From the Guidelines
Crossed weakness and sensory loss in the lower extremities typically localizes to the spinal cord, specifically suggesting a Brown-Séquard syndrome or a condition affecting the cauda equina, such as cauda equina syndrome (CES). This condition results from damage to the spinal cord or nerve roots, causing a range of symptoms including weakness, sensory changes, and numbness in the lower limbs. The most common causes of CES include lumbar disc herniation, neoplasm, infection/inflammation, spinal stenosis, and hemorrhage 1. Diagnosis requires a thorough neurological examination to confirm the crossed pattern, followed by imaging studies such as MRI or CT to identify the lesion.
Key Considerations
- The imaging study of choice in the evaluation of suspected CES or multifocal deficit is MRI because of its ability to accurately depict soft-tissue pathology, assess vertebral marrow, and assess the spinal canal patency 1.
- A recent prospective cohort study recommends urgent MRI assessment in all patients who present with new-onset urinary symptoms in the context of low back pain or sciatica 1.
- MRI lumbar spine without IV contrast is the preferred initial study, although MRI lumbar spine without and with IV contrast may be helpful to delineate the etiology of CES when underlying malignancy, infection, or inflammation is clinically suspected 1.
Management and Rehabilitation
Management depends on the underlying cause - surgical decompression for trauma or tumors, steroids for inflammatory conditions, or anticoagulation for vascular causes. Physical therapy is essential for rehabilitation regardless of etiology. The pathophysiology involves damage to the corticospinal tract (causing ipsilateral weakness), posterior columns (causing ipsilateral proprioceptive loss), and spinothalamic tract (causing contralateral pain/temperature loss). This pattern occurs because the corticospinal and posterior column tracts descend ipsilaterally, while the spinothalamic tract fibers cross to the opposite side shortly after entering the spinal cord.
Diagnostic Approach
A thorough neurological examination is crucial to confirm the diagnosis, and imaging studies should be guided by the clinical presentation. In cases where CES is suspected, urgent MRI assessment is recommended to promptly identify the cause and guide management 1. The clinical diagnosis of plexopathy, which may also present with similar symptoms, is confirmed by electrodiagnostic studies, but the primary consideration in cases of crossed weakness and sensory loss in the lower extremities should be conditions affecting the spinal cord or cauda equina 1.
From the Research
Localizing Crossed Weakness and Sensory Loss in Lower Extremities
- The localization of crossed weakness and sensory loss in the lower extremities can be attributed to various neurological conditions, including entrapment neuropathies and central nervous system diseases like multiple sclerosis (MS) 2, 3.
- Entrapment neuropathies, such as those affecting the common peroneal, lateral femoral cutaneous, femoral, and posterior tibial nerves, can cause pain, sensory loss, incoordination, and muscle weakness in the lower limbs 2.
- Multiple sclerosis, an autoimmune-mediated neurodegenerative disease, can lead to physical disability, cognitive impairment, and decreased quality of life, with symptoms including unilateral optic neuritis, partial myelitis, sensory disturbances, and brainstem syndromes 3.
- Central cord syndrome (CCS), a type of spinal cord injury, is characterized by disproportionate weakness in the upper extremities compared to the lower extremities, although the definition and criteria for CCS are still debated 4, 5.
- The pathophysiology of CCS is thought to involve injury to the corticospinal tracts in the medulla or cervical cord, which can result in relatively greater hand and arm weakness compared to leg weakness 5.
- Vascular abnormalities, such as those affecting cerebral endothelial cells, may also play a role in the pathogenesis of MS, highlighting the complexity of the disease and the need for further research 6.