Dorsal Midbrain Syndrome

Lesions of the dorsal midbrain produce a characteristic and highly localizing constellation of neuro-ophthalmic signs, which is known as the dorsal midbrain syndrome. In this chapter, we begin by summarizing the clinical features of the dorsal midbrain syndrome, which include supranuclear vertical gaze palsy, skew deviation, convergence insufficiency, convergence-retraction nystagmus, upper-eyelid retraction, and light-near dissociation of the pupils. We then list common causes of the dorsal midbrain syndrome, which include hydrocephalus, shunt malfunction, stroke, intrinsic brainstem tumors, and compression by extrinsic tumors, such as pineal and third ventricular tumors. Lastly, we discuss the neuro-ophthalmic features, diagnostic evaluation, and management of ventriculoperitoneal shunt malfunction.

Tonic Pupil

A tonic pupil is caused by a lesion affecting the postganglionic parasympathetic innervation of the pupil. It can be an incidental finding on examination or associated with visual symptoms, such as photophobia. In this chapter, we begin by briefly reviewing the differential diagnosis of photophobia. We next review the characteristic features of tonic pupil, which include poor pupil reaction to light, segmental palsy of the iris sphincter muscle, accommodation palsy, and tonic pupil reaction to near. We then review the causes of tonic pupil, which include viral infections, trauma, orbital surgery, or neurologic diseases, such as Miller Fisher syndrome. We then go on to discuss the clinical features, diagnostic evaluation, and prognosis of idiopathic tonic pupil, which is also known as an Adie pupil. Lastly, we briefly discuss the management options for tonic pupil, which include use of sunglasses and dilute pilocarpine eye drops.

Horner Syndrome

Horner syndrome can be caused by a lesion anywhere along the oculosympathetic pathway. Although there may be other signs that help with localization of the lesion, the syndrome often occurs in isolation. In this chapter, we begin by reviewing the anatomy of the oculosympathetic pathway. We next describe the clinical features of Horner syndrome, which include ipsilateral miosis and eyelid ptosis. We then discuss the role and potential pitfalls of pharmacologic pupil testing in the diagnostic evaluation of Horner syndrome. We review the potential causes for Horner syndrome, with a focus on causes for acute isolated painful Horner syndrome, such as internal carotid artery dissection. Lastly, we discuss the workup, management, and potential complications of internal carotid artery dissection.

Supranuclear Ophthalmoplegia

Supranuclear ophthalmoplegia results from an interruption of the saccadic, pursuit, optokinetic, or vergence inputs to the ocular motor nuclei. In this chapter, we begin by reviewing potential causes for difficulty reading. We next review the neuro-ophthalmic and neurologic features of progressive supranuclear palsy, which can include a vertical supranuclear ophthalmoplegia, convergence insufficiency, square-wave jerks, upper-eyelid retraction, reduced blink rate, apraxia of eyelid opening, and blepharospasm. We then discuss the differential diagnosis of progressive supranuclear palsy and point out clinical features that help to differentiate these conditions. Lastly, we present a practical approach to the management of the visual symptoms commonly caused by progressive supranuclear palsy.

Infranuclear Ophthalmoplegia

Infranuclear ophthalmoplegia is characterized by global weakness of the extraocular and levator muscles. It has a broad differential diagnosis that varies depending on the tempo of onset. In this chapter, we begin by describing how to differentiate nuclear-infranuclear ophthalmoplegia from supranuclear ophthalmoplegia at the bedside. We next list the common causes of acute onset infranuclear ophthalmoplegia, which include Miller Fisher syndrome, Guillain-Barré syndrome, stroke, and ocular myasthenia. We then list the common causes of chronic progressive infranuclear ophthalmoplegia, which include mitochondrial disorders, oculopharyngeal muscular dystrophy, and myotonic dystrophy. We discuss the clinical features and diagnostic workup of chronic progressive external ophthalmoplegia due to mitochondrial disease. Lastly, we briefly discuss the management of ptosis and diplopia in the setting of chronic progressive external ophthalmoplegia.

Ocular Myasthenia

Ocular myasthenia typically causes intermittent or fluctuating ptosis and diplopia yet can be difficult to diagnose definitively. In this chapter, we begin by reviewing the symptoms and signs of ocular myasthenia. We next discuss the laboratory workup for antibodies that are associated with ocular myasthenia and describe bedside tests that can helpful for confirming the diagnosis. We then discuss electrophysiology testing that can be helpful, including repetitive nerve stimulation testing and single-fiber electromyography. Lastly we review the management options for ocular myasthenia, which include symptomatic treatments (such as pyridostigmine), immunosuppression (such as corticosteroids and steroid-sparing agents), and surgical treatments (such as eyelid and strabismus surgery).

Fourth Nerve Palsy

Fourth nerve palsy is a common cause of binocular vertical diplopia. However, it can be difficult to diagnose because the clinical signs are often subtle. In this chapter, we begin by reviewing the symptoms of fourth nerve palsy. We next discuss clinical maneuvers for diagnosing fourth nerve palsy, including the Parks-Bielschowsky three-step test. We list the common causes for isolated fourth nerve palsy and review its differential diagnosis, which includes skew deviation and myasthenia gravis. We then discuss the indications for neuroimaging in a patient with fourth nerve palsy. Lastly, we discuss management options for fourth nerve palsy, which include prisms and strabismus surgery.

Autosomal Dominant Optic Atrophy

There is a broad differential diagnosis for bilateral optic neuropathies, including inflammatory, ischemic, compressive, traumatic, nutritional, toxic, and inherited causes. In this chapter, we begin by discussing the approach to the patient who has bilateral symmetric optic neuropathies. We next review the genetic basis, clinical features, and natural history of autosomal dominant optic atrophy. We list other deficits that can occur in up to 20% of patients with this condition, which can include sensorineural hearing loss, ataxia, myopathy, peripheral neuropathy, spastic paraparesis, and chronic progressive external ophthalmoplegia. Lastly, we discuss the evaluation and management approach for autosomal dominant optic atrophy.

Nonarteritic Ischemic Optic Neuropathy

Nonarteritic anterior ischemic optic neuropathy is the most frequent cause of acute-onset optic neuropathy in older adults. Its exact pathogenesis remains uncertain, although it often occurs in patients with a small, structurally congested optic disc (“disc at risk”). In this chapter, we begin by reviewing the clinical features of nonarteritic anterior ischemic optic neuropathy. We then discuss the prognosis for recovery of vision and fellow eye involvement. We review the risk factors and precipitating factors for this condition. We list the medications that have been associated with this condition. Lastly, we review the workup and management approach for this common condition.

Optic Neuritis

Optic neuritis is the most frequent cause of acute-onset optic neuropathy in young adults and is often encountered in clinical practice. In this chapter, we begin by reviewing the cardinal signs of optic neuropathy. We review the clinical characteristics and workup of optic neuritis. We review factors that increase the risk for developing multiple sclerosis. We discuss atypical clinical and imaging findings that should prompt further evaluation for other causes of optic neuritis, such as neuromyelitis optica. Lastly, we discuss the management options for optic neuritis, with reference to the findings from the Optic Neuritis Treatment Trial, and the prognosis for visual recovery.