Eighteen-month-old Roona Begum was diagnosed with hydrocephalus, in which cerebrospinal fluid builds up in the brain, just weeks after her birth in a government-run hospital in Tripura.
The potentially fatal illness has caused Roona's head to swell to a circumference of 91-centimetres (36-inches), putting pressure on her brain.
Her father, Abdul Rahman, 18, who lives in a mud hut with his family in the village of Jirania Khola, told AFP he prays for "a miracle" that will save his only child.
"Day by day, I saw her head growing too big after she was born," said the illiterate labourer who works in a brick-making factory.
Doctors told him to go to a specialist hospital in a big city such as Kolkata to get medical help but Rahman, who earns 150 rupees ($2.75) a day working in the brick plant, said he does not have the money to take her.
"It's very difficult to watch her in pain. I pray several times a day for a miracle - for something to make my child better," he said.
The US government's National Institute of Neurological Disorders and Stroke estimates about one in every 500 children suffers from hydrocephalus.
The most common treatment involves the surgical insertion of a shunt system to drain cerebrospinal fluid away from the brain and towards another part of the body where it can be easily absorbed into the bloodstream.
Cases like Roona's, where the head has doubled in size in a relatively short span of time, are extremely rare, according to leading 0neurosurgeon Sandeep Vaishya.
"It's difficult to assess the situation without seeing the patient, but a surgery, even at this late stage, would give her brain the best chance it has to grow and develop normally," Vaishya told AFP.
Vaishya, who is the head of neurosurgery at the privately run Fortis flagship hospital in Gurgaon, said that surgeries to treat hydrocephalus cases are "not particularly risky".
Although the cost differs from case to case, he estimated that a complex surgery like this one would cost about 125,000 rupees ($2,300) and require a three-day hospital stay.
Roona now is confined to her bed and unable to move her head but she is a playful child, quick to smile and giggle and is able to move her limbs, according to her father.
She has outlived an initial prognosis by doctors that she would survive only two months.
But her mother, Fatema Khatun, 25, says the little girl's health is getting worse and that she urgently needs help.
"She is deteriorating. She eats less and less, vomits often and I can see that she is getting thinner," Khatun told AFP.