In Vivo MRI Analysis of Cranial Nerve Morphology in a Patient with Inner Ear Disorder

Position a patient with a chronic inner ear disorder, injected with an MRI contrast agent, in the MRI scanner.

Ensure that the patient’s head is straight and aligned with the isocenter of the MRI scanner.

Secure the head coil around the patient’s head to receive MRI signals.

Initiate the scan.

The scanner detects MR signals from the cranial nerves and fluid-filled areas of the inner ear.

The contrast agent accumulates in the fluid-filled spaces, making them appear brighter on the MRI images.

In contrast, the cranial nerves absorb only a small amount of contrast agent, appearing darker and enabling clear visualization.

Using medical imaging software, reconstruct the cranial nerve images.

Measure the cross-sectional area, long diameter, and short diameter of the nerves.

Compare these measurements with those of a healthy individual to identify abnormalities in cranial nerve morphology.

Begin by escorting the patient into the MRI room and having them lie on the scanner table. Be sure to position their head straight at the isocenter of the scanner and then secure the head coil.

Next, perform the MRI scan according to the study protocol, including 3D FLAIR and 3D Real IR sequences for detection of endolymphatic hydrops in the patient group, as well as strongly T2 weighted 3D CISS for morphologic analysis of cranial nerves in the patient group and healthy controls.

After the scan is complete, check the MRI image quality with regard to artifacts like fold-over artifacts, pulsation artifacts, metal artifacts. And take special account of the target of evaluation, in this case, the cranial nerves VII and VIII throughout their course.

Finally, evaluate the endolymphatic hydrops in the MRI scans of patient group. Check for degree of cochlear and labyrinthine endolymphatic hydrops made visible by examining the acquired 3D FLAIR and 3D Real IR sequences.

Begin by running the DICOM viewer by double clicking the icon of the application to display the database window. Import the patient image data by left mouse clicking on File in the upper dropdown menu, then select Import, and then Import File.

In the file selector, select the patient image data in order to see the patient name and data in the database window. Next, in the database window, expand the patient image folder by left clicking onto the triangle symbol on the left side of the patient name.

Select the sequence of choice from this folder and double left click on it to open the corresponding image data. Next, prepare for reconstructing transverse sections of the cranial nerves to avoid measurement errors derived from oblique slices through the course of the nerve by selecting 3D MPR in the 3D viewer dropdown menu at the top of the screen.

Then adjust zoom levels to accommodate reconstruction by selecting the Zoom tool from the change mouse button function area in the toolbar in the upper left part of the MPR window. Move the mouse cursor to each of the three planes in the MPR window and adjust zoom levels by left clicking and dragging.

Reconstruct the central VIII nerve and set the reconstruction plane orthogonal to the nerves course in the middle of the cerebellopontine angle or CPA. Check and adapt the orientation of the reconstructed plane in all three planes windows.

Check for out of plane traversing of the nerve and correct the plane orientation, respectively. Adjust the orientation of the three axes to the nerves course using the Rotate function available by moving the mouse to the lateral aspects of each axis.

Then hold the left mouse button pressed and drag the mouse to adjust the plane orientation in all three windows of the MPR window. In order to reconstruct a plane traverse of the VIII nerves course at the end of the middle of the CPA, go to the left lower window of the MPR window and move the mouse to the middle of the axis crosshair so the mouse cursor will transform again into a hand symbol. Then left click and drag the plane to the desired location.

Left click onto the upper right window of the MPR window to select this plane. Select File, then Export, then Export to DICOM Files. In the DICOM Export window, select current image only.

Rename the series VIII CPA. Then click the OK button on the right lower aspect of the DICOM Export window. Next, we construct the orthogonal views of the branches of VIII nerve cochlear nerve, CN, superior vestibular nerve, SVN, and inferior vestibular nerve, IVN, at the level of the meatus of the IAC where representative visualization is usually well feasible.

Then grab the axis crosshair in each of the three planes with the grab tool indicated by a hand icon. And move the axis toward the CN, SVN, and IVN, respectively at the level of the meatus of the internal auditory canal or IAC.

Adjust their orientation to the nerves course using the Rotate function available at the lateral aspects of each axis depicted by the curved icon. Export and rename the reconstructed planes.