DILATED PUPILS (MYDRIASIS)

DILATED PUPILS (MYDRIASIS): Excerpt from Differential Diagnosis in Primary Care

Like that of myosis, the differential diagnosis of dilated pupils or mydriasis can best be developed by applying neuroanatomy (Table 24). “Knowing where the lesion is, tells us what the lesion is.” One simply follows the nerve pathway from the end organ up the oculomotor nerve to the termination in the brainstem. A dilated pupil, however, may also signify a lesion of the optic nerve and its pathways.

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DILATED PUPILS (MYDRIASIS)

	V	I	N	D
	Vascular	Inflammatory	Neoplasm	Degenerative
				and Deficiency
Oculomotor Nerve
End Organ		Orbital cellulitis
Peripheral portion of the oculomotor nerve	Aneurysm Sinus thrombosis	Tuberculosis Syphilis Cerebral abscess	Pituitary and brain tumors
Brainstem	Weber syndrome	Syphilis Encephalitis	Brainstem glioma	Wernicke encephalopathy
Optic Nerve
End organ	Occlusion of ophthalmic artery Occlusion of internal carotid	Keratitis Retinitis	Retinoblastoma	Cataract Retinitis pigmentosa
Peripheral portion	Cerebral aneurysm	Optic neuritis Basilar arachnoiditis	Pituitary and brain tumors Optic nerve glioma	Weber optic atrophy
Brainstem	Aneurysm Sinus thrombosis	Tuberculosis Syphilis	Pituitary and brain tumors

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1. Lesions of the oculomotor nerve and pathways
2. End organ. Lesions of the eye that cause dilated pupils include glaucoma, high myopia, anticholinergic drugs (e.g., atropine), and sympathomimetic drugs (such as neosynephrine).
3. Peripheral portion of the oculomotor nerve. Important lesions here include aneurysms of the internal carotid artery and its branches, herniation of the brain in brain tumors, subdural hematomas and other space-occupying lesions, cavernous sinus thrombosis, sellar and suprasellar tumors, tuberculosis and syphilitic meningitis, and sphenoid ridge meningiomas. Diabetic neuropathy of the third cranial nerve does not usually cause mydriasis. Most of these lesions are associated with ptosis and paralysis of the other extraocular muscles supplied by the oculomotor nerve.
4. Brainstem. Lesions here include multiple sclerosis, syphilis, encephalitis, Wernicke encephalopathy, brainstem gliomas, and Weber syndrome. Barbiturates and other drugs may cause dilated pupils by their central nervous system effects.
5. Optic nerve and pathways
6. End organ. Keratitis, cataracts, retinitis, and occlusion of the ophthalmic artery are included here.
7. Peripheral portion of the optic nerve. Aneurysms; optic neuritis; sellar and suprasellar tumors; optic nerve gliomas; primary optic atrophy from lues and other conditions; orbital fractures; exophthalmos; and cavernous sinus thrombosis are recalled in this category.
8. Brainstem. The lesions involving the optic tract here are similar to those that involve the oculomotor nerve discussed above. Optic cortex (calcerine fissure) lesions may cause blindness, but there is no mydriasis.

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DILATED PUPILS (MYDRIASIS)

	I	C	A	T	E
	Intoxication	Congenital	Allergic and	Trauma	Endocrine
			Autoimmune
	Anticholinergic drug	Glaucoma		Trauma to the globe	Pheochromocytoma
	Neosynephrine	Myopia		Hematomas Orbital fracture	Pituitary tumor (advanced)
	Barbiturate		Multiple sclerosis
		Cataract	Temporal arteritis		Cataract
	Methyl alcohol Tobacco		Multiple sclerosis	Orbital fracture	Exophthalmos
			Multiple sclerosis	Hematoma	Cranial concussion

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Approach to the Diagnosis

The clinical picture will often help to pinpoint the diagnosis. A history of drug use (narcotics, amphetamines, etc.) will suggest drug intoxication. Unilateral dilated pupil with ptosis would suggest oculomotor palsy, which may be due to a cerebral aneurysm or tumor or other space-occupying lesion. Early compression of the oculomotor nerve by a subdural hematoma or other mass may be indicated by a dilated pupil. Diabetic neuropathy may cause ptosis and extraocular muscle palsy without a dilated pupil. Unilateral or bilateral dilated pupils with blurred vision may be due to glaucoma or iritis. Dilated pupils may also be associated with blindness . A dilated pupil with other neurologic findings is a clear indication for referral to a neurologist or neurosurgeon. He or she can best decide whether a CT scan or MRI is indicated. Without focal neurologic signs the patient should have a drug screen. If that is negative, a referral to an ophthalmologist may be indicated. He or she may be able to do tonometry to rule out glaucoma and a slit lamp examination to evaluate for iritis and other conditions.

Other Useful Tests

1. Spinal tap (multiple sclerosis)
2. Visual evoked potentials (multiple sclerosis)
3. Arteriogram (cerebral aneurysm)
4. Visual field examination (multiple sclerosis, glaucoma)
5. Mecholyl test (Adie pupil)

Pictures

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.

More About Mydriasis

• Back to disease: Mydriasis: Introduction
• Next Book Extract About Mydriasis: Miosis
• More Book Extracts: All Online Books for Mydriasis

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

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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