[The anatomy of the temporal region viewed by magnetic resonance]

The study of the temporal region has been improved by technologic progress from conventional radiography to linear tomography, then to pluridirectional tomography, CT and, finally, MRI. Twenty-five patients were examined with MRI--50 temporal regions in all. MRI was performed with a brain coil, SE T1-weighted sequences (TR 500 ms, TE 25 ms, FOV 180 mm, matrix 256 x 512, 2 acquisitions, slice thickness: 3 mm, acquisition time: 5.30 minutes) before and after Gd-DTPA administration. SE T2-weighted sequences (TR 2000 ms, TE 20-80 ms, FOV 180 mm, matrix 256 x 256, 1 acquisition, slice thickness: 4 mm, acquisition time: 8.30 minutes), 3D CISS sequences (TR 20 ms, TE 8 ms, FOV 180 mm, matrix 256 x 256, acquisition time: 2.46 minutes) and MRA 3D TOF TONE sequences (TR 33 ms, TE 8 ms, FOV 180 mm, matrix 256 x 256, acquisition time: 9.30 minutes) were performed. Neither the temporal bone, made of compact tissue, nor the air spaces (mastoid, antrum, middle ear cavity) exhibit any MR signal. On the contrary, the fluid filling the membranous labyrinth (endolymph and perilymph) and the cerebrospinal fluid filling the internal acoustic canal and the cerebello-pontine angle have high signal. This pattern allows a detailed study, unfeasible with CT, of the inner ear structures (cochlea, vestibule and semicircular canal) and of the internal acoustic canal. Moreover, MRI allows the whole VII and VIII cranial nerves to be studied from their origin at the brain stem to the internal acoustic porus and into the internal acoustic canal. Finally, MRI permits the noninvasive study of temporal region vessels. To conclude, MRI yields new anatomical details of the temporal region useful to address major diagnostic issues--e.g., labyrinth, internal acoustic canal and cerebello-pontine angle lesions.