Abstract
ObjectivesTo compare the surgical outcomes of inferior oblique (IO) myectomy in congenital superior oblique palsy (SOP) according to the presence of the trochlear nerve identified with high-resolution MRI.Data ExtractionForty-one congenital SOP patients without a trochlear nerve (absent group) and 23 patients with a trochlear nerve (present group) who underwent IO myectomy as the primary surgical treatment were retrospectively reviewed. “Motor success” was defined as postoperative ipsilateral hypertropia ≤ 4 prism diopter (PD). “Head tilt improvement” was regarded as postoperative angle of head tilt < 5 degrees (°). Success rates for motor alignment and head tilt improvement, cumulative probabilities of success, and factors influencing surgical responses were evaluated.ResultsThe cumulative probabilities of motor success at 2 years after IO myectomy were 92% in patients with a trochlear nerve and 86% in patients without a trochlear nerve (P = 0.138). The cumulative probabilities of undercorrection and recurrence of hypertropia after 2 years were 0% in the present group versus 21% in the absent group (P = 0.014). The cumulative probabilities of persistent head tilt after 2 years were 14% in the present group and 20% in the absent group (P = 0.486). A younger age at operation was associated with reduced probabilities of motor success and head tilt improvement (P = 0.009, P = 0.022 respectively). A greater preoperative angle of head tilt was associated with persistent head tilt after surgery (P = 0.038).ConclusionsCongenital SOP without a trochlear nerve had a higher risk of hypertropia undercorrection after IO myectomy compared to patients with a trochlear nerve. A younger age at operation and larger preoperative head tilt was related to poor outcomes.
Highlights
Congenital superior oblique palsy (SOP) without a trochlear nerve had a higher risk of hypertropia undercorrection after inferior oblique (IO) myectomy compared to patients with a trochlear nerve
Recent advances in high-resolution thin-section magnetic resonance imaging (MRI) techniques provide another means of evaluating the pathogenic mechanism of congenital superior oblique palsy (SOP) allowing direct identification of congenital trochlear nerve agenesis in patients with superior oblique (SO) muscle hypoplasia. [1,2,3] Our recent studies introduced novel aspects in the classification of congenital SOP according to the presence of the trochlear nerve and demonstrated clinical differences between these groups in details
Surgical management of SOP consists of strengthening the SO muscle, weakening the inferior oblique (IO) muscle of the paretic eye, or operating on the vertical rectus muscles, as well as a combination of these operations. [4,5,6,7] IO weakening procedures are frequently applied as surgical options if secondary IO overaction is prominent without the evidence of SO tendon laxity or significant SO weakness. [4,5,6, 8,9,10,11] There have been numerous reports about the effects of IO myectomy in reducing the vertical deviation as well as eliminating the anomalous head postures. [5, 9, 11, 12] Toosi and von Noorden documented that IO myectomy was a simple, safe and effective surgery for SOP accompanying IO overaction
Summary
Recent advances in high-resolution thin-section magnetic resonance imaging (MRI) techniques provide another means of evaluating the pathogenic mechanism of congenital superior oblique palsy (SOP) allowing direct identification of congenital trochlear nerve agenesis in patients with superior oblique (SO) muscle hypoplasia. [1,2,3] Our recent studies introduced novel aspects in the classification of congenital SOP according to the presence of the trochlear nerve and demonstrated clinical differences between these groups in details. [2] In patients with congenital SOP, 73% showed ipsilateral trochlear nerve absence and a variable degree of SO hypoplasia, while the remaining 27% had a normal morphologic SO volume and the trochlear nerve on both sides, suggesting distinguished etiologies. [2] regardless of the etiology, the surgical treatment for congenital SOP is based on ocular motility patterns including ductions and versions, muscle restriction or torsional changes. [4, 5]Surgical management of SOP consists of strengthening the SO muscle, weakening the inferior oblique (IO) muscle of the paretic eye, or operating on the vertical rectus muscles, as well as a combination of these operations. [4,5,6,7] IO weakening procedures are frequently applied as surgical options if secondary IO overaction is prominent without the evidence of SO tendon laxity or significant SO weakness. [4,5,6, 8,9,10,11] There have been numerous reports about the effects of IO myectomy in reducing the vertical deviation as well as eliminating the anomalous head postures. [5, 9, 11, 12] Toosi and von Noorden documented that IO myectomy was a simple, safe and effective surgery for SOP accompanying IO overaction. [9] Helveston and associates described that IO myectomy had low complications such as an iatrogenic Brown syndrome and great efficacies to treat the symptoms from SOP as an initial procedure. [5] In addition, Shipman and Burke reported that IO myectomy resulted in the greatest reduction of hypertropia in the primary position up to 15 prism diopters (PD) or more with better predictable long term outcome compared to IO recession. [10] Ghazawy and associates identified that IO myectomy improved SO underaction irrespective of the accordance of primary or secondary IO overaction. [12] uncombined IO myectomy has been commonly preferred as the initial procedure, especially in SOP patients with overaction of the ipsilateral IO and preoperative hyperdeviation of 10 to 15 prism diopter (PD) or more. [9,10,11]There have been several studies about surgical results between various IO weakening surgeries in SOP. [10, 11, 13,14,15] In contrast, the comparable long-term outcomes of IO weakening surgery for the treatment of congenital SOP according to the 2 distinct pathologic mechanisms; the presence or absence of the trochlear nerve, have not yet been documented in the literature. [5] In addition, Shipman and Burke reported that IO myectomy resulted in the greatest reduction of hypertropia in the primary position up to 15 prism diopters (PD) or more with better predictable long term outcome compared to IO recession. [10, 11, 13,14,15] In contrast, the comparable long-term outcomes of IO weakening surgery for the treatment of congenital SOP according to the 2 distinct pathologic mechanisms; the presence or absence of the trochlear nerve, have not yet been documented in the literature. The present investigation was conducted to compare the surgical outcomes of IO myectomy as the primary intervention in congenital SOP, depending on the presence of the trochlear nerve identified with thin-section high-resolution MRI. Factors influencing the surgical outcomes were evaluated
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