Abnormal extraocular muscles may limit eye movements through decreased function or through restriction. The pattern of limitation may simulate neural and neuromuscular disorders
so closely that force ductions, special imaging (echography, CT, MRI), or even surgical exploration may be necessary for differentiation.
These disorders may be either congenital or acquired. Congenital anomalies of the extraocular muscles include agenesis, duplication, abnormal origins and insertions, fascial anomalies, and fibrous bands.297'500,508,509,529 Congenital absence of one or more extraocular muscles limits movement of the globe in the direction of action of the missing muscle(s) and may mimic a nerve palsy. Indeed, in one series of presumed congenital superior oblique palsies for which a superior oblique tuck was deemed necessary and attempted, 18% of the patients were found to have congenital absence of the superior oblique.201 Agenesis and other forms of maldevelopment of the extraocular muscles have long been recognized and associated with cranio-
At times, certain extraocular muscles mechanically restrict eye movements from birth, for example, in the congenital fibrosis syndrome (Fig. 5-13) or congenital Brown's syndrome. Acquired disorders such as trauma, dysthyroid myopathy, acquired Brown's syndrome, and orbital myositis may all cause weakness or restriction of extraocular muscles. Although investigation of these disorders requires careful attention to the history and systemic health of the child as well as local ocular and orbital signs, such advertence is frequently rewarded.
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