“I use a spoon instead of a fork, so I spill less,” the patient said. “I eat sandwiches and hamburgers so I can use both hands to hold my food.”

He was 73 and had suffered from essential tremor for the past decade. His hands would shake uncontrollably, more on the right than on the left, which would worsen if he tried using them.

“I could still do crowns, but giving injections became impossible,” he said. His disease, gradual and grasping, had forced the Baltimore-area dentist into early retirement.

The patient, who is not being named to protect his privacy, was going to undergo surgery to treat his tremor, which I was curious to observe. I headed to the MRI exam suite to meet him.

“It’s embarrassing,” he admitted. “It is not the way I want to live. I can’t write my own name anymore.”

The dentist had even parted with his hobbies. Painting, playing guitar and doing handiwork around the house were further victims of his disease. His wife, his right hand in his practice, assisted him however she could in his retirement, but it wasn’t the same.

He decided to be treated with MRI-guided focused ultrasound surgery.

In this bloodless surgery, 1,000 transmitters housed in a water-cooled helmet produce sound waves, all directed at a single spot in the brain. Where these waves merge, they increase the temperature of the tissue, and ultimately burn a hole the size of a sesame seed in the brain.

The neurosurgeon pinned a metal frame around his head. New MRI scans performed with this frame holding his head in place were aligned to his prior brain imaging, enabling a computer to precisely navigate his anatomy in 3-D space.

He lay down on the MRI table, with his bare scalp to the helmet. I peered over and asked him how he was faring.

“I feel fine,” he said, “I’m used to looking at people upside down anyway.”

A wall of glass separated him and the table from us, a team of his doctors and nurses. We were in a mission control center, but with sights on the cerebral, not the celestial.

Our target was a portion of his left thalamus, which controls his right side. An omniscient satellite, this dense collection of neurons receives data on sensation and movement in the right body and transmits it to the rest of the brain.

Like cartographers, the neurosurgeon and neuroradiologist measured and directed the initial position of the sound waves.

Here, more than most areas, the brain’s anatomy is unforgiving. One false millimeter in the wrong direction could mean transient or permanent side effects such as arm numbness or a wobbly gait. Each dose of sound applied to the brain can be tested first with a lower intensity, to check for reduced tremor and these effects, before the intensity is increased, and the lesion is made permanent.

This energy was intermittently applied to the target. With each application, a neurologist tested the patient’s right hand tremor, asking him to trace between two lines and to draw a spiral. This millimeter march progressed for two hours, until the neurologist tested his tremor one more time.

“If you had this control, this exact control for the rest of your life, would you be happy?” he asked our patient.

“Extremely happy,” he responded.

With that, his treatment ended. He was gently helped off the table. The head frame was removed and his scalp dried. A nurse gave him a pen and paper to demonstrate his control. He signed his name with delight, grinning at his penmanship.

His wife and son, brimming with anticipation, were brought in to see him. Their eyes met the papers he’d been writing on.

“That is your signature,” she asked in disbelief. “You did this?”

In his raw account of his neurosurgery training, “When the Air Hits Your Brain,” Frank Vertosick Jr. insists upon knowing the patient. “To have the audacity to cut into a person’s brain without the slightest clue of his life, his occupation . . . I find that most simply appalling,” he cautions.

There is no cutting in focused ultrasound surgery, but Vertosick’s words resurfaced in my mind as I watched a once tremulous dentist enjoy his recaptured freedom. To this man, itself a Latin root meaning hand, his dexterity was his livelihood.

With a steady hand, a first in years, he signed his name again for his wife.

Science is still explaining our patient’s tremor, and why interrupting the circuits in the thalamus as we did can treat it. Still, with such improvements, MRI-guided focused ultrasound surgery is being investigated for treating several neurological diseases. In a landmark trial for one-sided hand tremor, this procedure reduced symptoms significantly, and improved patients’ ability to eat, drink, dress themselves, write, work and socialize.

We were discussing this on a phone call two months after that day.

“I’ve been playing guitar, and I’m going to start painting again,” he said. “Ninety to 95 percent of my tremor is gone.”

With one set of frequencies and amplitudes, sound can burn a hole in the brain, with another, we hear the strumming of a guitar.

In neurosurgery, we are used to performing heroics. Within narrow time scales, we try to stave off human mortality. In cases like these, we hope to provide another, equally important aspect to life — quality.

We try to look for context when we meet patients. We ask about likes, hobbies, occupations. As healers, it helps us understand what we should be working toward. It helps us see the life behind the disease.

A shaky hand can have a large footprint.

Abdul-Kareem Ahmed is a resident in the Department of Neurosurgery at the University of Maryland Medical Center.