Down Syndrome

The torticollis in Down syndrome is usually musculoskeletal in origin. Down syndrome is one of several genetic syndromes (along with Morquio syndrome, mucopolysaccharidosis, and osteogenesis imperfecta) in which torticollis may be a manifestation of cerebral spine instability resulting from laxity of cervical ligaments or malformed vertebral bodies.14 Caution is therefore advised to avoid hyperextension of the neck when administering eyedrops.161

Children with Down syndrome and infantile esotropia may utilize a head tilt to restore horizontal ocular alignment.143 Lueder et al143 described six such patients without DVD in whom the head tilt resolved following horizontal strabismus surgery. How unilateral utricular stimulation influences horizontal misalignment, and why this phenomenon has been observed primarily in children with Down syndrome, is unknown. In our experience, children with Down syndrome may have esotropia with primary superior oblique overaction and A-pattern, necessitating a chin-up position for fusion in downgaze.

Spasmodic Torticollis

Spasmodic torticollis refers to a dystonia of the facial and cervical muscles resulting from neurological disease or medications affecting the basal ganglia.31,50 This diagnosis should be considered if dystonia in the face or limbs is present. Spasmodic torticollis associated with neurological disease has been successfully treated with botulinum toxin therapy and with selective surgical peripheral denervation of the sternocleidomastoid and splenius capitus muscle.18 Spasmodic torticollis in children may occur as an idiosyncratic reaction following a first dose of phenothiazine or haloperido1.77 In this setting, it may be accompanied by other dystonic reactions, including trismus, opisthotonos, and oculogyric crises.129 Drug-induced spasmodic torticollis resolves promptly when the child is treated with anticholinesterase medications (e.g., Cogentin). Spasmodic torticollis is uncommon in children except when drug induced.77 The highest frequency of drug-induced dystonia and oculogyric crises occurs in children under 15 years of age.129 Spasmodic torticollis may rarely occur as a familial condition.83

Paroxysmal dystonia in infancy is a condition that usually has its onset in the first months of life. Motor symptoms are characterized by torsion of the neck or trunk, opisthotonos, hypertonus of the upper limbs with flexion or extension of the arms and hyperpronation of the wrist, and no disturbance of consciousness.3 The attacks usually last several minutes and occur with a frequency ranging from several times a day to once a month. This entity differs from benign paroxysmal torticollis in infancy in that the trunk and arms are also involved, and no autonomic symptoms are detected.3 The attacks spontaneously remit in most cases.

Paroxysmal choreoathetosis is a rare disorder with onset between 1 and 2 years of age. It consists of paroxysmal episodes of abnormal posturing and choreoathetoid movements that may include torticollis and facial grimacing. The child is conscious and often uncomfortable during the episode.174 These children are otherwise in good health and neurologically normal between attacks.177 The disorder can be familial or sporadic. The episodes occur several times a month, but may vary in frequency from several times a day to several times a year. They last for 5 min to an hour and often appear to be related to excitement or fatigue.177 These transient episodes do not appear to be epileptiform or migrainous in nature.

Central nervous system pathology unrelated to the visual system should also be considered in patients with enigmatic torticollis (Table 9.2). Causes include syringomyelia and spinal cord tumors,127,197 arteriovenous fistula,10 as well as cervical epidural abscess with osteomyelitis,147 and Arnold-Chiari malformation.14,77 Torticollis associated with hyperactive tendon reflexes, ankle clonus, or extensor plantar responses suggests a cervical spinal cord disturbance and is an indication for MR imaging of the cervical spine.77

Head tilting has been described in the infectious disease literature as a rare manifestation of nuchal rigidity in patients with acute bacterial meningitis;146 however, no neuroophthalmologic examinations were performed to rule out the possibility of superior oblique palsy. Given the strong association between acute bacterial meningitis and cranial nerve palsies, an inflammatory superior oblique palsy must be the primary diagnostic consideration in the child with acute bacterial meningitis and an unexplained head tilt.

