Diagnostic imaging in acute para- and tetraplegia


Abel, R. (1); Gerner, H.J. (2); Meiners, T. (3); Mariss, G. (4)

Dr. Rainer Abel
Dept. of Orthopedic Surgery
University of Duesseldorf
Moorenstr. 5
40225 Duesseldorf
E-mail abel@uni-duesseldorf.de (1)

Keywords: spinal trauma, diagnostic imaging, MRI, computed tomography


Introduction

In the last few years there was a rapid developement and change in diagnosic imaging. Some of these technologies use new physical priciples like MRI, others were developed using computerized processing of information gained by well known methods such as reconstruction of CT scans. Older and well established methods like conventional x-ray imaging, tomography and myelography are still available. This situation gave us reason to reevaluate the position of these techniques in our clinical management, especially in the acute setting.

Differentialdiagnostic approach

The diagnostic approach to acute para and tetraplegia lined out in the following diagramms is based on the experience with our patients of the last five years. To define a pragmatic and clinically relevant way of using diagnostic procedures it is a must to have a clear scheme of differentialdiagnostic possibilites. This is why we build the decission-tree shown in Fig. 1.

A patient presenting with an acute paraplegia may or may not have been exposed to a trauma. Let us first focus on the majority of patients which had suffered a trauma. The important question is whether the trauma was adequate - such as a car or motorcyle accident - or inadequate - like lifting a case of bottles.

If there was a adequate trauma you have to look for destructed vertebrae - that is fractures - or destructed soft tissue which are disc herniations and ruptures of ligaments. Additional possibilites are intraspinal bleeding or a spinal contusion.

If there was a trauma you consider as inadequate compared to the damage to the spine, you have to look for destruction of vertebra because of osteoporosis, tumors or spondylitis. Other possibilities which involve no destruction of vertebra are arachnitis, discitis, stenosis of the spinal canal or adhesions of the spinal cord.

If the patient reports no trauma at all, there might be a intraspinal tumor, a vascular process, a hemorrhage or edema. An acute inflammation or any kind of neurologic disease producing the symptoms of para- or tetraplegia also have to be considered. Finally, there is always the possibility of a trauma which the patient does not report.

The diagramm (Fig. 2) demonstrates the frequency of the conditions that led to paraplegia in patients we admitted for primary care during the last five years. You see that the vast majority of paraplegia was caused by fractures. Other important groups are tumor and disc problems.

Imaging strategy - adequate trauma

In Fig. 3we outline our diagnostic strategy in patients with an adequate trauma. The first thing - which is always nescessary - is to get plain film x-rays of the segment of the spine which corresponds with the neurologic staging. The patient should not leave the x-ray department without readable films in two planes. In almost all cases at least the presence of fractures can be diagnosed on these films.

The next step depends on the overall approach to the management of these fractures. Since we do intend to stabilize all instable spinal fractures as soon as possible, with an anterior and posterior approach if appropriate - a film showing an instable spine as demonstrated in Fig. 4 gives us enough information to proceed with surgery.

If the fracure does not appear to be unstable or for example only a posterior stabilisation is discussed, a CT-scan should be obtained, to give the nescessary information about intraspinal fragments, fractured pedicles as well as traumatic herniations of intervertebral discs.

Fig. 5 demonstrates a case where the plain film does not show too much of a stenosis of the spinal canal through fractures.

Only the CT - Scan reveals the extend of an intraspinal fragment. In this case the fracture was reduced using a Kluger - System of fixateur interne. The result was controlled intraoperatively by myelography using a flouroscope and later documented with a CT-scan (Fig.6).

According to our experience, 3D reconstructions did not yield any additional information. It should be mentioned at this place that according to experience most surgeons do stick to the plain films while they are performing the surgery - even if CT-scan or MRI scans are available.

In cases where no definite fracture can be seen on the conventional x-ray films we used to follow a conservative stepladder of diagnostic imaging including CT-scans, Myelography and repeated CT-scan after Myelography. MRI was employed as a last resort.

The growing experience with MRI-Studies changed that. We now start with MRI imaging and feel confident to use it to diagnose soft tissue problems - for example disc herniations, as demonstrated in Fig. 7 - as well as fractures. According to our experience MRI is by no means "boneblind". Of course other conditions, such as intraspinal hemorrhage or edema following spinal contusion are also demonstrated precisely.

Only where Magnetic Resonance Imaging is not possible or avilable we still use a combination of Myelography and CT scaning.

Imaging strategy - no adequate trauma

Our diagnostic approach in these cases is outlined in Fig. 8. If there was no or no adequate Trauma, we still do plain film x-ray studies as described above, to diagnose destructed vertebra and tumor or spondylitis induced fractures. If these films or the patient history indicate a possibility of muliple lesions - such as a kown prostata carcinoma (Fig.9) - we obtain a MRI because it provides a fast overview to the extend of the disease. It also shows details of the impact to the myelon.

If it is reasonable to expect only a singular lesion we do a CT-scan. We found CT scans are very reliable to define the extend of intravertebral lesions. Fig. 10 shows the remnants of a vertebra with metastasis of a adrenocarcinoma.

If no fractures are visible and intraspinal changes such as tumors or hemorrhage are to be diagnosed, we proceed with an MRI-Scan. As example (Fig.11) a bleeding ependymoma which caused a paraplegia with an acute onset.

Table 1 summarizes frequent problems we encoutered. The first points underscore that imaging diagnostic has to be based on exact clinical neurological staging. Usually minor neurological deficts are missed, which are present in neurologic segments above the level of the dominating symptoms. This problem is especially important if the patient is unconscious, intoxicated or suffered a headinjury.

Secondary fractures are missed usually because a lesion is found, which explains the symptoms. It is important to keep this in mind and to look for associated fractures if the circumstances of the injury indicate the possibility.

An especially difficult area for conventional x-ray imaging is the cervico-thoracic transition. The American Trauma Life Support Manual gives the direction that no cervical collar is to be removed without an x-ray image demonstrating all seven cervical vertebrae. We can only support this, since there is a good chance of a fracture or luxation of the lower cervical spine.

If it is impossible to obtain readable images by applying traction to the shoulders, a conventional midline tomography should be done.

Concerning CT-scans there are three frequent problems. The first is a missing topogramm. If the topogramm is missing, there is always an incertainity where exactly the scans were done and where the lesion extends. Another mistake is a CT-scan which is only documented in a bone window. We had 3 patients where a traumatic disc herniation was missed out of this reason. The last point regarding CT scans which lead to missings of lesions is a inappropriate gapping between slides. We recommend a maximum sicethickness of 2 to 3 mm with no gap if a study of the cervical spine is done. To achieve this, a restriction of the examination area to two or a maximum of three cervical segments is nescessary.

As a last point we would like to warn against elaborate additional studies and reconstruction processes. Once you have the nescessary information you should terminate diagnostic imaging. As said earlier we do not see any benefit in added information if a timeconsuming 3D reconstruction is done.