[Intraneural topography of the median nerve at the elbow level--an analysis using intraneural neurography].
We examined intraneural topography of the median nerve at the elbow level by means of intraneural neurography in 38 individuals. A tungsten microelectrode was inserted into the median nerve trunk at the elbow where largest amplitude of the nerve action potential could be obtained with stimulations over median nerve trunk at the wrist. Each of six areas innervated by the nerve was stimulated supramaximally. The ratio of the amplitude of the nerve action potentials stimulated in each area to that stimulated over median nerve trunk at the wrist was arbitrary defined as territory index. the territory indices of six areas, i.e., thumb, index finger, middle finger, ring finger, little finger and thenar area, were 12%, 14%, 15%, 7%, 0% and 5%, respectively. Based on the investigation of permutations and combinations, the cutaneous fibers in the median nerve trunk at the elbow may be arranged in order of thumb-index-middle-ring fingers from the radial side, and the muscle fibers to the thenar muscles may be located at the palmar side to the index finger area. These results were in accordance with the previous reports obtained by near nerve recordings or anatomical analysis at the wrist. In 42% of the subjects a part of fibers in the median nerve were considered to innervate also little fingers, even though territory index was very small. This method has made it possible to estimate the intraneural topography of the median nerve at the elbow level and to detect Martin-Gruber anastomosis with a small number of sensory fibers.
Hasegawa
O
O
Department of Neurology, Yokohama City University School of Medicine, Japan.
Ohta
S
S
Komiyama
A
A
Kurita
R
R
Nara
Y
Y
D000200:Action Potentials; D000293:Adolescent; D000328:Adult; D000368:Aged; D004550:Elbow / Q000294:innervation*; D004558:Electric Stimulation; D004568:Electrodiagnosis; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000033:anatomy & histology / Q000502:physiology*; D008839:Microelectrodes; D008875:Middle Aged