DOI: https://doi.org/10.21203/rs.3.rs-1386358/v1
PURPOSE: To evaluate the first results of disinsertion-distal myektomi and tucking of inferior oblique muscle combined with full tendon advancement of superior oblique muscle in the patients with Knapp II or III superior oblique palsy.
METHODS: Disinsertion-distal myectomy and tucking of inferior oblique muscle combined Superior oblique muscle full tendon advancement surgery were performed under general anesthesia on 16 eyes of 13 patients with Knapp Class II or III superior oblique muscle palsy who were involved in the study. Before and after surgery, the degree of vertical deviation in the primary position, abnormal head position, the presence of diplopia, the amount of inferior oblique muscle hyperfunction and superior oblique muscle hypofunction, and the degree of torsion were examined, and the differences were compared.
RESULTS: In the preoperative period, twelve of the cases had abnormal head position and two had diplopia. The difference between the preoperative and postoperative period, the amount of the inferior oblique muscle hyperfunction and the superior oblique muscle hypofunction, the degree of vertical deviation in the primary position, and the amount of torsion were found statistically significant (p <0.01).
CONCLUSION: According to the first results, disinsertion-resection and tucking of inferior oblique muscle combined superior oblique muscle full tendon advancement surgery was an effective procedure in the patient with congenital and acquired Knapp Class II or III superior oblique muscle palsy.
Superior oblique muscle palsy is the most common type of cyclovertical and paralytic strabismus. It may be congenital or acquired. Possible causes of congenital superior oblique muscle palsy include hypoplasia of the trochlear nucleus or nerve, anatomic defects, the absence of the superior oblique muscle tendon, and trochlea. In adults, the most frequently observed cause of a fourth nerve palsy is head trauma. Especially in traumas to the back of the head, bilateral exposure should be expected. Vascular diseases such as hypertension, diabetes, and atherosclerosis are the causes of approximately one-fifth of the cases. Isolated fourth nerve palsies in advanced age occur due to infarct in the peripheral nerve and often resolve spontaneously.1–3
Superior oblique muscle palsy manifests itself with superior oblique muscle hypofunction. In the affected eye, the inferior oblique muscle hyperfunction, the increased hypertropia in adduction, and superior oblique muscle hypofunction are considered typical clinical manifestations.4–5
Knapp introduced a classification that describes the most common manifestations of superior oblique paralysis. Seven classes are distinguished depending on the magnitude of hypertropia in the diagnostic positions of gaze. In Class II patients (where the deviation is the greatest in the field of the paretic superior oblique muscle), superior oblique tuck (8–12 mm) is the primer procedure, while the recession of contralateral inferior rectus is considered as a second procedure. In Class III patients, if hypertropia is equal to or less than 25 PD, inferior oblique muscle weakening surgery is the primer procedure. If hypertropia is greater than 25PD, inferior oblique weakening surgery and superior oblique tuck are suggested.6
The most commonly used method for the surgical treatment of superior oblique muscle palsy is the interventions that weaken the inferior oblique muscle. These are surgical tenotomy, recession, myectomy, and anterior transposition. Myectomy and recession of the inferior oblique are the most commonly performed procedures. If there is no contracture in the superior rectus muscle of the patient, in this case, it is necessary to decide on the surgery which is required to be performed, according to the amount of torsion and vertical deviation of the patient. Improvement in torsion is achieved with strengthening surgeries to be performed on the superior oblique muscle. These are the Harada-Ito procedure, tucking, resection, resection and advancement, and full tendon advancement of süperior oblique muscle.6
This study performed disinsertion-distal myektomy and tucking of inferior oblique muscle, which is modified weakening surgery. In addition, at the same operation, superior oblique muscle full tendon advancement surgery, which is one of the strengthening methods of süperior oblique muscle was performed in the patient with Knapp Class II or III superior oblique muscle palsy, a subclass of vertical strabismus.
The records of the patients who were diagnosed with Knapp, Class II or III superior oblique muscle palsy and underwent surgical treatment in the strabismus outpatient at our tertiary care facility were examined retrospectively. Between 2015–2019, operated 16 eyes of 13 patients were included in the study. This study was approved by the Akdeniz University School of Medicine Ethics Committee. To publish these findings and images were gathered from the patient(s), informed consent was obtained from participants or their parents after a full explanation of the procedures. All procedures were conducted by the Declaration of Helsinki.
