Objective: Subacute combined degeneration (DSAC) of the spinal cord is a classic manifestation in the nervous system of vitamin B12 deficiency, clinically characterized by sensory ataxia due to the demyelinating commitment of thick fibers in the posterior cords, which can lead to disorders of movement secondary to proprioceptive loss such as pseudoatetosis occurs in this case.

Background: A 72-year-old patient with a 2-year history that begins with paraesthesia of the 4 extremities, progresses to hypoaesthesia in the hands, later in the feet associated with burning pain. Parallel to this he presented an unintended loss of 7kg the 6 months prior to his admission to the emergency room, as well as clumsiness in his hands and deterioration of the march that manifested as a slowing in the ambulation of which the patient refers to as a sensation of “walking between the clouds ”that ended up restricting the march completely.

Method: Blood count showed the presence of leukopenia with 3,890 whites, macrocytic anemia with hemoglobin of 8.7g / dl, high MCV of 110 fl. and mild thrombocytopenia 115,700mm3. Reduced vitamin B12 of 83 pg / ml and normal folic acid. EVDA biopsies with atrophic gastritis. Neuroconduction studies showed axonal sensory neuropathy of the 4 extremities, absence of the H reflex in the lower limbs with complete preservation of motor responses and F wave, suggestive of Ganglionopathy. MRI of the cervical-dorsal cord was carried out, showing marked hyperintensity of the dorsal horns throughout its entire length, with the presence of the inverted “V” sign, compatible with Subacute Combined Degeneration.

Results: Vitamin B12 deficiency,   these generates an abnormal insertion of even chain fatty acids, forming defective and unstable myelin sheaths.2 The selective demyelination of the posterior cords causes defects in proprioception and results in “pseudoatotic” movements that refer to the inability to keep the fingers in a fixed position when displaced by continuous involuntary movements, which differ from athetosis, due to its origin in sensitive deafferentation. 3

Conclusion: Vitamin B12 deficiency generates severe hematological and neurological complications, being an uncommon cause of myelopathy. Pseudoatetosis is a reversible sign of long-standing proprioceptive deficit. The DSAC due to vitamin B12 deficiency causes severe disability and is easily treatable, so it should always be considered in differential myelopathy diagnoses.

References: Cao J, Su ZY, Xu SB, Liu CC. Subacute Combined Degeneration: A Retrospective Study of 68 Cases with Short-Term Follow-Up. Eur Neurol. 2018;79(5-6):247-55. Stabler SP. Clinical practice. Vitamin B12 deficiency. N Engl J Med. 2013;368(2):149-60. Healton EB, Savage DG, Brust JC, Garrett TJ, Lindenbaum J. Neurologic aspects of cobalamin deficiency. Medicine (Baltimore). 1991;70(4):229-45.

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