Spontaneous atraumatic pediatric basal ganglia hemorrhage in the setting of COLGALT1-related collagenopathy: illustrative case.

backgroundSpontaneous intracranial hemorrhage (ICH) in children is rare and is most commonly attributed to vascular malformations or coagulopathies. When standard vascular and hematological evaluation is unrevealing, genetic small-vessel disease should be considered. Biallelic COLGALT1 variants represent an exceptionally uncommon cause of cerebral microangiopathy, with limited cases reported and minimal discussion of neurosurgical management. OBSERVATIONS: A 14-year-old female with a known biallelic COLGALT1 variant presented with an acute basal ganglia hemorrhage with intraventricular extension and obstructive hydrocephalus. Given salvageable neurological function, she underwent emergency decompressive hemicraniectomy and external ventricular drain (EVD) placement. Because the hemorrhage etiology was unknown at the time of surgery, the hematoma was not aggressively evacuated. Extensive postoperative vascular, infectious, and hematological evaluation revealed no alternative cause. She demonstrated steady neurological recovery, was weaned from the EVD, underwent uncomplicated cranioplasty, and ultimately returned to her prehemorrhage neurological baseline. LESSONS: When pediatric ICH remains unexplained after standard evaluation, genetic small-vessel disease should be included in the differential diagnosis. Recognition of collagenopathies such as COLGALT1 may influence operative strategy toward cautious decompression, inform family counseling regarding recurrence risk and inflammatory triggers, and support tailored long-term management. https://thejns.org/doi/10.3171/CASE251029.