MR of oculomotor nerve palsy
P Y Blake1, A S Mark, J Kattah
1Department of Neurology, Georgetown University Medical Center, Washington, DC 20007, USA.
Purpose:
To assess the utility of MR in third cranial nerve palsy.
Methods:
We reviewed precontrast and postcontrast MR of 50 patients with third cranial nerve palsy.
Results:
MR demonstrated an appropriate lesion in 32 cases. Of these patients, 6 had brain stem lesions and 15 had involvement of the nerve in the cavernous sinus; lesions of the cisternal segment of the nerve were present in 11 patients, with enhancement of this segment observed in 9 patients. An inflammatory or infiltrative source of the palsy was indicated in 19 of these 32 cases. Of 7 patients with pupillary involvement suggestive clinically of a compressive lesion, 4 demonstrated thickening and enhancement consistent with an infiltrative lesion of the nerve. Eighteen patients with pupil-sparing third cranial nerve palsies and a history of diabetes or vascular disease had normal MR findings, with no enhancement of the third cranial nerve observed.
Conclusions:
Patients who do not have a history of diabetes or hypertension and in whom a complete or incomplete third cranial nerve palsy develops with or without pupil sparing should undergo MR imaging initially (unless there are clear symptoms or signs of subarachnoid hemorrhage) to exclude the presence of an infiltrative lesion or intraparenchymal process. Patients who have a history of vascular disease and a clinical presentation that is suggestive of an ischemic event may be observed initially, but should undergo imaging if improvement does not occur within 3 months.
Insights
Magnetic resonance (MR) imaging is crucial for diagnosing third cranial nerve palsy, especially in patients without vascular risk factors. Early MR can identify infiltrative lesions or intraparenchymal processes causing nerve palsy.
Area of Science:
- Neurology
- Radiology
- Ophthalmology
Background:
- Third cranial nerve palsy presents with various etiologies, including ischemic, inflammatory, infiltrative, and compressive causes.
- Differentiating these causes is essential for appropriate patient management and prognosis.
Purpose of the Study:
- To evaluate the diagnostic utility of Magnetic Resonance (MR) imaging in patients presenting with third cranial nerve palsy.
- To determine the effectiveness of MR in identifying the underlying cause of third cranial nerve palsy.
Main Methods:
- Retrospective review of precontrast and postcontrast MR scans from 50 patients diagnosed with third cranial nerve palsy.
- Analysis of lesion location, nerve enhancement patterns, and correlation with clinical presentation and patient history.
Main Results:
- MR identified a causative lesion in 32 out of 50 patients.
- Commonly identified lesions included brainstem, cisternal segments, and cavernous sinus involvement.
- Inflammatory or infiltrative sources were suggested in 19 cases, with specific findings in patients with pupillary involvement.
- Normal MR findings, including absence of nerve enhancement, were observed in 18 patients with pupil-sparing palsy and a history of diabetes or vascular disease.
Conclusions:
- MR imaging is recommended as an initial diagnostic tool for third cranial nerve palsy, particularly in patients without a history of diabetes or hypertension, to rule out infiltrative or intraparenchymal lesions.
- Patients with a history of vascular disease and symptoms suggestive of ischemia may be initially managed conservatively but require MR imaging if symptoms persist beyond 3 months.
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