Hiroshi Ryu

MRI of Intracranial Neurovascular Compression

Twelve patients with clinical indications of intracranial neurovascular compression (6, hemifacial spasm; 4, trigeminal neuralgia; 2, vertigo and tinnitus) were studied by MRI. Axial 1 mm thick slices were obtained in a 1.5 T unit using a three-dimensional (3D) fast low angle shot data set of 32 contiguous slices. The data were postprocessed with multiplanar reconstruction algorithms to obtain oblique sagittal (along the long axis of a nerve) images or coronal images with a slice thickness of 0.8 mm. The MR angiographic images were also obtained from the same 3D data set with maximum intensity projection algorithms. The MR studies showed that 9 of 12 patients had neurovascular compression caused by one or two arteries. These findings were verified at surgery. In two of the remaining three patients, MRI failed to delineate the affected nerves compressed by a vein in one, and a previously applied prosthesis in the other. In the last patient no neurovascular compression was found by MRI or at surgery.

Usefulness of High-resolution Magnetic Resonance Cisternography in Patients with Hemifacial Spasm

To analyse the usefulness of preoperative magnetic resonance (MR) cisternography in patients with hemifacial spasm (HFS), MR observations were compared with surgical findings. High-definition images were obtained using MR cisternography which employed a long echo train length, fast spin-echo sequence, which revealed both nerves and blood vessels without any contrast media. In 35 HFS patients, certified radiologists examined the presence of vascular compression of the facial nerve and identified the offending vessels. MR cisternography depicted neurovascular compression in 31 patients (sensitivity 88.6%) and correctly determined the offending vessels in 28 patients. In 4 patients, MR cisternography revealed the presence of the vessel near the facial nerve, but the radiologist evaluated the compression as questionable (false-negative rate 11.4%). Even in these patients, MR cisternography revealed the precise anatomy of cerebellopontine (CP) cistern. High-resolution MR cisternography is useful in identifying the vessels and nerve bundles in the CP cistern, and in so doing can provide surgeons with valuable information regarding neurovascular decompression for HFS.To analyse the usefulness of preoperative magnetic resonance (MR) cisternography in patients with hemifacial spasm (HFS), MR observations were compared with surgical findings. High-definition images were obtained using MR cisternography which employed a long echo train length, fast spin-echo sequence, which revealed both nerves and blood vessels without any contrast media. In 35 HFS patients, certified radiologists examined the presence of vascular compression of the facial nerve and identified the offending vessels. MR cisternography depicted neurovascular compression in 31 patients (sensitivity 88.6%) and correctly determined the offending vessels in 28 patients. In 4 patients, MR cisternography revealed the presence of the vessel near the facial nerve, but the radiologist evaluated the compression as questionable (false-negative rate 11.4%). Even in these patients, MR cisternography revealed the precise anatomy of cerebellopontine (CP) cistern. High-resolution MR cisternography is useful in identifying the vessels and nerve bundles in the CP cistern, and in so doing can provide surgeons with valuable information regarding neurovascular decompression for HFS.