Subpial Dissection

Subpial dissection is a microsurgical technique in which the surgeon operates beneath the pia mater, maintaining it as a protective membrane between the surgical field and the underlying brain cortex. This approach allows lesion removal or exposure of deep structures while minimizing cortical injury and preserving vascular integrity.

• Identify the pial surface under high magnification.
• Incise the pia mater sharply using a microknife or fine bipolar forceps.
• Continue dissection beneath the pia, using gentle suction and blunt dissection tools.
• The pia is kept intact over the brain parenchyma, and the dissection proceeds between the pia and the lesion or arachnoid.
• Achieve meticulous hemostasis using bipolar coagulation at the pial edge, avoiding direct cortical coagulation.

• Tumor surgery: low-grade gliomas, meningiomas invading the cortex
• Vascular lesions: AVMs, cortical aneurysms
• Access to deep structures:
  • Transsylvian approach
  • Transcortical approach
  • Transplanum–transpolfar approaches (endonasal)
• Epilepsy surgery: selective amygdalohippocampectomy, disconnections

• Preserves cortical and vascular integrity
• Reduces risk of neurological deficits
• Minimizes postoperative seizures
• Allows safe retraction and exposure of eloquent areas

• Risk of damaging subpial vessels (possible infarcts)
• Infiltrative or inflammatory lesions may obscure the subpial plane
• Requires microsurgical precision and excellent visualization

• The pia mater contains pial vessels and marks the outermost layer of the cortex.
• Subpial dissection preserves arachnoid and vascular layers while accessing lesions directly beneath the cortical surface.

• Yasargil MG. Microneurosurgery. Volumes I–IV. Thieme.
• Berger MS, Hadjipanayis CG. Surgical techniques for infiltrating gliomas. Surg Neurol. 2007.
• Spetzler RF, et al. Use of subpial planes in eloquent cortex surgery. Neurosurgery. 1992.