EMERGENCY NEURORADIOLOGY - PART 9 pps

mation (5, 13). In the case of particularly extensive trauma, intramedullary gliosis and ex- tramedullary fibrous scarring may develop, with the formation of subarachnoid adhe- sions (13). In addition, the spinal nerves and roots can become traumatized. The most common occur- rence is radicular compression, which may result from bone or intervertebral disk material. Radicular avulsions are usually caused by the violent hyperextension of a limb. Most avulsions involve the cervical nerve roots, usually as a consequence of the forced adduction of the shoulder and arm in motorcycle accidents (2, 18). Pseudo-meningocele formation is associated with such avulsions as the meninges are torn together with the neural tissue. Finally, epidural haematomas result from the traumatic rupture of the epidural venous plexi. Because the spinal dura mater is not firmly ad- herent to the vertebral surface, extensive haematomas traversing multiple levels can develop. SEMEIOTICS MR investigations in cases of spinal trauma begin with the acquisition of sagittal images that yield an overview with which to select and orient subsequent axial imaging sequences fo- cused on the areas of abnormality. A coronal plane study may also prove to be useful. A combination of sequences must then be acquired directed toward critically examining all of the spinal tissues. These include the acquisition of sagittal T1-weighted spin-echo (SE) images that provide accurate anatomical- morphological information. This acquisition is followed by T2-weighted fast spin echo (FSE) sequences providing good detail and MR signal characteristics of the spinal cord and nerve roots (14, 20, 27, 31, 33). One limitation of T2- FSE sequences is the relative absence of fatty tissue suppression with persistence of the bright bone marrow fat signal, which can con- ceal the presence of oedema. This limitation can be overcome by using fat signal suppression techniques (35). Finally, it is imperative to acquire T2*-weighted gradient recalled echo (GRE) images that are sensitive to the effects of magnetic susceptibility and which thereby reveal the presence of certain haemorrhagic products (3, 13, 31). Specifically the GRE sequences are sensitive to small areas of acute haemorrhage (e.g., deoxyhaemoglobin), and in the chronic phase in detecting haemosiderin. Imaging of the container of the central spinal canal To some degree, MRI makes it possible to visualize gross bony fractures, disk herniations/extrusions, intersegmental subluxation and certain ligamentous injuries (Figs. 5.8, 5.9). However, subtle fractures, especially those that are not distracted and those of the posterior bony elements of the spine, are poorly seen on MRI (3, 4, 13, 24, 32) (Fig. 5.10). Thin fracture lines are better visualized with T2/T2*- weighted sequences (Fig. 5.11). In addition, the detection of small bony fragments has also been partly overcome by the use of T2*-weighted GRE sequences. It should be pointed out that MRI is unique in its ability to identify compression fractures of the vertebral bodies without gross evidence of fracture on conventional radiography. In such cases, the detection of MRI signal hyperintensi- ty on T2-weighted images and consonant hypointensity on T1-weighted sequences indi- cates oedema of the marrow and microfractures of the trabecular structure of the vertebrae (Fig. 5.12). One frequently encountered problem is that of the differentiation between benign posttraumatic fractures and pathological fractures resulting from underlying metastatic neoplastic disease. Unfortunately, it must be stated that there are no absolute differential diagnostic cri- teria that unquestionably confirm metastatic neoplasia on a first imaging study in an individ- ual patient. Sequential follow-up imaging studies may be the