July 2024

NEUROSCIENCES

CASE REPORT: A ONE-IN-A-MILLION HIGH-RISK COLLOID CYST

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A 67-year-old female patient presented with significant cognitive and motor issues, including gait ataxia, inability to write legibly, headaches, memory loss, confusion, blurry vision and fainting. These symptoms progressively worsened over several months. An MRI conducted by her primary care clinician revealed a mass deep within her brain. Subsequently, she was referred to Stephen Magill, MD, PhD, at Northwestern Medicine.
 
After evaluating the patient at Northwestern Medicine, Dr. Magill diagnosed her with a colloid cyst — a rare congenital and benign intracranial tumor located between the hemispheres of her brain. The cyst had caused brain swelling, necessitating immediate admission for urgent surgical intervention.
 
Colloid cysts usually develop in the brain at the junction between the lateral and third ventricles, and they can block cerebrospinal fluid flow, leading to hydrocephalus. As a result, these benign growths can cause headaches, visual changes, memory difficulties, and occasionally result in loss of consciousness, coma and sudden death.
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Often, a brain cyst starts before birth. A colloid cyst may be present through childhood but not large enough to cause symptoms until adulthood. Colloid cysts can block the brain’s spinal fluid circulation pathways, trapping fluid in the brain and increasing pressure in the skull. The increased pressure causes the brain to stretch and swell.
 
“Most people have about one-in-a-million chance of developing a colloid cyst,” says Dr. Magill. “They are so rare that, in training and in even in a busy brain tumor practice, you only see these kinds of cysts a few times a year.”
 
Dr. Magill and his team performed a minimally invasive craniotomy for port-assisted colloid cyst resection just 24 hours after the patient presented. Because of the location adjacent to the fornix, and rarity of the cyst, the surgery was considered high-risk. Working through a craniotomy less than 2 centimeters in the skull, Dr. Magill used a plastic tube to separate the folds of the brain and pass his instruments down to the cyst. Working under the operating microscope, this approach allowed Dr. Magill to protect the fornix. During the surgery, Dr. Magill used an 8x12 millimeter port with a microscope to pop the cyst, drain and suction out the fluid, and then he carefully cut the cyst wall away from the fornix and critical veins that drain the deep brain structures. The primary objective was to remove the cyst, which was obstructing the ventricles, to relieve symptoms by restoring the normal flow of spinal fluid.
 
“The majority of patients with colloid cysts may never require surgery. In this case, since fluid buildup was so great, we had to intervene,” says Dr. Magill. “Her cyst was located near the fornix, which is essential for memory and located very deep in the brain, so this surgery was considered high-risk.”
Pre-op MRI with colloid cyst (left); Post-op MRI (right)
Pre-op MRI with colloid cyst (left); Post-op MRI (right)
​Pre-op MRI with colloid cyst (left); Post-op MRI (right)
​Dr. Magill and his team carefully assessed various surgical approaches for the patient’s colloid cyst. These options included craniotomy, endoscope-assisted removal, and a minimally invasive, tube-based approach. Ultimately, they concluded that the latter option was the optimal choice for this patient due to its ability to completely remove the cyst wall, which reduces the risk of recurrence.
 
Following the successful extraction of the entire cyst, the pressure in the brain decreased, and spinal fluid returned to normal. Before surgery, the patient could not walk across the hospital lobby. However, just two days after the procedure, the patient left the hospital walking normally. Remarkably, within two months, she resumed work and her usual daily activities. Even three months post-surgery, her brain fluid levels remained stable, and no recurrence is anticipated.
 
This rare case underscores the need for awareness, early diagnosis, and management of colloid cysts with minimally invasive treatments.
Stephen T. Magill, MD, PhD, assistant professor of Neurological Surgery at Northwestern Medicine.

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