Morphometric quantification of the cervical limb motor cells in various neuromuscular diseases.

The number of motor cells was significantly reduced in the C8 segment of the cervical spinal cord in all 12 cases of amyotrophic lateral sclerosis (ALS), in the C6 and/or C8 segments in 1 case of adult onset spinal muscular atrophy, 2 cases of Werdnig-Hoffmann (W-H) disease, 3 of 4 cases of chronic polyneuropathy and in 1 case of poliomyelitis and 1 of ossification of the posterior longitudinal ligament in the cervical spine (OPLL). The numbers of motor cells were normal in the C6 or C8 segment in 6 cases of muscular dystrophy, except in one case of congenital muscular dystrophy, who showed reduced numbers of the motor cells. Examination of the distribution of motor cells per 500 micrometers thickness in serial sections revealed that reduction in numbers of the motor cells was diffuse and symmetrical in half the cases of ALS and W-H disease and in the cases of chronic polyneuropathy and congenital dystrophy; diffuse but asymmetrical in the other ALS and W-H disease cases and in a case of adult spinal muscular atrophy, and localized and asymmetrical in the cases of poliomyelitis and OPLL. In muscular dystrophy the distribution of motor cells showed segmental variations similar to controls.