Purpose <p>The management of large terminal syringomyelia (TS) at initial surgery varies in clinical practice, and outcome data stratified by spinal dysraphism subtype remain limited. We evaluated the mid- to long-term clinical course after tethered cord release (TCR) for large TS associated with terminal lipoma.</p> Methods <p>We retrospectively analyzed 12 patients with terminal lipoma (Morota Types 3–4) and large syrinx (syrinx index ≥ 0.5) who underwent TCR without routine additional syrinx procedures between 2012 and 2023. Patients with other spinal dysraphisms were excluded to evaluate a relatively homogeneous spinal dysraphism subtype. Radiological and clinical outcomes were assessed during follow-up.</p> Results <p>Median MRI and clinical follow-up periods were 54 and 71&#xa0;months, respectively. Postoperative syrinx reduction or resolution was observed in all patients. Neurological symptoms improved in symptomatic patients. One patient developed a new postoperative deficit, and no patient required reoperation for retethering or syrinx progression. The syrinx index decreased significantly from 0.67 to 0.00 (<i>p</i> = 0.00049). One holocord case underwent intraoperative minimal puncture for temporary pressure relief rather than definitive drainage.</p> Conclusion <p>In terminal lipoma–associated large TS, TCR without routine additional syrinx procedures was associated with a favorable clinical course during follow-up. These findings provide subtype-specific outcome data that may assist surgical decision-making, particularly when considering the need for additional syrinx procedures at initial surgery.</p> Trial Registration <p>Not applicable.</p>