Hypertrophic Olivary Degeneration in Brainstem Cavernous Malformations: An Analysis of Predictors and Clinical Implications.

Background and objectives: This study aimed to evaluate predictors of hypertrophic olivary degeneration (HOD) in patients with brainstem cerebral cavernous malformations (CCMs) and to examine its association with functional outcomes.

Methods: A cohort of 120 patients with brainstem CCM was analyzed using prospectively collected registry data and retrospective chart reviews. Demographic, clinical, radiological, and surgical data were evaluated. Predictors of HOD and poor functional outcomes were identified through univariate and multivariate analyses.

Results: The cohort included 54 females (45.0%), with a mean age at diagnosis of 43.8 years (SD = 16.5). Symptomatic hemorrhage was present in 70.8% of patients at diagnosis, and 28.3% underwent surgical intervention. Radiographic HOD was observed in 20% of patients (n = 24), with 87% of cases involving lesions within the Guillain-Mollaret triangle (GMT). Larger lesion size (odds ratio [OR] = 1.09, 95% CI: 1.01-1.19, P = .027), pontine location (OR = 19.81, P = .006), and GMT involvement (OR = 25.24, P < .001) were significantly associated with HOD. Repeated symptomatic hemorrhage and surgery, including the extent of resection, did not predict the development of HOD. Patients with HOD had worse functional outcomes at last follow-up (P = .012), with GMT involvement remaining the sole independent predictor of mRS ≥3 (OR = 3.44, P = .040).

Conclusion: HOD reflects trans-synaptic degeneration within the GMT and is strongly associated with lesion location and size. It serves as a radiological marker of cumulative damage to the brainstem. Preoperative imaging and risk stratification focusing on GMT involvement are critical for guiding management and counseling patients with brainstem CCM.