In a case highlighted in February by BMJ Case Reports, an 84-year-old man admitted himself into the emergency room of a Belfast hospital on advice from his general practitioner after he complained of feeling unsteady and falling for several months. In the three days leading up to his hospital visit, his left arm and leg had noticeably weakened.
Still, there were no red flags in the man's medical history. The man was a nonsmoker and drank rarely, the article continued. A blood test detected nothing abnormal.
"There was no confusion, facial weakness, visual or speech disturbance", the doctors wrote.
The BMJ report, which was authored by Dr. Finlay Brown, also said that the patient was "otherwise fit and well" and had been living relatively independently at home with his family.
In other words, doctors thought, there was nothing apparent that would have suggested a clear reason for his symptoms.
But a head CT and MRI scan revealed that where the right frontal lobe of his brain should be, the patient had only a large, empty void, called pneumocephalus. He said he had not. Usually, such air pockets are seen-on a smaller scale-in those who have undergone brain surgery. In this man's case, the air cavity measured 3.5 inches at its longest point - an enormous size.
The tumour's formation and location had allowed for something of a "one-way valve effect" that had gradually contributed to the cranial air cavity, he added. "When the patient sniffed/sneezed/coughed he would most likely be pushing small amounts of air into his head".
Doctors were surprised to discover the cause - a large air pocket in his skull where part of his brain should be.
After consulting with specialists about surgery to release the air and remove the bone tumor, the man opted to skip any such intervention, given the risks. However, due to the man's age and current state of health, he is declining surgery. He was later discharged and put on a secondary stroke prevention program, after which his left-sided weakness appeared to have been resolved.
His nonsurgical approach is not without risk: It's likely the patient will be at a greater risk for infection, since there remains a passageway for air - and therefore bacteria and viruses - into his brain cavity, Brown said.
As more air got in, it slowly pushed the brain aside, said Brown. His brain was still there, it had just been squished out of the way by the pocket of air.
Brown told LiveScience he wanted to publish this case study to stress "the importance of thorough investigation of even the most common of symptoms", as an octogenarian's frequent falls and imbalance could have easily been written off.
"Because every now and then, there will be a rare [or] unknown causation of these that could be overlooked", he told the science news site.