Subacute combined degeneration of the spinal cord: Current concepts of the disease process. Value of serum vitamin B 12 determinations in clarifying some of the common clinical problems

Abstract

Subacute combined degeneration of the spinal cord still poses many clinical problems, chiefly concerned with making an early diagnosis. The main reason for this difficulty is the lack of parallelism between the hematologic and neurologic manifestations. With the widespread administration of folic acid this problem has become more acute, since this drug may cause a hematologic remission for an indefinite period, while the neurologic signs worsen, often to an irreversible stage. Other problems concern the difficulty of distinguishing between intrinsic spinal cord disease of non-pernicious anemia type from combined system disease due to pernicious anemia; and of distinguishing pernicious anemia and subacute combined degeneration from other macrocytic anemias and their associated neurologic disturbances. In all these difficult clinical problems the estimation of vitamin B 12 in the serum affords a refined diagnostic method. A low serum B 12 level is a reliable index of B 12 deficiency, and may occur with or without hematologic and/or neurologic aberrations. It is particularly useful in the diagnosis of subacute combined degeneration of the cord when the anemia is mild or absent or when the anemia has been corrected by folic acid therapy. The practice of prescribing oral multiple vitamin preparations for patients with anemia, and more specifically of administering folic acid in the presence of vitamin B 12 deficiency, cannot be too strongly condemned.