Disorders of the Ocular Motor Cranial Nerves and Extraocular Muscles

The extraocular muscles have many anatomic, physiologic, and molecular characteristics distinct from those of other striated muscles. These characteristics, which likely developed in response to the specialized demands placed on the extraocular muscles (including tonic position-maintaining contractures, conjugate smooth pursuit and saccades, and dysconjugate vergence movements) may account for the often predictable involvement or sparing of extraocular muscle in specific pediatric neuromuscular disorders. Extraocular muscle dysfunction in neuromuscular disease typically presents with ptosis, ophthalmoplegia, or incomitant strabismus, or a combination of these symptoms, which can assist the clinician in formulating differential diagnoses for neuromuscular conditions. This chapter reviews the unique features of the oculomotor system and the neuromuscular disorders affecting it.