Complex Ocular Motor Disorders in Children
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Chapter 7 Complex Ocular Motor Disorders in Children Introduction cost-effective manner. A knowledgeable clinician is less likely to embark on “fishing expeditions.” A number of complex ocular motility disorders are discussed The emphasis of this chapter is on ocular motility disorders in this chapter. The diversity of these conditions reflects the of neurologic origin and their differential diagnosis. The most need for the ophthalmologist to maintain a broad working current pathophysiologic concepts of the disorders are sum- knowledge of pediatric neurologic disorders along with their marized. A section at the end of the chapter is devoted to a few ocular motor manifestations. Some clinical features of these common eyelid and pupillary abnormalities encountered in conditions (e.g., congenital ocular motor apraxia, congenital children. Some of these disorders, such as excessive blinking fibrosis syndrome) are sufficiently unique that the diagnosis in children, commonly represent benign transient tics that can be established solely on the basis of the clinical appear- receive very little attention in the ophthalmologic literature, ance. Other disorders either show overlapping manifestations but are not rare in clinical practice. These bear only superficial or effectively masquerade as other entities. Unique features resemblance to the more chronic benign essential blephar- of some conditions, such as conjugate ocular torsion in ospasm of adults although, rarely, childhood tics and adult patients with skew deviation, have been recently recognized blepharospasm show clustering in the same family, suggesting and are considered worthy of emphasis because they signifi- a possible link. Occasionally, underlying ocular surface abnor- cantly expand the differential diagnosis. Indeed, assessment malities and seizure disorders may be uncovered in children of objective torsion (and subjective torsion when possible) is with excessive blinking. Other disorders, such as hemifacial a necessary component of any comprehensive strabismo- spasm, which is more common in adults, may be the harbin- logical evaluation.323 Correction of coexisting torsion can be gers of more serious central nervous system (CNS) disorders integrated into the surgical plan, except when the torsion if encountered in very early childhood. Pediatric Horner syn- serves a compensatory function, as in patients with skew drome is treated in some detail at the end of the chapter, owing deviation. to its potentially ominous association with certain neoplasms, Although the clinical history and physical examinations especially neuroblastoma. The human immunodeficiency virus remain the “gold standard” for establishing the diagnosis, (HIV) infection has joined the ranks of other great mimickers neuroimaging has become an integral part of the diagnostic (e.g., myasthenia gravis, syphilis), with an ever-expanding list evaluation. High-resolution neuroimaging can now depict of neuro-ophthalmologic manifestations. No part of the the presence or absence of most ocular motor nerves and nervous system is spared. Even though it is not specifically the size, position, and dynamic function of the extraocular covered in this chapter, HIV-related neurological disease muscles. In patients with craniosynostosis, for example, should be included in the differential diagnosis of childhood 343 heterotopic extraocular muscles within the orbit can produce ocular motor disorders of cortical, brain stem, cerebellar, or a motility disorder indistinguishable from innervational infe- peripheral nervous system origin. rior oblique muscle overaction,736 absence of the isolated extraocular muscles can produce complex ocular motility dysfunction, and retrodisplacement of the trochlea can Strabismus in Children with Neurological produce a motility pattern indistinguishable from congenital superior oblique palsy.580 Optimal surgical treatment depends Dysfunction on accurate recognition of the specific cause of a given patient’s motility disturbance.204 Thus, a detailed know ledge Common neurologic disorders of children are frequently of clinical findings that characterize each condition is necessary associated with strabismus. These include cerebral palsy, to perform the diagnostic workup in an efficient, timely, and Down syndrome, myelomeningocele, and hydrocephalus. M.C. Brodsky, Pediatric Neuro-Ophthalmology, 309 DOI 10.1007/978-0-387-69069-8_7, © Springer Science+Business Media, LLC 2010 310 7 Complex Ocular Motor Disorders in Children The features of the associated strabismus are often indistin- eration. Children with neurologic disorders, who have hori- guishable from the varieties found in otherwise normal chil- zontal strabismus, have a higher prevalence of