Spinal cord

the inner core of the spinal canal, consisting of white and grey matter enclosed within the meninges. From the spinal cord originate 31 spinal nerves. Also, see spinal cord.

The spinal cord can be imaged with varying degrees of clarity using different techniques. With MR imaging, T1 weighting easily allows distinction of the spinal cord contours from the surrounding cerebrospinal fluid. However, the cord is demonstrated less effectively with T2 weighting because of the inferior signal-to-noise ratio and the intense signal from the cerebrospinal fluid. Nevertheless, for diagnosis of multiple sclerosis involving the spinal cord, the T2-weighted sequence is useful. Contrast enhancement may also be employed. In the spinal cord, enhancement may be seen in patients with demyelination, infarction, vascular engorgement or neoplasm. Pluridirectional tomography (e.g. MR imaging) is useful for evaluating patients with suspected spinal cord disruption and oedema secondary to trauma (central cord syndrome).

Although it is a safe and effective method for demonstrating the spinal cord, myelography is more costly and more invasive than CT or MR imaging. Myelography is also useful in detecting cysts within the spinal cord, as contrast material will demonstrate the cystic nature of the process and its communication with the subarachnoid space. Gas is an effective and safe contrast material for studying the spinal cord but its use requires pluridirectional tomography and special expertise on the part of the examiner.

On contrast-enhanced CT, severe disruption of the spinal cord can cause the cord to appear absent as contrast medium fills the spinal canal completely.

The processes that commonly affect the spinal cord include neoplasms, such as an astrocytoma, ependymoma and, rarely, haemangioblastoma or lipoma; cysts, such as syringomyelia or hydromyelia; and non-neoplastic conditions such as myelomalacia, demyelination, arteriovenous malformation, compression, tethering, physical trauma and atrophy.

Most of the mass lesions affecting the spinal cord are metastases to the vertebral column. MR imaging is the method of choice for evaluating these tumours. On myelography, narrowing or complete obliteration of the subarachnoid space and blocking of the flow of contrast medium may be noted. Frequently cysts and mass lesions result in expansion of the spinal cord.

In cases of trauma, MR imaging is clearly superior to all other imaging methods; the ability to survey long segments of the spine, the unsurpassed contrast resolution and the multiplanar capability afforded by MR imaging offer significant advantages over CT scanning. Spinal ultrasonography may also play a role in the intraoperative assessment of the traumatized spinal cord. Acute spinal cord injury may result from irreversible structural lesions such as laceration, transection or severe contusion; intrinsic reversible lesions such as concussion or mild contusion; or extrinsic reversible lesions such as cord compression. Spinal cord concussions (spinal shock), contusions, transections, lacerations and dissolution due to autodestruction after severe contusive injuries may also occur.

The clinical manifestations of spinal cord injury are variable. Eight major categories are described:

Post traumatic progressive myelopathy is a clinical syndrome occurring after spinal cord injury. Among the findings that may occur in this condition are atrophy, syringomyelia, myelomalacia, arachnoid cyst, tethering and compression (as from malalignment or retropulsed fracture fragments or disc).

Post-traumatic syringomyelia may also result from a spinal injury, sometimes not becoming evident until decades after the initial injury.

Tethering (also known as tethered cord syndrome or conus medullaris syndrome) may represent a manifestation of occult spinal dysraphism, but tethering may also be caused by intraspinal dermoids, lipomas, congenital bands and meningomyelocoele.

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