Chapter 9

Introduction

Children with visual or neurological disorders can exhibit abnormal head postures (torticollis) or rhythmic movements of the head (oscillations). Torticollis is not a diagnosis, but a sign of an underlying disorder.128 Although technically defined as a contraction, often spasmodic, of the muscles of the neck,128 for the purposes of differential diagnosis, most causes of abnormal head position (spasmodic or otherwise) are generally included under the umbrella term torticollis.

The neuro-ophthalmologic evaluation of torticollis is simplified by the frequent association of a head tilt with contralateral superior oblique palsy.162 While many ophthalmologists see a predominance of patients with superior oblique palsy (or at least diagnose them as such), a slight majority in the general pediatric population probably have congenital muscular torticollis.162 When strabismus and nystagmus are absent, the differential diagnosis includes a long list of ocular and systemic conditions. Head oscillations in children often signify spasmus nutans or congenital nystagmus; however, an awareness of other rare causes is necessary to provide a complete evaluation. Abnormal head movements are less likely to be overlooked by parents than abnormal head positions. Although we use the descriptive terms head shaking and head nodding, many children display a combination of horizontal and vertical oscillations, and some (especially those with spasmus nutans) show complex elliptical head oscillations when viewing objects of interest. The term head tremor has the advantage of being directionally nonspecific, but it connotes a rapid, small-amplitude head movement (as seen in benign essential tremor) that differs from the slower, larger-amplitude oscillations seen in children with neurological disease.

This chapter focuses on the distinctive clinical manifestations of the neurological and systemic conditions that lead to torticollis, head oscillations, or both. It includes extensive discussion of common conditions and brief mention of rare disorders that warrant consideration once common conditions are excluded. Although these disorders are dichotomized into visual or neurologic for purposes of classification, the reader will appreciate that neurologic disease underlies many of the

visual disorders that lead to torticollis. Although the term ocular torticollis is commonly used to describe anomalous head positions that result from visual input, many of these disorders are ultimately neurological in origin.211 Other forms of abnormal head movement (head thrusting, myoclonus, tics, and habit spasms) are covered in Chap. 7 in the context of their associated neuro-ophthalmologic findings.

Torticollis

Torticollis, derived from the Latin tortus (twisted) and collum (neck), is defined as “a contracted state of the cervical muscles, producing twisting of the neck and an unnatural position of the head.”72 In clinical practice, torticollis refers to any abnormal head tilt, face turn, or vertical position of the head. Also known as “wryneck” or “caput obstipum,” torticollis was first alluded to by Hippocrates (c. 500 BC) and later detailed by Plutarch (356 to 232 BC).122 Throughout medical history, treatments for torticollis have ranged from elaborate splints and traction techniques to tenotomy of the neck muscles. In 1873, Cuignet described torticollis as a manifestation of misalignment of the eyes.75

Head posture is maintained anatomically by the vertebral column supporting the head and the muscles of the neck and shoulders (the sternocleidomastoid, thoracic, and cervical semispinalis muscles).211 An erect head posture is not maintained by these muscles, unless the brain has the ability to recognize the position of the head in relation to the body and to the pull of gravity. This information is supplied primarily by labyrinthine and vestibular reflexes, the proprioceptive impulses from the cervical muscles, by visual input from the two eyes, and by integrative cortical centers for balance in the brain.16,67

Abnormal head positions involve rotation of the head around one of the three primary axes: the vertical axis for horizontal head positioning, the horizontal axis for chin elevation and depression, and the anterior–posterior axis for head tilting toward the shoulder.211 Many patients utilize a

head position that involves simultaneous rotation around two or more axes (Fig. 9.1). This situation may reflect the fact that it is physically difficult to tilt the head without turning it somewhat in the opposite direction or lowering the chin, or it may represent a more precise compensation to some of the conditions discussed in the following section. Rarely, the entire head can be retracted or pushed forward with respect to the median axis of the body.

Ocular Torticollis

Most ocular disorders that result in torticollis reflect a disturbance of neural output from the ocular motor nerves or the vestibular system or a disturbance of input from the afferent visual pathways. The abnormal head position may serve to restore single binocular vision (in the case of incomitant strabismus) or improve visual acuity (in the case of nystagmus).43 Alternatively, it may develop as a primitive tonus response to unequal visual input to the two eyes (in the case of dissociated vertical divergence, DVD) or to unequal visual input to the two sides of the visual field (in congenital homonymous hemianopia).24 Children with infantile esotropia take a head turn to “cross-fixate” with either eye in adduction.73,139 In this setting, it is not known whether this head turn simply serves to damp the latent nystagmus or whether both the esotropia and the latent nystagmus are parallel manifestations of a central tonus imbalance caused by unequal visual input to the two eyes.

Most commonly, binocular misalignment causes diplopia, which leads to compensatory adjustment to a new head posture that provides the perceptual reward of stable single binocular vision.211 In children with incomitant strabismus, the finding of an anomalous head position is a good prognostic sign that usually signifies the preservation of fusion. In this setting, the disappearance of torticollis may signify the onset of amblyopia and the need for occlusion therapy.210 Primitive visuo-vestibular reflexes also use binocular visual input to maintain vertical orientation.27 When congenital strabismus disrupts binocularity, these reflexes lead to compensatory head postures and additional ocular misalignment. Although it is often said that torticollis that is compensatory for strabismus begins around the sixth month of life, several reports have documented incomitant strabismus with compensatory torticollis in the first month of life.29,153 Central vestibular disorders (at the prenuclear level) can produce ocular misalignment, torsion, and torticollis that are not compensatory for binocular vision, as in the ocular tilt reaction.

Gamio81 has observed that head tilting can alter the magnitude of paretic horizontal strabismus in some patients. She attributes this phenomenon to monocular adaptations in the vestibulo-ocular reflex (VOR), which reduces asymmetrical movement of retinal images during head motion and the resulting retinal image disparity.213 Most forms of ocular torticollis (Table 9.1) are associated with a distinct constellation of clinical and neuroimaging abnormalities that allow definitive diagnosis of the underlying condition. Once the specific cause of the ocular torticollis is established, strabismus surgery has a high rate of success in eliminating the abnormal head position.131

Fig. 9.1  Child with ocular torticollis in costume for Halloween. Note head tilt and simultaneous head turn

Table 9.1  Ocular Torticollis