The disability originates with impaired functioning of the anterior horn cells of the lower cervical cord (lower neck), but the cause of the decline is not fully understood and is still considered unknown. Researchers, including Hirayama, believe that "forward displacement of the cervical dural sac and compressive flattening of the lower cervical cord during neck flexion" is the contributing factor. Studies consistently note a loss of normal neck curvature (the cervical lordosis) and compression of the cervical chord by the dural sac in forward flexion. :"There is a debate about whether this condition represents a focal form of primary LMN degeneration (ie, a focal form of spinal muscular atrophy) or a local consequence of chronic compression from a dural expansion in the cervical spine." A familial link has been found in a minor percentage of cases, including parent-child and sibling-sibling. Because of the unusual distribution of the disease, some researchers speculate that there could be an ethnic link.
Monomelic amyotrophy
Congenital distal spinal muscular atrophy
Chondrodystrophy
Spinal muscular atrophy with lower extremity predominance 1
Hereditary neuralgic amyotrophy
Spinal muscular atrophy
Congenital muscular dystrophy
Spinal and bulbar muscular atrophy