(Polenov Research Neurosurgical Institute, Saint Petersburg, Russia)
It is known, that normal localization of the spinal cord cone in adults varies, correlating with a body length. It can be localized at the level of the lower third of the 12th thoracic vertebra or a disk between the 2nd and 3rd lumbar vertebrae. At birth it is usually found between the bodied of the 3rd and 4th lumbar vertebrae and then it shifts upwards. Presence of data, indicative of a thick (more than 1.0-1.5 mm in diameter) terminal thread and a bit low (L2-L3) localization of the spinal cord cone, was not regarded by us as manifestation of some pathology. A clinical picture and MRI findings were the basis for diagnosis of syndrome of the fixed spinal cord (SFSC) in all cases.
SFSC in a lumbosacral area was diagnosed in 17 cases; it bore a relation to the thoracic spine in 2 cases (diastematomyelia at the level of Th6 and spinina bifida occulta at the level of Th3).
Clinical manifestations of SFSC were characterized by three groups of symptoms:
A clinical manifestation of the disease was strongly dependent on a dysraphic status of a patient. At the same time it was found out, that trauma (6) and physical loads (3) led to the disease progression.
An average number of dysraphic signs in one patient with SFSC was 5.3.
It turned out, that SFSC can be confirmed only by methods of radiation diagnosis. Plain films of 19 patients were indicative of spina bifida occulta, involving 2 and more vertebrae. At the same time there was scoliosis (8), which progressed and was accompanied by paresis of the lower extremities and augmentation of urinary bladder dysfunction. Myelograms with omnipaque showed, that subarachnoid space did not coat all sides of the spinal cord and horse's tail in 3 cases. The horse's tail root did not come off a posterior semisphere of a dural sac in a face-down position; it was indicative of possible presence of a fixed root of the spinal cord.
Use of MRI ensured visualization of signs of the fixed spinal cord. A level of the cone localization was seen quite clearly. MRI examination was carried out in sagittal and axial views. Fat was identified on sagittal and axial views without any difficulty, due to its high intensity on T1 sections. MRI diagnostic criterion of the fixed spinal cord was dislocation of the spinal cord below L2.
Surgical treatment of patients with pathology at the level of the lumbosacral spine lay in freeing the spinal cord and its roots from dense scarry tissue by its cutting off from cicatrices, lipomas or other fixing factors, as well as by dissection of a thickened short terminal thread. As a rule, after dissection this stretched terminal thread became 0.5-1.5 cm shorter.
All patients were in a face-down position during 21 days after an operation. It was done with the purpose of preventing repeated fixation of the spinal cord, which shifts in the direction of an anterior part in this position.
The results in the nearest postoperative period were as follows: pain regressed in 9 patients; strength of muscles increased in 5 cases; enuresis turned into urine retention in 3 cases; enuresis was watched only at nights and was not constant in 5 patients. There was no progressive spinal deformity, pain in the back in 8 patients in a year after an operation; besides considerable improvement of functions of pelvic organs was watched in all of them. There is no information about the rest 6 patients.
Thus, MRI allowed to diagnose SFSC in 16 out of 19 cases with this pathology. All the patients with the fixed spinal cord were operated on the basis of MRI and myelography findings. Treatment consisted in laminectomy and freeing of the spinal cord and its roots from fixing structures (lipoma, bony formations, congenital trabeculae, postoperative cicatrices and ligatures).
Data of an operation and MRI examination were indicative of low localization of the spinal cord cone. Usually the spinal cord was fixed to a dorsal surface of dura mater. There was scarry tissue in a caudal segment of the spinal cord in all cases. Its visualization with the help of MRI was insufficient.
MRI data in a fixed root of the horse's tail were less informative. But the picture became much clearer, when contrast myelography was used.
On the whole, MRI allowed to identify a low position of a terminal segment of the spinal cord, intradural lipoma, diplomyelia and bony formations quite clearly.
Comparative study of MRI and surgical findings in patients with SFSC makes us believe in usefulness of MRI as an initial means of examination of cases with suspected SFSC. May be, it is the only method of diagnosis of this disease, existing at present moment.
The goal of surgical treatment was preventing progression of neurologic deficit and orthopedic deformities, improvement of functions of pelvic organs.
It is expedient to make an operation as early as possible due to a progradient character of SFSC course.