Buzz
At first glance, Elena del Peral appears to be a typical high-achieving college senior. She enjoys spending time with friends on the campus quad at Massachusetts’ Curry College, shares photos of birthday celebrations on Facebook, and excels academically, earning a spot on the dean’s list. She works at a foundation dedicated to childhood cancer and is known for her cheerful, intelligent, and active demeanor. One of her most notable quirks is wearing both a Yankees cap and a Red Sox jersey simultaneously, symbolizing her role as a mediator between the two rival teams.
However, what truly sets her apart lies beneath her cap: Elena del Peral possesses just half of her brain.
Image courtesy of Elena del Peral
Soon after her birth in 1992, Elena’s parents observed that she favored her right side. As a toddler, she only used her left arm to move around, keeping her right arm close to her chest. By 18 months, she began experiencing intense seizures, and at two years old, she had a major tonic-clonic seizure during a family trip to the Adirondack Mountains. Determined to find the cause of her persistent seizures and hemiparesis, her parents, Sonya and Casiano, consulted numerous specialists across the northeastern United States.
It was discovered that Elena had experienced a left-sided congenital stroke while still in the womb. This caused abnormal electrical activity in her brain, spreading from the damaged left side through the corpus callosum—the bridge between the brain’s hemispheres—to the healthy right side. Over the next four years, she tried every available epilepsy medication. While these drugs numbed her senses, they failed to control her seizures.
When Elena was six, she underwent a series of diagnostic tests, including MRIs, EEGs, and CAT scans. A team of neurologists and neurosurgeons reviewed the findings and concluded that her condition met the criteria for a rare and seemingly drastic procedure known as a hemispherectomy. This surgery, which involves removing half of the brain, had shown encouraging outcomes for patients with similar conditions. Essentially, they proposed removing the left half of Elena’s brain.
Dr. Howard Weiner, a pediatric neurosurgeon and professor at NYU Langone Medical Center and NYU School of Medicine, has performed hemispherectomies on children for many years, including Elena. He explained to mental_floss that in cases like hers, the healthy side of the brain is hindered by excessive electrical activity from the damaged side. This can lead to developmental delays, partial paralysis, behavioral challenges, social difficulties, and other complications. By severing this connection, the unaffected hemisphere can function without interference.
Following the evaluation, Dr. Weiner performed a left-sided hemispherectomy on Elena, removing the damaged half of her brain. Recovery from such a procedure is typically positive, and with intensive occupational and physical therapy, most children go on to live normal, fulfilling lives. Reflecting on her experience, Elena told mental_floss, “Everything became easier. I became smarter, made friends, and became more social. I just need a bit of extra support.”
Her parents took full advantage of her determined spirit and self-motivation. She participated in specialized programs designed for children with disabilities and later enrolled at Darrow School, a co-educational boarding school in New York, where her abilities were nurtured. Over time, she thrived and achieved remarkable success.
A BOLD NEW APPROACH TO BRAIN SURGERY
The earliest successful hemispherectomies trace back to the 1920s, when Walter Dandy, a trailblazer in neurosurgery, removed entire brain hemispheres to treat cerebral glioma, a form of brain tumor. In 1938, Canadian neurosurgeon K.G. McKenzie conducted a similar operation to address left hemiplegia (paralysis on the body's left side) and epilepsy in a patient, resulting in reduced seizures after the right hemisphere was excised. Over the decades, techniques have varied, ranging from removing small affected sections to entire hemispheres.
Over the last 25 years, the procedure has advanced significantly due to a better grasp of complications like hydrocephalus, which involves the buildup of cerebral spinal fluid in the brain cavity, refined surgical techniques to prevent seizure recurrence, precise mapping of affected areas, and a deeper understanding of brain plasticity. Notably, Ben Carson, a pediatric neurosurgeon and 2016 Republican presidential candidate, revitalized this surgery in the 1980s at Johns Hopkins Hospital—the same institution where Dandy once practiced.
