Lower Limb Peripheral Mononeuropathy
February 15th, 2021
On this page:Sciatic Nerve PalsyLateral Cutaneous Nerve PalsyCommon Peroneal Nerve PalsyPosterior Tibial Nerve PalsyFemoral Nerve Palsy
Overview
Peripheral mononeuropathy is a type of peripheral neuropathy affecting a single peripheral nerve.
Causes of Peripheral Mononeuropathy
- Compression (particularly carpal tunnel and ulnar tunnel) - prolonged pressure, hereditary neuropathy with liability to pressure palsies (HNPP)
- Trauma - blunt trauma, penetrating injury (e.g. knife, gunshot, glass)
- Nerve ischaemia - trauma, thromboembolism, diabetes, atherosclerosis, excessive tourniquet use
- Radiation injury
Peripheral Nerves of the Lower Limb
-
Nerve Sensory Motor Sciatic Nil Knee flexion Lateral Cutaneous Lateral thigh Nil Common Peroneal Lateral calf
Dorsum of the footDorsiflexion
Eversion
Toe extensionPosterior Tibial Plantar aspect of the foot Plantar flexion Femoral Anterior thigh
Medial calfHip flexion
Knee extension
Sciatic Nerve Palsy
The sciatic nerve branches into the tibial nerve and the common peroneal nerve, and as such palsy of the sciatic nerve will affect both of these nerves
Signs of Sciatic Nerve Palsy
- Sciatic nerve proper - weakness of knee extension
- Common peroneal nerve - sensory loss over the lateral calf and dorsum of the foot; weakness of dorsiflexion, foot eversion and toe extension
- Posterior tibial nerve - sensory loss over the plantar aspect of the foot; weakness of plantar flexion
Causes of Sciatic Nerve Palsy
- Direct trauma
- Stretch injury
- Hip dislocation
- Intramuscular injections incorrectly performed in the gluteal region
- Total hip replacement
Lateral Cutaneous Nerve Palsy
Lateral cutaneous nerve palsy is also known as meralgia paraesthetica.
Signs of Lateral Cutaneous Nerve Palsy
- Sensory loss over the lateral thigh
- No motor manifestations
Causes of Lateral Cutaneous Nerve Palsy
Occurs due to entrapment of the lateral cutaneous nerve beneath the inguinal ligament.
- Increased intra-abdominal pressure - obesity, pregnancy
- Tight clothing - particularly belts and suspenders
Common Peroneal Nerve Palsy
Signs of Common Peroneal Nerve Palsy
- Foot drop
- Weakness of ankle dorsiflexion and foot eversion
- Sensory loss over the dorsum of the foot and lateral shin
Causes of Common Peroneal Nerve Palsy
- Trauma - tibial or fibular fracture, ligamentous injury, nerve injury during surgery
- Compression - tight casts, positioning during surgery, prolonged bed rest
Posterior Tibial Nerve Palsy
Signs of Posterior Tibial Nerve Palsy
- Weakness of ankle plantar flexion
- Sensory loss over the plantar aspect of the foot
- Positive tinel's sign over the nerve posterior to the medial malleolus
Causes of Posterior Tibial Nerve Palsy
- Tarsal tunnel syndrome - entrapment within the tarsal tunnel posterior to the medial malleolus
- Distal tibial fracture
Femoral Nerve Palsy
Signs of Femoral Nerve Palsy
- Wasting of the quadriceps
- Weakness of hip flexion and knee extension
- Reduced / absent patellar reflexes
- Reduced sensation over the anterior thigh and medial calf
Causes of Femoral Nerve Palsy
- Hanging leg syndrome - prolonged hanging of a leg over an edge e.g. off a mattress
- Total hip replacement
- Stretch injury
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