Oscillopsia, Nystagmus, Saccadic Oscillations, and Intrusions

Nystagmus, defined as an involuntary repetitive, rhythmic to-and-fro movement of the eyes initiated by a slow drift that shifts an image off the fovea, is discussed in detail. The steps to take in evaluating nystagmus are emphasized , including the importance of close observation with the patient supine, prone, and lying on either side Central vestibular nystagmus due to disease of the central nervous system is covered fully and case studies include patients with upbeat nystagmus and with acquired pendular nystagmus.. When a saccadic eye movement takes the eye away from fixation (saccadic intrusion), a variety of saccadic oscillations can occur, in particular multidirectional saccades without an intersaccadic interval, which is diagnostic of opsoclonus; ocular flutter; or the two oscillations combined. . Two paraneoplastic syndromes illustrate these disorders , a case of ocular flutter associated with paraneoplastic encephalitis and cancer of the lung, and an infant with opsoclonus as the herald syndrome of a neuroblastoma.

Dizziness, Vertigo, and Syndromes of the Medulla

reviews the medulla’s vestibular components (the vestibular, perihypoglossal, and inferior olivary nuclei ), and the components of the vestibular labyrinth (the semicircular canals and the otolith receptors) preparatory to a full discussion of dizziness and vertigo as diagnostic symptoms. The model used for history-taking is extensive and allows for clear distinction to be made between the two symptoms and their implications for risk of stroke. Direction- changing nystagmus as a localizing sign is discussed in depth, and provocative tests to elicit nystagmus by suppression of fixation are presented in clinical detail. The head-thrust (head impulse) test is also described as a simple way to identify a complete unilateral or bilateral loss of vestibular function at the bedside. Medullary syndromes illustrated by case studies include oculopalatal tremor, benign paroxysmal positional vertigo, upbeat and apogeotropic nystagmus, Wallenberg’s syndrome due to infarction of the medulla, and a case of intractable hiccups.

The Extraocular Muscles and Diplopia

deals with action and innervation of the extraocular muscles. In their intact state, the extraocular muscles and the cranial nerves that innervate them are responsible for every movement of the eyes signaled by the cortex. Diplopia, or double vision, is the commonest subjective complaint associated with a lesion affecting the extraocular muscles, their neuromuscular junctions, the oculomotor nuclei or nerve, or pathways in the brainstem that maintain alignment of the eyes. The diplopia history focuses on distinguishing monocular from binocular diplopia and the diplopia examination pays attention to head position, ocular alignment, and the range of eye movements during monocular and binocular viewing as keys to diagnosis. Diplopia with full eye movements is fully discussed. Four illustrative cases are presented: episodic diplopia due to ocular myasthenia gravis; a case of esotropia (paresis of the lateral rectus with inward deviation of the eye) due to an abducens nerve palsy; a case of exotropia (paresis of the medial rectus with outward deviation of the eye) due to a fascicular oculomotor nerve palsy; and a case of hypertropia (vertical misalignment of the eyes due to paresis of the superior oblique muscle vs. skew deviation) caused by a post-traumatic trochlear nerve palsy.

Ptosis and Neuromuscular Syndromes

emphasizes the clinical importance of a careful patient history detailing the onset of ptosis, its variability, and its progression. A pattern of ocular and generalized muscle weakness is a central diagnostic attribute of impaired nerve conduction due to disease of the neuromuscular junction. Generalized myasthenia gravis, ocular myasthenia gravis, MuSK-myasthenia gravis, and a case of the Lambert-Eaton syndrome illustrate the spectrum of disorders of neuromuscular transmission. The syndrome known as chronic progressive external ophthalmoplegia is by far the most common of the mitochondrial myopathies progressing to the multisystem failure that is characteristic of the Kearns-Sayre syndrome. A case of Kearns-Sayre syndrome followed for 34 years is a unique case study. Two inherited forms of myopathy, oculopharyngeal muscular dystrophy and myotonic dystrophy, are included, together with a patient with the Guillain-Barré syndrome variant, Fisher syndrome. These disorders should always be considered in the differential diagnosis of bilateral progressive ptosis.

How the Brain Moves the Eyes

discusses the brain’s visual architecture for directing and controlling of eye movements:the striate, frontal and parietal cortical areas; and the eye movements themselves—saccades, smooth pursuit, and vergence. The susceptibility to disorders of these systems is illustrated in four detailed cases that follow disease progression from initial symptoms and signs to diagnosis and treatment. The case studies and video displays include a patient with Pick’s disease (frontotemporal dementia), another with Alzheimer’s dementia, and two examples of rare saccadic syndromes, one a patient with the slow saccade syndrome due to progressive supranuclear palsy and one with selective saccadic palsy following cardiac surgery.

