Computerized tomography angiography in isolated third nerve palsies

Imaging of intracranial aneurysms causing isolated third cranial nerve palsy

Isolated third cranial nerve palsies may be caused by compressive intracranial aneurysms located at the junction of the internal carotid and posterior communicating arteries or, less commonly, at the apex of the basilar artery or its junction with the superior cerebellar or posterior cerebral arteries. Such aneurysms typically measure at least 4 mm in diameter. Technical improvements in noninvasive techniques, including CT and MRA, have yielded a detection rate of such aneurysms that approaches that of catheter cerebral angiography (CCA), which itself carries a small but serious risk. Multidetector technology, which allows a rapid scan time, has promoted CT to the first choice for investigating aneurysms in this setting except when dye or radiation exposure is unacceptable, as with pregnant women, children, and those with renal or severe cardiac disease. Major impediments to accurate detection are a lack of availability of trained technicians, who must perform manipulation of the raw imaging data ("post-processing"), and a paucity of certified neuroradiologists with the time, skill, and experience to devote to interpreting difficult cases. To avoid diagnostic mishaps, noninvasive studies should be reviewed by at least one neuroradiologist before aneurysm is rejected as the cause or before the patient undergoes CCA.

Rate of third nerve palsy recovery following endovascular management of cerebral aneurysms

Endovascular management of cerebral aneurysms resulting in third nerve palsies has been proposed as an alternative to microsurgical clip ligation. Third nerve function recovery following endovascular treatment in a large patient population has not been evaluated. A literature search of MEDLINE, PubMed, and Cochrane databases for third nerve palsies and endovascular management of cerebral aneurysms was performed. All reported patients in these studies were systematically compiled. Fifty-two patients with third nerve palsies secondary to cerebral aneurysms underwent endovascular treatment. Endovascular management resulted in some degree of third nerve recovery in 65% of patients. The extent of recovery was reported in 21 patients. Of these, 71% had complete recovery. At least two procedure-related third nerve palsies are reported in the literature. One was permanent. One case of recurrent painful palsy is also reported. Microsurgical clip ligation of cerebral aneurysms has a 93% rate of third nerve palsy recovery and a 43% rate of complete third nerve recovery. Endovascular management of cerebral aneurysms can alleviate third nerve palsies in some patients. In reviewing the world literature, however, microsurgical clip ligation is associated with a higher rate of third nerve recovery. Endovascular management, in the subset of patients in whom extent of recovery was documented, demonstrated a higher rate of complete recovery.

Intracranial aneurysms

PURPOSE OF REVIEW

To review the neuroophthalmic manifestations of cavernous and posterior communicating artery aneurysms as well as the diagnosis and treatment options for patients with these kinds of aneurysms.

RECENT FINDINGS

The natural history of cavernous aneurysms has recently been systematically followed. Comparison of coiling and clipping for posterior communicating artery aneurysms has yielded new suggestions on how to best treat these patients.

SUMMARY

The review discusses how to follow these cases, diagnose and treat, and assess for complications after treatment decisions have been made.

Magnetic resonance angiography and clinical evaluation of third nerve palsies and posterior communicating artery aneurysms

Object

The authors conducted a study to determine the utility of the clinical profile and magnetic resonance (MR) angiography in evaluating patients with isolated third cranial nerve palsies or posterior communicating artery (PCoA) aneurysms.

Methods

Three-dimensional time-of-flight MR angiography was performed in a consecutive series of patients with isolated acute third cranial nerve palsy not due to a ruptured aneurysm and in patients with unruptured PCoA aneurysms. A neuroradiologist, masked to the identities of the patients, interpreted reformatted maximum intensity projection (MIP) and source images of the PCoAs and aneurysms. The investigators assessed clinical features of oculomotor nerve dysfunction and focal head pain. Cases involving cranial third nerve palsy without aneurysms were classified as Group 1 (no case entailed catheter-based angiography), and cases involving PCoA aneurysms seen on MR angiography (42 cases confirmed by catheter-based angiography) were classified as Group 2.

