Introduction: Colloid cysts are histologically benign, congenital malformations and are a rare cause of sudden death. In 1858, Wallmann described a 57-year-old man who presented with urinary incontinence, memory disturbance, and ataxic gait. It is unclear if the patient had undergone a lumbar puncture but the patient died suddenly. Post-mortem examination identified a colloid cyst in the third ventricle. To our knowledge, that was the earliest report of a lethal colloid cyst. To date, the literature has not been systematically surveyed, so clinical picture of impending death remains obscure.

Methods: A systematic literature search of three popular databases was performed. Inclusion criteria were individuals with sudden-onset death and colloid cysts identified on imaging and/or autopsy. The cause of death must have been ascribed to the colloid cyst. Deaths precipitated by lumbar puncture were excluded. Subgroup analyses were performed for multiple patient populations.

Results: A total of 60 articles comprised of 122 patients were included. Mean age was 29.1 years. The sharpest rise in the probability of death by age was in the third decade. Males and females were equally affected. Headache was the most frequent symptom (n = 85, 83.3%). Positional headaches were infrequent (n = 6, 7.05%). Mean duration of signs and symptoms was shorter in adults versus pediatric patients (2.16 days vs 6.59 days, p = .036) and more adults presented with signs and symptoms for less than 24 hours than did pediatric patients (34.7% vs 5.88%, p = .025). Colloid cyst mean diameter was 2.01 cm and 96.7% measured over 1 cm.

Conclusions: Our data suggests that the sharpest rise in the probability of death is in the third decade of life, the prodrome preceding sudden death appears shorter in adults with more adults presenting with symptoms for less than a day, and nearly all colloid cysts were over one centimeter.

Patient Care: This systematic review provides clinicians a concise quantitative summary of nearly sixteen decades of literature and may be of value when counseling patients with colloid cysts. Perhaps the most salient findings of this study are that the sharpest rise in the probability of death appeared to be in the third decade, the prodrome preceding sudden death was shorter in adults, more adults presented with symptoms for less than a day, and nearly all colloid cysts measured over one centimeter.

Learning Objectives: To accurately characterize the presentation and provide a comprehensive review of the pathophysiological mechanisms underlying the feared lethal colloid cyst.

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