The Eyelid and Its Signs

presents the anatomy of the eyelid and places major emphasis on interpreting the significance of the wide range of diagnostic signs that the eyelids can show. The position of the eyelid in coma is determined by the tone of the levator palpebrae superioris muscle, and a new coma scale that takes the eyelid in coma into account is now used to grade the depth of coma. Blink reflexes in coma are also fully discussed, with particular attention to the corneal reflex. Those syndromes characterized ptosis due to weakness of the levator muscle, or partial ptosis due to weakness of Mueller’s muscle, accompanied by constriction of the pupil,are commonly seen . The diagnostic characteristics of many of these syndromes are illustrated in the eight case studies and video displays published in this chapter and they include cerebral ptosis, apraxia of lid opening, apraxia of lid closure, essential blepharospasm, and rare unilateral syndromeshemifacial spasm and the Marcus-Gunn jaw winking synkinesis.

The Cerebellum and its Syndromes

discusses a wide range of cerebellar syndromes and links them to specific topographic areas of the cerebellum. The hereditary ataxic syndromes include spinocerebellar ataxia, the Louis-Bar syndrome, spastic ataxia of Charlevoix-Saguenay, and the syndrome of the dorsal vermis. Oculomotor syndromes of the cerebellum—the syndrome of the flocculus/paraflocculus (tonsil), characterized by downbeat nystagmus; the syndrome of the nodulus and uvula, resulting in periodic alternating nystagmus; the syndrome of the fastigial nucleus, responsible for saccadic dysmetria; and the pancerebellar syndrome, characterized by paraneoplastic opsoclonus or flutter—are illustrated by six case studies in this chapter.

Horizontal Gaze and Syndromes of the Pons

covers deviations and disorders of horizontal gaze, which are so significantly linked to lesions of the pons that an emphasis on pontine signs is an important focus of this chapter. The pontine syndromes presented include a congenital case of horizontal gaze palsy and progressive scoliosis, and syndromes associated with adjacent tegmental structures, especially the paramedian reticular formation, the facial nerve, and the medial longitudinal fasciculus. A lesion of the medial longitudinal fasciculus causes internuclear ophthalmoplegia Examples are provided of internuclear ophthalmoplegia in childhood, combined unilateral conjugate gaze palsy and internuclear ophthalmoplegia, the one-and-a-half syndrome, and other variants. A case of bilateral horizontal gaze palsy permits discussion of the caloric test, one of the most widely used clinical test of the vestibulo-ocular reflex.

Cranial Nerves Three, Four, Six, and Their Syndromes

is the longest chapter in the book and perhaps the most important. Syndromes of the oculomotor nuclear complex, the fasciculus and the nerve[BluM2] include disorders such as acute dilation of the pupil due to uncal herniation, aneurysmal compression of the nerve with pupil involvement or with pupil sparing, and microinfarction of the nerve with pupil sparing due to ischemia associated diabetes mellitus. Important syndromes of the sphenocavernous sinus characterized by painful ophthalmoplegia are generally associated with multiple unilateral cranial nerve palsies. Common lesions include aneurysms, meningiomas, pituitary tumors, lymphoma, and infectious and idiopathic granulomatous infiltration (the Tolosa-Hunt syndrome). A patient with primary aberrant regeneration of the oculomotor nerve due to prolonged compression by a meningioma in the cavernous sinus is illustrated by video display.

Vertical Gaze and Syndromes of the Midbrain

reviews the architecture of the midbrain and extensively discusses the linkage of specific diagnostic signs to areas of the midbrain. Paralysis of up- and downgaze, pretectal pupils, eyelid and vergence disorders are among the signs discussed. Here again, case studies and video displays allow detailed presentations of patient history, analysis, diagnosis, and treatment of a range of disorders characterized by supranuclear vertical gaze paralysis: the pretectal syndrome, the Sylvian aqueduct syndrome, syndromes of the top of the basilar artery, and a rare case of supranuclear paralysis of downgaze with clinicopathological correlation. A short section on vergence disorders covers paralysis of convergence, the third “Parinaud” sign, convergence retraction nystagmus, pretectal pseudobobbing, and oculogyric crises.