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LETTER TO EDITOR
Year : 2013  |  Volume : 61  |  Issue : 2  |  Page : 167-169

Reversible disconnection syndrome: An unusual presentation of vitamin B12 deficiency


Department of Neurology, King George Medical University, Lucknow, Uttar Pradesh, India

Date of Submission02-Dec-2012
Date of Decision10-Dec-2012
Date of Acceptance10-Mar-2013
Date of Web Publication29-Apr-2013

Correspondence Address:
Rajesh Verma
Department of Neurology, King George Medical University, Lucknow, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.111126

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How to cite this article:
Verma R, Raut TP, Praharaj HN. Reversible disconnection syndrome: An unusual presentation of vitamin B12 deficiency. Neurol India 2013;61:167-9

How to cite this URL:
Verma R, Raut TP, Praharaj HN. Reversible disconnection syndrome: An unusual presentation of vitamin B12 deficiency. Neurol India [serial online] 2013 [cited 2019 Aug 23];61:167-9. Available from: http://www.neurologyindia.com/text.asp?2013/61/2/167/111126


Sir,

Disconnection syndromes are a constellation of clinical features occurring as a result of, disruption of the cortical interconnecting fibers, alexia without agraphia is one such syndrome. [1] Stroke is the most common cause of this syndrome. Nutritional vitamin B12 deficiency is common in India. Rarely, it can cause transient splenial lesions, which improve with treatment. However, disconnection syndromes due to these reversible lesions have not been reported. We report a case of transient pure alexia and right homonymous hemianopia secondary to vitamin B12 deficiency.

A young male presented with recurrent episodes of difficulty in reading and difficulty in visualizing objects on his right side of 3 months duration. He had no difficulty in understanding spoken words and writing. Initially, these episodes were transient, which subsequently became fixed. On examination, he had pure alexia and right homonymous hemianopia with no other deficits. Investigations revealed a low serum vitamin B12 levels (158 pg/ml), elevated plasma homocysteine and urinary methylmalonic acid (MMA). Magnetic resonance imaging (MRI) revealed hyperintensity involving entire splenium on diffusion weighted imaging (DWI). Fluid attenuated inversion recovery (FLAIR) sequence revealed signal changes in the left half of splenium [Figure 1]. Computed perimetry revealed right homonymous hemianopia [Figure 2]. After 4 weeks of treatment with vitamin B12, there was complete clinical recovery. There was near normalization of his field defect [Figure 3] with complete radiological resolution of splenial lesion [Figure 4].
Figure 1: Magnetic resonance imaging sequences during fixed episode of disconnection syndrome (a) Diffusion weighted image showing hyperintensity of entire splenium (Boomerang). (b) Axial T2 Fluid attenuated inversion recovery showing hyperintensity in splenium more on the left side (Arrow). (c) Apparent diffusion coefficient Sequence showing hypointensity in the entire splenium. (d) Magnetic resonance Angiography showing hypoplastic right posterior cerebral artery P1 segment (normal variant)

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Figure 2: Computerized Perimetry during fixed episode of disconnection syndrome (a) Left eye Computed perimetry showing nasal hemianopia. (b) Left eye Patterned deviation showing nasal hemianopia. (c) Right eye Computed perimetry showing temporal hemianopia. (d) Right eye Patterned deviation showing temporal hemianopia

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Figure 3: Computerized Perimetry after 4 weeks of treatment (a) Right eye Computed perimetry showing near total resolution of temporal hemianopia. (b) Right eye Patterned deviation showing near total resolution of temporal hemianopia. (c) Left eye Computed perimetry showing near total resolution of nasal hemianopia. (d) Left eye Patterned deviation showing near total resolution of nasal hemianopia

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Figure 4: Magnetic resonance imaging Sequences after 4 weeks of treatment (a) Diffusion weighted image showing normalization of splenial hyperintensity. (b) ADC Sequence showing no obvious abnormality. (c) Axial T2 Fluid attenuated inversion recovery sequence showing normalization of splenial hyperintensity. (d) Axial T2-weighted image showing no obvious abnormality

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Splenial involvement results in the visual part of the disconnection syndrome. The most common etiology is ischemic or thromboembolic stroke. Other causes include transtentorial herniations, left occipital neoplasms, migraine, and brain abscess. [2] Our case initially had transient episodes, which later became fixed. Reported causes of transient alexia without agraphia include toxoplasma encephalitis with ring lesion in the left posterior white matter, herpes simplex encephalitis, mitochondrial cytopathy and left occipital lobe neurocysticercosis. [3]

