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Neurology India
Medknow Publications on behalf of the Neurological Society of India
ISSN: 0028-3886 EISSN: 1998-4022
Vol. 52, Num. 4, 2004, pp. 507-509

Neurology India, Vol. 52, No. 4, October-December, 2004, pp. 507-509

Short Reports

Vitamin B12 deficiency presenting with an acute reversible extrapyramidal syndrome

Neurology Unit, Department of Neurological Sciences, Christian Medical College Hospital, Vellore - 632004
Correspondence Address:Department of Neurological Sciences, Christian Medical College Hospital, Vellore - 632004, Tamilnadu,

Code Number: ni04171


Vitamin B12 deficiency usually presents with pernicious anemia or various neuropsychiatric manifestations. Commonly seen neuropsychiatric manifestations include large fiber neuropathy, myelopathy (subacute combined degeneration of the spinal cord), dementia, cerebellar ataxia, optic atrophy, psychosis and mood disorders. The present report highlights an unusual presentation of vitamin B12 deficiency- acute onset extrapyramidal syndrome in a 55-year-old man. The patient presented with a 10-day history of slowness of all activities including a slow gait, mild tremors of hands and low volume speech. On examination, he had features of mask-like facies, reduced blink rate and cogwheel rigidity. He was investigated for the possible causes and was found to have laboratory features of vitamin B12 deficiency. Other causes for acute onset parkinsonism were excluded by appropriate investigations. He showed a dramatic improvement following treatment with intramuscular vitamin B12 injections. At a five-year follow up, he was found to be functionally independent with no neurological deficits.

Key Words: Vitamin B12, Neuropsychiatric manifestations, Acute extrapyramidal syndrome, Parkinsonism


Vitamin B12 deficiency resulting in various neuropsychiatric abnormalities such as neuropathy, myelopathy, myeloneuropathy, dementia, cerebellar ataxia, optic atrophy, psychosis and mood disturbances is well known.[1] In addition, recurrent seizures have been reported as a rare manifestation of vitamin B12 deficiency.[2] Extrapyramidal system involvement in the form of involuntary movements is common in infants, whereas similar involvement in adults has been described only recently.[3] However, acute onset parkinsonism has not been reported and this report describes one such patient.


55-year-old man presented with bradykinesia and tremors of hands of ten days duration. There was no history of seizures or altered sensorium. On examination, he had expressionless face and reduced blink rate. Higher mental functions were normal. Speech was hypophonic and saccadic eye movements were slow. He had cogwheel rigidity of all limbs and resting tremors of both hands. Tendon reflexes were normal except for sluggish ankle jerks. Plantar reflexes were extensor. Sensory, cerebellar and autonomic systems were normal. His Hoehn and Yahr score was stage III.

There was no preceding history of encephalitis or prior use of antipsychotic or antiemetic medications. He had no risk factors for atherosclerosis. There was no history of exposure to carbon monoxide or organophosphate compounds. He consumed non-vegetarian diet.

Investigations were as follows: Hemoglobin was 10.2 G%, reticulocyte count was 0.1% and mean corpuscular volume (MCV) was 118 fl. Blood picture showed hypersegmented neutrophils and bone marrow showed features of severe megaloblastic anemia. Serum vitamin B12 level was 5 pg/ml and folate was 98 ng/ml. Anti-intrinsic factor antibody was positive and antral biopsy showed features of atrophic gastritis. Work up for malabsorption was negative. Serum parathormone, ceruloplasmin and thyroid function tests were normal. HIV (ELISA) was negative. CT scan of the brain and cerebrospinal fluid analysis were normal.

A diagnosis of acute onset parkinsonism with mild myeloneuropathy secondary to vitamin B12 deficiency was made. He was started on vitamin B12 injections at a dose of 1000 mg/day with which he showed improvement within three days. At the time of discharge at seven days, he had mild bradykinesia, no tremors and was functionally independent. He was advised to continue injections once a week for four weeks and monthly thereafter. He has been followed up periodically since then and at the last follow up at five years, he had no neurological deficits.


This patient presented with acute onset parkinsonism secondary to vitamin B12 deficiency. Typical laboratory features supported the diagnosis and other causes of acute parkinsonism [Table - 1] were excluded. Marked improvement with vitamin B12 therapy further strengthened the diagnosis.

Extrapyramidal involvement due to vitamin B12 deficiency in adults is rare and previously reported features include myoclonus-like involuntary movements[3] and chorea and focal dystonia.[4] There are no previous reports of acute parkinsonism due to vitamin B12 deficiency. The mechanism of extrapyramidal involvement in vitamin B12 deficiency is incompletely understood. However, indirect evidence may be obtained from two facts. Firstly, methymalonic acidemia (MMA), an inborn error of metabolism, usually presents with acute extrapyramidal syndrome in infants, and some cases respond to vitamin B12 therapy. Brain imaging and autopsy studies in MMA have shown symmetrical involvement of basal ganglia.[5] Secondly, folates interact with excitatory kainic acid receptors in mammalian brain and have agonistic activity at these receptors. Since kainic acid is a potential neurotoxin, folate too may share this property. Methytetrahydrofolate levels are markedly elevated in vitamin B12 deficiency and may be responsible for neuronal destruction. Injection of kainic acid into the basal ganglia in experimental animals leads to a pattern similar to Huntington′s chorea.[6]

In conclusion, acute onset extrapyramidal syndrome can be a rare manifestation of vitamin B12 deficiency, which is reversible with therapy. Serum B12 levels should be checked in patients who do not have an obvious cause for an acute extrapyramidal syndrome.


1.Healton EB, Savage DG, Brust JC, Garrett TJ, Lindenbaum J. Neurologic aspects of cobalamin deficiency. Medicine (Baltimore) 1991;70:229-45.  Back to cited text no. 1  [PUBMED]  
2.Kumar S. Recurrent seizures: An unusual manifestation of vitamin B12 deficiency. Neurol India 2004;52:122-3.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]
3.Celik M, Barkut IK, Oncel C, Forta H. Involuntary movements associated with vitamin B12 deficiency. Parkinsonism Relat Disord 2003;10:55-7.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Pacchetti C, Cristina S, Nappi G. Reversible chorea and focal dystonia in Vitamin B12 deficiency. N Engl J Med 2002;347:295.  Back to cited text no. 4  [PUBMED]  
5.Larnaout A, Mongalgi MA, Kaabachi N, Khiari D, Debbabi A, Mebazza A, et al. Methylmalonic acidaemia with bilateral globus pallidus involvement: A neuropathological study. J Inherit Metab Dis 1998;21:639-44.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Brennan MJ, van der Westhuyzen J, Kramer S, Metz J. Neurotoxicity of folates: Implications for vitamin B12 deficiency and Huntington's chorea. Med Hypotheses 1981;7:919-29.  Back to cited text no. 6  [PUBMED]  

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