|Nerve: Sural nerve|
The small saphenous vein (sural nerve visible running vertically)
|From||Medial sural cutaneous nerve, communicating branch with the common fibular nerve (S1, S2)|
The sural nerve is a sensory nerve in the leg made up of collateral branches off of the tibial nerve and common fibular nerve. Two cutaneous branches, the medial and lateral, form the Sural Nerve. The medial cutaneous branch arises from the tibial nerve and the lateral branch arises from the common fibular nerve. The tibial nerve and the common fibular nerve arise as the sciatic nerve divides into two branches in the popliteal fossa. As the tibial nerve travels down the popliteal fossa, and before it goes beneath the gastrocnemius, it gives off a cutaneous branch which is the medial sural cutaneous nerve. This nerve courses laterally over the lateral head of the gastrocnemius. The common fibular nerve also gives off a small cutaneous branch which is the lateral sural cutaneous nerve. When the common fibular nerve is divided from the sciatic nerve, it travels parallel to the distal portion of the biceps femoris muscle and towards the fibular head. The small cutaneous branch arises as the common fibular nerve travels towards the fibular head. The nerve then continues down the leg on the posterior-lateral side, then posterior to the lateral malleolus where it runs deep to the fibularis tendon sheath and reaches the lateral tuberosity of the fifth toe, where it ramifies. 
|This section requires expansion. (December 2013)|
The sural cutaneous nerve consists of the communication between the medial sural cutaneous nerve which is a terminal branch of tibial nerve and the lateral sural cutaneous nerve which is one of the termianal branch of common fibular nerve. These two branches, MSCN and LSCN are connected by the sural communicating branch and form the sural nerve. The way and how the two branches approach together, the exact location of the connection, and also if the connection is identical in both legs give a vast range of variability onto this nerve.
The variations of the sural nerve can be divided mainly into three categories:
I. According to the way of union of sural nerve. Which may be connected from LSCN or MSCN or both, so that’s why divided into three varieties, type A, type B and type C. II. The rest two categories essentially are subdivisions of type A. In this category differentiated into symmetrical and asymmetrical groups, according to identical type of structure in the both legs or not. III. In the last category subdivided into other fives groups, which are the five possible regions for sural nerve union.
The nerve transmits signal from the posterior lateral corner of the leg, and the lateral foot and 5th toe.
The sural nerve subserves a purely sensory function, and therefore its removal results in only a relatively trivial deficit. For this reason, it is often used for nerve biopsy, as well as the donor nerve when a nerve graft is performed.
Sural Nerve Block
A sural nerve block can be used for quick anesthetization to the foot and lower leg. Because this technique requires few injections to reach adequate anesthesia, a smaller volume of anesthetic is needed. The sural nerve is rather superficial, which makes it more accessible to surgeons, therefore it is relatively easier than other procedures. Also, due to its superficial properties, the sural nerve is also easily blocked at multiple levels at or above the ankle. In one study, regional anesthesia of the foot and ankle, when performed by surgeons, was completely successful 95% of the time. Sural nerve block is not advised if a patient is allergic to the anesthetic solution, has infected tissue at the injection site, has severe bleeding disorder, or has preexisting neurological damage.
||This section needs attention from an expert in Medicine, Medicine/Neurology task force or Alternative Medicine. (February 2014)|
Radiofrequency can be a successful use in treatment of chronic pain conditions. However, continuous radiofrequency ablation can have a neurodestructive effect. Due to this fact, pulsed radiofrequency is a better treatment for peripheral sensory nerves. Radiofrequency is an alternating current with an oscillating frequency of 500,000 Hz. Pulsed radiofrequency uses radiofrequency currents in short, high-voltage bursts. Each burst lasts about 20 milliseconds, which is then followed by 480 milliseconds of rest to allow the heat to dissipate. Allowing the heat to dissipate avoids temperature increases. The advantage of pulsed radiofrequency over the continuous radiofrequency is that its effect does not rely on the thermal destruction of nerve tissue. Since the sural nerve is a sensory nerve, if applying continuous radiofrequency to a sensory nerve can cause a neuroma formation and could cause pain to worsen. Pulsed radiofrequency is a much better option because it does not affect the structural integrity of the nerve and may cause only transient mild edema. Pulsed radiofrequency produces a very weak magnetic field without any significant biologic effects and it has a much stronger electric field than continuous radiofrequency. The electric field can induce changes on tissue and distort and dislocate charged molecular structures, which disrupts cell functioning without substantial elevations in temperature. Pulsed radiofrequency causes transient inhibition of evoke excitatory transmission with full recovery of synaptic activity within a few minutes, whereas continuous radiofrequency produces a long-lasting blockade. It is concluded that continuous radiofrequency results in neurodestructive effects, whereas pulsed radiofrequency produces neuromodulation. One case study implies that pulsed radiofrequency may provide long-term pain relief in cases of sural nerve injury.
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- Anatomy photo:11:07-0202 at the SUNY Downstate Medical Center
- Sural_nerve at the Duke University Health System's Orthopedics program
- sural+nerve at eMedicine Dictionary
- Cutaneous field