Imaging of Intramedullary Spinal Cord Lesions on MRI

Abstract

Lesions originating from parenchyma of the spinal cord present with a myriad of symptoms and signs more commonly via direct compression, followed by infiltration into the spinal parenchyma. Pain can be radicular, posterior midline, dull and aching. Rare presentations include paravertebral tightness/stiffness, and syringomyelia. Deficits were most commonly motor, followed by, sensory or bladder dysfunction [1]. Astrocytomas are second most common intramedullary tumours, and most common among paediatric age group. They are neoplasms of astrocytic origin and infiltrate into the surrounding spinal cord tissue, ill-defined margins, lack well defined capsule or cleavage plane, making them prone for incomplete resection and recurrence. They present with long multi-segment, eccentric and holocord involvement. They are associated with neurofibromatosis and cyst formation. Tumoural cysts are usually intra substance and reflect necrosis, haemorrhage, or degeneration that shows in-homogeneous signal intensity and peripheral contrast enhancement on MRI [Table/Fig-1(a-e),2(a-e)]. Canal widening with kyphoscoliosis is more frequently encountered in paediatric age group. On Magnetic Resonance Imaging (MRI), they appear to expand the cord and are hypo to isointense on T1 weighted images, hyper intense on T2 and Short Tau Inversion Recovery (STIR) images, with varying degrees of patchy enhancement [1,2]. Ependymomas are most common intramedullary tumours in adults, with predilection in cervico-thoracic segments. However, myxopapillary variant of ependymomas tends to occur more commonly in filumterminale and conusmedullaris. They are known to arise from ependymal lining of cord with central location, and extend peripherally as they grow. Rare variant of extramedullary ependymoma can initially be intramedullary and become eventually exophytic, growing out of the medulla. Ependymomas have well defined margins, and compress the cord [1,2]. Traversing vessels at the junction,get stretched and eventually bleed; giving the “cap sign” [Table/Fig-3(a-e),4(a-e)]. Non enhancing non tumoural (polar) cysts are commonly associated with ependymoma, and show Cerebrospinal Fluid (CSF) signal extends beyond the cranial or caudal pole of the neoplasm. Presence of syringohydromyeliais seen more consistently with ependymoma, than astrocytoma. Most of the ependymomas were T1 iso to hypointense, with hyperintensity on T2 and STIR images, and homogenous intense enhancement with persistent hypointense “cap sign”. Ependymomas tend to occur commonly in association with Neurofibromatosis 2 [2,3]. Haemangioblastomas are benign tumours of vascular origin, and show short segment involvement with prominent flow voids, usually extending along pial surface [Table/Fig-5]. They have cystic component with enhancing highly vascular nodular component. They have surrounding oedema, syrinx and association with Van HippelLindau disease. Enlarged spinal arteries may be seen, and they should be differentiated from vascular malformation [4]. Intramedullary spinal cord metastases are comparatively rare, especially in absence of known primary malignancy. Drop metastasis with CSF dissemination through the spinal cord, central canal or contiguous spread from carcinomatous meningitis [Table/Fig-6(a-d),7(a-e)]. Most common route of spread through haematogenous dissemination leading to arterial embolisation (most common primaries include carcinoma lung). Other routes include retrograde spread through Batson’s spinal venous plexus; metastatic perineural spread to the spinal cord, CSF dissemination through drop metastasis or intraspinal through perineural sheaths. Cystic change/haemorrhage are seen rarely. They show postcontrast enhancement with extensive disproportionate oedema (extensive T2 hyper intensity, which can be on average multifold larger than that of the enhancing portion of the lesion) [3]. Postcontrast complete or partial rim enhancement along margins is noted.Another rarer proposed route of spread is via penetrating vessels within the Virchow-Robin spaces penetration of the spinal cord parenchyma. Rare subtype of exophytic ependymoma [Table/Fig-8(a-d)] has similar features as ependymoma, with additional exophytic soft tissue component. Infective granulomas present with fusiform cord swelling with ill-defined iso to hyperintensity on T1WI [Table/Fig-9(a-d)]. Surrounding oedema maybe present with T2 hypointense area. Adjacent disc, soft tissue may show enhancement, depending on involvement.Varying amount of caseous necrosis and liquefaction present as central hyperintensities. An iso-hypointense rim, showing enhancement was seen surrounding a hyperintense centre [4]. [Table/Fig-10] describes the radiological findings of all the nine cases. Malignant intramedullary spinal tumours may escape early diagnosis, as patients bearing these lesions may be initially asymptomatic. With use of MRI; T1, T2 and STIR weighted images should be accessed, in atleast two different imaging planes with large field-of-view, to allow visualisation of the entire cord, and demarcate location and extent of these tumours. Haemorrhagic components should be assessed on Gradient echo images. Postcontrast images demonstrate solid enhancing tumour components and helps in differentiating tumour cysts from peritumoural cysts [5].

Keywords

• astrocytoma
• ependymoma
• magnetic resonance imaging
• metastasis
• spinal tumours