The human nervous system is an intricate communication network divided into the Central Nervous System (CNS)—the brain and spinal cord—and the Peripheral Nervous System (PNS), which includes all nerves branching out from the CNS. When nerve damage occurs, the resulting disorders cause disability, but their symptoms depend on which part of the network is affected. Myelopathy and Neuropathy are two distinct disorders that are often confused, yet they represent damage to fundamentally different parts of the nervous system. Differentiating these complex conditions begins with understanding the specific location of the injury: the spinal cord (CNS) versus the outlying nerves (PNS).
Understanding Myelopathy
Myelopathy refers specifically to a disorder resulting from compression or injury to the spinal cord. This condition frequently develops due to degenerative changes in the spine, such as spinal stenosis or cervical spondylosis, where bone spurs or thickened ligaments narrow the spinal canal and press directly on the cord. Trauma, tumors, or severe disk herniation can also cause this compression, interrupting signals traveling between the brain and the body.
Myelopathy causes upper motor neuron damage, affecting nerve tracts originating in the brain. Disruption leads to dysfunction below the level of compression. Patients often notice difficulty with fine motor skills, such as buttoning a shirt, which is a common early sign. Because the spinal cord is centralized, symptoms of weakness and sensory changes tend to be bilateral, affecting both sides of the body simultaneously.
Understanding Neuropathy
Neuropathy involves damage to the peripheral nerves that lie outside the brain and spinal cord. These nerves transmit sensory information and motor commands to and from the extremities, organs, and glands. Unlike myelopathy, which is typically a focal compression issue, neuropathy is often a systemic problem affecting nerves throughout the body.
The most common cause of neuropathy is chronic metabolic conditions like diabetes, leading to progressive nerve fiber deterioration. Other causes include toxins, autoimmune disorders, nutritional deficiencies, or infections. Damage results in lower motor neuron signs, characterized by a loss of direct connection between the spinal cord and the muscle, primarily affecting the distal limbs first.
Key Clinical Differences in Presentation
Myelopathy, involving the central upper motor neurons, results in the brain’s inability to properly regulate the spinal reflex arc, leading to exaggerated responses. This manifests as hyperreflexia, where a simple tap on a tendon produces a brisk reflex, and often spasticity (abnormal muscle stiffness).
Conversely, neuropathy affects the peripheral lower motor neurons, severing the direct connection needed to complete the reflex arc. This causes reflexes to become diminished or entirely absent (hyporeflexia or areflexia). The muscles may also show flaccidity and visible muscle wasting (atrophy) can occur over time.
Sensory loss also differs markedly in its pattern. Myelopathy often presents with a generalized sensory change below the level of compression, involving large areas of the body. Neuropathy frequently follows a characteristic “stocking-glove” distribution, where the longest nerves are affected first, causing numbness and tingling in the feet and hands.
Gait provides strong clues for differentiation. A person with myelopathy typically exhibits a stiff, spastic, or uncoordinated gait due to muscle stiffness and poor balance. In contrast, a patient with significant sensory neuropathy may have a high-stepping gait, known as sensory ataxia, because they must visually monitor their feet to compensate for the lack of sensation and poor proprioception. Motor neuropathy can also cause foot drop, where the weakened muscles cannot lift the front of the foot.
Diagnostic Tools Used for Differentiation
Medical professionals rely on specific diagnostic tools to definitively distinguish between these two conditions. For suspected myelopathy, the primary tool is structural imaging, most commonly Magnetic Resonance Imaging (MRI). MRI provides detailed visualization of the spinal cord and surrounding structures, allowing clinicians to confirm the presence and severity of compression, disk herniation, or other structural lesions.
In contrast, neuropathy is primarily diagnosed using functional electrical tests, specifically Nerve Conduction Studies (NCS) and Electromyography (EMG). NCS measures how quickly electrical signals travel along the peripheral nerves, helping to pinpoint the location and type of damage. EMG assesses electrical activity within the muscles, revealing whether weakness stems from the nerve or the muscle fibers. These electrical tests provide a functional assessment of the peripheral nervous system.