Magnetic resonance imaging of spinal cord trauma: a pictorial essay Neuroradiology (2006) 48: 223–232 Int.阮威勝

Introduction Fractures and joint dislocations can be detected accurately by plain radiology or CT Imaging the spinal cord is more difficult spinal cord injury can occur in the absence of bone changes The focus of this review is the role of magnetic resonance imaging (MRI) in the assessment of spinal cord injury following trauma, in both the acute and the chronic stages

Acute Spinal Cord Injury

true cord injury or compression with secondary cord damage minor injury or more severe trauma five criteria for a minor injury : “five no’s” no focal neurological signs no midline spinal tenderness no intoxication no painful injury no depression of consciousness complete or incomplete lesions A complete lesion involves loss of both functions in the lower sacral segments.

Central cord syndrome Trauma to the mid cervical and lower cervical spinal cord Degenerative bone changes are often present Greater motor impairment in the upper rather than the lower extremities bladder dysfunction and varying degrees of sensory loss below the level of the lesion

Anterior cord syndrome Secondary to a disruption of the anterior spinal artery Typically affects the upper thoracic cord Predominant motor loss with absent or insignificant sensory deficit

Brown-Séquard syndrome Hemisection of the spinal cord Ipsilateral weakness and loss of proprioceptive and vibratory sensation, due to disruption of the corticospinal tracts and dorsal columns Pain and temperature sensation are lost on the contralateral side because of the affected spinothalamic tract.

Cauda equina syndrome Trauma at the level of the cauda equina Difficulty in walking due to weakness of the legs Sensory disturbance, characteristically found in the perineal region

Spinal cord injury without radiographic abnormality (SCIWORA) Paediatric population Relatively large head size and skeletal mobility of the neck of younger children Can also occur in adults

Clinical evaluation can be difficult and that imaging is of particular importance in evaluating these patients MRI is the modality of choice for the evaluation of patients with neurological signs or symptoms Even in the absence of a traumatic lesion on either of these examinations, emergency MRI is indicated and should be obtained as soon as possible and certainly within the first hours after injury to prevent irreversible damage to the spinal cord.

In the acute setting, MR images can show transection, haemorrhage, contusion or oedema of the spinal cord Oedema or contusion is seen after secondary temporary or permanent cord compression Intramedullary haemorrhage is usually associated with a clinically complete and irreversible spinal cord injury

Spinal cord oedema Crushed vertebra Sagittal TSE T2WI

Traumatic pseudomeningocele STIR Sagittal TSE T2WI Axial GE T2WI

Spinal cord haematoma Axial GE T2WI Sagittal GE T2WI

Axial SE T1WI Sagittal TSE T2WI Axial GE T2WI

MRI can demonstrate ligamentous injuries, muscular lesions, facet joint dislocations and bone marrow oedema MRI is sensitive and has a high negative predictive value in the assessment of ruptured ligaments

In injury to the upper cervical level, the tectorial membrane can be disrupted The tectorial membrane lies close to the dens and clivus as an extension of the posterior longitudinal ligament The integrity plays a crucial role in the stability of the upper cervical region.

Detachment of the tectorial membrane Sagittal TSE T2WI

MRI as Prognostic role Poor prognosis complete cord syndrome and abnormal MRI finding cord contusion (cyst formation) pre-existing degenerative changes presence and extent of spinal cord haematoma

Good prognosis partial cord syndrome and normal MRI findings absence of spinal cord oedema The ratio of the maximal anteroposterior diameter of an epidural haematoma to the spinal canal diameter may have prognostic value Ratios of less than 60% are associated with a full recovery

Pre-existing cervical spondylosis and spinal stenosis Sagittal TSE T2WI Sagittal TSE T2WI Turbo STIR

