The Study On MR Imaging Of Normal Cranial Nerves And Invasion Of The Trigeminal Nerve In Head And Neck Neoplasms

【Part 1】Values of 3D-FIESTA,2D T1-weighted SE,2D and 3D T2-weighted FSE MR sequences on visualization of cranial nervesⅢ-Ⅻin their intracisternal segmentsObjective:To evaluate the sensitivities of three-dimensional(3D) fast imaging employing steady-state acquisition(3D-FIESTA) sequence(effective slice thickness 1mm) and three-and two-dimensional T2-weighted fast spin echo(FSE) sequences, and two-dimensional(2D) T1-weighted spin echo(SE) sequence(slice thickness 2mm) for the visualization of cranial nervesⅢ-Ⅻin their cisternal courses. Methods:Twenty-six healthy volunteers underwent MR examinations by using the 3D-FIESTA,2D and 3D T2-weighted FSE sequences,and 2D T1-weighted SE sequences.Two radiologists evaluated independently the cranial nerves(CN)Ⅲ-Ⅻin their cisternal courses.Results:The rates for visualization of CNⅤ,ⅦandⅧfor the four sequences were 100%(52/52).The cranial nerveⅣwas only revealed on the images by using 3D-FIESTA sequence with a rate for visualization of 23%.The rates of visualization on cranial nervesⅢ,Ⅴ2,Ⅴ3,Ⅵwith the 3D-FIESTA sequence was higher than those of 3D FSE sequence without statistic difference.And the 3D FSE sequence was better than 2D FSE and even more better than 2D SE in the rates of visualization for the above cranial nerves(P＜α=0.05/6).The rates for visualization of nervesⅨ-Ⅺcomplex andⅫfor the four sequences showed respectively: 3D-FIESTA＞3D FSE＞2D FSE＞2D SE and 3D FIESTA＞3D FSE＞2D FSE=2D SE(P＜α=0.05/6).Conclusions:Most of the cranial nervesⅢ-Ⅻin their cisternal courses can be reliably assessed when using the 3D-FIESTA,3D FSE and 2D SE T2WI sequences.Using 3D-FIESTA sequence is superior to increasing the rates of visualization of nervesⅣ,Ⅸ-ⅪandⅫthan that by using T2-weighted 3D FSE sequences.The 3D-FIESTA and 3D FSE T2WI sequence are superior to increasing the rates of visualization on cranial nervesⅢ,Ⅴ1,Ⅴ2,Ⅴ3,Ⅵ,Ⅸ-ⅪandⅫthan that of 2D FSE T2WI sequence.Except for cranial nervesⅤ,ⅦandⅧ,the 2D SE T1-weighted sequence is difficult to indicate the others of cranial nervesⅢ-Ⅻ.Part 2 Essential study on the diameter measurement of cranial nervesⅢ,Ⅴ,Ⅵ,Ⅶ-ⅧandⅨ-Ⅺcomplex in their cisternal segments by using 3D-FIESTA sequence MR imagingObjective:To measure the diameters of the cranial nervesⅢ,Ⅴ,Ⅵ,Ⅶ-ⅧandⅨ-Ⅺcomplex in their cisternal segments by using the three dimensional fast employing steady-state acquisition sequence(3D FIESTA sequence) so as to obtain the normal data as a reference.Methods:Forty healthy volunteers and forty-five patients without clinical symptoms and abnormal MRI appearances associated to cranial nerves underwent MR scans by using the 3D-FIESTA sequence.On the transversal images,measurement of the diameters of the cranial nervesⅢ,Ⅴ,Ⅵ,Ⅶ-ⅧandⅨ-Ⅺcomplex in their cistemal segments was performed.And the differences of the diameters of the above cranial nerves were tested according to the sex and left or right sides.Results:The median diameters of the right and left sides of the above cranial nerves exhibited as follow respectively:CNⅢfor 2.58mm and 2.72mm,CNⅤfor 3.32mm and 3.38mm,CNⅥfor 1.60mm and 1.72mm,CNⅦfor 1.52mm and 1.56mm,CNⅧfor 2.00mm and 2.00mm,and CNⅨ-Ⅺfor 1.52mm and 1.33mm.There was no statistical difference between the right and left sides of the cranial nervesⅢ,Ⅴ,Ⅵ,Ⅶ-ⅧandⅨ-Ⅺcomplex(P＞0.05).The diameter of the cranianl nerveⅦin