Computerized tomographical study of dorsal neck muscles for insertion of EMG wire electrodes.

A computerized tomographical (CT) study of the main dorsal neck muscles was performed on 60 subjects (30 males and 30 females) in order to quantify individual anatomical variations and to describe valid means of accurately inserting intramuscular wire electrodes in these deep and superimposed muscle layers. Depth and thickness of transverso-spinalis (TS), semispinalis capitis (SSC) and splenius capitis (SPL) muscles were measured on a cross-sectional image of the neck at the level of the fith cervical vertebrae. Thickness and depth were significantly greater in males than in females. SSC and SPL thicknesses were less than 10 mm in most subjects and their depths were highly variable depending on the subject's morphology. TS was thicker but its depth was also variable. This CT study clearly demonstrated that the interindividual variations of dorsal neck muscles are important and CT may provide a valid way to position wire electrodes accurately in most cervical muscles.