Individuals who had a neurological and muscular disease, patients who had undergone strabismus surgery in the past, as well as those who missed the follow-up regularly, were excluded from the study.
The gender of the cases and their ages during surgery were recorded. If exist, an abnormal head position was noted. A detailed anamnesis was obtained from all patients, including the time when the deviation started, prenatal history, family history, history of trauma if any, history of febrile illness, and presence of diplopia.
Visual acuity was measured using the Snellen chart. Refraction was performed with and without cycloplegia by using an auto refractometer and retinoscope. In patients with refractive errors, the correction was prescribed and recorded.
The fundus examination of all patients was performed from the dilated pupil by direct and/or indirect ophthalmoscopy.
Torsion changes were graded in the patients by taking photographs using a fundus camera. Changes in torsion were performed by evaluating the relationship between the optic disc and the macula. The average location of the fovea about the optic nerve head is 0.3 disk diameter below a horizontal line extending through the geometric center of the optic disc. Incyclotropia is present when the fovea appears above a normal line extending horizontally from the center of the optic nerve head, and excyclotropia is present when the fovea is below a line extending horizontally from just below the lower pole of the optic disc.7 The deviation of the fovea from the extending horizontal line by 1/4 disc up or down was evaluated as (+ 1) intorsion or extorsion.
Muscle functions in the primary and nine cardinal gaze positions of the cases were evaluated. In all cases, the degree of superior oblique muscle hypofunction was graded according to the relationship of the pupil with the lower lid in adduction; and the degree of inferior oblique muscle hyperfunction was graded according to the relationship of the pupil with the upper lid in adduction. Hypofunction was classified in four different severities − 1, -2, -3, and − 4, while hyperfunction was classified as + 1, +2, + 3, and + 4.
Vertical and if exist, horizontal deviation degree measurements, in nine diagnostic positions of gaze, were performed with the prism cover test at a far, near, and medium distance. The Krimsky test was used to determine the amount of near deviation in cases in which this evaluation could not be made due to their age and in whom fixation was poor.
Bielschowsky head-tilt test was performed for each patient and its results were noted.
Postoperative follow-ups were performed on the first day, in the first week, the first month, and the third month. Afterward, the patients were called to the controls every year. Orthoptic examinations applied before the surgery were repeated in the follow-ups, and the results were recorded. It was checked whether there was new-onset inferior oblique muscle hyperfunction in the other eye.
All patients were operated on by the same surgeon under general anesthesia. At the beginning of surgery, the traction test for the superior oblique muscle was performed as described by Guyton.8
The eye was adducted and elevated using a 6 − 0 virgin silk suture on inferotemporal limbus. A fornix incision was performed in the same quadrant and 8 mm away from the limbus. After being passed to the subtenon space to directly visualize the muscle fold, the tissue overlaying the inferior oblique muscle was pulled inferiorly using a Graefe hook. The muscle was disinserted using Westcott scissors. Four millimeters myektomy at the distal part of the muscle was performed. The stump of each muscle was cauterized. The muscle ends were checked to confirm that there was no bleeding, tucking the muscle stump into Tenon’s the capsule was performed. If the muscle stump was not outside the borders of the Tenon’s capsule, the wound was closed using interrupted 7 − 0 Vicryl (polyglactin 910, Ethicon) sutures (Fig. 1,2).
After performing inferior oblique weakening surgery, superior oblique muscle full tendon advancement was added on all patients. In the superior quadrant adjacent to the limbus, the globe deviated passively to the inferior with the traction suture passing through the conjunctiva and episclera. A two-step incision was applied to the conjunctiva and Tenon’s capsule, at a distance of eight mm from the limbus, is in the superior temporal quadrant. The superior rectus muscle was found with the hook, and depression was made to the globe in adduction. The Desmarres retractor was placed along the temporal border of the superior rectus muscle. The insertion of the superior oblique muscle was uncovered and suspended using a strabismus hook. After passing full-thickness from the middle of the muscle with a double-ended 6/0 Ethibond suture, a lamellar suture was put on both sides of the muscle and the muscle was fixed by knotting. Using Wescott scissors, disinsertion of the tendon was performed. The amount of the procedure that would be applied was determined by stretching it with the help of a suture in the direction in which muscle advancement was going to be performed. This amount was 3–6 mm temporally and inline with the original insertion. Both ends of the suture were passed through the sclera the upper and lower point of the muscle's new attachment site. Each of the sutures is knotted bypassing through the middle of the end of the muscle (Fig. 3–4).
