measurement of saccadic velocity, the forced duction test, and the forced generation test. In the child with no abduction past midline, the finding of a “floating saccade” as the eye moves from a position of adduction toward primary gaze is a useful clue that the lateral rectus muscle is completely paralyzed.470 In contrast, a rapid saccade from adduction to midline is evidence that the lateral rectus muscle is functioning and that the abduction limitation results from a medial rectus contracture. In cooperative children, a forced generation test is also useful in clinically confirming the presence or absence of lateral rectus function, which can be estimated or felt as a “pull” on the forceps when the child attempts to abduct the paretic eye. These clinical tests can be supplemented by a forced duction test (performed either in clinic or under anesthesia prior to strabismus surgery) to further assess the degree of medial rectus contracture.

Children with little or no recovery of sixth nerve function require a transposition procedure of the vertical rectus muscles to the lateral rectus muscle to create a new abduction force.179,254,508 A large resection of a completely paralytic rectus muscle accomplishes little and sacrifices a portion of the anterior ciliary circulation. Vertical rectus muscle transposition can be performed in conjunction with a recession of the antagonist medial rectus muscle469; however, this procedure creates a risk of anterior segment ischemia in adults. A large recession (>7 mm) of the contralateral medial rectus muscle also works well and does not risk anterior segment ischemia. In this setting, most surgeons now utilize augmented vertical rectus muscle transposition.170,171 Because this procedure can induce complicated vertical deviations, however, we have continued to utilize transposition in conjunction with preoperative or intraoperative injection of botulinum toxin into the ipsilateral medial rectus muscle. Botulinum functions as a “chemical traction suture” by creating a temporary medial rectus paralysis, thereby positioning the eye in abduction for several months.167,355,500 Parents must be warned that this procedure creates an initial postoperative exotropia and that continued part-time occlusion therapy will be necessary until the paretic medial rectus recovers.

Kraft and Clarke298 found that patients with isolated lateral rectus palsy with a compensatory head posture undergoing surgery to eliminate the head position had a 75.6% incidence of success from the surgery. A therapeutic dilemma arises in the child who is undercorrected after a recess–resect procedure for a complete sixth nerve palsy. In such a case, vertical rectus muscle transposition would disrupt the remaining anterior ciliary circulation, raising the risk of anterior segment ischemia. In this setting, microdissection of the anterior ciliary vessels of the vertical recti prior to transposition reduces the risk of anterior segment ischemia.353 Finally, microsurgical repair has been used to restore functional recovery following surgical transection of the abducens nerve.493

Multiple Cranial Nerve Palsies in Children

In a retrospective study of children with cranial nerve palsies, Holmes et al234 found trauma to be the most common cause for multiple cranial nerve palsies. Harley218 described nine children with multiple acquired cranial nerve palsies and found orbital inflammation in four, trauma in three, and a neoplasm in two. Any infectious, inflammatory, or neoplastic disease process confined to the brainstem, skull base, cavernous sinus, or orbital apex can involve multiple cranial nerves.97,239,559 Bilateral trochlear and abducens palsies can follow halo spinal traction in children.435 Oculomotor and abducens palsies can develop following shunt misplacement.221 Bilateral abducens and facial nerve palsies can follow ventriculo-peritoneal shunting.525 The oculomotor and abducens palsies that can arise in the setting of leukemia are recognized to respond to whole-brain radiation.208 Leukemia can cause multiple cranial nerve palsies of unclear etiology. Intrinsic orbital disorders, such as Graves’ ophthalmopathy556 and a syndrome of unilaterally congenitally enlarged extraocular muscles,144 are extremely rare but should also be included in the differential diagnostic considerations. Most congenital disorders with multiple bilateral cranial nerve palsies are now classified as congenital cranial dysinnervation syndromes553 and are discussed in the following chapter.

Table 6.6 summarizes the neurological and systemic disorders that, in our experience, warrant consideration in the child with multiple cranial nerve palsies. Most of these conditions are discussed elsewhere.369

Table 6.6  Causes of multiple cranial nerve palsies in children

1. Trauma

Basilar skull fractures

Closed head trauma without fractures

2. Neoplasm

Pontine glioma and other structural brainstem lesions Lymphoma

Pituitary apoplexy

Metastasis (rhabdomyosarcoma, neuroblastoma, leukemia) Gliomatosis cerebri

3.Inflammation

Guillain–Barré disease Multiple sclerosis

Acute disseminated encephalomyelitis Neurosarcoidosis

Graves ophthalmopathy

4.Infection

Acute bacterial meningitis

Septic cavernous sinus thrombosis Brainstem cysticercosis

5. Congenital

Congenital Cranial Dysinnervation Syndromes (CCDS)

6. Teratogenic

Thalidomide exposure