188 11 Diseases of the Cranial Nerves

	Supranuclear Oculomotor Disturbances				eyes (and the head) deviate to the side of the lesion: dé-
					viation conjuguée, the patient “looks at the lesion.” Dé-
	These disturbances are defined as those in which the				viation conjuguée is usually accompanied by con-
	voluntary movements and involuntary pursuit move-				tralateral hemiparesis.
	ments of both eyes are simultaneously impaired. The				Active gaze movements toward the midline rapidly
	eyes generally remain parallel to each other, but they				become possible again; so, later, do movements to the
	cannot be moved together in the horizontal or vertical				opposite side. As contralateral movements begin to re-
	plane. The lesion lies above the level of the cranial nerve				emerge, they are accompanied by gaze-paretic nystag-
	nuclei and is thus “supranuclear.” In disorders of the				mus, whose rapid component beats away from the side
	brainstem, supranuclear lesions may coexist with nu-				of the lesion.
	clear lesions, so that a skew deviation can also be pre-				Lesions of the posterior hemispheric cortex. Horizon-
	sent.
					tal gaze palsy due to an occipital lesion is often accom-
	Horizontal Gaze Palsy				panied by hemianopsia. The gaze palsy is characterized
					by saccadization of ocular pursuit movements and op-
	A patient with horizontal gaze palsy cannot make a con-				tokinetic nystagmus (p. 185) is impaired.
	jugate movement of the eyes to the right, to the left, or				Lesions of the paramedian pontine reticular forma-
	(rarely) in either direction. The causative lesion may be
	at any of several sites in the central nervous system:				tion (PPRF) affect the last supranuclear “relay station”
	cortical centers generating the impulses for horizon-				for horizontal gaze movements. They usually cause
	tal gaze movements, particularly the frontal eye field				long-lasting or permanent gaze palsy to the side of the le-
	of the frontal lobe;				sion.
	the paramedian pontine reticular formation (PPRF),				Lesion of the abducens n. nucleus affects not only the
	which receives the impulses from the higher cortical
	centers and relays them to the ipsilateral abducens n.				neurons whose axons constitute the sixth cranial nerve,
	nucleus (innervation of the lateral rectus m.) and				but also interneurons that connect the nucleus by way
	simultaneously, by way of interneurons, to the con-				of the adjacent medial longitudinal fasciculus (MLF) to
	tralateral oculomotor n. nucleus (innervation of the				the contralateral oculomotor n. nucleus, which inner-
	medial rectus m.). This projection lies within the me-				vates the contralateral medial rectus m. The clinical pic-
	dial longitudinal fasciculus (MLF, Fig. 11.3). The result				ture is initially very similar to that of a PPRF lesion. PPRF
	is an ipsilateral, conjugate, horizontal gaze move-				lesions, however, spare the vestibulo-ocular connec-
	ment (i. e., to the left on activation of the left PPRF				tions in the MLF and do not directly involve the cranial
	and to the right on activation of the right PPRF);				nerve nuclei subserving eye movement; thus, in PPRF
	a lesion of the abducens n. nucleus has the same ef-				lesions, the gaze palsy can be overcome by a vestibular
	fect as a PPRF lesion, i. e., a conjugate horizontal gaze				stimulus. In contrast, gaze palsy due to a lesion of the
	palsy to the side of the lesion (see above).				abducens n. nucleus cannot be overcome either volun-
					tarily or through any kind of reflex.
	Lesions of the frontal eye field. This field occupies area
	eight in the middle frontal gyrus. The right eye field				Vertical Gaze Palsy
	generates conjugate gaze movements to the left and the
					Impairment of upward or downward conjugate gaze is
	left eye field generates conjugate gaze movements to
	the right. When the frontal eye field is affected by an				always due to a midbrain lesion involving either the ros-
	acute lesion, the influence of the contralateral field pre-				tral interstitial nucleus of the medial longitudinal
	dominates for a few hours (or, rarely, days), so that the				fasciculus (the Büttner−Ennever nucleus) or its efferent
					fibers (Fig. 11.3). In most patients, both upward and
					downward gaze are impaired, but pretectal lesions can
		right	left		cause isolated upward gaze palsy. Vertical gaze palsy is
					one of the clinical features of progressive supranuclear
					palsy (p. 130).
	gaze straight ahead
					Internuclear Ophthalmoplegia
					This condition is caused by a lesion of the medial longi-
	rightward gaze:				tudinal fasciculus (MLF). When the patient attempts to
	in left eye, impaired				look away from the side of the lesion, the ipsilateral (ad-
	adduction; in right				ducting) eye cannot fully adduct, and the contralateral
	eye, normal				(abducting) eye exhibits end-gaze nystagmus. The ina-
	abduction and				bility of the ipsilateral eye to adduct is not due to a le-
	nystagmus				sion of the oculomotor n. nucleus, as is demonstrated by
	Fig. 11.6 Internuclear ophthalmoplegia		(INO), left (diagram).		a preserved ability to adduct (converge) in the near re-
					flex. Internuclear ophthalmoplegia (INO) can also be bi-
	When the patient looks straight ahead, the eyes are parallel. On at-
					lateral if the MLF is damaged on both sides.
	tempted rightward gaze, the left medial rectus m. fails to contract
	(no adduction of the left eye) and there is nystagmus of the ab-				The diagram in Fig. 11.6 illustrates the clinical findings
	ducted right eye.				in internuclear ophthalmoplegia with total loss of ad-

