Subacute combined degeneration (SCD) is a rare neurological complication of vitamin B12 deficiency, characterized by demyelination of the dorsal and lateral spinal cord. Herein, we describe three cases, who presented with SCD, one related to reduced intake of vitamin B12 because of a vegetarian diet and two related to nitrous oxide exposure during surgery. MR images of our patients revealed symmetrical hyperintense signals in dorsal and lateral columns in T2 weighted series. After treatment with intramuscular B12 injections (1 mg daily for 2 weeks, once weekly thereafter for three months) all patients showed improvement of their symptoms. Abnormalities of the spinal cord on MRI resolved in three months. In conclusion, SCD either due to nitrous oxide exposure or due to reduced intake of vitamin B12 is a reversible condition, when detected and treated early.
Vitamin B12 deficiency causes a wide range of hematological, gastrointestinal, and neuropsychiatric disorders [
A 58-year-old female patient presented with gradually worsening unsteady gait as well as numbness and tingling in hands and feet. She had undergone thyroidectomy operation 6 weeks before her admission, for which she had 60 minutes general anesthesia with nitrous oxide. At the time of admission neurological examination revealed slight weakness of distal muscles, bilaterally absent ankle jerk reflexes, bilaterally extensor plantar reflexes, and loss of position and vibration senses in all extremities. She could walk with assistance and Romberg’s sign was positive. Memory and other cognitive functions were preserved. Laboratory tests showed no anemia (hemoglobin: 12.4 g/dL; normal range 11.5–15.5 g/dL) but an increased mean corpuscular volume (MCV) (103 fL; normal range 80–100 fL). The level of vitamin B12 was low (143 pg/mL; normal > 211 pg/mL) while folate and serum copper levels were normal. Cerebrospinal fluid (CSF) examination was normal. Brain MRI was unremarkable. T2 weighted MRI of the cervical spinal cord showed high signal lesions in the posterior columns extending to the upper thoracic spinal cord (Figures
((a), (b)) At the baseline sagittal and axial T2 weighted MRI study, hyperintensity of the posterior columns can be seen in the cervical cord. (c) Posttreatment sagittal T2 magnetic resonance images showed total regression of the MRI abnormalities.
A 28-year-old man was admitted to the hospital with gait imbalance, unsteadiness, and numbness in hands and feet. He had a history of a generalized tonic-clonic seizure 6 weeks ago and his cranial MR images showed agenesis of the corpus callosum and a cystic lesion in the interhemispheric fissure. He had undergone ventriculoperitoneal shunting under nitrous oxide anesthesia 5 weeks before his admission. One month after the operation gait imbalance, unsteadiness and paresthesia were developed. Neurological examination revealed slight left hemiparesis and symmetrically increased patellar and ankle reflexes. Plantar reflexes were extensor. There was complete absence of vibration and proprioception senses in the lower limbs and impairment in the upper limbs. Romberg’s sign was positive. There was no sphincter dysfunction. Memory and other cognitive functions were preserved. Laboratory findings showed macrocytic anemia (hemoglobin: 9.9 g/dL and MCV: 101.3 fL) and decreased vitamin B12 level (<100 pg/mL). MRI of cervical and thoracic spinal cord showed symmetrical hyperintense signal changes on T2 weighted images of the posterior columns at C6-D3 segments (Figures
((a), (b)) Sagittal and axial T2 magnetic resonance images on patient admission showed T2 hyperintensity of the posterior columns. (c) Sagittal T2 magnetic resonance images 2 months later showed striking reduction of the MRI abnormalities.
A 44-year-old female patient presented with gradually worsening paresthesia and tingling of both hands and feet for 6 weeks. She had been taking a vegetarian diet for nine months. On neurological examination there was slight paresis of both hands. Deep tendon reflexes were increased and plantar reflexes were flexor. Proprioception and vibration senses were impaired in both hands and feet. Romberg’s sign was positive. She denied any bladder or bowel dysfunction. Memory and other cognitive functions were preserved. Laboratory investigations revealed macrocytosis but no anemia (hemoglobin: 13.5 g/dL and MCV: 110 fL). The serum vitamin B12 level was 135 pg/mL. Serum copper was 106
((a), (b)) Sagittal and axial T2 weighted images of the cervical cord before treatment demonstrate high signal bilaterally in the posterior columns of the cord. (c) The posttreatment images 2 months later show a striking reduction of the MRI abnormalities.
Vitamin B12 deficiency is a systemic disease that often affects the nervous and hematological systems. Megaloblastic anemia is a common early manifestation pointing to an underlying vitamin B12 deficiency, although neurological symptoms may occur in the absence of hematological abnormalities [
Methyl-vitamin B12 (Met B12) and 5′-deoxy-5′-adenosylcobalamin (Ado B12) are two physiologically active forms of vitamin B12 in the human body [
Pathways of intracellular vitamin B12 metabolism. MTHFR: methylenetetrahydrofolate reductase; 5,10-MTHF: 5,10-methylenetetrahydrofolate; 5-MTHF: 5-methylenetetrahydrofolate; THF: tetrahydrofolate; SAH: S-adenosyl homocysteine.
MRI findings in SCD can be diagnostically extremely helpful. MRI shows a very typical pattern with T2 hyperintense signal alterations usually confined to the posterior columns, which may involve the lateral columns and rarely brainstem [
Ataxic myelopathy might be seen in patients with copper deficiency. Copper deficiency myelopathy is associated with symmetric involvement of the pyramidal tract and posterior columns, and it shares same clinical and radiologic pictures with SCD. Therefore copper deficiency should be kept in mind in the differential diagnosis in patients with ataxic myelopathy. Malnutrition, prematurity, parenteral or enteral feeding without copper supplementation, gastrectomy, ingestion of copper-chelating agents, and excessive zinc therapy are among the most common causes of copper deficiency [
In conclusion a prompt diagnosis of SCD and early vitamin B12 treatment could avoid irreversible neurologic damages and prevent disability.
The authors report no conflict of interests in this work.