This was the reality for Susannah Cahalan, a 24-year-old journalist whose remarkable story would later become the bestselling memoir Brain on Fire. Her case would not only reveal a rare neurological disorder known as NMDA receptor encephalitis but would also challenge how medicine distinguishes between psychiatric illness and neurological disease.
Before her illness began, Susannah’s life appeared to be on an upward trajectory. She was building a successful career in New York City, enjoying an active social life, and in a stable relationship with her boyfriend, Stephen. By all accounts, she was healthy, ambitious, and thriving, but then subtle symptoms began to emerge.
At first, she felt tired and flu-like. She became lethargic and increasingly irritable. What seemed like minor health concerns gradually transformed into something far more disturbing. She became obsessed with the idea that her apartment was infested with bed bugs. Despite repeated attempts to solve the problem, she could not let the issue go. Furniture was thrown away. Belongings were packed into garbage bags. Exterminators were called repeatedly. What began as concern evolved into fixation.
At the same time, she began experiencing headaches, numbness, tingling, and pain on the left side of her body. Medical professionals initially suspected mononucleosis, but treatment offered no relief. As her symptoms progressed, her behavior became increasingly erratic and difficult to explain.
When Personality Begins to Change
Susannah became increasingly suspicious and emotionally unstable. She accused her boyfriend of infidelity without evidence. Her moods swung rapidly from happiness to despair. She struggled with concentration, balance, and memory. Everyday tasks became difficult. She lost weight, withdrew socially, and appeared increasingly disconnected from reality. Then came the seizures.
While dining with her boyfriend, Susannah experienced a grand mal seizure that sent her to the hospital. Physicians considered several possibilities. Statistically speaking, more common explanations seemed likely. Mental health disorders, substance-related issues, epilepsy, and bipolar disorder were all considered. She was discharged with anti-seizure medication and later evaluated by a psychiatrist. A diagnosis of bipolar disorder was explored, and treatment began. Yet instead of improving, her condition continued to deteriorate.
A Descent Into a Living Nightmare
As weeks passed, Susannah’s symptoms became impossible to ignore. She began experiencing hallucinations involving multiple senses. This detail was particularly unusual. While auditory hallucinations are commonly associated with certain psychiatric disorders, multisensory hallucinations are less typical and can sometimes suggest an underlying neurological cause.
Her thinking became increasingly disorganized. She accused her parents of kidnapping her. She developed impulsive behaviors and jumped rapidly from one idea to another. After another severe seizure, she was admitted to NYU Langone Medical Center for extensive evaluation. Teams of specialists examined her. Psychiatrists, neurologists, psychologists, and other physicians proposed various diagnoses. Bipolar disorder, psychosis, substance use disorders, epilepsy, borderline personality disorder, and post-seizure psychosis were all considered. Yet none of the treatments seemed to help.
Eventually, Susannah entered a catatonic state. She would become frozen in unusual positions or display repetitive facial movements. She was physically present but increasingly trapped within her own mind. The most baffling aspect of the case was that her MRI scans, CT scans, blood work, and neurological testing appeared largely normal. Doctors knew something was wrong, but they could not identify what.
The Clock Drawing That Changed Everything
The breakthrough came from neurologist Dr. Souhel Najjar. Unlike many others involved in the case, Dr. Najjar suspected that an underlying neurological disease was causing her psychiatric symptoms. He believed there was an organic explanation that had not yet been discovered. During one evaluation, he asked Susannah to perform a simple task: draw a clock.
Every number she drew appeared on the right side of the clock face. The left side was completely neglected. This phenomenon is known as left-sided neglect and often indicates dysfunction in the right hemisphere of the brain, which helps process the left side of the visual world. The clock drawing provided a critical clue. Rather than suffering from a purely psychiatric illness, Susannah appeared to have inflammation affecting specific regions of her brain. Further testing ultimately confirmed the diagnosis: anti-NMDA receptor encephalitis.
What Is NMDA Receptor Encephalitis?