Epidural haematoma Axialal TSE T2WI Sagittal TSE T2WI Sagittal SE T1WI

SCIWORA Sagittal SE T1WI Turbo STIR

Chronic Spinal Cord Injury

A number of victims of spinal cord trauma may develop new symptoms several weeks or years later MRI is unequivocally the modality of choice in the diagnostic work-up of these patients

Posttraumatic syringomyelia 3–4%. 8 weeks ~ several years Caused by cystic degeneration of the injured spinal cord at or near the site of the trauma Clinical presentation is non-specific Ascending sensory signs and motor deficit Treatment：shunting

Non-communicating syringomyelia often associated with a Chiari malformation, spinal stenosis or basilar impression Communicating syringomyelia mainly seen in children and always associated with hydrocephalus.

A benign widening of the central canal occurs in approximately 1.5 % Syringomyelia must be differentiated from the “benign” widening of the central canal typically seen at the junction of the anterior one-third and the posterior two-thirds of the spinal cord and is generally not wider than 2–3 mm A benign widening of the central canal occurs in approximately 1.5 %

High-pressure and low-pressure syringomyelia No non-invasive method of distinguishing the two states, but MRI appears to display a flow void within the cavity of a high-pressure syrinx on T2-weighted images. High-pressure syrinx may correspond to an acute expanding syrinx that, following prompt treatment, is more likely to improve than the low-pressure syrinx

Posttraumatic syringomyelia Sagittal SE T1WI Sagittal TSE T2WI Axial SE T1WI Sagittal TSE T2WI

Sagittal TSE T2WI Sagittal SE T1WI Sagittal TSE T2WI Sagittal SE T1WI

Enlargement of the central canal Axial GE T2WI Axial SET2WI Sagittal TSE T2WI

Progressive posttraumatic myelomalacic myelopathy (PPMM) 0.3–3.2% 2 months ~ 30 years PPMM is a possible precursor of syringomyelia. Clinically, PPMM and posttraumatic syringomyelia are neurologically indistinguishable; however, MRI can be used to differentiate the two entities. PPMM is less well defined than cystic myelopathy and has been reported to return high signal on proton density-weighted images

Pathology shows reactive gliosis, microcysts and thickening of the meninges. It is important to diagnose PPMM since it is potentially treatable. Local adhesions with cord tethering seem to cause PPMM and surgical untethering with expansive duraplasty leads to clinical improvement in the majority of patients Intraoperative ultrasound can be helpful in differentiating between myelomalacia and intramedullary cyst formation in this situation

PPMM Sagittal TSE T2WI Sagittal SE T1WI

Sagittal TSE T2WI Sagittal SE T1WI

Spinal cord atrophy 15–20% Aeduction in the anteroposterior dimensions of the spinal cord from the normal 6 mm at the cervical level to 7 mm at the thoracic level Usually observed many years after the traumatic event

Difficult to differentiate atrophy from a subarachnoid cyst with cord compression Sometimes, both entities may coexist The most frequent location of intradural arachnoid cysts is the thoracic thecal sac. It has been suggested that adhesions secondary to bleeding may impair CSF flow with dilatation of the subarachnoid space and the development of a cyst

Spinal cord atrophy Axialal GE T2WI Normal size of spinal cord

Posttraumatic subarachnoid cyst Sagittal TSE T2WI Axial GE T2WI

patients who have had spinal surgery for stabilization of vertebral fractures can still be examined by MRI when chronic spinal cord injury is suspected. Operative implanted materials are now usually MR-compatible and do not significantly interfere with the interpretation of images of the spinal cord

operative materials Sagittal TSE T2WI Axial GE T2WI

Conclusion Patients with focal neurological signs, evidence of cord or disc injury or whose surgery requires cord assessment should be imaged by MRI. Moreover, the demonstration of lesions on MRI can be predictive and help to provide a functional prognosis. In the chronic stage of a spinal cord trauma, MRI is the investigation of choice for evaluating complications and late sequelae in patients who develop new neurological symptoms. Since some of these lesions are treatable, detecting them is extremely important.