Two decades later, Alex Simpson has reached 20 years of age, despite being born with hydranencephaly—a condition so severe that most infants don’t survive infancy.
Her case is one of extreme medical rarity: Alex was born missing nearly all of her cerebral hemispheres, the brain regions responsible for thought, movement, and sensation. And yet, supported by a dedicated family and round-the-clock care, she continues to live far beyond any documented expectations.
Hydranencephaly is a congenital disorder that begins in early fetal development. In Alex’s case, it left her with a brain cavity mostly filled with cerebrospinal fluid instead of functioning brain tissue. She retains only a tiny portion of her cerebellum, “about half the size of my pinky finger,” as her father described in an interview with KETV. Her brainstem and basal ganglia are intact, allowing her body to sustain vital functions. The rest is a medical void—and a mystery that continues to challenge neurology.
Extremely Rare, Almost Always Fatal
Statistically, hydranencephaly occurs in about one in 10,000 births worldwide, and less than one in 250,000 in the United States. Most cases are identified through prenatal ultrasounds, often during the second trimester. When confirmed, the prognosis is grim. As ScienceAlert explains, many affected infants die shortly after birth. Those who survive rarely live beyond their first year.
Alex’s diagnosis came two months after her birth, when signs such as irritability, seizures, and unusual muscle tone began to emerge. Before that, she showed no visible abnormalities. This delay is common, as newborns with the condition often present with normal head sizes and typical reflexes. Once diagnosed, her survival became a question of palliative care and time.
According to pediatric neurologist Sumit Parikh of the Cleveland Clinic, hydranencephaly is thought to result from early destructive processes in the brain, most likely due to vascular events such as stroke or infection. While some genetic mutations related to blood vessel formation have been linked to the condition, such cases are rarely identified due to the relatively recent availability of whole-genome sequencing.
Limited Brain, Unexpected Awareness
Alex cannot walk, talk, or see clearly. Yet her parents say she recognizes familiar voices and responds emotionally to her surroundings. Her cerebellum, though minimal, allows for some sensory perception, and her basal ganglia contribute to basic motor and emotional functions.
“She knows when good things are going on around us, she knows when bad things are going on around her,” her father told KETV during a birthday segment years ago. While it’s impossible to measure the full extent of her awareness, the family describes her responses as meaningful and consistent.
According to the same source, the preservation of her brainstem is what allows her to breathe, swallow, and maintain a heartbeat without external support. These functions, while automatic, are critical—and their presence highlights the complexity of the human brain’s hierarchical structure.
Science Still Searching for Answers
No cure exists for hydranencephaly, and treatment remains purely supportive. In some cases, like Alex’s, families choose to continue care for years, often at great emotional and financial cost. Others, when diagnosed early in pregnancy, may opt for termination, faced with the certainty of severe disability and limited lifespan.
The exact cause of the condition is still undetermined. While vascular injury remains the leading hypothesis, the range of potential contributing factors is wide. “Considering we have not had comprehensive testing like whole-genome sequencing until relatively recently,” said Parikh, “it is possible that genetic causes have been underestimated.”