To comprehend why removing half a brain could improve a patient’s condition, we must revisit the 19th century and the case of Phineas Gage, one of neuroscience’s most iconic figures. In 1848, while working on a railroad construction site in Vermont, an explosion propelled a 43-inch tamping iron through Gage’s skull, entering his left cheek and exiting the top of his head. This incident revealed the brain’s extraordinary resilience and adaptability.
Remarkably, Gage survived the incident and lived a relatively normal life for 12 more years, working as a stagecoach driver in Chile before moving back to San Francisco to stay with family. While he experienced neurological impairments and significant personality shifts—such as frequent swearing and a lack of social awareness—reports indicate that his brain regained considerable functionality. In a studio photograph, Gage is depicted holding the iron rod that had penetrated his skull.
Wikimedia Commons // CC BY-SA 3.0
Gage’s story is one of many historical examples where individuals suffered severe brain injuries but recovered significantly. The brain, an incredibly intricate organ, serves as the body’s central command system, with specialized regions governing thoughts, movements, and actions. For instance, Broca’s area, situated in the left hemisphere’s frontal lobe, manages speech. Yet, the brain adapts. Despite losing her left hemisphere, del Peral speaks fluently and with remarkable clarity.
Both Gage’s and del Peral’s experiences highlight neuroplasticity—the brain’s capacity to reorganize neural pathways and transfer functions to other areas.
“Language development typically occurs by ages two to four, when we learn to speak,” explains Dr. Weiner. “If the language center is damaged, it can relocate. The earlier the injury, the greater the likelihood of this shift due to the brain’s plasticity.” This phenomenon occurred in del Peral’s case. Her left hemisphere was damaged before birth, prompting language and motor functions to migrate to the right side. By the time of her surgery, her left hemisphere, the source of her epilepsy, was causing more harm than benefit.
HOPE FOR CALMING THE BRAIN'S ELECTRICAL STORM
Hemispherectomies have been shown to reduce or completely stop seizures in up to 89% of children with specific neurological conditions, such as brain infarcts (tissue death), cortical development malformations, Rasmussen’s encephalitis (a rare inflammatory disease affecting one brain hemisphere), and Sturge-Weber syndrome (a vascular disorder).
The current approach favors performing the surgery on younger children, even infants, to maximize the brain’s plasticity at an early stage. For instance, if the left hemisphere is removed after age 10, the child may lose the ability to speak permanently, as language functions are already firmly established by that age.
Modern techniques have made the procedure far less invasive, often preserving more of the brain’s vascularized tissue. Surgeons now often call it a hemispherotomy, as complete removal of a hemisphere is not always necessary. Before the surgery, subdural electrode grids are sometimes implanted to help neurologists and neurosurgeons identify damaged tissue. During the operation, they meticulously work from the inside out, severing the corpus callosum to disconnect communication between the brain’s hemispheres. Advanced microscopes and micro-surgical tools, handled with precision, are used to remove problematic areas. Any resulting cavity is naturally filled with cerebral spinal fluid, which safeguards the remaining tissue.
“The term disconnect is crucial,” Dr. Weiner explains. “We’ve shifted from complete removal to simply disconnecting the affected areas.”
By isolating the damaged part of the brain, the electrical disturbances no longer spread to the healthy hemisphere. Many patients, including Elena, can experience a complete cessation of seizures and no longer require anti-epileptic medications.
Data from the Kids' Inpatient Database (KID), collected every three years between 2000 and 2009, recorded 552 hospital admissions for hemispherectomies in the U.S., with an average patient age of 6.7 years. Currently, around 42 hospitals in the U.S. and 13 international facilities perform the surgery. Demand exceeds availability; when speaking to mental_floss, Dr. Weiner was traveling to Panama to treat children with uncontrollable seizures.
Next spring, del Peral will graduate from Curry College, having earned a place on the dean’s list every semester since her freshman year. “I have to put in 10 times more effort than the average person, but it’s worth it,” she says. “No one has a story like mine. Living with half a brain? I don’t want this to define me.”
