Cerebral atrophy (brain shrinkage) in an infant: Sad story with a happy ending

1. 10-month old infant was brought by his parents with generalized weakness & lethargy for 4 months. His motor milestones had also slowed down. He was evaluated by a local pediatrician. 
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2. Thyroid profile was normal. MRI brain showed severe, diffuse cerebral atrophy (generalized shrinkage of brain).
Anticipating a neurodegenerative disease, pediatrician referred the infant for a neurologist’s opinion. 
I took a detailed history and ordered for a blood test.

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3. I reserved my opinion regarding prognosis, until the blood report came. I also did not want to send the infant for a series of investigations to rule out rare neurodegenerative diseases before seeing the blood test report. 
Mother was a strict vegetarian, which gave the clue.

4. The infant was exclusively breastfed.
The blood test- vitamin B12- was very low (<50 pg/ml).
We had the diagnosis now- severe vitamin B12 deficiency as a possible cause of diffuse cerebral atrophy in an infant. 
Whether brain atrophy would reverse or not remained questionable.

5. I discussed the diagnosis & treatment options with parents. They decided to defer further investigations at this stage, and first wanted to see the response to vitamin B12 supplements. 
Infant was started on vitamin B12 injections.

6. Clinical improvement was dramatic. Within a few days, the infant became active & energetic. His limb movements also improved. 
Head size that had remained smaller (for his age), started to grow faster in circumference.
The most heartening news was still awaited.
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7. MRI Brain done three months after starting vitamin B12 supplements showed that brain shrinkage had disappeared and no cerebral atrophy was evident now.
Within a space of 90 days, the world had totally changed for the infant as well as his parents. Happiness had replaced gloom!

8. Final diagnosis was: 
Severe vitamin B12 deficiency causing diffuse cerebral atrophy; which completely reversed with vitamin B12 supplements.
I am thankful to Prof U K Mishra Sir (Lucknow), from whom I learnt about a similar patient (presented in a medical conference). 

9. Take home message
*In an infant (born to a strict vegetarian mother) with cerebral atrophy (who is exclusively breastfed), it is important to check vitamin B12 level in blood.
*Vitamin B12 deficiency can be a reversible cause of cerebral atrophy in an infant.