only recourse in such cases. Posttraumatic herniations are similar or identical to non-traumatic forms (Fig. 5.13). In fact it is usually impossible to distinguish the 5.3 MRI IN EMERGENCY SPINAL TRAUMA CASES 323 posttraumatic degenerative disk herniations. Generally speaking, the presence of other associated posttraumatic injuries at the same level suggests the diagnosis of traumatic disk herniation (7, 13, 15). Ligamentous trauma can be detected direct- ly or indirectly on medical imaging studies. However, while MRI is capable of visualizing the spinal ligaments, it may not be able to dif- ferentiate between ruptured ligaments and adjacent tissue injury, all of which may be hypointense. Serious vertebral trauma demands an evaluation of the stability of the spine. This type of assessment is aimed at recognizing those conditions that may require surgical stabiliza- tion in order to prevent secondary damage to the neural structures. Of the various methods employed to evaluate spinal stability, the sim- plest is that of Denis which identifies three functional columns of the spine (9, 10): the anterior column (the anterior longitudinal ligament and the anterior 2/3 of the vertebral body); the middle column (the posterior 1/3 of the vertebral body and the posterior longitudinal ligament); and the posterior column (the bony and ligamentous structures behind the posterior longitudinal ligament). Accord- ing to this model, vertebral instability occurs with the loss of integrity of at least two con- tiguous columns. A more recent method identifies five sepa- rate signs of spinal instability (6): intersegmental vertebral subluxation of more than 2mm; increase in the interlaminar space of more than 324 V. SPINAL EMERGENCIES Fig. 5.8 - Acute thoracic spine trauma. The MRI images show a burst fracture of the T12 vertebral body, with posterior displacement of bony fragments into the central spinal canal and resulting stenosis. There are no visible signal alterations of the spinal cord. [a) Sagittal T1-weighted MRI; b, sagittal T2- weighted MRI; c) axial T2-weighted MRI]. a b c 2 mm in relation to the adjacent levels; widen- ing of the joint space of one or more posterior spinal facet joints; interruption of the posterior cortical margin of a vertebral body; and increase in the interpedicular distance of more than 2 mm between adjacent vertebrae. 5.3 MRI IN EMERGENCY SPINAL TRAUMA CASES 325 Fig. 5.9 - Acute lumbar spine trauma. The MRI reveals an L2 burst fracture with posterior displacement of the upper portion of the vertebral body into the central spinal canal and conse- quent canal stenosis. [a) sagittal T1-weighted MRI; b) sagittal T2-weighted MRI]. Fig. 5.10 - Acute lumbar spine trauma. The MRI images show a burst fracture of the L1 vertebral body with anterior epidural tissue within the central spinal canal. The vertebral bone marrow of L1 is hypointense on T1-weighted acquisitions and hyperintense on T2-weighted images indicating posttraumatic oedema/haemorrhage. The axial MRI T1-weighted image shows compression of the thecal sac by indeterminate tissue. The supplemental CT examination better demonstrates an interruption of the bony cortex of the right posterolateral surface of the L1 vertebral body and better characterises the bone frag- ment that is displaced into the central spinal canal. [a, d) sagittal T1-weighted MRI; b, c) sagittal, coronal T2-weighted MRI; e) axial CT]. a b b a Imaging of the spinal cord Unquestionably, MRI is the imaging examination technique of choice in the evaluation of spinal cord injury (1, 2). In the acute phase, this facilitates the identification of those conditions that may benefit from emergency surgical treat- ment, while also enabling an immediate prog- nostic judgement to be made. MR examina- tions should aim in particular to detect