A Case of Congenital Absence of the Superior Oblique Muscle Treated With Anterior and Nasal Transposition of the Inferior Oblique Muscle

PURPOSE: To report a patient with absence of the superior oblique (SO) muscle of the left eye, who showed improvement after anterior and nasal transposition of the inferior oblique muscle for left hyperdeviation and right head tilt. CASE SUMMARY: A two-year-old boy presented with hypertropia of the left eye and right head tilt. Alternate prism-cover test in the primary position demonstrated 18 prism diopters (PD) of left hypertropia, which increased to 35 PD in the left head tilt position. A version test demonstrated overaction of the left inferior oblique muscle and underaction of the left superior oblique muscle. As an orbit CT scan showed absence of the SO muscle, the patient was diagnosed with congenital absence of SO and left anterior and nasal transposition of the inferior oblique muscle was performed. Three weeks after surgery, the patient presented with orthotropia at distant and near. The version test revealed normal oblique muscles. There was no vertical deviation shown on the Bielschowsky head tilt test. The abnormal head posturing was no longer observed. CONCLUSIONS: The authorsreport a patient manifesting abnormal head posture and hypertropia, diagnosed with absence of SO muscle, which was successfully corrected using anterior and nasal transposition of the inferior oblique muscle.

A Case of Congenital Absence of the Superior Oblique Muscle

PURPOSE: To report a patient with adsence of the superior oblique (SO) muscle of the right eye, who showed improvement after surgery for hyperdeviation and exotropia. METHODS: A four-year-old girl who presented with 14 PD exotropia, and 25 PD hypertropia of the right eye had a history of myectomy of the right inferior oblique (IO) muscle for bilateral SO palsy as a two-year-old. At the time of surgery, severely fibrotic pseudotendon of IO and Tenon's capsule attached to the insertional area of the inferior rectus muscle was found. IO was remyectomized with adhesiolysis. Lateral rectus and superior rectus (SR) muscles were recessed 6.5mm and 7mm, respectively. After exposure of SR, the absence of SO was found. MRI taken at postoperative one day showed definite SO absence. RESULTS: Three weeks after surgery, 4 PD of left hyperphoria at distant and 5 PD of left hyperphoria at near were observed. Right hyperdeviation was not detected. At postoperative 7 months, 4 PD of exophoria, 6 PD of right dissociated vertical deviation (DVD) and 10 PD of left DVD were seen at distant. A small left hyperdeviation was intermittently noted at upgaze and was cautiously followed. CONCLUSIONS: Absence of the superior oblique muscle is rare. However, such absence should be suspected when apparent superior oblique palsy accompanies with severe hyperdeviation and horizontal deviation. MRI or CT is helpful in the diagnosis of this condition and direct confirmation is needed.