Splenial hyperintense lesions are rarely encountered in clinical practice, often asymptomatic and occur as a result of cytotoxic or vasogenic edema due to a variety of neurological and non-neurological causes. Reversible lesions have been reported in an association with epilepsy and antiepileptic drugs, alcoholism, malnutrition, vitamin B12, and folate deficiency, trauma, diffuse axonal damage, infections, hydrocephalus, posterior reversible encephalopathy, lymphoma, fluid electrolyte disorders, extrapontine myelinolysis, hypertensive encephalopathy, and systemic lupus erythematosus. [4] These lesions are totally reversible and have not been reported in association with any disconnection syndromes. [5] Changes in DWI appear earlier than T2 and FLAIR. [5] Involvement can be oval, uniform with well-defined borders as described in patients with seizures or wider with less regular borders (Boomerang sign) mainly due to the hypoxic injury of corpus callosum.

Malnutrition including, vitamin deficiencies (folate and vitamin B12) have been postulated as a pre-disposing cause of splenial lesions. [6] Kori described a patient with B12 deficiency having reversible splenial lesion not associated with any disconnection syndrome. [7] Methylcobalamin deficiency leads to an increase in serum homocysteine and MMA, which is vasculotoxic and neurotoxic resulting in various neurologic complications. White-matter hyperintensities and areas of demyelination on brain MRI have been described in patients with vitamin B12 deficiency. [8] Similar T2-weighted hyperintense changes also occur in subacute combined degeneration which if recognized and treated early results in complete resolution of changes. Disorders such as central pontine myelinolysis, [9] Wernickes encephalopathy [10] have a multifactorial etiology along with vitamin deficiency resulting in white matter hyperintensities. Theeler et al. [11] reported a case of optic neuropathy and reversible splenial lesions post-gastrectomy due to nutritional deficiency suggesting a shared pathophysiology, which improved fully after treatment. Demyelination and white matter edema occurring due to the B12 deficiency results in splenial lesions (a form of extrapontine myelinolysis), which if treated early is entirely reversible.

 
  References Top

1.Adams RD, Victor M. Principles of Neurology 4 th ed. New York: McGraw Hill; 1989. p. 347-95.  Back to cited text no. 1
    
2.Quint DJ, Gilmore JL. Alexia without agraphia. Neuroradiology 1992;34:210-4.  Back to cited text no. 2
    
3.Verma A, Singh NN, Misra S. Transitory alexia without agraphia: A disconnection syndrome due to neurocysticercosis. Neurol India 2004;52:378-9.  Back to cited text no. 3
[PUBMED]  Medknow Journal  
4.Conti M, Salis A, Urigo C, Canalis L, Frau S, Canalis GC. Transient focal lesion in the splenium of the corpus callosum: MR imaging with an attempt to clinical-physiopathological explanation and review of the literature. Radiol Med 2007;112:921-35.  Back to cited text no. 4
    
5.Oster J, Doherty C, Grant PE, Simon M, Cole AJ. Diffusion-weighted imaging abnormalities in the splenium after seizures. Epilepsia 2003;44:852-4.  Back to cited text no. 5
    
6.Kosugi T, Isoda H, Imai M, Sakahara H. Reversible focal splenial lesion of the corpus callosum on MR images in a patient with malnutrition. Magn Reson Med Sci 2004;3:211-4.  Back to cited text no. 6
    
7.Kori S. Hyperintense splenium in vitamin B12 deficiency. Neurol India 2005;53:377-8.  Back to cited text no. 7
[PUBMED]  Medknow Journal  
8.Vry MS, Haerter K, Kastrup O, Gizewski E, Frings M, Maschke M. Vitamine-B12-deficiency causing isolated and partially reversible leukoencephalopathy. J Neurol 2005;252:980-2.  Back to cited text no. 8
    
9.Ramaekers VT, Reul J, Kusenbach G, Thron A, Heimann G. Central pontine myelinolysis associated with acquired folate depletion. Neuropediatrics 1997;28:126-30.  Back to cited text no. 9
    
10.Zuccoli G, Pipitone N. Neuroimaging findings in acute Wernicke's encephalopathy: Review of the literature. AJR Am J Roentgenol 2009;2:192.  Back to cited text no. 10
    
11.Theeler BJ, Wilson DJ, Crawford CM, Grazko M. Optic neuropathy and a reversible splenial lesion after gastric bypass: Shared pathophysiology? J Neurol Sci 2010;291:92-4.  Back to cited text no. 11
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

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