Types of Plexopathy
Plexopathies are classified primarily by anatomical location, with brachial and lumbosacral plexopathies being the two main types, each with distinct etiological subtypes that determine their clinical presentation and management. 1
Anatomical Classification
Brachial Plexopathy
- Involves the nerve network formed from C5-T1 ventral rami, affecting the shoulder and arm 1
- Characterized by pain, weakness, and sensory loss in the C5-T1 distribution 1
- Clinically presents with symptoms crossing multiple peripheral nerve distributions in the upper limb 2
Lumbosacral Plexopathy
- Involves the lumbar plexus (L1-L4) and sacral plexus (L4-S4) connected via the lumbosacral trunk 1
- Presents with pain and weakness in the back, hip, and leg 1
- Affects muscles of the anterior/medial thigh (lumbar plexus) or gluteal region/posterior thigh/lower leg (sacral plexus) 1
Etiological Classification
Traumatic Plexopathy
- Results from blunt force injuries (falls, sports injuries, motor vehicle accidents) or penetrating injuries 3
- Can be classified as preganglionic (involving intraspinal nerve roots) or postganglionic (involving plexus lateral to dorsal root ganglion) 3
- Imaging findings may include pseudomeningocele, spinal cord edema/hemorrhage, or neuroma formation 3
Neoplastic Plexopathy
- Primary tumors: Most commonly benign peripheral nerve sheath tumors (schwannomas and neurofibromas) 3
- Malignant peripheral nerve sheath tumors: More common in patients with neurofibromatosis 3
- Secondary involvement: Direct invasion or metastasis from adjacent tumors (e.g., Pancoast tumors of the lung affecting brachial plexus) 3
Inflammatory/Immune-Mediated Plexopathy
- Brachial neuritis (Parsonage-Turner syndrome): Characterized by acute onset of severe pain followed by weakness and atrophy 3, 4
- Idiopathic lumbosacral plexopathy: The lower limb equivalent of neuralgic amyotrophy 5
- Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP): Can present with plexopathy features 3
Diabetic Plexopathy
- Diabetic amyotrophy: Most common cause of lumbosacral plexopathy 6
- Typically presents with pain, weakness, and atrophy in proximal lower limb muscles 2
Radiation-Induced Plexopathy
- Delayed complication of radiation therapy, particularly for breast or lung cancer (brachial) or pelvic malignancies (lumbosacral) 1
- Characterized by progressive, painless weakness and sensory loss 7
Idiopathic Plexopathy
- Diagnosis of exclusion after ruling out other causes 5
- Often characterized by intense pain followed by motor and sensory deficits 5
- Recovery is typically slow (6-36 months) and may be incomplete 5
Hereditary Plexopathy
- Hereditary neuralgic amyotrophy: Autosomal dominant disorder with recurrent episodes of painful plexopathy 4
- Characterized by repeated episodes of paralysis and sensory disturbances preceded by severe pain 4
Diagnostic Approach
- Clinical diagnosis is confirmed by electrodiagnostic studies showing abnormalities in multiple nerve distributions 1
- MRI is the imaging modality of choice, providing superior definition of intraneural anatomy 1
- High-resolution ultrasound is emerging as an alternative for dynamic evaluation 7
Clinical Pearls
- Plexopathies must be distinguished from radiculopathies, which typically follow a single dermatome distribution 1
- The most difficult aspect of diagnosing plexopathy is maintaining clinical suspicion and having thorough anatomical knowledge 6
- Symptoms affecting multiple peripheral nerve distributions that cannot be explained by a single nerve root lesion should raise suspicion for plexopathy 2