Head Turns

Some head turns in children are physiological and purposeful. For example, one young girl took a large head turn when looking through a microscope monocularly so that she could use her nose to block her other eye because she did not know how to squint.178a Because visual head turns are compensatory (contraversive to the eye position in the orbits), while neurological head turns often produce an oculocephalic synkinesis with the head and eyes deviated in the same direction, it is important to document whether the head turn is ipsiversive or contraversive to the position of the eyes in the orbit. Visual disturbances may produce a head turn in several different ways (Table 9.1).

Incomitant Strabismus

A head turn is often used to restore binocular single vision in patients with incomitant paralytic or restrictive strabismus. A patient who assumes an abnormal head posture for visually related reasons does so at least partly to frontalize their field of

Table 9.2  Nonocular torticollis

vision relative to their body.211 For example, a child with a sixth nerve palsy prefers to turn his or her head toward the affected side to realign the eyes, despite the fact that ocular alignment could also be obtained without a head turn by shifting the head and trunk laterally together while maintaining fixation in the direction opposite to that of the paresis.5 In children with Duane syndrome and esotropia, optical correction of hyperopia can significantly reduce a head turn, sometimes obviating the need for surgery.124,180 A head turn can be the salient clinical sign in patients with incomitant vertical strabismus who have good alignment in one lateral field of gaze. A head turn can occasionally overshadow a head tilt in unilateral superior oblique muscle palsy.

Nystagmus

Head turns are utilized by patients with congenital or mani- fest-latent nystagmus to move the eyes into a null zone, where the nystagmus is reduced and optimal visual acuity is achieved. In these disorders, it is critical to have the child fixate on the smallest recognizable object to elicit the full extent of the head turn. At times, a subtle nystagmus may not be visible unless the optic disc is viewed with a direct ophthalmoscope. Stevens and Hertle192 found that children with congenital nystagmus

and anomalous head postures have better mean visual acuities than those without anomalous head positions. In this light, the presence of an anomalous head position in a child with congenital nystagmus correlates with good vision and can be considered a positive prognostic sign.

Children with unilateral microphthalmos, unilateral aphakia, or other conditions associated with congenital visual loss often develop manifest latent nystagmus with a large face turn toward the better-seeing eye. Similarly, the child with congenital esotropia and manifest latent nystagmus often turn his/her head to damp the nystagmus by placing the preferred eye in adduction. In spasmus nutans, head turns may function to directionalize the head oscillations to the necessary trajectory to improve vision.91

Congenital Homonymous Hemianopia

Children with congenital homonymous hemianopia often turn their heads toward the hemianopic field while maintaining fixation on objects of interest.111,211 As this maneuver does not change the position of the intact visual field in space, its etiology remains a matter of some speculation. Children with congenital homonymous hemianopia are generally unaware of their abnormal head posture and are unable to explain why they maintain it. In patients with acquired homonymous hemianopia, a head turn does not manifest unless the causative hemispheric injury occurs in infancy.171

Most proposed explanations have assumed that torticollis must serve a compensatory function for visual orientation or navigation. For example, it has been suggested that the head turn may be an adaptive response to frontalize the visual world relative to the body, permitting the child to use saccades to increase the effective visual field during ambulation,69,171 or it may serve to minimize a subclinical nystagmus that is damped in one lateral field of gaze.87 Brodsky proposed that this form of torticollis may represent a nonpurposeful postural tonus imbalance of hemispheric origin, whereby early loss of visual input from one field directly increases neck muscle tonus on one side.24 Mechanistically, a postural tonus would circumvent any element of will or choice on the part of the individual; the head simply goes where the neck muscles pull it.

Because these children are often also exotropic, it has been suggested that the development of exotropia may be an adaptive mechanism to expand their limited visual field.89 It is noteworthy, however, that the exotropic eye is frequently on the side of the intact visual field. However, Hoyt and Good111 have argued that the exotropia seen in children with congenital homonymous hemianopia could well be an epiphenomenon rather than a visual adaptation. Because an exotropia of either side serves to expand the functioning visual field, strabismus surgery may be contraindicated in these patients.