The mean age of the 73 patients in Group 1 was 60.1 years and that of the 45 patients in Group 2 was 59.1 years (p = 0.37). The pattern and severity of oculomotor (p = 0.61) and lid (p = 0.83) dysfunction and pain frequency (p = 0.2) were similar for the 73 patients with vasculopathy in Group 1 and the 15 symptomatic patients in Group 2. Abnormal pupils were observed in 38% of the patients in Group 1 and 80% of those in Group 2 (p = 0.016). In cases of complete external third nerve palsy, nine of 22 in Group 1 and none of four in Group 2 had normal pupil function. For all patients, source imaging showed 206 PCoAs (85%) and MIP imaging demonstrated 120 PCoAs (49%). Of 48 aneurysms (three bilateral), MIP imaging showed 44 (92%) and source imaging showed 47 (98%). Only a 2-mm aneurysm seen on catheter-based angiography was missed by MR angiography. Symptomatic aneurysms were equal or greater than 4 mm in size.

Conclusions

Only the presence of complete external third nerve palsy and normal pupil function allowed ischemia to be clinically distinguished from a PCoA aneurysm in a patient with isolated third nerve palsy and no subarachnoid hemorrhage. When source image MR angiography demonstrates normal findings, catheter-based angiography need not be performed in these patients, even if pupil function is abnormal.

Case Studies in Neuro-Ophthalmology for the Neurologist

In summary, neurologists should be aware of emergent neuro-ophthalmic conditions: (1) temporal arteritis (GCA), (2) IIH, (3) intracranial shunt malfunction, (4) pituitary apoplexy, and (5) pupil-involved TNP. Earlier recognition and treatment of these disorders makes a difference in final out-come. Appropriate evaluation and management may be vision or life saving.

A review of isolated third nerve palsy without subarachnoid hemorrhage using computed tomographic angiography as the first line of investigation

INTRODUCTION

Digital subtraction angiography is recognized as the standard investigation for isolated third nerve palsy thought to be caused by an expanding aneurysm. We reviewed our experience in using computed tomographic angiography (CTA) as the first line investigation for patients presenting with isolated third nerve palsy without subarachnoid hemorrhage.

METHOD

We retrieved the medical records of 34 patients who had presented with isolated third nerve palsy without associated subarachnoid hemorrhage to our institution between January 1998 and July 2001. The clinical history, course and outcome as well as the radiological data was reviewed.

RESULTS

A total of nine structural lesions (26%) were noted as the etiology of the third nerve palsy. All of the five posterior communicating artery aneurysms were picked up by the CTA. Neither the presence nor the absence of painful complete third nerve palsy was of diagnostic value for intracranial aneurysm.

CONCLUSION

A good quality CTA is sufficient to detect a compressive aneurysm and may detect other structural lesions. This allows neurosurgeons to plan the management of patients with isolated third nerve palsy. Patients in whom CTA results are inconclusive should be further investigated with catheter angiography.

Multislice computerized tomography angiography in the evaluation of intracranial aneurysms: a comparison with intraarterial digital subtraction angiography

OBJECT

The goal of this study was to assess the diagnostic accuracy of computerized tomography (CT) angiography performed with the aid of multislice technology (MSCT angiography) in the investigation of intracranial aneurysms, by comparing this method with intraarterial digital subtraction (IADS) angiography.

METHODS

Fifty consecutive adult patients, who successively underwent MSCT angiography (four rows) and IADS angiography of intracranial vessels, were prospectively identified. The MSCT angiography studies consisted of 1.25-mm slices, with 0.8-mm reconstruction intervals, a pitch of 0.75, and timing determined by a test bolus. Two neuroradiologists, who were blinded to the initial interpretation of the MSCT angiograms as well as to those of the IADS angiograms, independently reviewed the MSCT angiograms for the detection and characterization of intracranial aneurysms. Forty-nine intracranial aneurysms were identified in 40 patients; 33 of these lesions were responsible for subarachnoid hemorrhage. The sensitivity, specificity, and accuracy of MSCT angiography in the detection of intracranial aneurysms were 94.8, 95.2, and 94.9%, respectively, on a per-aneurysm basis and 99, 95.2, and 98.3%, respectively, on a per-patient basis. Interobserver agreement was 98%. There was an excellent correlation between aneurysm size assessed using MSCT angiography and that determined by IADS angiography (slope = 0.916, r = 0.877, p < 0.001); however, 2 mm stood as the cutoff size below which the sensitivity of MSCT angiography was statistically lower. That method displayed great accuracy in characterizing the morphological characteristics of the aneurysm.

