and the deviation decrease were evaluated. RESULTS: Four patients (three males and one female, age range 29-56 years) with congenital unilateral SOP and mean vertical deviation of 21.0 ± 5.3PD (range 14-25D) in primary position were included. Mean correction of hypertropia in primary position with this technique was 15.5 ± 5.3PD (range 10-20PD). The mean hypertropia on gaze to the contralateral side changed from 30.0 ± 10.8D before surgery to 9.3 ± 7.9D after surgery. Torsion had a mean change of 4.8° of incyclodeviation. Preoperatively, all patients had head tilt and diplopia, which was resolved in all but one patient, who will need surgery. Patients were followed an average of 18 months. No adverse events were reported in any subjects. CONCLUSION: When performing recession of inferior oblique muscles in SOP associated to a full recession of the contralateral inferior rectus, there is a risk of overcorrection in those with moderate angles. Performing a partial recession in the contralateral inferior rectus eye corrected up to 20PD in primary position in our series, reducing this risk.

Torsional incomitance after asymmetrically adjusted Harada-Ito procedures for the simultaneous correction of vertical and torsional deviations in bilateral trochlear nerve palsy.

BACKGROUND: Adjustable bilateral Harada-Ito procedures have been described, sometimes with asymmetric adjustment used to correct vertical misalignment when coexisting with torsional strabismus. We investigated the causes of significant postoperative torsional incomitance noted in some patients undergoing these procedures. METHODS: The medical records of patients who underwent bilateral Harada-Ito procedures for bilateral trochlear nerve palsy between 1980 and 2018 were reviewed retrospectively. Cases with simultaneous operation on any other oblique or vertical rectus muscle were excluded. Surgical results, especially using Lancaster red-green (Lan R-G) plots, were correlated with the procedures performed. RESULTS: A total of 17 patients were included. At their last follow-up visit (mean, 12 months after surgery), 9 were diplopia free. Of the 8 with continuing diplopia, 2 had undercorrection and 1 had Brown syndrome. In 5 patients with continuing diplopia, there was relative intorsion of the eye movement paths in upgaze and relative extorsion of these paths in downgaze, a type of torsional incomitance. Asymmetric adjustment with tightening of one superior oblique tendon, and often loosening of the contralateral superior oblique tendon, had been performed in those 5 cases. Only 1 of the successful cases had the same type of asymmetric adjustment. There was a positive association between the severity of the preoperative Lan R-G pattern and postoperative diplopia. CONCLUSIONS: Asymmetric adjustment of bilateral Harada-Ito procedures when attempting to correct the coexisting vertical misalignment can cause significant torsional incomitance with incomplete correction of extorsion in downgaze and intorsion in upgaze. This pattern may result in postoperative diplopia that is surgically challenging to correct.

Frequency of Diplopia after Intraoperative Nerve Disturbance in Trochlear Nerve Schwannoma: A Case Report and Systematic Review.

Schwannomas of the trochlear nerve are relatively rare, and most patients present with preoperative diplopia because of trochlear nerve palsy. We describe the case of a 61-year-old male patient with a trochlear nerve schwannoma and no pre- and postoperative diplopia, despite his trochlear nerve being cut during the operation. We aimed to investigate the frequency of postoperative diplopia associated with intraoperative trochlear nerve disturbance by reviewing previous case reports, wherein postoperative diplopia did not occur after the trochlear nerve was cut intraoperatively. We recorded the frequency of diplopia because of intraoperative trochlear nerve disturbance, such as the trochlear nerve being cut, in cases without pre- and postoperative diplopia. We searched the PubMed, Medline, and Google Scholar databases for works published from 1976 to 2020 and followed the preferred reporting items for systematic reviews and meta-analyses guidelines. We reviewed 36 publications and found 92 cases of trochlear nerve schwannoma. Surgical resection was performed for 43 patients, of whom 40 were kept under observation and 9 were treated with radiation therapy. Of the 43 cases, 9 without preoperative diplopia underwent gross total resection. We analyzed ten cases (including ours) without preoperative diplopia to check for postoperative diplopia. In total, four cases, including ours, did not display postoperative diplopia despite the trochlear nerve being cut. This may be attributed to the preoperatively acquired motor and sensory fusion in the patient's vision because of tumor progression. Our findings may benefit neurosurgeons who treat patients with schwannomas and help them predict patients' outcomes.

Inferior Oblique Recession with 5 mm Loop to Correct Vertical Deviation and Inferior Oblique Overaction Secondary to Superior Oblique Palsy.

Purpose: To evaluate the effect of augmented inferior oblique recession (recession +5 mm loop) on the vertical deviation in primary position (PP) and the inferior oblique overaction (IOOA) in patients with unilateral congenital or acquired superior oblique palsy.Patients and methods: The medical records of patients who underwent unilateral inferior oblique recession with 5 mm loop during 2012 and 2019 were retrospectively reviewed. All patients had small to moderate manifest or intermittent hypertropia in PP and overaction of the inferior oblique muscle of +2 or +3 in lateral gaze. Patients who had combined inferior rectus surgery of the contralateral eye or who had previous vertical muscle surgery were excluded.Results: A total of 26 patients were included. Of these, three patients had combined horizontal muscle surgery. In 22 patients, the superior oblique palsy was congenital or longstanding, in 4 it was acquired and stable for more than 9 months. The mean preoperative vertical deviation in PP at distance and near was 14.7Δ and 11.2Δ, respectively. The mean postoperative vertical deviation was 5.7Δ and 4.1Δ after a mean follow-up of 19 months. The IOOA improved in all patients, 16 patients had an improvement of +2 and 10 patients had an improvement of +1.Conclusion: Inferior oblique recession with a 5 mm loop is a simple and quick technique to correct small to moderate hypertropia in primary position and inferior oblique overaction in contralateral gaze in patients with congenital, longstanding or acquired superior oblique palsy without risk of overcorrection.