Objective: To compare enhancement of the central auditory pathway in cats receiving auditory stimulation between manganese enhanced magnetic resonance imaging (MEMRI) with intraperitoneal manganese injection route and MEMRI with intratympanic manganese injection route, and investigate the optimal method for displaying enhancement of the central auditory pathway.
Methods: Twenty-seven normal hearing adult cats were randomly divided into three groups, receiving intraperitoneal manganese injection, left intratympanic manganese injection or left intratympanic gadolinium injection respectively.All cats received white noise stimulation of 80 dB in twenty-four hours after injection.Three dimensionally coronal T1-weighted imaging of the cat brain was obtained with an animal dedicated MRI scanner.The signal noise ratios (SNRs) of bilateral cochlear nuclei (CN), dorsal nuclei of the trapezoid bodies (DNTB), caudal colliculi (CC) and auditory cortices (AC) were measured on reconstructed images and compared.
Results: Obvious increased SNRs on both sides were shown in intraperitoneal mangasese injection group while left predilection was shown in intratympanic manganese injection group: left CN 45.7±6.0, 37.4±11.9, 23.9±2.7, F=17.694, P=0.000; left DNTB 50.5±11.2, 37.1±11.2, 27.6±7.3, F=11.781, P=0.000; left CC 37.6±3.9, 22.6±3.1, 17.9±0.7, F=111.898, P=0.000; left AC 27.7±2.5, 17.3±2.3, 14.5±1.0, F=105.132, P=0.000; right CN 42.7±8.3, 23.9±3.0, 22.7±2.1, F=41.492, P=0.000; right DNTB 44.1±8.3, 21.9±3.0, 23.9±4.0, F=27.862, P=0.000; right CC 38.0±4.0, 21.9±3.0, 17.6±0.9, F=120.032, P=0.000; right AC 26.7±3.4, 17.1±2.9, 14.9±1.3, F=64.587, P=0.000.Compared with the left intratympanic gadolinium injection group, the intraperitoneal manganese injection group showed higher SNRs in bilateral CN and CC (P<0.05), and the left intratympanic manganese injection group showed higher SNRs in left CN, AC and bilateral CC.The SNRs of right CN, bilateral DNTB, CC and AC were significantly higher in the intraperitoneal manganese injection group than those in the left intratympanic manganese injection group (P<0.05).
Conclusion: MEMRI with intraperitoneal manganese injection might be the optimal method for displaying enhancement of the central auditory pathway in cats receiving auditory stimulation.