Third Nerve Palsy

Etiology and Systemic Associations In childhood, a third nerve palsy typically keeps company with other neurological findings, which aid in localization and diagnosis (Table 5-6), but isolated palsies do occur and are generally congenital, traumatic, infectious, or migrainous.191,225,257,326,339,440

An acquired, isolated oculomotor nerve palsy in a child may also result from tumor, preceding viral illness, bacterial meningitis (most commonly pneumococcal, Haemophilus influenzae type b, or Neisseria meningitidis), or immunization.76,77,86,191,225,257,309,

326,339,347,430,440,446 Rarely, children may demonstrate gradually progressive paresis because of a slowly growing tumor1 or a truly cryptogenic oculomotor palsy. Posterior communicating aneurysms, although extremely rare in children, should be considered as well.313 Microvascular infarction due to atherosclero-

TABLE 5-6. Etiology of Infranuclear Third Nerve Palsy.

Location/signs

Etiologies

Fascicle

Demyelination; hemorrhage; infarction

Ipsilateral cerebellar ataxia;

(rare in childhood)

contralateral rubral tremor;

contralateral hemiparesis; vertical

gaze palsy

Subarachnoid space

Meningitis; trauma or surgery; tumor;

Papilledema; other cranial nerve

increased intracranial pressure;

palsies

uncal herniation

Cavernous sinus/superior orbital fissure

Cavernous sinus thrombosis; tumor;

Ipsilateral Horner's syndrome;

internal carotid artery aneurysm;

ipsilateral IVth, Vth, VIth nerve

carotid-cavernous fistula; Tolosa-

involvement; proptosis; disc edema;

Hunt syndrome; pituitary apoplexy;

orbital pain; conjunctival/episcleral

sphenoid sinusitis, mucocele;

injection

mucormycosis

Orbit

Trauma; tumor; inflammation

Ipsilateral IVth, Vth, VIth nerve

involvement; proptosis;

enophthalmos; disc edema; orbital

pain; conjunctival/episcleral

injection

Uncertain location

After febrile illness or immunization;

migraine; idiopathic

sis, hypertension, or diabetes mellitus, a common cause of isolated third nerve palsy in adults, is extremely rare in children.

Clinical-Anatomic Correlation The anatomic organization of the third nerve nucleus, like that of the sixth nerve nucleus, provides constraints that help differentiate the rare nuclear third nerve palsy from an infranuclear third nerve palsy. Because the superior rectus subnucleus supplies the contralateral superior rectus muscle, and the central caudal nucleus innervates both levator muscles, damage to a single oculomotor nerve nucleus gives rise to contralateral superior rectus weakness and bilateral ptosis. Also, because of the arrangement of the three medial rectus subnuclei and the visceral nuclei within the oculomotor nucleus, a nuclear third nerve palsy is not likely to produce isolated medial rectus involvement or unilateral pupillary involvement. In addition, other midbrain signs such as vertical gaze abnormalities are often associated with lesions of the oculomotor nucleus (see Fig. 5-6).

Because the oculomotor nerve innervates the levator palpe-brae superioris, the sphincter of the pupil and ciliary body, as well as four extraocular muscles (the medial rectus, superior rectus, inferior rectus, and inferior oblique), it is easy to identify a complete infranuclear third nerve palsy by the presence of ptosis; a fixed, dilated pupil; and a "down-and-out" eye position resulting from the unopposed lateral rectus and superior oblique muscles (Fig. 5-10). However, third nerve palsies can be "partial"; any individual sign or combination of signs may be present and, if present, may be complete or incomplete. Numerous patterns can therefore arise.

Clinical Features and Assessment/Natural History

Oculomotor nerve palsies, like abducens and trochlear nerve palsies, should be distinguished from myasthenia and mechanical restrictions. Clinically observable involvement of the pupil or signs of oculomotor synkinesis (aberrant regeneration) establish involvement of the third nerve, assuming pharmacological and traumatic mydriasis can be excluded.

The manner through which neural impulses become misdirected is not always clear.455 Misrouting of regenerating motor axons is firmly documented152,392,456 and corroborates the frequent clinical observation of the appearance of synkinesis at about 8 to

Scheme Iii Cranial Nerve Palsy

FIGURE 5-10. Patient with traumatic left third nerve palsy. The top photograph shows the classic appearance of a left third nerve palsy with ptosis and the eye in a down and out position. The left photograph shows full abduction, left eye. The bottom right photograph shows left eye with limited adduction. Note, there is lid retraction and miosis, left eye, on attempted adduction indicating aberrant innervation of the levator muscle and pupillary sphincter with part of the medial rectus nerve.

FIGURE 5-10. Patient with traumatic left third nerve palsy. The top photograph shows the classic appearance of a left third nerve palsy with ptosis and the eye in a down and out position. The left photograph shows full abduction, left eye. The bottom right photograph shows left eye with limited adduction. Note, there is lid retraction and miosis, left eye, on attempted adduction indicating aberrant innervation of the levator muscle and pupillary sphincter with part of the medial rectus nerve.

