Neurovascular bundle

A Neurovascular bundle (Neuro: Nerve, Vascular: Veins, Lymph vessels and arteries) is a term applied to the body nerves, arteries, veins and lymphatics that tend to travel together in the body.

Superficial and deep neurovascular bundle

There are two types of neurovascular bundle: superficial neurovascular bundle and deep neurovascular bundle. As arteries do not travel within the superficial fascia (loose connective tissue under the skin), superficial neurovascular bundle differs from deep neurovascular bundle in both composition and function.

Superficial neurovascular bundle, without arteries in it, is mostly made up of capillaries running through different body tissues. Because capillaries function as the sites for material exchange between interstitial fluid and blood, they tend to have large surface area and short diffusion path. Normally, capillaries are consist of a central lumen lined with an endothelium, a single layer of smooth epithelial cells.

In contrast, deep neurovascular bundle, with arteries in it, has a more complicated composition. Arteries are the vessels that transfer the blood pumped by the heart to the entire body. The blood in arteries have high blood pressure. So outside the endothelium structure, arteries also have a smooth muscle and a connective tissue structure. These compositions enable the arteries to contract and transfer the blood.

Risks of neurovascular bundle in surgeries

Both superficial and deep neurovascular bundles are at risk during incisions in surgeries.

In surgeries, the principle superficial neurovascular bundles at risk are, medially, the great saphenous vein and its accompanying nerve, and laterally, the superficial peroneal nerve. The superficial peroneal nerve origins from the common peroneal nerve near the neck of the fibula and passes between the peroneus longus and brevis muscles, supplying motor branches to these muscles. The superficial branch then continues onto the dorsum of the foot to supply sensory fibers to the skin there.

The main deep neurovascular bundle at risk is the posterior tibial. It lies on the posterior aspect of the tibialis posterior and flexor digitorum longus muscles, and medial to the belly of flexor hallucis longus. It also gives rise to medial plantar artery and lateral plantar artery.^[1]

Preserving neurovascular bundle in surgeries

In surgeries, these neurovascular bundles, both superficial and deep, are tried to be protected in order to prevent neurological damages.

The common technique of anatomy in surgeries to prevent the damage of neurovascular bundles is that after reaching the fascia, undermine anteriorly to the posterior tibial margin, in order to avoid the saphenous vein and nerve. The deep posterior compartment here is superficial and readily accessible. The fascia of the deep posterior compartment is carefully opened distally and proximally, under the belly of the soleus muscle, paying special attention to the posterior tibial neurovascular bundle. Through the same incision, the fascia of the superficial posterior compartment is opened widely, two centimeters posterior and parallel to the incision in the fascia of the deep compartment.

The application of preserving neurovascular bundles in surgeries demonstrates that preservation of both neurovascular bundles during nerve-sparing (NS) radical prostatectomy (RP) improves urinary continence and erectile function.^[2] Consequently, NS is recommended in elderly men and those with pre-existing erectile dysfunction, who many surgeons would previously have only offered non-NS surgery. It is also found during surgeries that when neurovascular bundles are preserved, the frequency of positive margins was only 5.8 percent.^[3]

References

• Gray's Anatomy: The Anatomical Basis of Clinical Practice, Expert Consult, 40e. By Susan Standring, PhD, DSc, Emeritus Professor of Anatomy, Head of Anatomy and Human Sciences, King's College London, London, UK. 9780443066849