Damage to the inferior oblique muscle branch of the oculomotor nerve: a complication during orbital fat decompression

A Rare Case of Cyclotorsion Due to Medial Rectus Displacement Following Orbital Trauma

We describe a rare case of cyclotorsion likely secondary to medial rectus and inferior rectus pathology in a patient with orbital trauma. Sequential orthoptic measurements including Hess charts are presented alongside relevant sections of the orbital CT scans over the course of the patient’s treatment. Following the insertion of a plate to repair an orbital floor fracture, the patient developed cyclotorsion. A combined approach of sequential orthoptic assessment and imaging revealed the likely underlying mechanism. Inferior rectus mechanical restriction combined with displacement of the medial rectus pulley appear to be the likely culprits. Once the orbital plate was exchanged for a smaller sized plate the patient’s symptoms and clinical features resolved. Although orbital plate malpositioning is not an uncommon event, medial rectus deviation as a cause of cyclotorsion has not previously been described. We discuss the alternative differentials for patients with similar orthoptic findings and how they were excluded.

Location of the myoneural junction of the inferior oblique muscle: An anatomic study

PURPOSE

To examine both the horizontal and vertical locations of the myoneural junction of the inferior oblique muscle (IOM) in reference to the ala nasi, IOM origin, and inferior orbital rim.

MATERIALS AND METHODS

Fifty-six orbits from 56 Japanese cadavers (15 male and 41 female cadavers; average age at time of death, 86.5±9.4 years) were used in this experimental anatomical study. The inter-alae-nasi distance and the horizontal distances from the ipsilateral ala nasi to the IOM origin (ala-nasi-origin distance) and to the myoneural junction (ala-nasi-junction distance) were measured. The horizontal distance from the IOM origin to the myoneural junction (origin-junction distance) was calculated by subtraction of the ala-nasi-origin distance from the ala-nasi-junction distance. The vertical distance from the inferior orbital rim to the myoneural junction (rim-junction distance) was also measured.

RESULTS

The ala-nasi-junction, origin-junction, and rim-junction distances were 12.2±3.2mm, 10.6±3.2mm, and 3.4±1.0mm, respectively. Males had a longer inter-alae-nasi distance than females (P<0.001), although the other distances did not show statistically significant sex-related difference (P>0.050). The ala-nasi-junction distance tended to be negatively correlated with the inter-alae-nasi distance (r=-0.222, P=0.050).

CONCLUSIONS

The ala-nasi-junction distance can be affected by the inter-alae-nasi distance, which was found to be longer in males. Therefore, the IOM origin and the inferior orbital rim can be considered as more practical and reliable reference points to predict the location of the myoneural junction during the posterior inferior orbitotomy, irrespective of sex.