Clinical And Basic Study Of Subacute Combined Degeneration Of The Spinal Cord

Objective: To investigate the clinical, neuroelectrophysiologic, neuropathologic and magnetic resonance imaging (MRI) characteristics of patients with subacute combined degeneration (SCD) of the spinal cord, and evaluate the significance of neuroelectrophysiological examinations and MRI in the diagnosis of SCD.Materials and Methods: The clinical data were collected in 38 cases of SCD. Their serum Vitamin B₁₂ and folic acid were measured in 34 cases and the serum homocysteine was measured in 15 cases. Their serum Vitamin B₁₂ and folic acid were compared before and after treatment in 20. All the patients underwent electromyogram, nerve conduction and somatosensory evoked potentials (SEP) of tibial nerve. 13 of them were given visual evoked potentials (VEP), 8 underwent brainstem auditory evoked potential (BAEP) and 4 were undertaken the biopsy of sural nerve. According to their clinical findings 33 patients were undertaken MRI study which was included sagittal T1 weighted image, T2 weighted image, and axial T1 weighted image and T2 weighted image. 10 of them were scanned after Gd-DTPA enhancement intravenously.Results: (1) All the cases represented variable extent in symptoms and signs of dorsal and dorsallateral column, and/or peripheral neuropathy. (2) In 25 of them, the serum level of Vitamin B₁₂ and folic acid were below the normal range and in 7 patients, the folic acid was below the normal respectively, and in 6 patients, the serum homocysteine was higher than the normal. (3) All the eletromyogram was normal except two patients. 41 motor nerves' and 70 sensory nerves' conducts were abnormal, 67 tibial mervi of SEP, 16 sides of VEP and 5 sides of BAEP were abnormal. (4) Under the light microcopy, the biopsy of sural nerve showed segmental loss of myelin sheaths in different extent, incrassation, regeneration, atrophy and inflammatory cell infiltration. Occasionally, fibers showed axonal degeneration, rupture and imperfect. The Schwann cells showed hyperplasia. Electron microscopy showed sparseness, delamination, degeneration, twist, and dissolution in medullated nerve fiber. Vacuoles were irregular in marrowless fiber. Someshowed regeneration fiber, degeneration axonal. The stroma was thicken and collagen fibers were edema and hyperplasia. (5) Among the 33 cases undertaken central nervous system MRI study, T2 weighted image showed high intensity signal in posterior column of the spinal cord in 14 cases, and high intensity signal in the lateral column in 8 of them. Those findings were in accordance with the clinical manifestation, and no enhancement was found after administration of Gd-DTPA. (6) Compared with the serum Vitamin Bi2 and folic acid before and after the treatment respectively, the former value of t=6.71, P=0.000, the later value t=1.44, P=0.166. (7) Compared with the correlation between the extent of nervous system lesion and the course of diseases, the pearson=0.052, P=0.758. Between the former and mean cell volume (MCV), pearson=0.33, P=0.043<0.05.Conclusions: (1) The diagnosis of SCD must be depended on clinical manifestation and the measurement of serum level of Vitamin Bn, but the later was not the only standard. It is necessary to measure the value of homocysteine, espicialy when the serum Vitamin B12 was normal. (2) Neuroelectrophsyology examination correspond with SCD was also used to monitor responses to therapy and the changes of disease. Nerve conduction of peripheral nerve showed that the main lesion of nerve was loss of myelin sheaths. Abnormal of SEP proved the direct evidence of the lesion of posterior columns. Abnormal of VEP and BAEP proved that the second way of the lesion of visual and audition nerve conduction gateway were damaged. (3) The biopsy of sural nerve showed that the main lesion also was loss of myelin sheaths, and occasionally fibers showed axonal degeneration. (4) MRI study was helpful in the diagnosis of SCD, especially when the serum level of Vitamin Bn was in normal range. (5) Our observation also suggested that the extent of nervous system lesion was not related to the course of the diseases but related to the value of MCV. There was statistical value compared with the serum of B12 Vitamin before and after the treatment but no statistical value in folic aicd .