Subpial Dissection
🔍 Definition
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.
⚙️ Surgical Technique
- 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.
🧭 Indications and Applications
- 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
🛡️ Advantages
- Preserves cortical and vascular integrity
- Reduces risk of neurological deficits
- Minimizes postoperative seizures
- Allows safe retraction and exposure of eloquent areas
⚠️ Risks and Considerations
- Risk of damaging subpial vessels (possible infarcts)
- Infiltrative or inflammatory lesions may obscure the subpial plane
- Requires microsurgical precision and excellent visualization
🧠 Key Anatomical Notes
- 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.
📚 References
- 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.