Post-operative remnants of brainstem cavernomas: incidence, risk factors and management

The risk of leaving a remnant after surgery for a cavernous malformation in the brainstem is generally not stressed enough, even though such remnants appear to have a high risk of re-bleeding. At least 40% of known cavernoma remnants after surgery have further bleeding episodes. A retrospective analysis of 30 patients with brainstem cavernoma who underwent surgery is presented, focusing on incidence, risk factors and management of post-surgical residuals. The sites were, medulla in three patients, pons-medulla in four, pons in 16, pons-midbrain in four and midbrain in three. All 30 patients came to our clinical observation with at least one episode of acute-onset neurological deficit and all were operated in the sub-acute phase. Only one patient had a worse stable outcome than the pre-surgical state, and 29 did better or were stable. All patients had a brain MRI scan within 72 h after surgery to confirm that complete removal had been achieved. In three, although the surgical cavity and its border appeared clean at the end of surgery, with no lesion remaining, post-operative MRI detected a residuum. These three patients were re-operated, but one had a further bleed prior to excision.

In our series, the surgical finding of a multi-lobular cavernoma (as opposed to the more frequent finding of a discrete lesion with a thick capsule), with a thin wall and satellite nodules separated by a thin layer of apparently intact white matter, was common (seven patients). This group included the three patients with evidence of residuum on post-operative MRI. In our experience, the surgical finding of a multi-lobular cavernoma carries a higher risk of residuum and post-surgical re-bleeding.

Immediate post-operative brain MRI scans are therefore strongly recommended for their detection, especially in this group of patients, and if a residual is detected early re-intervention is less risky than the natural history.