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The Application of MR Tomographic Angiography in Essential Hemifacial <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
Spasm: The Significance of Various Evaluating Indicator
PURPOSE: To investigate the role of MR Tomographic Angiography in demonstrating the relationship between essential hemifacial spasm and neurovascular contact/compression (NVC) at the root entry zone (REZ) of facial nerve and evaluate the usefulness of various MR indicator for preoperative assessment.
METHOD AND MATERIALS:Three-dimensional time-of-flight MR tomographic angiography (3D-TOF-MRTA) was performed on both sides of the facial nerve of 102 patients who suffering from unilateral hemifacial spasm and 70 asymptomatic volunteers as control cases (symptomatic sides: n=102; asymptomatic sides: n=242).No patient with secondary causes was included. Images of three planes including transverse, oblique coronal and coronal sections were obtained in each case. The relationship between the REZ of facial nerve and adjacent vessels was graded into four types: no touch, suspicious contact, definite contact and compression. The diameter of suspicious responsible vessels and minimum distance between the point of NVC and the point at which facial nerve exit the brainstem were measured. The crossing angle of NVC and the sign that vessels passing through the bundle of facial nerve and vestibulocochlear nerve were also observed. MR images were reviewed by two experienced radiologists blinded to the clinical symptoms of patients.
RESULTS: Comprehensive evaluation based on MR images of all three planes could obtain better sensitivity (83.33%), specificity (86.78%),accuracy (85.76%) and correspondence with clinical symptom (Kappa=0.672) than any single plane. Neurovascular suspicious contact should be regarded as negative result because of the improvement of specificity and accuracy of MRTA with such definition. NVC was detected by MRTA in 32 asymptomatic sides (13.22%) and 85 symptomatic sides (83.33%), respectively; the difference between the two positive rates was statistically significant (p<0.01). The diameter of responsible vessels discovered in symptomatic sides (1.52±0.81mm) was larger than that of the vessels in asymptomatic sides (1.08±0.34mm) (p<0.01).The minimum distance between the point of NVC and the point at which facial nerve exit the brainstem measured in symptomatic sides (0.87±0.66mm) was shorter than that in asymptomatic sides (1.97±1.16mm) (p<0.01). The incidence rate of neurovascular cross-contact/compression at right-angle was higher in symptomatic sides (29.41%) than in asymptomatic sides (17.01%) (p<0.05).The results of two radiologists corresponded well (Kappa=0.581).
CONCLUSIONS: The severity and location of NVC, the diameter of responsible vessels and cross-contact/compression at right-angle are the key points of diagnosis by MRTA. Multiplanar MRTA may achieve optimal correspondence with the clinical symptoms and improve the sensitivity, specificity and accuracy in detecting NVC and provide neurosurgeons with objective evidences in patients screening and operative planning.
原发性面肌痉挛（Essential Hemifacial Spasm，EHFS）是指排除了肿瘤、炎症和血管性病变等继发因素的病因不明的单侧部分或全部面肌阵发性不自主抽搐。自六十年代Gardner[1,2]提出神经血管接触或压迫（Neurovascular Contact/Compression，NVC）可能是EHFS的主要病因，长期以来已有许多研究分别在组织病理学、神经外科学以及医学影像学领域对这种假设进行了验证。目前，这一学说已经得到了广泛的认可[3-5]。近年来随着医学影像技术的发展，MR已逐渐成为EHFS术前诊断与评估的重要工具[6,7]。MR断层血管成像（MR Tomographic Angiography，MRTA）是一种比较常用的方法，我科自1997年以来多采用这种方法对临床拟诊EHFS患者的面神经脑池段与邻近血管的关系进行评估。本文是一项前瞻性研究，旨在探讨MRTA中各项评价指标与临床发生症状之间的关系，以期获得更为准确实用的MRTA评价体系。 |
