Journal of neuro-ophthalmology : the official journal of the North American Neuro-Ophthalmology Society
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Comparative Study
Frequency-selective fat suppression MR imaging. Localized asymmetric failure of fat suppression mimicking orbital disease.
Our objectives were to further characterize an artifact related to the localized failure of the frequency-selective (FATSAT) fat suppression magnetic resonance (MR) imaging technique. We constructed two phantoms simulating human orbital anatomy and imaged them on a 1.5-T MR scanner using (FATSAT) and short T1 inversion recovery (STIR) techniques of fat suppression. The first phantom resembled orbit structural configurations; it was imaged in coronal and axial planes and in varying orientations with respect to the main magnetic field (Z axis) to study the features of the artifact and to reproduce the asymmetry seen in clinical cases. ⋯ We concluded that failure of FATSAT fat suppression may mimic orbital disease, particularly if asymmetric. As predicted by the Maxwell electromagnetism equation, slight variations in orientation of the fat-air interface to the Z axis may produce large asymmetries in fat suppression failure in the orbit. Confirmation may require either comparison with additional pulse sequences [T1-weighted spin echo (T1W SE) or STIR] or repositioning the patient's head to check for persistence of the finding with varying orientations.
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Ophthalmoparesis and ptosis are extremely rare in nemaline myopathy. A 45-year-old man with a long history of bilateral ptosis and a 1-year history of diplopia is reported. Leg and arm weakness and wasting had been present since childhood, with a very slow deterioration over time. ⋯ Triceps muscle biopsy showed small multiple collections of rod-like structures in > 50% of fibers. This patient presented with a clinical picture that did not primarily suggest nemaline myopathy. This case illustrates the heterogeneity of this disorder and the need for muscle biopsy to make an accurate diagnosis in patients with ptosis and progressive external ophthalmoparesis.