CONCLUSIONS

Multislice CT angiography is an accurate and robust noninvasive screening test for intracranial aneurysms. It performs better than that reported for single-slice CT angiography. Introduction of eight- and especially 16-row MSCT angiography will provide further progression through thinner slices, a lower pitch, and a purely arterial phase.

The evaluation of isolated third nerve palsy revisited: an update on the evolving role of magnetic resonance, computed tomography, and catheter angiography

The evaluation and management of the neurologically isolated third nerve palsy continues to evolve. The major concern for the clinician confronted with a patient with a third nerve palsy has been the exclusion of an intracranial aneurysm. The evolution of new imaging techniques, such as computed tomography angiography and magnetic resonance angiography, have provided new imaging options for clinicians. This article reviews the pertinent recent literature on the use of these imaging studies in evaluating the patient with a third nerve palsy.

Early resolution of third nerve palsy following endovascular treatment of a posterior communicating artery aneurysm

A 69-year-old man underwent successful endovascular treatment of a posterior communicating artery aneurysm that had caused a third nerve palsy. Pupil size became normal within 10 days and ptosis and ocular ductions became normal within 3 weeks of the procedure. Based on the reported recovery rates of third nerve palsy after aneurysmal clipping, recovery may occur more rapidly in patients who undergo endovascular treatment. Further data are necessary to substantiate this hypothesis.

What is the most sensitive non-invasive imaging strategy for the diagnosis of intracranial aneurysms?

OBJECTIVES

To determine whether combining non-invasive tests for intracranial aneurysms together would significantly improve aneurysm detection over individual tests.

METHODS

114 patients undergoing intra-arterial digital subtraction angiography to confirm or exclude an intracranial aneurysm were also examined by CT angiography, MR angiography, and transcranial power Doppler ultrasound. The reviewers and ultrasonographers were blinded to the angiogram result, other imaging results and all clinical information.

RESULTS

The combination of non-invasive tests did improve diagnostic performance on a per patient basis. The combination of power Doppler and CT angiography had the greatest sensitivity for aneurysm detection (0.83; 05% confidence interval (95% CI) 0.66-0.93) and the level of agreement for this strategy with the reference angiographic standard was excellent (kappa 0.84; 95% CI 0.72-0.95). The improvement in sensitivity of adding power Doppler to CT angiography was not significant (p=0.55) but the improvement in the level of agreement with the reference standard was substantial. However, even the most sensitive combination strategy performed poorly in the detection of small (3-5 mm) and very small (<3 mm) aneurysms with a sensitivity of 0.43 (95% CI 0.23-0.66) and 0.00 (95% CI 0.00-0.31) respectively.

CONCLUSIONS

The addition of transcranial power Doppler ultrasound to either CT angiography or MR angiography does improve diagnostic performance on a per patient basis but aneurysms of 5 mm or smaller can still not be reliably identified by current standard clinical non-invasive imaging modalities.

Power transcranial Doppler ultrasound in the detection of intracranial aneurysms

BACKGROUND AND PURPOSE

We sought to perform a large, prospective, multicenter, blinded study comparing power transcranial color duplex sonography (power TCDS) with intra-arterial digital subtraction angiography (IADSA) in the detection of intracranial aneurysms.

