Management Tips for Spinal Lipoma

Author

Dominic Thompson, FRCS (SN)

Exposure

• Ultrasound vs MRI and radiography: In infants up to age 4 months, ultrasound can be used to identify the correct level before the laminectomy. In older children, radiography correlated with MRI findings is more helpful.
• Remove lipoma and untether cord during same surgery: Where possible, the subcutaneous lipoma should be removed during the same surgical procedure as cord untethering. Otherwise, a sizable subdermal space is created where cerebrospinal fluid could collect under tension, potentially hindering wound healing and increasing the risk of infections.
• Clear identification essential: Having an anatomically normal upper level of the spinal cord is essential. It allows the surgeon to identify the beginning of the lipoma, the last set of normal nerve roots, and the DREZ.

Detachment and Resection

• Crotch dissection: Crotch dissection involves pulling the overhanging fat medially against the dura and using dissecting scissors to divide the fat-dura attachment. Care must be taken to avoid injuring the nerve roots located slightly medial to the crotch.
• Nerve root dissection: Pulling back the detached fat makes the hidden nerve roots visible so they can be gently separated from the dura through blunt dissection towards the exit foramina. This step allows the ventral CSF space and the pia-covered surface of the neural placode to come into view.
• Lipoma removal: Lipoma resection starts at the rostral end, where the anatomical relationships are clear. A distinct white plane between the fat and cord is located, and sharp dissection follows this plane.
• Bleeding: If bleeding arises from the surface of the resected lipoma over the white plane, it can be handled with the ultrafine irrigating bipolar cautery and a very low current setting. The cold irrigation mitigates against sticking, but more importantly, it dissipates heat rapidly from the cord.
• Fusion line appearance: The appearance of the fusion line can vary significantly depending on the complexity of the lipoma. The fusion line is typically easily identified in dorsal lipomas but can be obscured or irregular in transitional and chaotic lipomas.

Dorsal vs transitional lipoma: (Top) A dorsal lipoma is shown. Note the clarity of the fusion line and the caudal end. (Bottom) A transitional lipoma is shown. Note the degree to which the caudal limit is compromised in this type of lipoma.

• MEPs: At our center, MEPs are monitored in all spinal lipoma surgeries. We measure MEPs at frequent intervals during the detachment and resection stage of the procedure.
• Placode rotation: The placode is often rotated — this can be anticipated on the preoperative MRI. We believe it is usually the dorsal and never the ventral part of the lipoma that tethers the spinal cord.
• Chaotic lipomas: Chaotic lipomas may require electrophysiological determination of the functional extent of the placode for final untethering.

Chaotic lipoma: The image shows a chaotic lipoma with indistinct DREZ (solid white arrows) and fat extending beyond the dorsal roots (dotted white arrow).

Neurulation and Dura Expansion

• Neurulation: A well-executed neurulation reduces the adhesive surface on the placode to a single seam and, by transforming a broad, sticky sheet into a trim, sturdy pia-covered tube, minimizes the probability of it interacting with the dura.
• Sutures: Leaving a narrow cuff of pia along the cut edges of the white plane is helpful to accommodate the sutures, which are tied with inverted knots.
• CSF: A neurulated placode floating in ample CSF within a spacious sac is less likely to reattach to the dura.
• Graft position: The opposing edges between the graft and the patient’s dura are first lined up with judiciously placed 4-0 sutures.
• Watertight closure: Running 5-0 prolene sutures are then used to achieve a watertight closure.