Apr 13, 2011
Spinal Intradural Cysts
During the normal development of the human embryo. a trilaminar germ disc is formed during the third week of development. The outer layer, the ectoderm faces the amniotic cavity. The inner layer, the endoderm faces the yolk sac in the opposite direction. Between these lies the mesoderm. The mesodermal cells that will give rise to the notochord pass forward from Hensen's node under the ectodermal surface. By the eighteenth day, the floor of this tubular notochord and the underlying endoderm disintegrate. The notochordal canal, now known as the neurenteric canal. connects the yolk sac and the amniotic cavity through the blastopore. Thus there is a temporary direct connection between the anlagen of the spinal cord, spine and gastrointestinal tract.
Knowing this, one would predict that malfunctions at this stage of development might result in combined anomalies of the spinal cord, spine and gut. In fact, such combined anomalies have been recognized since the nineteenth century and were classified by Feller and Sternberg in 1929. In 1960, Bentley and Smith unified to some degree the previous hypotheses of the origin of neurenteric malformations, especially those of Feller and Sternberg 1929 and Saunders ( 1943), under the label the split notochord syndrome.
On the basis of different embryologic information. one would expect to occasionally encounter neurenteric cysts within the spinal canal, and such is the case. Between 1926 and 1972, at least 47 intraspinal neurenteric cysts (also known as enterogenous cysts, endodermal cysts, archenteric cysts, gastrocystomas, intestinomas, cystic teratomas, foregut cysts. etc.) were reported. Wilkins and Rossitch subsequently reviewed 72 additional cases of a similar nature. Of the 119 patients. 76 were male and 43 were female. In some instances. abnormalities were noted at birth. The diagnosis was established during the first decade in 41 (34 percent) patients and in the second decade in 27 (23 percent) patients. Only eight of the patients were 50 years old or older.
Of the 119 cysts. 63 were totally or partially in the cervical spinal canal. 53 were totally or partially in the thoracic spinal canal. and 27 were totally or partially in the lumbosacral canal (cysts at the cervicothoracic junction were counted in both cervical and thoracic categories. and cysts at the thoracolumbar junction were counted in both thoracic and lumbosacral categories). The most common cervical or thoracic cyst location (in 57 cases) was anterior or anterolateral to the spinal cord, perhaps with intramedullary involvement as well.
Pathologically, these cysts vary in composition and complexity and form a spectrum that merges with intraspinal teratomas on the one hand and intraspinal dermoids and epidermoids on the other. The simplest examples of intraspinal neurenteric cysts are those lined by a single layer of simple. pseudostratified. or stratified cuboidal or columnar epithelial cells. with or without cilia, lying on a basement membrane and supported by a layer of more or less vascular connective tissue. Varying numbers of the epithelial cells can be demonstrated to contain mucin by appropriate stains. The more complex types have a similar epithelial lining but, in addition, they have one or more of the other elements found along the course of the gastrointestinal tract or tracheobronchial tree.
Intraspinal neurenteric cysts cause the neurological symptoms and signs and the radiologic features one would expect from any slowly enlarging intraspinal mass. Pain in the affected region of the spine is a common and prominent symptom. which may be accompanied by appropriate radicular pain or by meningismus. Unless an early diagnosis is made, the total course of the illness is usually prolonged over many years, often marked by remissions and exacerbations.
Myelography with postmyelographic CT and/or MRI are the best techniques at present for visualizing intraspinal neurenteric cysts and their coexisting vertebral abnormalities. In addition, plain roentgenograms and tomograms may add to the identification and depiction of the vertebral abnormalities. such as anterior or posterior spina bifida, widened vertebral bodies, fused vertebrae, hemivertebrae, and diastematomyelia.
The treatment of intraspinal neurenteric cysts is surgical. They are frequently adherent to the spinal cord or cauda equina to the extent that complete excision is not feasible. but even so. evacuation and partial resection of these lesions is usually followed by the same good results as complete excision. In either case, neurological function usually improves and recurrence after partial resection may take years to become symptomatic.