oedema, contusions, intramedullary haemorrhage, and spinal cord transection, in addition to deter- mining if cord compression is present (Figs. 5.14, 5.15, 5.16). The study involves the acquisition of sagittal T1-weighted SE and T2-weighted FSE or T2*- GRE images; the acquisition of axial images, preferably utilizing T2*-GRE. FLAIR (fluid at- tenuated inversion recovery) sequences can also provide useful information regarding spinal cord injury, due to the high contrast definition between the lesion, normal tissue and CSF (26). In the acute phase, the spinal cord may ap- pear swollen due to the presence of oedema and haemorrhage. Spinal cord swelling is easily shown on T1-weighted sequences. This swelling is hyperintense on T2-weighted sequences in relation to the normal cord tissue, an expression of intramedullary oedema (1, 3, 4, 6) (Fig. 5.17). This is defined by several authors as medullary contusion (16, 22) (Fig. 5.18). The presence of haemorrhagic products in the spinal cord injury is termed haemorrhagic contusion (Fig. 5.19). As mentioned above, frank intramedullary haemorrhage (i.e., haemato- myelia) may be encountered. In any case, the MR appearance of haemorrhagic products varies depending upon the time that has elapsed since the traumatic event, the modifica- tions undergone by the haemoglobin molecules 326 V. SPINAL EMERGENCIES c e Fig. 5.10 (cont.). d 5.3 MRI IN EMERGENCY SPINAL TRAUMA CASES 327 Fig. 5.11 - Acute cervical spine trauma. MRI in a patient with bilateral C2 pedicle fractures (Hangman fracture). a), b) Sagit- tal, axial T2-weighted MRI. a b Fig. 5.12 - Acute thoracic spine hyperflexion trauma. The MRI study shows a fracture of the T9-10 vertebrae with anterior wedging of the vertebral bodies. There is also evidence of oedema of the involved vertebral bone marrow. The spinal cord, al- though deflected by posterior displacement of the T9 vertebra, does not show intrinsic signs of MRI signal alteration. [a) sagittal T1-weighted MRI; b) c) sagittal, axial T2-weighted MRI]. a b c present, and the strength of the magnetic field. In the acute phase, deoxyhaemoglobin yields a hypointense signal on T2-, and even more strongly, on T2*-GRE sequences. A week or more after the trauma, the transformation of the deoxyhaemoglobin into methaemoglobin changes the signal to hyperintense on T1- and T2-weighted acquisitions. It should be noted that the evolution times of the various species of the haemoglobin molecule are slower than in 328 V. SPINAL EMERGENCIES Fig. 5.13 - Acute cervical spine trauma. The images show a posttraumatic C4-C5 disk herniation and anterior subluxation of C4 on C5, with minor impingement upon the anterior surface of the cervical spinal cord. A minor C4 compression fracture is also noted. a) Sagittal T1-weighted MRI; b) sagittal T2- weighted MRI. Fig. 5.14 - Acute cervical spine trauma. Identified is a burst fracture of C6 and with associated narrowing of the central spinal canal and cervical spinal cord compression. Note the hy- perintensity of the spinal cord on the T2-weighted images indicating contusion. [a) sagittal T1-weighted MRI; b) sagittal T2- weighted MRI]. a b b a 5.3 MRI IN EMERGENCY SPINAL TRAUMA CASES 329 Fig. 5.15 - Acute thoracic spine trauma. The MRI images demonstrate a T11-12 fracture-subluxation. In addition, the central spinal canal is narrowed, and there is an anterior epidural haematoma at the T11 level. The thoracic spinal cord is hyperintense on T2-weighted imaging at the T11-12 levels compatible with oedema/contusion. The MRI re-evaluation following surgical fixation and stabilisation shows good intervertebral realignment and a reduction of the spinal cord de- flection-compression (note the metallic artefact). [a) Sagittal proton density (PD)-weighted MRI; b) sagittal T2-weighted MRI; c) sagittal T1-weighted MRI; d) postoperative sagittal