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Oculomotor Nerve Palsy Workup

  • Author: James Goodwin, MD; Chief Editor: Andrew G Lee, MD  more...
Updated: Mar 18, 2016

Approach Considerations

Angiographic imaging studies (eg, computed tomographic angiography [CTA], magnetic resonance angiography [MRA], digital subtraction angiography [DSA]) are often necessary in the evaluation of acute oculomotor nerve palsy.

The combination of CT scanning/CTA followed by MRI/MRA is often necessary in the evaluation of unexplained oculomotor nerve palsy. Standard catheter angiography may be required upon high clinical suspicion for aneurysm.


Imaging Studies


MRI is a more sensitive imaging technique than CT scan for picking out a small intraparenchymal brainstem lesion, such as infarction, small abscess, or tumor.

MRI is also the procedure of choice for demonstrating meningeal and dural inflammation and infiltration.

Abnormal signal intensity and enhancement in the intracavernous portion of the third cranial nerve has been demonstrated in a case of herpes zoster with third cranial nerve palsy.[8]

Diffusion tensor imaging with 3-mm slice thickness has even demonstrated a small infarct in the midbrain involving the intraparenchymal segment of the third cranial nerve in a patient with acute onset third cranial nerve palsy.[9]

MRI/MRA also gives more specific information than CT scan on vascular flow patterns and is better for picking up lesions in the cavernous sinus, including aneurysm.

MRA using 1.5-Tesla or lower strength magnet is probably not adequate to rule out berry aneurysm causing third cranial nerve palsy, although 3-Tesla MRA with special attention to the circle of Willis can be definitive in this regard on account of enhanced resolution.

CT scanning

CT scan is more sensitive than MRI to demonstrate subarachnoid hemorrhage.

CT scan is also better than MRI for demonstrating calcification within lesions, as may be found in certain tumors and in large aneurysms.

Sixteen-row multislice CT angiography rivals digital subtraction catheter angiography in sensitivity and specificity for detecting intracranial aneurysms.[10, 11]



Lumbar puncture

The main purpose of lumbar puncture is to demonstrate the presence of blood in cerebrospinal fluid, an inflammatory reaction, neoplastic infiltration, or infection.

Bloody spinal fluid with oculomotor nerve palsy usually results from rupture of a posterior communicating artery berry aneurysm.

Meningeal inflammatory reaction may be idiopathic or may result from a specific infection that should be diagnosed by bacterial and fungal cultures and by fungus, protozoan, or virus-specific serology or specific antigen (polymerase chain reaction).

Cerebral angiography

Conventional angiography is the definitive test for berry aneurysm in all intracranial locations.

A small but definite risk of angiography causing serious complication, such as embolic stroke, exists. This risk varies with each institution and individual who does the procedure.

Angiography is indicated in a patient with third cranial nerve palsy and dilated, light-fixed pupil. It may be indicated in a patient younger than 55-60 years, especially without a history of long-standing diabetes, hypertension, or both.

When external ophthalmoplegia is partial, pupil sparing is not a reliable indicator of ischemia as opposed to aneurysm as the etiology, so angiography may be warranted in this setting, especially if the patient is young or lacks ischemic risk factors. See the image below.

Angiography anteroposterior and lateral views, lef Angiography anteroposterior and lateral views, left posterior communicating artery aneurysm, indicated by red arrow. Courtesy of James Goodwin, MD.

Histologic Findings

Cytologic examination of cerebrospinal fluid is used to diagnose meningeal carcinomatosis and lymphomatous or leukemic infiltration.

Contributor Information and Disclosures

James Goodwin, MD Associate Professor, Departments of Neurology and Ophthalmology, University of Illinois College of Medicine; Director, Neuro-Ophthalmology Service, University of Illinois Eye and Ear Infirmary

James Goodwin, MD is a member of the following medical societies: American Academy of Neurology, Illinois State Medical Society, North American Neuro-Ophthalmology Society, Royal Society of Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Andrew G Lee, MD Chair, Department of Ophthalmology, Houston Methodist Hospital; Clinical Professor, Associate Program Director, Department of Ophthalmology and Visual Sciences, The University of Texas Medical Branch; Clinical Professor, Department of Surgery, Division of Head and Neck Surgery, University of Texas MD Anderson Cancer Center; Professor of Ophthalmology, Neurology, and Neurological Surgery, Weill Medical College of Cornell University; Clinical Associate Professor, University of Buffalo, State University of New York School of Medicine

Andrew G Lee, MD is a member of the following medical societies: American Academy of Ophthalmology, Association of University Professors of Ophthalmology, American Geriatrics Society, Houston Neurological Society, Houston Ophthalmological Society, International Council of Ophthalmology, North American Neuro-Ophthalmology Society, Pan-American Association of Ophthalmology, Texas Ophthalmological Association

Disclosure: Received ownership interest from Credential Protection for other.

Additional Contributors

Edsel Ing, MD, FRCSC Associate Professor, Department of Ophthalmology and Vision Sciences, University of Toronto Faculty of Medicine; Consulting Staff, Hospital for Sick Children and Sunnybrook Hospital

Edsel Ing, MD, FRCSC is a member of the following medical societies: American Academy of Ophthalmology, American Association for Pediatric Ophthalmology and Strabismus, American Society of Ophthalmic Plastic and Reconstructive Surgery, Royal College of Physicians and Surgeons of Canada, Canadian Ophthalmological Society, North American Neuro-Ophthalmology Society, Canadian Society of Oculoplastic Surgery, European Society of Ophthalmic Plastic and Reconstructive Surgery, Canadian Medical Association, Ontario Medical Association, Statistical Society of Canada, Chinese Canadian Medical Society

Disclosure: Nothing to disclose.


Brian R Younge, MD Professor of Ophthalmology, Mayo Clinic School of Medicine

Brian R Younge, MD is a member of the following medical societies: American Medical Association, American Ophthalmological Society, and North American Neuro-Ophthalmology Society

Disclosure: Nothing to disclose.

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Angiography anteroposterior and lateral views, left posterior communicating artery aneurysm, indicated by red arrow. Courtesy of James Goodwin, MD.
Patient with left posterior communicating artery aneurysm and third cranial nerve palsy. Courtesy of James Goodwin, MD.
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