STRABISMUS JOURNAL CLUB Rachel Chang Ophthalmology registrar 16/5/17

Patients & METHOD Prospective study 1996-2009 Imaging technique: T1 or T2 fast spin echo with surface coil orbital MRI. Correlate MR imaging with clinical findings Result: * 118 orthotropic  1 (0.8%) * 453 strabismus patient  11 (2.4%) [p=0.48] Conclusion: 2% of study population have supernumerary EOM bands. Non- oculorotatory. In 2 cases, band from MR to LR causes clinical restriction of supraduction by contact with optic nerve

Cases 1 14 month old with belpharoptosis & upward gaze palsy in both eyes

CASE 6 38-year-old woman presented with a history of an unspecified strabismus surgery at age 9 years 17Δ right exotropia and 12Δ right hypotropia in central gaze, with limitation of supraduction & mild limitation to infraduction OD. On supraversion, the EOM band appeared to contact the inferior edge of the optic nerve.

CASE 8 35 F hx 80 PD infantile ET. multiple surgery including BMRR  Bilateral lateral rectus resect  L) IO recession, bilateral lateral rectus recession. Residual 25 PD ET with limitation of abduction and over elevation on adduction CASE 8

SUMMARY

Clinical relevance/DISCUSSION Supernumerary EOM bands, although too deep to access with traditional strabismus surgery, recognition pre-op is helpful to inform surgical decisions. For example, provide information that restriction from a band might persist after strabismus surgery. 5/12 with EOM bands had CCDDS (congenital cranial dysinnervation disorder) – either CFEOM (congenital fibrosis of extraocular muscle) or Duane Syndrome  supernumerary muscle may be regarded as additional components of CCDDS

Compare T1 to T2FSE MRI Group 1 (T1 MRI): 506 human, 10 cadavers, 21 monkey cadavers – retrospective comparison Group 2 (T2FSE MRI): 21 normal individual & 113 strabismus Group 3 (both T1 & T2FSE) – prospectively scanned METHOD: high resolution scan surface coil with fixation target

Image quality Comparable between T1 & T2 axial images of two different patients with left abducens paralysis with atrophy of the involved lateral rectus muscle & bowing and inflection of the lateral rectus path. Of note, T2: uveal tract cannot be differentiated from vitreous Image quality

Duration of scan INTRINSIC CONTRAST T1 218 seconds T2FSE 150 seconds While both T1 and T2FSE provided excellent delineation of tissue boundaries demarcated by orbital fat, only T2FSE demonstrated additional boundaries delineated by variations in tissue water content.

The same patient with sinusitis, periorbital tissue in T1 is uniformly dark

Comparison with contrast Active thyroid ophthalmopathy R) LR cicatrisation post orbital decompression T1: both EOM & cicatricial band dark T1 with contrast: EOM enhance, band dark T2 (no contrast): EOM & band both have good contrast against orbital fat

Orbital pulley

While not as effective in demonstrating the rectus pulleys as gadodiamide-enhanced T1 MRI, T2FSE may still demonstrate these pulleys adequately without IV contrast

T2FSE * all modern MRI are capable of T2FSE without modification * avoids use of IV contrast * faster scanning resulting in better image quality from less motion artefact