Lumbar-ventricular cerebrospinal fluid pressure discrepancy in leptomeningeal metastasis associated intracranial hypertension.

BACKGROUND: Leptomeningeal metastasis (LM) frequently causes intracranial hypertension (IH) due to disruption of cerebrospinal fluid (CSF) circulation. However, the relationship between lumbar and ventricular CSF pressures in LM has not been systematically evaluated. We investigated the frequency, magnitude, and determinants of lumbar-ventricular CSF pressure discrepancy in LM patients undergoing ventriculoperitoneal shunt (VPS) placement. METHODS: We retrospectively analyzed 34 patients with LM who underwent VPS between 2015 and 2023. Lumbar opening pressure was measured preoperatively by lumbar puncture, and ventricular pressure was measured intraoperatively before CSF diversion. A clinically significant pressure discrepancy (SPD) was defined as a lumbar-ventricular pressure difference (ΔP) ≥ 5 cmH₂O, and a marked pressure discrepancy (MPD) as ΔP ≥ 10 cmH₂O. Clinical, radiologic, and cytologic variables were compared between groups. Univariate logistic regression was performed to identify predictors of SPD and MPD. RESULTS: Mean lumbar and ventricular CSF pressures were 20.9 ± 8.9 cmH₂O and 31.1 ± 11.3 cmH₂O, respectively (mean ΔP = 10.2 cmH₂O; p < 0.001). SPD was present in 25 patients (73.5%), and MPD in 18 patients (52.9%). Ventricular CSF pressure was significantly higher in patients with SPD and MPD, whereas lumbar pressure did not differ between groups. More than half of the cohort (52.9%) exhibited IH without ventriculomegaly. In logistic regression analyses, ventricular pressure was the only variable significantly associated with both SPD (OR 1.216, p = 0.012) and MPD (OR 1.137, p = 0.009). CONCLUSIONS: Lumbar-ventricular CSF pressure discrepancies are common in LM and are primarily driven by elevated ventricular pressure, reflecting impaired craniospinal pressure transmission. Lumbar pressure may substantially underestimate true intracranial pressure, particularly in the absence of ventriculomegaly. Recognition of this dissociation is critical for accurate assessment and management of LM-associated intracranial hypertension.