The intramedullary spinal cord serves as a central pathway for communication between the brain and the rest of the body. This neural tissue extends from the brainstem, from the base of the skull down to the upper lumbar region, typically around the L1-L2 vertebral level in adults. It is part of the central nervous system, enabling movement, sensation, and automatic bodily processes. Its proper functioning is essential for overall health and neurological well-being.
Anatomy and Function
The spinal cord is a cylindrical structure encased by three protective membranes, the meninges, and shielded by the bony vertebral column. Unlike the brain, the spinal cord’s gray matter is centrally located and surrounded by white matter. The gray matter, shaped like a butterfly or an “H,” contains nerve cell bodies, while the surrounding white matter consists of nerve fibers organized into ascending and descending tracts.
Ascending tracts carry sensory information, such as touch, pain, temperature, and proprioception (awareness of body position), from the body to the brain. Conversely, descending tracts transmit motor commands from the brain down to muscles for voluntary movement. The spinal cord also plays a role in reflex arcs, which are rapid, involuntary responses to stimuli that do not require brain involvement, allowing for quick reactions.
The intramedullary region refers to the tissue within the spinal cord, distinguishing it from extramedullary regions outside the cord but within the spinal canal, such as nerve roots or the meninges. The spinal cord receives its blood supply from three main longitudinal arteries: one anterior spinal artery and two posterior spinal arteries, which branch from the vertebral arteries and are reinforced by radicular arteries along its length. The central canal, a vestigial extension of the brain’s ventricular system, runs the length of the spinal cord within the gray matter.
Conditions Affecting the Intramedullary Spinal Cord
A range of medical conditions can affect the intramedullary spinal cord, often leading to neurological deficits. Intramedullary spinal cord tumors (IMSCTs) are abnormal growths arising from cells within the spinal cord tissue. These are less common than brain tumors, accounting for 5-10% of all intrinsic central nervous system tumors.
Ependymomas and astrocytomas are the most common types, constituting 80-90% of IMSCTs. Ependymomas are often slow-growing and common in adults; astrocytomas are more prevalent in children. Hemangioblastomas, benign, highly vascularized tumors, are also found in the intramedullary region, sometimes associated with von Hippel-Lindau disease.
Syringomyelia involves the formation of a fluid-filled cyst, known as a syrinx, within the spinal cord. These cysts can expand, causing damage to the surrounding spinal cord tissue. While many cases are linked to Chiari malformations, where brain tissue extends into the spinal canal, syringomyelia can also result from spinal cord tumors, injuries, or inflammation.
Inflammatory conditions, such as transverse myelitis, involve inflammation of the spinal cord. This condition can present with symptoms similar to spinal cord compression and may involve long segments of the cord. It can be idiopathic (of unknown cause) or associated with other conditions like multiple sclerosis or neuromyelitis optica.
Vascular malformations, abnormal formations of blood vessels, can also affect the intramedullary spinal cord. These include arteriovenous malformations (AVMs), where arteries and veins are abnormally tangled, or fistulas, direct connections between an artery and a vein. Such malformations can disrupt blood flow, potentially leading to hemorrhage or ischemia within the cord.
Identifying Symptoms
Symptoms arising from intramedullary spinal cord issues often reflect the disruption of nerve pathways responsible for sensation, movement, and autonomic functions. Sensory changes are common and include numbness, tingling, or a reduced ability to feel pain and temperature. For lesions in the upper spinal cord, this sensory loss might present in a “cape-like” distribution across the shoulders and arms. Dissociated sensory loss, where pain and temperature sensation are impaired while touch and position awareness remain intact, occurs because the spinothalamic tracts carrying pain and temperature traverse the central gray matter.
Motor weakness is a frequent symptom, manifesting as difficulty moving limbs, muscle wasting, or spasticity, muscle stiffness and uncontrolled spasms. Reflexes may also be altered, becoming either diminished or overly brisk. Balance issues and gait instability can arise due to impaired coordination and muscle control.
Autonomic dysfunction also occurs, affecting involuntary bodily processes. This includes issues with bladder and bowel control, such as urinary incontinence or difficulty with bowel movements. In some cases, autonomic dysreflexia, characterized by severe hypertension and increased sympathetic activity, can occur in patients with spinal cord injuries above the T6 level. Symptoms often progress gradually, making early recognition challenging.
Approaches to Diagnosis and Treatment
Diagnosing conditions affecting the intramedullary spinal cord begins with a comprehensive neurological examination. This assessment evaluates a patient’s reflexes, muscle strength, sensation, and coordination to pinpoint affected areas of the spinal cord. Magnetic Resonance Imaging (MRI) with contrast is the primary imaging technique for visualizing the spinal cord. MRI provides detailed images of soft tissues, allowing professionals to differentiate between normal spinal cord tissue and abnormalities such as tumors, cysts, or inflammation. The use of gadolinium contrast enhancement helps highlight lesions, as many tumors and inflammatory processes will show enhancement.
Other diagnostic tools may be employed in specific situations. Cerebrospinal fluid (CSF) analysis, obtained through a lumbar puncture, might be performed, though it is often non-diagnostic for intramedullary spinal cord metastases, with elevated protein being the most common abnormal finding. A biopsy, taking a tissue sample for microscopic examination, may be necessary to confirm the diagnosis, especially when imaging findings are unclear or to distinguish between a tumor and an inflammatory condition.
Treatment approaches for intramedullary spinal cord conditions vary widely, depending on the specific diagnosis, its severity, and the patient’s overall health. Surgical intervention is a common treatment, particularly for tumors or cysts. The goal of surgery for tumors is often gross resection when possible, aiming to remove as much abnormal growth safely to preserve neurological function and alleviate symptoms. For syringomyelia, surgical options may include procedures to drain the syrinx or address underlying causes like Chiari malformations.
Radiation therapy, using high-energy beams to target and destroy abnormal cells, is frequently used, especially for tumors that cannot be fully removed surgically or for metastatic lesions. This treatment can help improve or prevent neurological deterioration. Chemotherapy, using medications to kill cancer cells, may also be part of the treatment plan, particularly for certain types of tumors or metastatic disease. Physical therapy is a component of treatment, helping patients regain strength, improve mobility, and manage symptoms. Overall, treatment aims to alleviate symptoms, prevent further neurological damage, and, in some instances, cure the underlying condition.