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Disturbances of Ocular and Pupillary Motility 189

duction of the left eye. Fig. 11.7 shows a more common type of INO, in which the inward movement of the adducting eye is merely delayed and eventually takes place with slow, horizontal saccades. This type of INO is particularly common in multiple sclerosis.

One-and-a-Half Syndrome

This name is given to the combination of horizontal gaze paresis to one side (“one”) with internuclear ophthalmoplegia on attempted gaze to the other side (“half”). As one might expect, it is due to combined lesions of the

PPRF or abducens n. nucleus on one side and of the ipsilateral MLF. The single horizontal eye movement that remains possible is abduction of the contralateral eye on attempted contralateral gaze.

Oculomotor Disturbances of Cerebellar Origin

These disturbances are listed in Table 11.3.

Other Supranuclear Disturbances

of Eye Movement

Another disturbance worth mentioning here is oculomotor apraxia. In the congenital form (Cogan syndrome), the patient is unable, for example, to direct his or her gaze voluntarily to the beginning of a line of text while reading. Instead, the entire head must be moved into position so that the beginning of the line lands in the center of the visual field. Once this is done, the head can be moved back to its original position without loss of fixation on the text.

Fig. 11.7 Right internuclear ophthalmoplegia in a patient with multiple sclerosis. In the initial phase of leftward gaze (upper photograph), only the left eye is abducted. The right eye follows, after a delay (lower photograph).

Table 11.3 Oculomotor disturbances due to cerebellar dysfunction

saccadic pursuit

diminished optokinetic nystagmus

gaze-deviation nystagmus

dysmetric saccades (under and overshoot)

inability to suppress the oculovestibular reflex by fixation

overshooting oculovestibular reflex

special types of nystagmus, such as upbeat nystagmus, downbeat nystagmus, rebound nystagmus, periodically alternating nystagmus, acquired pendular nystagmus, central positional nystagmus, other types

skew deviation

unilateral cerebellar lesions produce nystagmus to the ipsilateral side (as in spontaneous vestibular nystagmus)

Lesions of the Nerves to the Eye Muscles and Their Brainstem Nuclei

Lesions of this type, like lesions of the eye muscles themselves, cause deviation of the axis of one eye, i. e., paralytic strabismus.

Oculomotor Nerve Palsy

An infranuclear lesion of the third cranial nerve causes paralysis of the medial, superior, and inferior rectus

muscles, the inferior oblique mm., and the levator palpebrae m. (external ophthalmoplegia). In addition, the smooth muscle of the pupillary sphincter is paralyzed: the pupil is “fixed and dilated,” i. e., it is enlarged and responds neither to light, nor to convergence (internal ophthalmoplegia). The typical clinical aspect of oculomotor nerve palsy is thus immediately recognizable when the patient looks straight ahead (Fig. 11.8). The diagrams in Fig. 11.9 illustrate the typical findings in

a	b
Fig. 11.8 Complete left oculomotor palsy. a Severe ptosis of the	parasympathetically innervated sphincter pupillae m.). (From: Mu-
left eye, which is also mildly abducted (predominant effect of lateral	menthaler, M.: Didaktischer Atlas der klinischen Neurologie. 2nd edn,
rectus m., innervated by the abducens n.). b The examiner lifts the	Springer, Heidelberg 1986)
ptotic eyelid to reveal the fixed (unreactive) pupil (paralysis of the

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190	11 Diseases of the Cranial Nerves
			straight-ahead gaze (= primary position)							Fig. 11.9 Right oculomotor nerve
										palsy. Note the position of the eyes and
							left eye
										the position of the two visual images
							right eye
										(diplopia) depending on the direction of
							no diplopia			gaze.
							left			right
			greatest disparity of images			compensatory
						head position:
						none if ptosis is present,
						because there is no
						diplopia
			fixed, dilated pupil in				weakness mainly
			total CN III palsy				of the medial rectus
							muscle
		Table 11.4 Localization and etiology of oculomotor nerve palsy
		Site of lesion				Clinical features				Etiology
		Nuclear				oculomotor nerve palsy, bilateral vertical gaze				infarct, hemorrhage, trauma, tumor, multiple
						palsy, bilateral ptosis				sclerosis, inflammation, congenital hypoplasia
		Fascicular (nerve fibers within the				oculomotor nerve palsy, contralateral hemi-				infarct, hemorrhage, multiple sclerosis
		brainstem)				paresis, ataxia or rubral tremor (differential di-
						agnosis: transtentorial herniation)
		Subarachnoid space				isolated oculomotor nerve palsy				aneurysm (internal carotid a., rarely other ar-
										teries such as the basilar a.), basilar meningitis,
										cranial polyradiculitis, intracranial hyperten-
										sion, trauma, neurosurgical complication,
										tumor of the oculomotor n., transtentorial
										herniation