T1weighted MRI; e) postoperative sagittal T2*-weighted MRI]. b a c d e 330 V. SPINAL EMERGENCIES Fig. 5.16 - Acute cervical spine flexion trauma. The MRI examination shows anterior dislocation of C6-C7 associated with marked stenosis of the central spinal canal. The spinal cord is severely compressed at this level, revealing oedema and swelling of the cord above and below the compression. [a) sagittal T1-weighted MRI; b) sagittal T2-weighted MRI]. Fig. 5.17 - Acute cervical spine trauma. The MRI images reveal straightening of the physiologic cervical lordotic sagittal spinal curvature. In addition, there is a compression fracture of the C6 vertebral body. The spinal cord is swollen and is hyperintense on T2*-weighted MRI due to oedema associated with cord contusion, but no evidence of acute haemorrhage can be identified. [a) sagittal T1-weighted MRI; b) Sagittal T2*-weighted MRI]. a b a b 5.3 MRI IN EMERGENCY SPINAL TRAUMA CASES 331 Fig. 5.18 - Acute cervical spine trauma. The MRI examination shows a loss of the physiologic cervical lordotic sagittal spinal curvature and pre-existent central spinal canal stenosis. A focal area of spinal cord contusion (i.e., oedema and swelling) can be seen on the right side at the C4 level as well as a presumed traumatic posterior disk herniation associated with underlying spinal cord compression. [a, sagittal T2-weighted MRI; b) axial T2-weighted MRI]. Fig. 5.19 - Acute thoracic spine trauma. The MRI acquisitions reveal a compression fracture of the body of T12 associated with T12-L1 anterior subluxation and central spinal canal narrowing. In addition, there is a small anterior epidural haematoma at T11. MRI signal hypointensity is present within the spinal cord on the T2* acquisition due to acute haemorrhagic contusion (deoxyhaemoglobin). a) [sagittal T1-weighted MRI; b) sagittal T2*-weighted MRI]. a b a b the brain due to the reduced oxygen tension in the spinal cord (16). In the chronic phase, the presence of haemosiderin in the macrophages causes a marked signal hypointensity on T2- /T2*-weighted sequences. The spinal cord is often more easily assessed in the sagittal plane due to the simplicity of de- termining an alteration in the continuity and uniformity of the medullary MR signal along the longitudinal axis of the cord. Axial and 332 V. SPINAL EMERGENCIES Fig. 5.20 - Chronic spinal cord trauma. MRI images in a case of late follow up of a burst fracture of L1 revealing diffuse spinal cord atrophy and a focal area of myelomalacia within the conus medullaris. [a) sagittal T1-weighted MRI; b) sagittal T2- weighted MRI]. Fig. 5.21 - Chronic spinal cord trauma. MRI in the chronic phase following spinal cord trauma reveals a posttraumatic sy- ringomyelia cavity extending from C6-T1. [a) sagittal T1- weighted MRI; b) sagittal T2-weighted MRI, c) axial T2- weighted MRI]. a b a b [...]... Neuroradiologia 11:32 9- 3 35, 199 8 27 Posse S, Aue WP: Susceptibility artifacts in spin-echo and gradient-echo imaging J Magn Reson 88:47 3-4 92 , 199 0 28 Quencer RM, Sheldon JJ, MJD et al: MRI of the chronically injured cervical spinal cord AJR 147:12 5-1 32, 198 6 29 Ramon S, Dominguez R, Ramirez L et al: Clinical and magnetic resonance imaging correlation in acute spinal cord injury Spinal Cord 35:66 4-6 73, 199 7 30 Rogenbogen... treatments A review Spine 14:2 3-3 2, 198 9 20 Jones KM, Mulkern RV, Schwartz RB et al: Fast spin-echo MR Imaging of the brain and spine: current concepts AJR 158:131 3-1 320, 199 2 335 21 Kakulas BA: Pathology of spinal injuries CNS Trauma 1:11 7-1 29, 198 4 22 Kalfas I, Wilberger J, Goldberg A et al: Magnetic resonance imaging in acute spinal cord trauma Neurosurgery 23(3): 29 5-2 99 , 198 8 23 Kwo S, Young W, De Crescito... reduction with fast spin echo techniques Radiology 190 :56 5-5 69, 199 4 34 Tator CH, Fehlindgs MJ: Review of