Peroneal Nerve Palsy
Department- Human Anatomy and Histology
Varna 2020
Peroneal Nerve Anatomy
The common Peroneal nerve, also known as the common Fibular nerve, is one of two main muscular branches of the Sciatic nerve (L4-S3).
The common Peroneal nerve originates from the sciatic nerve in the posterior compartment of the thigh or in the Popliteal fossa and follows the medial margin of the biceps femoris tendon over the lateral head of the gastrocnemius muscle and toward the fibula. It then gives origin to 2 cutaneous branches, which descend in the leg:
- The Sural Communicating Nerve, which joins the sural branch of the tibial nerve and contributes to innervation of skin over the lower posterolateral side of the leg.
- The Lateral Sural Cutaneous Nerve, which innervates skin over the upper lateral leg.
The common Peroneal nerve continues around the neck of the fibula and enters the lateral compartment by passing between the attachments of the fibularis longus muscle to the head and shaft of the fibula. Here, the common Peroneal (fibular) nerve divides into its 2 terminal branches:
- The Superficial Fibular nerve
- The Deep Fibular nerve
The superficial fibular (or peroneal) nerve arises from the common fibular nerve in the proximal leg and travels distally in the leg through the lateral compartment. After providing muscular innervation to the fibularis (peroneus) longus and brevis muscles in the lateral compartment of the leg, the terminal sensory branch supplies sensation to the lower two-thirds of the anterolateral leg and the dorsum of the foot, except for the first web space.
It becomes superficial within the muscular compartment about 5 cm above the ankle joint where it pierces the fascia to become subcutaneous. It divides into its two terminal sensory branches, the intermediate and medial dorsal cutaneous nerves.
- The intermediate dorsal cutaneous nerve travels to the third metatarsal space and then divides into the dorsal digital branches to supply sensation to the lateral two digits.
- The medial dorsal cutaneous branch passes over the anterior aspect of the ankle overlying the common extensor tendons, runs parallel to the extensor hallucis longus tendon and divides distal to the inferior retinaculum into three dorsal digital branches.
The Deep Fibular (Peroneal) Nerve supplies motor innervation to all anterior compartment muscles (the tibialis anterior, the extensor digitorum longus, and extensor hallucis longus) and the fibularis tertius, also known as the peroneus tertius. The anterior tibialis is the strongest foot dorsiflexor, although the extensor digitorum longus and the fibularis tertius assist with this movement.
The deep fibular nerve travels distally in the calf and at the level of the ankle joint, fascia overlying the talus and the navicular bind the deep fibular nerve dorsally. Ventrally, the extensor hallucis longus muscle fibers and tendon and the inferior extensor retinaculum overlay the nerve. The inferior extensor retinaculum is a Y-shaped band anterior to the ankle; the anterior tarsal tunnel is considered the space located between the inferior extensor retinaculum and the fascia overlying the talus and navicular. Just rostral or under the inferior extensor retinaculum, the deep fibular nerve branches into medial and lateral branches.
- The lateral branch of the deep fibular nerve travels under the extensor retinaculum, as well as the extensor digitorum and hallucis brevis muscles to innervate these muscles and nearby joints.
- The medial branch travels under the extensor hallucis brevis tendon to supply sensation to the skin between the first and second toes.
Peroneal Nerve Palsy
Palsy is a medical term which refers to various types of paralysis often accompanied by weakness and the loss of feeling and uncontrolled body movements such as shaking and involuntary tremors.
Peroneal nerve palsy is the most common entrapment neuropathy of the lower extremity. Numerous etiologies have been identified; however, compression remains the most common cause. Although injury to the nerve may occur anywhere along its course from the sciatic origin to the terminal branches in the foot and ankle, the most common site of compressive pathology is at the level of the fibular head. The most common presentation is acute, complete, or partial foot drop. Associated numbness in the foot or leg may be present, as well.
