Section of the cervical region of the spinal cord from a case of syringomyelia. In this condition a cystic degeneration begins in the region of the central canal and extends upwards and downwards in cylindrical form along a length of the cord, involving a number of segments. As it spreads out peripherally from the central canal, it involves quite early the anterior commissure of the cord, interrupting the spino-thalamic tracts which are decussating here. Consequently, it leads to bilateral loss of pain and temperature sensibility over a corresponding number of segments in the body. In later stages, the degenerative process extends out to the anterior horns, destroying the anterior horn cells (and thus leading to a wasting of the limbs). Still later it may involve the pyramidal tracts, and posterior column tracts, with a corresponding extension of motor and sensory disturbances. In this case, the condition affected the cervical region of the cord, and in its early stages led to a loss of pain and temperature sensation in both upper limbs. As the section shows, the disease became very extensive before the patient died, destroying the whole of the central region of the cord.