Cavernous sinus, superior orbital	oculomotor nerve palsy accompanied by dys-
fissure, or orbit	function of CN IV, V/1, and VI in varying com-
	binations
Orbital apex	oculomotor nerve palsy accompanied by dys-
	function of CN II, IV, V/1, and VI in varying
	combinations
Orbit	ptosis and superior rectus palsy (superior
	branch of CN III) or palsy of inferior and medial
	recti and inferior oblique mm. (inferior branch
	of CN III)
No localizing significance	isolated external ophthalmoplegia (i. e., pupil-
	lary sparing)

aneurysm (internal carotid a.), carotid− cavernous fistula, cavernous sinus thrombosis, parasellar tumor or pituitary tumor with parasellar extension, sphenoid sinusitis, Tolosa− Hunt syndrome, herpes zoster

see lists of causes above and below (cavernous sinus, orbit)

trauma, orbital tumor, orbital pseudotumor, infection, mucocele

diabetes, hypertension, arteritis, migraine

primary position and in the position of greatest deviation, as well as the positions of the two visual images depending on the patient’s direction of gaze.

The third cranial nerve can be affected by a lesion at its nucleus in the brainstem (nuclear lesion), at various points along its course within the brainstem (fascicular lesion), or in the periphery (peripheral nerve lesion). There are many possible causes and the corresponding neurological deficits are correspondingly varied. Typical symptom constellations involving oculomotor nerve palsy and various other findings, depending on the location and etiology of the lesion, are presented in Table 11.4. Lesions of the oculomotor n nucleus also cause bilateral ptosis and upward gaze paresis.

Trochlear Nerve Palsy

Lesions of the fourth cranial nerve cause paralysis of the superior oblique m. The patient can no longer depress the affected eye in adduction, or internally rotate it in abduction. The resulting diplopia arises when the patient looks down; the images are vertically displaced and slightly tilted. The typical clinical situation is shown schematically in Fig. 11.10. The two images can be brought together again by tilting the head to the normal side; the distance between the images increases if the head is tilted to the affected side (Bielschowsky phenomenon).

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	Disturbances of Ocular and Pupillary Motility 191
Fig. 11.10 Right trochlear nerve palsy.	straight-ahead gaze (= primary position)
Note the position of the eyes, the com-
pensatory head tilt, and the position of		left eye
the two visual images depending on the		right eye
direction of gaze.
	greatest disparity of images compensatory head position	no diplopia
	(= least disparity of images)
		left	right

head tilt to side of paretic muscle (Bielschowsky phenomenon)

head tilt away from side	weakness of the
of paretic muscle	superior oblique
	muscle

Fig. 11.11 Right abducens nerve palsy.	straight-ahead gaze (= primary position)
Note the position of the eyes, the com-		left eye
pensatory rotation of the head, and the
position of the two visual images de-		right eye
pending on the direction of gaze.
	greatest disparity of images compensatory head position	no diplopia
	(= least disparity of images)
		left	right

	head rotation to side of	weakness of the
	paretic muscle	lateral rectus m.

Causes. The more common causes of trochlear nerve palsy are:

congenital aplasia,

trauma,

midbrain hemorrhage,

multiple sclerosis,

ischemic neuropathy of the nerve, e. g., in diabetes mellitus,

pathological processes in the cavernous sinus

or in the orbit.

Pathological processes affecting the superior oblique m. The tendon of the superior oblique m. changes direction in the trochlea, sliding within it in the manner of a pulley. The tendon can sometimes be caught in the ring of the trochlea, thus becoming “stuck” in the middle of a movement. This causes intermittent vertical diplopia, typically when the patient looks up just after looking down, and typically only lasting for a very short time (Brown syndrome). Myokymia of the superior oblique muscle may occur as a sequela of a trochlear nerve palsy, or independently. Its typical clinical sign is mono-

cular, high-frequency nystagmus with oscillopsia and diplopia.

Abducens Nerve Palsy

Paralysis of the abducens m. caused by a lesion of the sixth cranial nerve causes inward strabismus of the affected eye. Horizontal diplopia is sometimes present even in the primary position of gaze and worsens as the patient looks toward the affected side. The findings are presented schematically in Fig. 11.11 and the more common causes are listed in Table 11.5.

Combined Lesions of Multiple Cranial Nerves Innervating the Muscles of Eye Movement, and Other Disorders in the Differential Diagnosis of Diplopia

If multiple cranial nerves innervating the muscles of eye movement on one side are affected, the lesion usually lies in the cavernous sinus, at the orbital apex, or in the orbit itself. Bilateral, multiple palsies of the muscles of

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