constant dren, but sufficient differences exist in a distinct minority of exotropia and primary superior oblique muscle overaction neurologically affected children to warrant separate consid- than otherwise healthy strabismic children (Fig. 7.1).334,341 Fig.7.1 (a) Bilateral superior oblique overaction in child with lumbar myelomeningocele. Note resemblance to alternating skew deviation. (b) 1MR imaging characteristically associated Chiari II malformation with pronounced peaking of tectum and herniation of cerebellar vermis into cervical spinal canal Strabismus in Children with Neurological Dysfunction 311 Cerebral palsy is perhaps one of the most common condi- esotropic children with cerebral palsy convert spontaneously tions seen in a pediatric neuro-ophthalmology practice.32 The to an exotropia over several years. For this reasons, current term cerebral palsy defines a group of chronic neurologic trends toward early surgery for infantile esotropia should not disorders resulting from damage to the immature brain. Most be loosely applied to these patients, and it is important to rule cases nowadays are due to prematurity. Care should be taken out occult neurologic disease when early strabismus surgery to distinguish the static nature of cerebral palsy from the is contemplated in seemingly normal children. inexorably progressive neurodegenerative disorders such as As children with cerebral palsy and esotropia seem to Pelizaeus–Merzbacher disease. have a strong predilection for surgical overcorrection,371 Cerebral palsy is characterized by the onset of neurologic standard surgical doses for treating esotropia should be deficits in the neonatal period and absence of progression. In reduced. In our experience, however, it is not necessary to addition to motor disorders, such as paralysis, weakness, and reduce doses for bilateral lateral rectus muscle recession in incoordination, children with cerebral palsy may display neurologic exotropia. As detailed in Chap. 1, children with sensory deficits, as exemplified by the frequent findings of cerebral palsy may have abnormalities of gaze affecting optic atrophy, deafness, and cortical visual impairment. pursuit and saccadic movements and vestibulo-ocular reflex Patients with cerebral palsy show ophthalmologic abnormal- suppression by fixation.417,618 ities with a frequency ranging from 50 to 90%. These include The craniosynostosis syndromes often present with com- optic atrophy, amblyopia, refractive errors, visual field plex forms of horizontal and vertical strabismus that are defects, congenital cataracts, corneal leukomas, retinal dys- both neurologic and anatomical in origin.144,206,280,541,558,580,646 plasia, choroiditis, macular or iris colobomas, retinopathy of Although hypertelorism is classically associated with exotro- prematurity, ptosis, spastic eyelids, abnormal head postures, pia with a V pattern, esotropia can also be seen.431 Good and ocular motility disorders.395,740 The latter include con- stereopsis is rare in the syndromic craniosynostosis and may comitant strabismus, ocular motor nerve palsy, nystagmus, sometimes be confined to certain positions of gaze.576 Some gaze palsy, and other supranuclear disturbances of ocular patients develop esotropia following craniofacial surgery, movements.489 which can disrupt stereopsis.788 Children with cerebral palsy have a markedly increased The frequent finding of overelevation of the adducting eye incidence of strabismus.489 The strabismic deviations are usu- in children with bilateral craniosynostosis was previously ally horizontal and nonparalytic. Associated vertical incomi- attributed to recession of the frontal processes, creating a tance is often seen, with A-pattern strabismus being particularly mechanical disadvantage for the superior oblique muscle. It common. In one series, 691 54% of strabismic children with now appears that excyclorotation of both orbits alters the cerebral palsy showed A pattern, and 46% showed V pattern. horizontal rectus muscle positions, positioning the lateral Variability of the magnitude and direction of the strabismus rectus muscles lower than normal and the medial rectus mus- are commonly noted in cerebral palsy.40 Some studies note a cles higher than normal (Fig. 7.2).156 This orbital excycloro- predominance of esotropia,40,489 while others have found tation is associated with marked excyclorotation of the exotropia to be more common. globes, as is evident on retinal examination.736 Although the Momentary fluctuation from esotropia to exotropia has resulting motility pattern is indistinguishable from that pro- been termed dyskinetic strabismus and is considered unique duced by primary inferior oblique muscle overaction, infe- to cerebral palsy.129 Dyskinetic strabismus is unrelated to rior oblique weakening procedures produce negligible