METHODS

Contemporaneous TCDS and IADSA examinations were performed in 171 subjects with suspected intracranial aneurysm. Via the temporal bone window, a 2-dimensional hand-held noncontrast transcranial duplex ultrasound imaging system was used operating in power and spectral modes. Sonographers were blinded to clinical history and results of brain CT and IADSA.

RESULTS

We found that 157 subjects (92%) had an adequate bone window. Sensitivity per patient was 0.78 (95% CI, 0.66 to 0.87) and 0.46 (95% CI, 0.36 to 0.56) for any anterior circulation aneurysms. Sensitivity was 0.35 (95% CI, 0.24 to 0.46) for aneurysms </=5 mm and 0.81 (95% CI, 0.62 to 0.94) for aneurysms >5 mm. Accuracy was lower for aneurysms on the cavernous and terminal internal carotid arteries, including posterior communicating artery origin (0.71; 95% CI, 0.63 to 0.79), than for those on the anterior (0.82; 95% CI, 0.74 to 0.89) or the middle cerebral arteries (0.79; 95% CI, 0.71 to 0.86).

CONCLUSIONS

Power TCDS is a promising, inexpensive, noninvasive test for anterior circulation intracranial aneurysms but is less sensitive per aneurysm than alternatives such as CT angiography or MR angiography. Sensitivity is poor for aneurysms </=5 mm in diameter. The internal carotid artery is the most difficult segment to interpret.

Intracranial aneurysms: CT angiography and MR angiography for detection prospective blinded comparison in a large patient cohort

PURPOSE

To compare computed tomographic (CT) angiography and magnetic resonance (MR) angiography with intraarterial digital subtraction angiography (DSA) in the detection of intracranial aneurysms.

MATERIALS AND METHODS

One hundred forty-two patients underwent intraarterial DSA to detect aneurysms. CT angiography, three-dimensional time-of-flight MR angiography, and intraarterial DSA were performed contemporaneously. Film hard-copy images and maximum intensity projection reconstructions of the CT angiograms and MR angiograms were reviewed at different times.

RESULTS

The accuracy per patient for the best observer was 0.87 at CT angiography and 0.85 at MR angiography. The accuracy per aneurysm for the best observer was 0.73 at CT angiography and 0.67 at MR angiography. Differences between readers and modalities were not significant. Interobserver agreement was good: kappa value of 0.73 for CT angiography and of 0.74 for MR angiography. The sensitivity for detection of aneurysms smaller than 5 mm was 0.57 for CT angiography and 0.35 for MR angiography compared with 0.94 and 0.86, respectively, for detection of aneurysms 5 mm or larger. The accuracy of both CT angiography and MR angiography was lower for detection of internal carotid artery aneurysms compared with that at other sites. With low observer confidence, the likelihood of correct interpretation was significantly poorer.

CONCLUSION

CT angiography and MR angiography have limited sensitivity in the detection of small aneurysms but good interobserver agreement. There is no significant difference in diagnostic performance between the noninvasive modalities.

Paralytic strabismus

In the past 12 months there have been many interesting publications on paralytic strabismus. Many investigators have reported on various imaging techniques helping both the clinician and the basic scientist better evaluate the causes and effects of paralytic strabismus on the extraocular muscle environment. Some interesting cases of neurologic and systemic associations have also been reported, including a unilateral pupil-sparing third nerve paralysis developing after the use of sildenafil citrate (Viagra; Pfizer, New York, New York). Advances in genetics are now helping us further understand complex entities such as progressive external ophthalmoparesis and congenital fibrosis syndrome. At the other end of the spectrum, colleagues are reporting clinical findings to help specify the diagnosis of conditions as diverse as degenerative ataxic disorders and masked bilateral superior oblique muscle paresis. Unfortunately, there were very few papers on proven new effective surgical techniques for the treatment of paralytic strabismus this year. Finally, to help clarify terminology, and when at all possible depending on the reports reviewed, the following nomenclature will be used in this paper: paralysis--complete loss of function of a muscle or group of muscles innervated by a specified (when applicable) cranial nerve or branch; paresis--incomplete loss of function; and palsy--when the authors failed to specify the degree of weakness.