NYSTAGMUS

NYSTAGMUS: Excerpt from Differential Diagnosis in Primary Care

Why not consider the differential diagnosis of nystagmus under vertigo, because anatomic pathophysiology is the key to the differential in both? The reason is that there are two forms of nystagmus (ocular and cerebellar) that do not necessarily occur with vertigo. In addition to these two categories, nystagmus that usually occurs with vertigo is divided into nystagmus of middle ear diseases, nystagmus of inner ear diseases, nystagmus due to auditory nerve involvement, and nystagmus due to brainstem and cerebral diseases.

1. Ocular nystagmus. This is a pendular to-and-fro nystagmus with no fast component, which is usually due to congenital visual defects but which may be due to working in poor lighting (miner’s nystagmus). It is really an effort of the eye to find a better visual image. Infants with spasmus nutans have this type of nystagmus.
2. Middle ear disorders. Nystagmus may result from otitis media, which causes associated inflammation of the labyrinth.
3. Inner ear diseases. Labyrinthitis may be viral, postinfectious, traumatic, or toxic (e.g., from salicylates, quinine, streptomycin, or gentamycin). A cholesteatoma also causes nystagmus, as does Ménière disease.
4. Auditory nerve. Acoustic neuromas, internal auditory artery occlusions, or aneurysms and basilar meningitis may be considered in this category. Diabetic neuritis is another cause.
5. Brainstem. Transient ischemic attack (TIA) from basilar artery insufficiency, multiple sclerosis, gliomas, syphilis, and tuberculosis are the major conditions to consider here. Thrombi, emboli, and hemorrhages in the branches of the basilar artery are important too. With TIA the possibility of migraine and emboli from SBE or atrial fibrillation should be investigated. Dissemination encephalomyelitis and other forms of encephalitis should not be overlooked. Degenerative diseases such as syringobulbia and olivopontocerebellar atrophy are possibilities.
6. Cerebellum. In addition to the causes of nystagmus mentioned under brainstem, the physician should consider cerebellar tumors, abscesses, posterior fossa subdural hematomas, and diphenylhydantoin toxicity, as well as Friedreich ataxia and other forms of hereditary cerebellar ataxia. Alcoholic cerebellar degeneration is a significant cause of nystagmus. Acute cerebellar ataxia of children cannot be forgotten. Platybasia may compress the cerebellum and cause nystagmus. Cerebellar degeneration associated with carcinoma of the lung is often misdiagnosed.
7. Cerebrum. Curiously enough, frontal lobe tumors may cause nystagmus. Head injuries, encephalitis, chronic subdural hematomas, occipital meningiomas, and the aura of an epileptic seizure may also cause nystagmus.

Approach to the Diagnosis

The workup here is similar to that of vertigo. Nystagmus without other signs of central nervous system (CNS) disease is usually ocular or peripheral in the middle or inner ear. Vertigo is almost invariably present in nystagmus of aural origin. Nystagmus with long tract signs such as hemiplegia or hemianesthesia is invariably brainstem in origin. Purely cerebellar nystagmus is not easily fatigued and is associated with dyskinesia and dyssynergia of the extremities as well as ataxia. There are no long tract or cranial nerve signs. Nystagmus with vertigo, nausea, vomiting, tinnitus, and deafness suggests Ménière disease. Confirmation of the diagnosis is made by audiograms, caloric tests, skull x-rays (with special views of the mastoids and petrous bones), angiography, CT scans, and myelography. MRI scans are useful, especially in diagnosing brainstem lesions and multiple sclerosis. They also provide a better view of the internal auditory canal. A spinal tap will help in the diagnosis of multiple sclerosis and neurolues as well as acoustic neuromas.

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Book Source Details

• Book Title: Differential Diagnosis in Primary Care
• Author(s): R. Douglas Collins MD, FACP
• Year of Publication: 2007
• Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.

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More About This Book: Title: Differential Diagnosis in Primary Care Authors: R. Douglas Collins MD, FACP Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 0-7817-6812-8

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