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|LETTER TO EDITOR
|Year : 2015 | Volume
| Issue : 3 | Page : 430-431
Vigabatrin-induced reversible changes on magnetic resonance imaging of the brain
Charul Goyal1, Tejas H Kapadia1, Pradnya Gadgil2, Darshana Sanghvi1
1 Department of Radiology, Kokilaben Dhirubhai Ambani Hospital and Medical Research Institute, Mumbai, Maharashtra, India
2 Department of Paediatric Neurology, Kokilaben Dhirubhai Ambani Hospital and Medical Research Institute, Mumbai, Maharashtra, India
|Date of Web Publication||5-Jun-2015|
Department of Radiology, Kokilaben Dhirubhai Ambani Hospital and Medical Research Institute, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Goyal C, Kapadia TH, Gadgil P, Sanghvi D. Vigabatrin-induced reversible changes on magnetic resonance imaging of the brain. Neurol India 2015;63:430-1
Infantile spasms (ISs), a rare subtype of seizure disorder, manifests in infancy and early childhood. Vigabatrin (VGB), an irreversible inhibitor of γ-amino-butyric acid (GABA) transaminase (GABA-T), is a first-line drug used in the management of ISs.  Here, we present an uncommon case of VGB-induced reversible changes on magnetic resonance imaging (MRI).
A 7-month-old girl presented with seizures at 3 months of age. Initially, the seizures were focal clonic and treated with carbamazepine. At 4 months of age, she developed IS and was started on VGB (135 mg/kg/day). An MRI of the brain was requested to evaluate the cause of IS. The patient had completed 6 weeks of VGB therapy at the time of the MRI study. Symmetric restricted diffusion was seen in the globi palladi, thalami and dorsal brainstem along the dorsal tegmental tracts [Figure 1]. Clinical reassessment showed no corresponding new symptoms or examination findings to explain the signal alterations in the deep grey nuclei and brainstem. Also noted were focal areas of polymicrogyria in the right frontal and left temporal lobes [Figure 2], explaining the probable etiology of IS. In view of the changes seen on MRI, VGB was withdrawn. A repeat MRI was performed 8 weeks after the withdrawal of VGB; it showed resolution of the above mentioned findings, establishing the reversible nature of these MRI changes [Figure 3].
|Figure 1: Diffusion-weighted images (a-c) and apparent diffusion coefficient images (d-f) demonstrate a symmetrical restricted diffusion in the globi palladi, thalami and dorsal brainstem along the dorsal tegmental tracts|
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|Figure 2: Oblique coronal T2-weighted magnetic resonance imaging shows polymicro-gyria in the left temporal lobe|
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|Figure 3: Follow-up magnetic resonance imaging. Diffusion-weighted images (a-c) and apparent diffusion coefficient images (d-f) demonstrate resolution of the diffusion abnormality in the globi palladi, thalami and dorsal brainstem along the dorsal tegmental tracts (as seen in Figure 1)|
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A literature search showed VGB-induced MRI changes in approximately one-third of patients.  These were seen in children below 18 months of age and were demonstrated to be reversible. , No clinical changes were documented correlating with these imaging findings. A few studies attributed these findings to intra-myelinic edema and microvacuolation as a result of fluid accumulation and separation of the outer layers of the myelin.  One study conducted by Simao et al., however, showed that axonal abnormalities might have contributed to the altered signal intensities on MRI rather than changes in myelin.  The precise etiology of these changes remains unclear.
In conclusion, restricted diffusion in the deep gray nuclei and brainstem is an uncommon but documented finding in infants on VGB and should not be mistaken for a more ominous pathology. The neurologist/pediatrician and radiologist need to be aware of VGB-induced reversible MRI changes, as misdiagnosis as mitochondrial or amino acid metabolism disorders may trigger unwarranted investigations and unnecessary concern for the family.
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[Figure 1], [Figure 2], [Figure 3]
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