title: Distance between intramuscular nerve and artery in the extraocular muscles: a preliminary immunohistochemical study using elderly human cadavers.
abstract: OBJECTIVE
  Extraocular muscles are quite different from skeletal muscles in muscle fiber type and nerve supply; the small motor unit may be the most well known. As the first step to understanding the nerve-artery relationship, in this study we measured the distance from the arteriole (25-50 μm in thickness) to the nerve terminal twigs in extraocular muscles.
  
  
  METHODS
  With the aid of immunohistochemistry for nerves and arteries, we examined the arteriole-nerve distance at 10-15 sites in each of 68 extraocular muscles obtained from ten elderly cadavers. The oblique sections were nearly tangential to the muscle plate and included both global and orbital aspects of the muscle.
  
  
  RESULTS
  In all muscles, the nerve twigs usually took a course parallel to muscle fibers, in contrast to most arterioles that crossed muscles. Possibly due to polyinnervation, an intramuscular nerve plexus was evident in four rectus and two oblique muscles. The arteriole-nerve distance usually ranged from 300 to 400 μm. However, individual differences were more than two times greater in each of seven muscles. Moreover, in each muscle the difference between sites sometimes reached 1 mm or more. The distance was generally shorter in the rectus and oblique muscles than in the levator palpebrae muscle, which reached statistical significance (p < 0.05).
  
  
  CONCLUSIONS
  The differences in arteriole-nerve distances between sites within each muscle, between muscles, and between individuals might lead to an individual biological rhythm of fatigue in oculomotor performance.
authors.affiliation: Department of Anatomy, Tokyo Dental College, Tokyo, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Kitamura
authors.affiliation: Department of Neurology, Wonkwang University School of Medicine and Hospital, Institute of Wonkwang Medical Science, 895, Muwang-ro, Iksan, Jeonbuk, 570-711, Republic of Korea. neurlogy@wonkwang.ac.kr.
authors.forename: Kwang Ho
authors.initials: KH
authors.lastname: Cho
authors.affiliation: Division of Physical Therapy, Ongoul Rehabilitation Hospital, Jeonju, Republic of Korea.
authors.forename: Hyung Suk
authors.initials: HS
authors.lastname: Jang
authors.affiliation: Department of Anatomy, Tokyo Dental College, Tokyo, Japan.|Division of Internal Medicine, Iwamizawa Asuka Hospital, Iwamizawa, Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Murakami
authors.affiliation: Department of Anatomy, Tokyo Dental College, Tokyo, Japan.
authors.forename: Masahito
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: Department of Anatomy, Tokyo Dental College, Tokyo, Japan.
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Abe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019412:Anatomy, Cross-Sectional; D001160:Arterioles / Q000033:anatomy & histology*; D002102:Cadaver; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D009801:Oculomotor Muscles / Q000098:blood supply* / Q000294:innervation*; D009802:Oculomotor Nerve / Q000033:anatomy & histology*
keywords: Arteriole; Extraocular muscles; Global and orbital layers; Human anatomy; Nerve; Poly-innervation