The traction test was repeated after removing the lid retractor. Only in one case, it was determined that the muscle became more functional than desired during this test. The proper correction was made by resolving the temporary suture. The conjunctiva was sutured in its place with 7/0 Vicryl suture. Antibiotic and steroid drops were given to all cases four times a day, and drug use was reduced and terminated two weeks later. No surgical a complication was observed in the postoperative period of the cases.
Statistical analysis was performed using the Statistical Package for Social Science (SPSS 18) program. The Wilcoxon signed-rank test was used in the examination of preoperative and postoperative values, and the value of p < 0.01 was considered statistically significant.
Of the thirteen patients included in the study, seven (53.8%) were female, and six (46.2%) were male. The mean age of the patients was found to be 16.5 (2.25–73.6) years.
The mean follow-up time was 6.2 months.
In two (15.4%) cases, acquired superior oblique muscle palsies, and congenital superior oblique muscle palsies in 11 (84.6%) cases were detected. Four of the thirteen patients (30.8%) included in the study were found to have right, six (46.2%) had left, and three (23.1%) had superior oblique muscle palsy in both eyes.
Two acquired cases (15.4%) had diplopia. In these two cases, superior oblique muscle palsy was detected in the left eye. After the surgery, it regressed completely.
Twelve of the thirteen cases (92.3%) had an abnormal head position. After the surgery, it was monitored to have improved in all of the patients.
Preoperatively, the average amount of extorsion was found to be + 1.76 (+ 1, + 3), while postoperatively it was found to be -0.25 (-1, + 1). The difference between them was statistically significant (p < 0.01).
The average score of the superior oblique muscle hypofunction was − 2.23 (-3, -1) preoperatively, and it was determined to be -0.19 postoperatively. The difference between them was statistically significant (p < 0.01).
The average score of the inferior oblique muscle hyperfunction was + 3.38 (+ 3, + 4) preoperatively and it was + 0.25 postoperatively. The difference between the results of two separate periods was observed to be statistically significant (p < 0.01).
It was observed that the amount of vertical deviation determined in the primary position was 20.44 Prism Diopters in the preoperative period and disappeared in all cases after surgery.
There was no horizontal deviation at the primary position in any case.
After performing the full tendon advancement of the süperior oblique muscle, only in one patient, the sutures were loosened and the adjustment was performed intraoperatively.
Superior oblique muscle palsy is one of the common causes of vertical strabismus in adults and children. Patients may apply with the complaint of vertical diplopia, or they have developed an abnormal head position to provide a single vision. Clinical findings associated with congenital superior oblique muscle palsy are torticollis and facial asymmetry (Fuller Face). Especially the presence of an abnormal head position is a strong indicator that the event is long-term. However, studies also question the relationship between facial asymmetry and superior oblique muscle palsy.9
It is known that most of the acquired superior oblique muscle palsy cases develop secondary to trauma. In the present study, there were predominantly congenital cases. In both of the acquired cases, the etiology is trauma. In traumatic cases, masked bilaterality is common. Therefore, in our study, we considered etiology was congenital if we could not find any other reason in patients without a history of trauma.
The head is generally in the direction of the shoulder, which is opposite to the affected eye, the chin is tilted down, and the face turns to the opposite side. Abnormal head position (92.3%) and diplopia (15.4%) were observed in the preoperative examination of the cases, and these features helped to diagnose superior oblique muscle palsy.
As determined in the present study, children often apply with the abnormal head position instead of diplopia. This is because the developing brain represses the central perception coming from a single eye in the presence of deviation. Older children with acquired superior oblique muscle palsy who have diplopia can express this symptom verbally. Adults may apply with the abnormal head position, vertical deviation, or with diplopia complaints developing due to excyclotorsion. When our cases were examined, diplopia was determined more frequently in adults in a similar way.10,11
Superior oblique muscle palsy may be bilateral. The degree of excyclotorsion is typically higher in bilateral cases than in unilateral cases.12 In masked bilateral cases, in cases in which mostly unilateral surgery is performed and the clinical picture is improved, similar problems arise on the opposite side after some time. In our case series, we did not encounter any problem in the early period in cases in which unilateral surgery had been applied.
