Lumbosacral Plexus Injury
Damage to the nerve network that powers and feels the legs
Quick Facts
- Type: Peripheral nerve injury
- Common causes: Pelvic fracture, trauma, compression
- Main symptoms: Leg weakness, numbness, pain
- Recovery: Often slow; depends on severity
Overview
The lumbosacral plexus is a network of nerves in the lower back and pelvis formed from the spinal nerves of the lumbar and sacral spine. These nerves join and divide to supply movement and sensation to the hips, legs, and feet. A lumbosacral plexus injury is damage to this network, which can cause weakness, numbness, and pain in one or both legs depending on which parts are affected.
Because the plexus lies deep in the pelvis, it is well protected, so injuries usually result from major trauma, compression, or other significant causes. Recovery can be slow, as nerves heal gradually, and the outlook depends on how severe the injury is and whether the nerves are stretched, compressed, or torn.
Symptoms
Symptoms depend on which nerves of the plexus are damaged and how badly. They may include:
- Weakness in the leg, hip, or foot
- Numbness or tingling in parts of the leg or foot
- Difficulty walking, lifting the foot, or bearing weight
- Burning or shooting pain in the leg or buttock
- Reduced reflexes in the affected leg
- In severe cases, problems with bladder or bowel control
Sudden leg weakness or numbness, especially with loss of bladder or bowel control after trauma, needs urgent evaluation to identify and treat the cause.
Causes
A lumbosacral plexus injury can result from several causes, including:
- Pelvic fractures and trauma: A leading cause, as bone fragments or stretching forces damage the nerves.
- Compression: A large blood collection (hematoma), tumor, or abscess in the pelvis can press on the plexus.
- Surgical or procedural injury: Operations in the pelvis or hip, or prolonged positioning during surgery.
- Childbirth: The plexus can be compressed during a difficult delivery.
- Medical conditions: Diabetes, radiation, or inflammation can affect the plexus.
The cause helps determine whether the nerves are stretched, compressed, or torn, which affects the chances of recovery.
Risk Factors
- Major pelvic trauma and pelvic fractures
- Pelvic or hip surgery
- Pelvic tumors, abscesses, or large blood collections
- Difficult or prolonged childbirth
- Diabetes and previous pelvic radiation
- Bleeding disorders or blood-thinning medication
Diagnosis
Doctors diagnose a lumbosacral plexus injury with a neurological exam and tests:
- Physical and neurological exam: Testing strength, sensation, and reflexes to map the pattern of nerve involvement.
- MRI: Shows the nerves and any compression from a hematoma, tumor, or other cause.
- Nerve conduction studies and electromyography (EMG): Measure how well nerves and muscles are working and help judge severity.
- CT scan: Useful for assessing pelvic fractures and bony injury.
These tests help distinguish a plexus injury from a problem in the spine or a single nerve, which guides treatment.
Treatment
Treatment depends on the cause and severity and often focuses on supporting recovery while the nerves heal.
- Treating the underlying cause: Draining a hematoma, removing a tumor, or stabilizing a fracture that is pressing on the nerves.
- Physical and occupational therapy: Exercises to maintain strength, flexibility, and function, and to retrain walking.
- Pain management: Medicines for nerve pain, along with other supportive measures.
- Bracing and aids: A foot or ankle brace and walking aids can improve mobility.
- Surgery: In selected cases, surgery to relieve compression or repair nerves may be considered.
Nerve recovery is slow and may take many months. Some injuries recover well, while severe ones may leave lasting weakness or numbness.
Prevention
- Wear seatbelts and protective equipment to reduce pelvic trauma
- Manage diabetes to protect nerve health
- Seek skilled care during childbirth and surgery
- Report new leg weakness or numbness promptly so causes can be treated early
- Manage bleeding disorders and review blood thinners with your doctor
When to See a Doctor
See a doctor for new or worsening leg weakness, numbness, or nerve pain, especially after a pelvic injury or surgery. Seek emergency care right away for:
- Sudden weakness or numbness in one or both legs
- Loss of bladder or bowel control
- Numbness around the groin or inner thighs
- Severe leg symptoms after major trauma
These can signal serious nerve compression that may need urgent treatment. Early evaluation gives the best chance of recovery and helps rule out other causes.
Frequently Asked Questions
What is a lumbosacral plexus injury?
It is damage to the network of nerves in the lower back and pelvis that supply the legs. Depending on which nerves are affected, it can cause weakness, numbness, and pain in one or both legs.
What causes this type of nerve injury?
Major pelvic trauma and fractures are leading causes. The plexus can also be compressed by a blood collection, tumor, or abscess, injured during pelvic or hip surgery, or affected by difficult childbirth, diabetes, or radiation.
Can a lumbosacral plexus injury heal?
Nerves can heal, but slowly, often over many months. Mild injuries where nerves are stretched or compressed tend to recover better, while severe injuries with torn nerves may leave lasting weakness or numbness.
How is it treated?
Treatment addresses the underlying cause, such as draining a hematoma or stabilizing a fracture, and supports recovery with physical therapy, pain control, and braces or walking aids. Surgery is considered in selected cases.
When should I seek urgent care?
Sudden leg weakness or numbness, loss of bladder or bowel control, or numbness around the groin after trauma or surgery are emergencies. Get prompt care, as these can mean serious nerve compression that needs urgent treatment.
References
- National Institute of Neurological Disorders and Stroke (NINDS). Peripheral Neuropathy and Nerve Injury.
- Mayo Clinic. Peripheral nerve injuries.
- MedlinePlus, U.S. National Library of Medicine. Nerve injury.
- American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM). Plexopathy.