NMDA receptor encephalitis is a rare autoimmune disease in which the body’s immune system mistakenly attacks NMDA receptors in the brain. These receptors play critical roles in memory, learning, behavior, and personality. When these receptors become targets of the immune system, patients can experience a wide range of symptoms, including:
- Sudden psychiatric symptoms
- Hallucinations
- Paranoia
- Personality changes
- Memory problems
- Seizures
- Language difficulties
- Abnormal movements
- Catatonia
- Autonomic dysfunction affecting heart rate, blood pressure, and temperature regulation
The condition is rare, occurring in roughly 1.5 cases per million people annually. Because psychiatric symptoms often appear first, diagnosis can be delayed while more common mental health conditions are investigated.
The Unexpected Cause: Tumors With Hair and Teeth
One of the most fascinating and unsettling aspects of NMDA receptor encephalitis is what can trigger it. Many cases are associated with ovarian teratomas, a type of tumor that can contain tissues such as hair, teeth, skin, bone, and even nervous system tissue. The prevailing theory is that the immune system attacks the abnormal tissue within the tumor. Unfortunately, the immune response can become misdirected and begin attacking NMDA receptors in the patient’s own brain.
Although not every case is linked to a tumor, the association has become one of the most important discoveries in understanding this disease. Certain infections, particularly herpes simplex encephalitis, have also been implicated as possible triggers in some patients.
Why Diagnosis of NMDA Receptor Encephalitis is So Difficult
One reason NMDA receptor encephalitis can be challenging to identify is that standard testing may appear normal. MRI scans are often unremarkable. Routine blood tests may not provide definitive answers. The most reliable diagnostic testing frequently involves examining cerebrospinal fluid for specific antibodies targeting NMDA receptors. Blood tests alone can sometimes produce misleading results, including false positives and false negatives.
As a result, physicians must maintain a high index of suspicion when psychiatric symptoms appear abruptly, progress rapidly, and are accompanied by seizures, neurological deficits, or autonomic instability.
Treatment of NMDA Receptor Encephalitis
Once Susannah received the correct diagnosis, treatment began immediately. She underwent plasmapheresis, a procedure that removes harmful antibodies from the bloodstream. She also received intravenous immunoglobulin therapy (IVIG), designed to help regulate the immune response.
Early treatment is associated with significantly better outcomes. Additional therapies may include corticosteroids, immunosuppressive medications, tumor removal when appropriate, seizure management, respiratory support, and intensive care monitoring for severe cases.
Recovery from NMDA receptor encephalitis is rarely immediate. Susannah spent years rebuilding her life. She moved back in with her mother and gradually relearned basic tasks such as dressing, bathing, speaking, and functioning independently. Recovery occurred slowly and unevenly. Some symptoms disappeared quickly, while others lingered for months or years.
Perhaps most disturbing was the fact that she had no memory of much of her hospitalization. When she later watched footage of herself during the illness, she saw a person she did not recognize. The woman screaming, hiding, and behaving erratically felt like a stranger. Her own immune system had effectively erased an entire chapter of her life.
Lessons From a Brain on Fire
Susannah Cahalan’s story highlights an important reality in medicine: psychiatric symptoms can sometimes be the first sign of a neurological disease. Her case reminds healthcare professionals and families alike to remain curious when symptoms do not fit neatly into a diagnostic box. Abrupt personality changes, new psychiatric symptoms, seizures, unusual movement disorders, and unexplained neurological signs deserve careful investigation.
Most importantly, her story demonstrates the value of persistence. While many clinicians considered common explanations, Dr. Souhel Najjar continued searching for answers. A simple clock drawing ultimately revealed what sophisticated scans and countless tests had missed.
Today, increased awareness of NMDA receptor encephalitis has helped countless patients receive earlier diagnoses and more effective treatment. Susannah’s experience transformed a rare medical mystery into a lesson that continues to save lives. Sometimes the difference between being labeled “crazy” and receiving life-saving treatment is one physician willing to keep asking questions.
Author: Dr. Hong Yin
Hong Yin, MD, has been a practicing medical professional in the Milwaukee community since 2012. She understands that your health and wellness concerns extend beyond routine medical care. She’s a highly trained, board-certified psychiatrist who provides an array of comprehensive services and procedures to help people overcome mental health problems.