Bhola et al. performed superior oblique muscle folding surgery in the isolated unilateral superior oblique muscle palsy. They stated that in acquired and congenital cases, in the postoperative period elevation limitation (Iatrogenic Brown Syndrome) was observed in adduction, but the limitation decreased over time. They reported that in acquired cases, while Iatrogenic Brown Syndrome was observed in the early postoperative period, the cases in both groups were asymptomatic.13 In the present study, Brown syndrome or the relapse of the clinical picture with the sutures getting loose was not observed in the postoperative early period. This situation supports our opinion, arguing that this surgical method may be appropriate to avoid complications.
Morris and Scott reported in their study that there was a 3.6 Prism Diopters improvement in the vertical deviation in the primary position after superior oblique muscle tucking surgery. They found the improvement amount to be 15.3 prism diopters also in the direction of eye movements, where the deviation was the highest.14 In our study, the deviation in the primary position, which was an average of 20.44 PD in the primary position, was lost in the early postoperative period. This result demonstrates that our surgical methods are effective in correcting vertical deviation.
Ludwig stated that the superior oblique muscle full tendon advancement method could be used in all kinds of superior oblique muscle weakness, including unilateral congenital or bilateral V patterned superior oblique muscle weakness and acquired superior oblique muscle palsy due to head trauma or vascular causes. The cause of congenital superior oblique muscle weakness was mostly observed to be tendon laxity or abnormal insertion. This method ensures that the insertion site of patients with this feature is changed and brought to a more anatomic position. Ludwig indicated that torsional diplopia could be observed postoperatively in some adult patients who had undergone unilateral superior oblique muscle full tendon advancement, but that this situation spontaneously regressed within 10–20 days.15 In the cases involved in our study, no symptoms related to torsional diplopia were observed in the postoperative examination.
Bata et al. stated that both in symmetric and asymmetric bilateral superior oblique muscle palsies, superior oblique muscle full tendon advancement surgery applied using an adjustable suture technique provides the independent control of the vertical and torsional components of the deviation. They indicated that a similar rate of excyclotorsion was observed in the postoperative period with the Harada-Ito procedure; therefore, more incyclotorsion correction was needed during torsional alignment. In their study, the postoperative adjustment was required in 80% of the patients, and they applied a correction with five mm regression or three mm advancement.16 In our series, an intraoperative adjustment was required only in one patient. The reason for this is the determination of the amount of advancement by the traction we applied after disinsertion during the surgery. This procedure seems to eliminate the need for post-surgical adjustment.
In one of our studies; we investigated the effectiveness and safety of disinsertion-distal myectomy and tucking of the inferior oblique muscle in patients with unilateral long-standing superior oblique muscle palsy and secondary inferior oblique muscle overaction. This technique was safe, simple, and effective. However, in cases with a high vertical deviation in the primary position, inferior oblique muscle weakening surgery alone is not sufficient and süperior oblique muscle strengthening surgery is required. According to Hatz et all isolated inferior oblique muscle weakening is an effective treatment option for superior oblique palsy up to 15 PD of vertical deviation in primary position. Two-muscle surgery should be reserved for patients with larger vertical deviations.17–18
In this study, the degrees of torsion, inferior oblique muscle hyperfunction, superior oblique muscle hypofunction, and the amount of vertical deviation in the primary position were examined preoperative and postoperative periods. The difference between them was found to be statistically significant (p < 0.01).
Surgical complications such as orbital cellulitis, endophthalmitis, scleral perforation, and Iatrogenic Brown Syndrome did not develop due to the low traumatic effect of our method.
The conducted studies demonstrate that the surgical method to be performed in superior oblique muscle palsy should be selected according to the condition of the patient and the experience of the surgeon.14,15,19,20 The short-term results of the methods we performed are satisfactory. However, studies with more cases and longer-term are needed.
Acknowledgments; The authors would like to thank Prof.Dr.ADN MURRAY who taught the surgical management of süperior oblique muscle palsy.
Authors' contributions; All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by AKDERE Burçin and BEĞENDİ Diğdem. The first draft of the manuscript was written by KAYA Burçin and writing reviewed and edited by DURANOĞLU Yaşar. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Informed consent statement; General consent was obtained in which the patient agrees with the research use of residual body parts and clinical records and data with anonymization.
Declaration of conflicting interests We declare that the authors have no competing interests as defined by Springer, or other interests that might be perceived to influence the results and/or discussion reported in this paper.
Funding The author(s) received no financial support for the research, authorship, and/or publication of this article.
Financial Support: The Author(s) declare(s) that no financial support was received for this submission.
This study was performed in line with the principles of the declaration of Helsinki and approved by the Akdeniz University School of Medicine Ethics Committee on 07.03.2018 /206.