males was larger than that of females with a statistical difference(P＜0.05).The median diameters of the right and left sides of CNⅤ1-Ⅴ3 were respectively CNⅤ1 1.81mm and 1.75mm,CNⅤ2 1.79 mm and 1.77mm,CNⅤ3 1.93mm and 2.10mm.Conclusions:The 3D-FIESTA MR sequence seems to be suitable to indicate the cranial nervesⅢ,Ⅴ,Ⅵ,Ⅶ-ⅧandⅨ-Ⅺcomplex in their cisternal courses and may be used in the diameter measurement. Because of a great anatomic variance in the cranial nerveⅦ,we should keep an eye on the sex factor in the evaluation of the abnormality of diameter mesurement of the nerveⅦ.Part 3 Infiltration of the trigeminal nerve by head and neck neoplasms: comparative analysis by using the 3D-FIESTA and gadalinium-enhanced FSPGR MR sequencesObjective:To evaluate the value of the three dimensional fast employing steady-state acquisition(3D-FIESTA) sequence MR imaging in the detection of the trigeminal nerve invasion in head and neck neoplasms in comparison to gadalinium-enhanced FSPGR T1-weighted imaging(T1WI) with fat-saturation and to analyze the MR features of perineural spread(PNS) of the trigeminal nerve by using the two sequences.Methods:Sixteen patients with head and neck neoplasms and symptoms of impairment of the trigeminal nerve underwent MR examinations by using the 3D-FIESTA sequence and gadalinium-enhanced FSPGR T1W imaging with fat-saturation. The visibility of invasion of the trigeminal nerve in six segments including cisternal, pterygopalatine fossa,foramen rotundum,foramen ovale and masticatory muscle space were observed and evaluated by consensus of two radiologists using an evaluation scale from 1(not visible) to 3(excellently visible ).By using an eFilm 2.0 software the diameters of invaded maxillary nerves and mandibular nerves in foramen rotundum and foramen ovale were measured on the images of enhanced FSPGR sequence.Results:The visualization of invasion of the trigeminal nerve in intracisternal segment by using the two sequences is satisfied without statistic difference(P＞0.05).However,the visualization of invasion of the trigeminal nerve out of cistemal segment by using enhanced FSPGR T1 WI with fat-saturation is better than that by using 3D-FIESTA sequence(P＜0.05).On the T1WI by using FSPGR sequence the invaded trigeminal nerve manifested an irregular hyperintense mass or nodular mass,hypointense node or the "target" sign—high signal margin with low signal in the centre.And the trigeminal nerve infiltration presented as a hypointense node or mass and irregular enlargement of foramen exhibited a hypointense mass instead of normal fat signal on the images by using 3D-FIESTA sequence.The median diameter of invaded maxillary nerve and mandibular nerve in foramen rotundum or foramen ovale were respectively 4.435mm and 6.365mm.Conclusions: The normal and invaded trigeminal nerves in cisternal segment are easily visualized by using the 3D FIESTA sequence without enhancement.But in visualization of invasion of the trigeminal nerves out of cisternal segments by using 3D FIESTA sequence without enhancement it is inferior to that by using enhanced FSPGR sequence with fat-saturation T1-weighted imaging.A combination of the two sequences is most useful for the detection of the invasion of the trigeminal nerves in all courses and observation of different appearance in the two MR sequences.The diameters of invaded maxillary nerve and mandibular nerve are larger than that of normal nerves.