12 weeks after an acute palsy.277 However, aberrant regeneration cannot comfortably account for transient oculomotor synkinesis239,289,454 or spontaneous "primary" oculomotor synkinesis.66,105,289,436,493 Ephaptic transmission, conduction of a nerve impulse across a point of lateral contact, and synaptic reorganization of the oculomotor nucleus are two proposed theories of synk-inesis.289,455 The presence of oculomotor synkinesis has not been reported with demyelination, but it does not otherwise narrow the differential diagnosis of third nerve palsy in the pediatric age group.

Congenital third nerve palsy is usually incomplete and unilateral and is frequently associated with oculomotor synkinesis and "miosis" of the pupil in the affected eye.191,326,504 Although many children with congenital oculomotor nerve palsies have no associated neurological findings, some do,41 and a thorough neurological evaluation of these infants is suggested. If there are additional neurological signs or bilateral third nerve palsies, MRI may also provide useful information.175

Rarely, paresis and spasm of the extraocular and intraocular muscles innervated by the third nerve may alternate, typically every few minutes, to produce oculomotor palsy with cyclic spasms.295 With few exceptions, these cycles accompany congenital, rather than acquired, oculomotor palsies and continue throughout life. In some instances, several months to several years may elapse between the discovery of the paresis and the onset of the cyclic spasms. Investigation is not necessary unless the third nerve palsy is acquired or there is progressive neurological dysfunction. The pathogenesis of this phenomenon remains obscure.272

ophthalmoplegic migraine generally begins in childhood40 but may even be seen in infancy.13,534 It is an uncommon disorder despite the fact that 2.5% of children experience a migraine attack by age 7 and 5% by age 15.43 Symptoms of migraine in children include nausea, vomiting, abdominal pain, and relief after sleep in 90%.419 The headaches, which may be accompanied by an aura, are often unilateral and throbbing in quality. Family history is positive in 70% to 90%. With ophthalmoplegic migraine, the patient characteristically experiences pain in and about the involved eye, nausea, and vomiting; often the third nerve palsy ensues as the pain resolves. Full recovery of third nerve function within 1 to 2 months is typical, but resolution may be incomplete and oculomotor sykinesis has been reported.355 Multiple attacks may occur, and years may pass between episodes.133 Most patients with ophthalmoplegic migraine have normal angiograms, but one 31-year-old with recurrent episodes of ophthalmoplegic migraine, which had begun at age 5, and partial third nerve palsy since age 7, demonstrated a small perimensencephalic vascular anomaly.224

Aneurysms have been reported to cause isolated third nerve palsies during the first and the second decades of life71,135,157,158,313,383 and carry a high risk of mortality or significant morbidity if left undetected and untreated. On the other hand, aneurysms appear to be rare in children.158,495 Angiography with general anesthesia can be risky in the childhood age group, and the gap between the sensitivity of angiography and MRI for detecting aneurysms continues to narrow. The clinician assesses all these variables along with the history and physical examination to decide on the appropriate workup for each patient. For example, in the child under age 10 with a family history of migraine who presents with nausea, vomiting, and headache, followed by third nerve palsy as these symptoms resolve, that is, with typical ophthalmoplegic migraine, angiography may not be necessary.166 However, when a third nerve palsy acquired in childhood cannot be explained on the basis of the clinical examination or noninvasive neuroimaging, the cerebrospinal fluid should be evaluated and angiography considered.

Treatment

After diagnosis and treatment of the underlying disorder, observation of any recovery of oculomotor nerve function is necessary before surgical intervention. When partial or full recovery occurs, it often does so within 3 to 6 months but it may take 1 year or more. Surgical treatment includes strabismus surgery and ptosis correction. The latter is approached with caution in an eye that lacks a functional Bell's phenomenon because of the risk of exposure keratopathy.

Prognosis

Two recent series have found fair to poor visual and sensori-motor outcome in oculomotor nerve palsy/paralysis of children with comparable mix of congenital, traumatic, and neoplastic cases.339,440 The best ophthalmologic outcome with measurable stereopsis was in the resolved cases (3 of 20; 15%) in the first study, and in 4 of 31 patients with partial third nerve palsy in the second study, 2 of whom had spontaneous resolution. In the first series, amblyopia therapy was most effective with congenital causes, but treatment results were poor with other causes; young children with posttraumatic and postneoplastic oculomotor nerve injuries demonstrated the worst ophthalmologic outcomes.

Naturally Cure Your Headaches

Naturally Cure Your Headaches

Are Headaches Taking Your Life Hostage and Preventing You From Living to Your Fullest Potential? Are you tired of being given the run around by doctors who tell you that your headaches or migraines are psychological or that they have no cause that can be treated? Are you sick of calling in sick because you woke up with a headache so bad that you can barely think or see straight?

Get My Free Ebook


Post a comment