Other ocular disorders have also been documented to produce head turns in children. The combination of a large

convergent or divergent ocular deviation and limited ocular movements necessitates a head turn to direct the preferred eye toward the object of fixation.211 Head turns may also be seen in children with horizontal gaze palsy or gaze deviations without strabismus. Children with retinopathy of prematurity and macular heterotopia may take a head turn to fixate eccentrically with the better-seeing eye.134 Childrenwith nystagmus blockage syndrome also turn their heads to foveate objects of interest while utilizing excessive convergence.134

Seizures

Involuntary head turning is a common feature of focal motor seizures.140 Certain associated features may help to clinically localize the seizure focus. If the patient remains conscious during the episode, then the head turning is usually away from the side of the seizure focus, and the seizure focus is usually frontal.148,198,214,215

A contralateral seizure focus is also likely when patients show a sustained, unnatural, lateral positioning of their head and eyes. In patients who are unconscious, whose seizures generalize, or who show milder deviations of the head and eyes, about half manifest an ipsiversive movement of the head. The site of the seizure focus may be localized to any lobe, but frontal and temporal are the most common.140

Cortical Visual Insufficiency

Children with cortical visual insufficiency often display an oculocephalic dyskinesia characterized by horizontal conjugate gaze deviation with a large ipsiversive head turn.24a It is often difficult to determine whether a seizure focus or a postural tonus imbalance from asymmetrical hemispheric injury is driving these large head turns. In some case, these children appear to be trying to look back behind their bodies. In this setting, it is especially difficult to determine whether a homonymous hemianopia is present, especially when exotropia coexists. The pathophysiologic basis and the prognosis for spontaneous improvement remain to be determined.

Congenital Ocular Motor Apraxia

As detailed in Chap. 7, children with congenital ocular motor apraxia are unable to generate volitional horizontal saccades and compensate by large head turns to fixate on peripheral objects of interest. Curiously, infants with congenital ocular

motor apraxia may intermittently jerk or shake their heads when fixating stationary objects.

Vertical Head Positions

Visual input has been shown to influence vertical head position, with darkness producing increased extension of the neck.183 Most abnormal vertical head postures occur in children with congenital ptosis, A- or V-pattern horizontal strabismus, restrictive vertical strabismus, or incomitant vertical strabismus (Table 9.1).6 Children with unilateral congenital ptosis raise the chin to obtain binocular vision, whereas those with bilateral congenital ptosis raise the chin to see. While chronic head tilts and head turns can both produce facial asymmetry, no facial boney remodeling from vertical head postures has been recognized. Children with congenital fibrosis syndrome may have a combination of bilateral ptosis and fixed downgaze, each necessitating a chin-up position to compensate for their restrictive strabismus.62,134 Children with tonic upgaze or downgaze may maintain vertical head positions that are compensatory for vision (i.e., chin down with tonic upgaze) (Fig. 8.16) or ipsiversive when the eye and head positions are both neurologically driven (as seen in some patients with cerebral palsy).

Patients with bilateral superior oblique palsy notoriously maintain a chin-down position, even when they are orthotropic in primary position. This compensatory head-down position probably serves to reduce binocular extorsion and to provide a larger working window of single binocular vision. In the setting of either A- or V-pattern strabismus or vertical restrictive strabismus, the chin-up or chin-down position places the eyes in a position of minimal deviation to establish some degree of binocularity.211

Stuart and Burian stated that “convergence” of the visual axes on downgaze and divergence on upgaze are normal physiologic variants, producing the so-called physiologic V- pattern.195 Havertape and Cruz102 have noted that some patients with high hyperopia maintain a chin-down head position for fixation without the spectacle correction in place. This abnormal head position was eliminated under monocular conditions and by having them wear the full refractive correction. They postulated that, because of a normal physiologic V-pattern, a chin-down position allows these children to maintain increased accommodation in an elevated ocular position without the development of an esodeviation.

Some children with infantile nystagmus have a vertical null zone, necessitating a chin-up or chin-down position. Infantile nystagmus patients with even small A- or V-pattern may utilize a vertical head position to create a large exophoria, which enables them to increase convergence tone and improve visual acuity. Therefore, it is critical in the child with infantile nys-