Morphometric and signal intensity benchmarks of 3D CRANI MR neurography sequence for extraforaminal cranial and...

Lack of evidence exists related to the reporting of benchmark values of MR neurography sequences required for extraforaminal cranial and occipital nerve visualization. This study aimed to establish benchmarks of morphometric and signal intensity values of 3D CRANI MR neurography sequence in healthy subjects.

A total of 10 healthy participants (5 males, 5 females; age range:14-83 years) were recruited. Imaging was conducted using a 3.0 Tesla MRI system fitted with a 32-channel head coil. The assessed extraforaminal cranial and occipital nerves included auriculotemporal, buccal, facial, greater occipital, hypoglossal, inferior alveolar, lingual, mandibular, masseteric, and maxillary. These nerves were semi-automatically segmented and divided into five segments: proximal, mid-proximal, middle, mid-distal, and distal. Measurements were performed for per nerve and segment diameter, signal intensity, apparent signal-to-noise (aSNR) and apparent nerve-muscle contrast-to-noise ratios (aNMCNR).

All nerves exhibited a decreasing trend in diameter and signal intensity from the proximal to the distal end, except for the facial, maxillary, and auriculotemporal nerves. The mid-proximal section of the nerves under examination showed notably higher values for diameter (p < 0.01), signal intensity (p < 0.0001), and aNMCNR (p < 0.05). On the other hand, the distal segment recorded the lowest values across all parameters. The aSNR and aNMCNR values confirmed good discrimination of each observed nerve.

The proposed benchmark for 3D CRANI MR neurography enhances the neuroradiological understanding of cranial and occipital nerves. It could act as a reference guide in various head and neck scenarios, particularly when distinguishing between healthy and pathological conditions.