Intramedullary cystic lesions of the conus medullaris.

Intramedullary cystic lesions of the conus medullaris are rare. Although an extensive literature describes syringomyelia as being a frequent basis for cystic cervico-thoracic lesions it is apparent that this does not occur frequently in the lumbosacral region (Kirgis and Echols, 1949; Netsky, 1953; Rand and Rand, 1960; Love and Olafson, 1966). Poser (1956), in a review of 234 cases of syringomyelia, found that the cavity extended into the lumbosacral region in only 12-6% and in only five cases were the cavities restricted to the lumbosacral segments. Some authors (Thevenard, 1942; Andre, 1951) question the occurrence of syringomyelia in the lower spinal cord. Nevertheless a high incidence of constitutional defects has been noted among syringomyelia patients and members of their families, the most frequent of which are spina bifida occulta,pes cavus, syndactylism, andchest deformities (Henneberg and Koch, 1923; Chavany and Thiebaut, 1933; Thevenard and Coste, 1935; Jackson, 1949). These defects have been found to occur at times with cystic cavitations of the lumbosacral region, lending support to the developmental aetiology of at least some intramedullary cysts. Localized cysts of the conus and epiconus have also been reported in association with trauma, tumours, and vascular disease (Kirgis and Echols, 1949; Netsky, 1953; Hughes, 1966). Haemorrhage into the substance of the-cord has been described as a cause of cavitary disease following severe trauma. Liquefaction of the haemorrhage results in the formation of a fluid-filled cavity that may remain unchanged or slowly enlarge at the expense offunctioning neural elements. Sudden haemorrhage, of course, results in a rapid progression of neurological symptoms and the syndrome of haematomyelia. Cavitations may also be produced by vascular impairment to the cord structure from extraneural inflammatory or compressive pathology. Another process of cyst formation may be ischaemic necrosis of the cord with resulting liquefaction. Irrespective of the aetiology, these cysts may simulate the clinical picture of syringomyelia. The cases of cysts of the conus medullaris reported here simulated the clinical picture of syringomyelia, tumour, or lumbar disc disease. The radiographic findings in each case were interpreted as indicating the presence ofan intramedullary tumour. The correct diagnosis was made in each case only at operation.