Clinical Findings

Total loss of function in the third cranial nerve produces paralysis of the levator palpebrae superioris, with complete ptosis of the upper lid. The sympathetically innervated smooth muscle of the upper lid (Muller's muscle) can shorten the levator aponeurosis but will not cause any opening of the palpebral fissure. With passive elevation of the upper lid, the examiner will find the eye resting in an abducted position of 20 to 30°. Attempts at adduction in fresh cases will produce a weak movement toward, but not all the way to, the primary position. Cases that are more chronic will stop the adducting motion even more short of the primary position. Elevation and depression will be <n completely absent. (If the trochlear nerve is spared, at- ° tempts at downgaze will cause an incyclotorsional move- § ment (■ Fig. 10.3). i|

If there is also an internal ophthalmoplegia, there will be a paretic mydriasis, pupillary sphincter paralysis, and an anisocoria that increases in bright light surroundings, and a paralysis of accommodation. m

With subtotal damage of the third cranial nerve, several patterns of paresis can appear: §

■ External ophthalmoplegia: Only the extraocular muscles are affected. (Usually called a pupillary-sparing third nerve palsy.)

■ Internal ophthalmoplegia: Only intraocular muscles are affected.

■ Complete external and/or internal oculomotor paraly- ® sis: The function of all external or internal ocular mus- § cles has been lost.

Fig. 10.4. Gaze-direction photos of a partial internal and external ophthalmoplegia in the right eye: Upper lid movement, elevation, depression, and adduction are all limited, but not completely gone

Fig. 10.4. Gaze-direction photos of a partial internal and external ophthalmoplegia in the right eye: Upper lid movement, elevation, depression, and adduction are all limited, but not completely gone

Oculomotor Paralysis

Fig. 10.5. Schematic section through the rostral midbrain at the level of the oculomotor nuclei. X probable location of the sympathetic tract

Superior colliculi

Posterior commissui

Cerebral aqueduct

Lateral and medial lemniscus

Red nucleus

Central caudal r* i irlm i r

Central caudal r* i irlm i r

Red nucleus

Caudal Cerebellar Peduncle

Substantia nigra Pyramidal tract

Nuclear complex of the 3rd cranial nerve

Medial longitudinal fasciculus

Decussation of the superior cerebellar peduncle

Substantia nigra Pyramidal tract

Table 10.2. Brainstem syndromes with fascicular oculomotor pareses

Name

Affected structures

Associated brainstem signs and symptoms

Weber's syndrome (third nerve palsy with contralateral hemiplegia)

third nerve, pyramidal tract

Contralateral hemiparesis

Nothnagel Claude's syndrome (inferior red nucleus syndrome)

Red nucleus, superior cerebellar peduncle (brachium conjunctivum)

Contralateral ataxia, rubral tremor

Benedikt's syndrome

Red nuclei, substantia nigra

Contralateral ataxia, contralateral hemichorea

■ Incomplete external and/or internal oculomotor paralysis: Not all muscles innervated by the third nerve are paralyzed. ■ Figure 10.4 illustrates a patient with a partial oculomotor paralysis.

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