Common peroneal nerve palsy may be due to:
- Traumatic causes
- Knee dislocation
- Direct impact or cut on the fibular neck
- Following surgery to the knee
- Atraumatic causes
- Entrapment neuropathy
- Intraneural ganglion
- Peripheral nerve tumors
- Systemic illnesses (diabetes mellitus, inflammatory conditions, motor neuron disease)
Levels of Damage; Skin and Muscle impairment
The common peroneal nerve branches from the sciatic nerve and provides sensation to the front and sides of the legs and to the top of the feet. This nerve also controls the muscles in the leg that lift the ankle and toes upward. Injuries to the peroneal nerve and peroneal nerve palsy can cause numbness, tingling, pain, weakness, and a gait problem called foot drop.
Affected Muscles (Peroneal Palsy)
Muscles of the lateral compartment of the leg:
- Fibularis Longus – Superficial Fibular Nerve (L5, S1, S2)
- Involved in the eversion and plantarflexion of foot; supports arches of the foot
- Fibularis Brevis – Superficial Fibular Nerve (L5, S1, S2)
- Involved in the eversion of the foot
Muscles of the Anterior Compartment of the leg:
- Tibialis Anterior – Deep Fibular Nerve (L4, L5)
- Involved in the dorsiflexion of the foot at the ankle joint; inversion of foot; dynamic support of medial arch of foot
- Extensor Hallucis Longus – Deep Fibular Nerve (L4, L5)
- Involved in the extension of great toe and dorsiflexion of foot
- Extensor Digitorum Longus – Deep Fibular Nerve (L4, L5)
- Involved in extension of lateral four toes and dorsiflexion of foot
- Fibularis Tertius – Deep Fibular Nerve (L4, L5)
- Involved in dorsiflexion and eversion of foot
Muscles of the Dorsal Aspect of the Foot:
- Extensor Digitorum Brevis – Deep Fibular Nerve (S1, S2)
- Involved in extension of toes II to IV
- Extensor Hallucis Brevis – Deep Fibular Nerve (S1, S2)
- Involved in extension metatarsophalangeal joint of great toe
Affected Skin Areas:
The common peroneal nerve provides sensory innervation to the skin over the upper third of the lateral aspect of the leg via the lateral sural cutaneous nerve, as well as the lower leg and dorsum of the foot. It gives the aural communicating nerve which joins the sural nerve in the midcalf.
Peroneal Nerve Palsy most often occurs in people who are confined to bed or a wheelchair with pressure on the side of the knee. A knee injury or fracture or crush injury of the lower leg may also cause this problem. The injury is more common in very thin people and in people with diabetes.
This condition may improve when nerve compression is relieved. Corticosteroids injections into the area may help to reduce swelling and pressure on the nerve.
Peroneal nerve palsy may cause problems with lifting your foot. The foot may then drag when you walk. This is called foot drop.
Foot Drop
Foot drop may occur if there is dysfunction of the nerve supply controlling dorsiflexion of ankle. The common sites of involvement are either at the spine (lumbar nerve roots) or at the knee (common peroneal nerve). Specifically, when the peroneal nerve is involved, it is the deep branch that is responsible for the loss of action.
Consequences of foot drop
- the affected foot catches on the floor when walking
- high stepping gait – the affected leg is lifted high to clear the floor
- swinging of the affected leg to clear the floor
Signs and symptoms of peroneal nerve palsy are related to mostly lower legs and foot which are the following: Decreased sensation, numbness, or tingling in the top of the foot or the outer part of the upper or lower leg. Foot drops (unable to hold the foot straight across) and toes dragging while walking.
In order to locate and fully determine the extent of the nerve injury, specific tests to evaluate how the muscles and nerves are functioning are performed, including:
- Electromyography, which measures ongoing muscle activity and response to a nerve’s stimulation of the muscle.
- Nerve conduction study, which measures the amount and speed of conduction of an electrical impulse through a nerve.
Treatment options for nerve palsy (Peroneal Nerve Palsy) include both operative and non-operative techniques. Initial treatment includes physical therapy and ankle-foot orthosis. Physical therapy mainly focuses on preventing deformation by stretching the posterior ankle capsule.
Some injuries may require peripheral nerve surgery, including one or more of these procedures:
- Decompression surgery
- Nerve repair
- Nerve grafting
- Nerve transfer
- Tendon transfer