the secondary injury theory of acute spinal cord trauma with emphasis on vascular mechanisms J Neurosurg 75:1 5-2 6, 199 1 35 Tien RD: Fat suppression MR imaging in neuroradiology: techniques and clinical application Am J Roentgenol 158:36 9- 3 79, 199 2 36 Weirich SD, Cotler HB, Narayana PA et al: Histopathologic... MRI Imaging of acute spinal cord trauma AJNR 8(1): 5-1 0, 198 7 5 Curati WL, Kingsley DPE, Kendall BE et al: MRI in chronic spinal cord trauma Neuroradiology 35:3 0-3 5, 199 2 5.3 MRI IN EMERGENCY SPINAL TRAUMA CASES 6 Daffner RH, Deeb ZL, Goldeberg AL et al: The radiological assessment of post-traumatic vertebral stability Skeletal Radiology 19: 10 3-1 08, 199 0 7 Davis SJ, Teresi LM, Bradley WG et al: Cervical... 2° edition Lippincott-Raven: 116 1-1 206, 199 6 14 Flanders AE, Tartaglino LM, Friedman DP et al: Application of fast spin-echo MRI imaging in acute cervical spine injury Radiology 185(P):220, 199 2 15 Goldberg AL, Rothfus WE, Deeb ZL et al: The impact of magnetic resonance on the diagnostic evaluation of acute cervico-thoracic spinal trauma Skeletal Radiol 17(2):8 9- 9 5, 198 8 16 Hackney DB, Asato LR, Joseph... 180(1):245251, 199 1 8 Demaerel P, Van Hover P, Broeders A et al: Rapid lumbar spine MR mielography: imaging findings using a single-shot technique Rivista di Neuroradiologia 10:18 1-1 87, 199 7 9 Denis F: The three column spine and its significance in the classification of acute thoraco-lumbar spinal injuries Spine 8:81 7-8 31, 198 3 10 Denis F: Spinal instability as defined by the three-column spine concept... Radiology 161:38 7-3 90 , 198 6 17 Hall ED, Braughler JM: Central nervous system trauma and stroke II Physiological and pharmacological evidence for involvement of oxygen radicals and lipid peroxidation Free Radical Biol Med 6:30 3-3 13, 198 9 18 Hayashi N, Yamamoto S, Okubo T et al: Avulsion injury of cervical nerve roots: enhanced intradural nerve roots at MR Imaging Radiology 206:81 7-8 22, 199 8 19 Janssen L,... cord injuries in patients with cervical spondylosis Am J Radiol 146:27 7-2 84, 198 6 31 Scarabino T, Polonara G, Perfetto F et al: Studio RM Fast Spin-Echo dei traumi vertebro-midollari acuti Rivista di Neuroradiologia 9: 56 5-5 71, 199 6 32 Tarr RW, Drolshagen LF, Kerner TC et al: MRI Imaging of recent spinal trauma J CAT 11(3):41 2-4 17, 198 7 33 Tartaglino LM, Flanders AE, Vinitski S et al: Metallic artifacts... 1 89: 6576, 198 4 11 Faccioli F: La biomeccanica del trauma vertebro-midollare In: Dal Pozzo G, Syllabus XV congresso nazionale AINR Centauro, Bologna: 7-1 0, 199 8 12 Falcone S, Quencer RM, Green BA et al.: Progressive posttraumatic myelomalacic myelopathy AJNR 15:74 7-7 54, 199 4 13 Flanders AE, Croul SE: Spinal trauma In: Atlas SW: Magnetic resonance imaging of the brain and spine 2° edition Lippincott-Raven:... magnetic resonance signal patterns in a spinal cord injury model Spine 15(7):63 0-6 38, 199 0 37 White AA, Panjabi MM: Clinical biomechanics of the spine PA JB Lippincott, Philadelphia: 16 9- 2 75, 199 0 337 5.4 EMERGENCY IMAGING OF THE SPINE IN THE NON-TRAUMA PATIENT G Polonara, M.G Bonetti, T Scarabino, U Salvolini INTRODUCTION Non-traumatic spinal emergencies include all those clinical situations that present . Spinal trauma. Rivi- sta di Neuroradiologia 11:32 9- 3 35, 199 8. 27. Posse S, Aue WP: Susceptibility artifacts in spin-echo and gradient-echo imaging. J Magn Reson 88:47 3-4 92 , 199 0 28. Quencer RM,. emphasis on vascular mechanisms. J Neurosurg 75:1 5-2 6, 199 1. 35. Tien RD: Fat suppression MR imaging in neuroradiology: techniques and clinical application. Am J Roentgenol 158:36 9- 3 79, 199 2. 36 injuries. CNS Trauma 1:11 7-1 29, 198 4. 22. Kalfas I, Wilberger J, Goldberg A et al: Magnetic resonance imaging in acute spinal cord trauma. Neurosurgery 23(3): 29 5-2 99 , 198 8. 23. Kwo S, Young W,