What are the etiologies of lumbosacral plexopathy (Lumbosacral Plexus Disorder)?

From the Guidelines

Lumbosacral plexopathy is a complex condition with multiple etiologies, including entrapment, inflammatory, autoimmune, hereditary, ischemic, and idiopathic causes, as well as neoplasms or extrinsic compressive lesions, as noted in the 2021 update of the ACR Appropriateness Criteria for Plexopathy 1. The etiologies of lumbosacral plexopathy can be broadly categorized into several groups, including:

• Entrapment neuropathies, which can result from spinal or extraspinal compression 1
• Inflammatory and autoimmune conditions, such as diabetic amyotrophy, acute inflammatory demyelinating polyneuropathy (Guillain-Barré syndrome), and chronic inflammatory demyelinating polyneuropathy 1
• Hereditary conditions, such as Charcot-Marie-Tooth disease 1
• Ischemic nerve injury 1
• Idiopathic causes 1
• Neoplasms, including primary tumors of the lumbosacral plexus, such as benign peripheral nerve sheath schwannomas and neurofibromas, as well as malignant peripheral nerve sheath tumors 1
• Extrinsic compressive lesions, such as hematoma, abscess, aneurysm, amyloidosis, and endometriosis 1 The diagnosis of lumbosacral plexopathy typically requires a thorough history, neurological examination, electrodiagnostic studies, and imaging, such as MRI with contrast, to identify the underlying etiology and guide appropriate treatment 1. Key points to consider in the diagnosis and management of lumbosacral plexopathy include:
• The use of MRI with contrast to evaluate nontraumatic lumbosacral plexopathy, which can provide superior soft-tissue contrast and good spatial resolution, allowing for the localization of pathologic lesions and the definition of intraneural anatomy 1
• The importance of considering the clinical presentation and physical findings in the diagnosis of lumbosacral plexopathy, as the clinical diagnosis can be challenging and may require the use of electrodiagnostic studies and imaging to confirm the diagnosis 1
• The need for a thorough history and physical examination to identify potential underlying causes of lumbosacral plexopathy, such as trauma, malignancy, radiation, diabetes, infection, and inflammatory conditions 1

From the Research

Etiologies of Lumbosacral Plexopathy

The etiologies of lumbosacral plexopathy are diverse and can be categorized into several groups, including:

• Neoplastic processes: Malignant lumbosacral plexopathy can occur in patients with a prior history of abdominal or pelvic malignancy 2
• Traumatic processes: Pelvic trauma, such as sacral fractures or sacroiliac joint separation, can cause lumbosacral plexopathy 3
• Infectious processes: Infections can affect the lumbosacral plexus, leading to lumbosacral plexopathy 4, 5
• Radiation processes: Radiation therapy can cause lumbosacral plexopathy 4, 2
• Inflammatory/microvasculitic processes: Ischemic injury due to a perivascular inflammatory process and microvasculitis can cause lumbosacral plexopathy 4, 5
• Diabetic processes: Diabetic amyotrophy is a common cause of lumbosacral plexopathy, and diabetic lumbosacral radiculoplexus neuropathy can also occur 4, 6
• Idiopathic processes: Some cases of lumbosacral plexopathy may be idiopathic, although many cases previously thought to be idiopathic have been shown to be caused by ischemic injury from microvasculitis 4
• Postsurgical processes: Lumbosacral plexopathy can occur after spinal surgery, such as discectomy and fixation 5
• Vasculitis: Vasculitis can cause lumbosacral plexopathy 5
• Intravenous drug abuse: Intravenous drug abuse can cause lumbosacral plexopathy 5

Clinical Features

The clinical features of lumbosacral plexopathy depend on the part of the plexus involved and the temporal course of the disease. Common symptoms include:

• Acute or subacute onset of pain and paresthesia
• Profound motor weakness asymmetrically involving the lower limbs
• Weight loss
• Sensory deficits
• Reflex changes
• Muscle atrophy

Diagnosis and Management

Diagnosis of lumbosacral plexopathy is based on clinical and electromyographic (EMG) findings, as well as imaging studies such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET)/CT. Management depends on the cause of the lumbosacral plexopathy and may include immunotherapy, pulse steroid therapy, and other treatments 4, 5, 2.