Playing in his 58th Test, Karunaratne was 46 not out when a rising Pat Cummins ball appeared to glance off his shoulder and onto his helmet, close to the neck area.
Canberra: Opener Dimuth Karunaratne was stretchered off in a neck brace after being hit by a bouncer on Saturday as Sri Lanka chased a massive Australian first innings total built on the back of three centuries.
In overcast conditions, the home team resumed day two of the second Test in Canberra on 384/4 and extended their lead to a massive 534/5 when skipper Tim Paine declared.
At stumps, Sri Lanka were 123/3 in reply with Kusal Perera on 11 and Dhananjaya de Silva not out one.
Paine's declaration looked premature given the ease with which Sri Lanka's openers weathered the new-ball attack led by under-pressure Mitchell Starc.
On a flat Manuka Oval track conducive to batting Karunaratne and Lahiru Thirimanne saw off some lightning quick deliveries and a bouncer barrage and had built an 82-run stand before disaster struck.
Playing in his 58th Test, Karunaratne was 46 not out when a rising Pat Cummins ball appeared to glance off his shoulder and onto his helmet, close to the neck area.
He slumped to the ground, dropping his bat as Australian players ran to assist.
A doctor and physio sprinted onto the ground and called for more medics and after some 10 minutes, he was put on a stretcher and taken off the field on a golf buggy.
Cricket Australia said he complained of pain in the neck and tingling to the hands and was taken to hospital to be assessed.
It clearly unsettled Thirimanne who fell to spinner Nathan Lyon for 41 in the next over, caught by Usman Khawaja at slip.
Cummins then clean-bowled Kusal Mendis for six and when captain Dinesh Chandimal gloved a Starc ball to Paine behind the stumps for 15, the tourists were in trouble.
Read Exclusive COVID-19 Coronavirus News updates, at MyNation.