EMERGENCY NEURORADIOLOGY - PART 10 doc

lae. In such clinically suspected but MRI-negative cases, myelography and spinal angiography may be indicated, and when positive will defin- itively reveal the site of the dural fistula, the feeding arteries and the dilated draining veins. In any case, angiography is a prerequisite for therapeutic dural fistula embolization, the treatment of choice in these patents. Cavernous angiomas are usually indolent vascular malformations that are nevertheless prone to haemorrhage and intrinsic thrombosis. T1- and T2-weighted MRI typically shows a central hyperintense core with a peripheral margin or margins of hyper- and hypointensity due to the presence of mixed subacute and chronic haemoglobin metabolites (Fig. 5.46). Some cases demonstrate central enhancement after IV contrast medium administration, rep- resenting the residual patent vascular component of the angioma. Cavernous angiomas can present acutely with signs and symptoms relat- ed to intramedullary haemorrhage (Fig. 5.47). Acute spinal cord syndromes can also be caused by viral or granulomatous infections. In 364 V. SPINAL EMERGENCIES Fig. 5.47 - Acute haemorrhage within intramedullary cavernous angioma. The spinal T1-weighted spinal MRI images demonstrate an extensive acute-subacute (deoxyhaemoglobin and methaemoglobin) thoracic intramedullary haemorrhage associated with an intramedullary cavernous angioma showing intrinsic hypointensity on T2-weighted acquisitions consistent chronic peripheral microhaemorrhages (haemosiderin). The MRI of the brain showed several cavernous angiomas demonstrating the multicentric potential of this pathologic process. [a) sagittal T2- weighted spinal MRI b) sagittal T1-weighted weighted spinal MRI; c) sagittal T2*-weighted spinal MRI; d) axial T1-weighted spinal MRI; e) axial T2*-weighted cranial MRI]. a b Fig. 5.46 - Chronic haemorrhage within thoracic intramedullary cavernous angioma. T2*-weighted sagittal MRI reveals hypointensity within the upper thoracic spinal cord as a conse- quence of deposition of haemosiderin associated with thrombosis-haemorrhage within an intramedullary cavernous angioma. cases of infectious myelitis, MRI demonstrates multisegmental non-specific intramedullary hyperintensity on T2-weighted sequences, with a variable enhancement after contrast medium administration. Spinal cord abscess formation is rare and is usually caused by the direct extension of infections from adjacent perispinal tissues or from penetrating trauma. T2-weighted MRI demonstrates an intramedullary mass that is hyperintense on T2-weighted sequences and reveals rim enhancement after IV gadolinium administration. Distinguishing this pattern from other spinal cord lesions such as neoplasia is not always possible on the basis of the images alone. Acute transverse myelitis is an acute inflammatory process with a poor prognosis. The aetiology is unknown, however it is prob- ably autoimmune in nature. Acute transverse myelitis can be associated with various conditions such as multiple sclerosis, paraneo- plastic syndromes, prior vaccinations, vas- culitis or known autoimmune disorders. Clin- ically there is an acute onset of a profound spinal cord neurological deficit in the absence of other findings. It is for this reason that transverse myelitis is always a diagnosis of ex- clusion. On MRI, acute transverse myelitis demonstrates areas of hyperintensity on T2- weighted imaging associated with spinal cord swelling and irregular contrast enhancement following gadolinium administration due to an associated breakdown in the blood-cord barrier. In the chronic phase, the spinal cord 5.4 EMERGENCY IMAGING OF THE SPINE IN THE NON-TRAUMA PATIENT 365 Fig. 5.47 (cont.). e c d can appear atrophic, and areas of high signal on T2-weighted images may persist due to gliosis. Acute disseminated encephalomyelitis is a monophasic autoimmune disease that follows within days or weeks of an antiviral vaccination or viral infection. As the name indicates, it in- volves the brain but also concomitantly affects the spinal cord. Pathologically the lesions are similar to those of MS. The prognosis is typically good and the majority of patients respond rapidly to steroid treatment. MRI shows hyperintense areas on T2-weighted sequences within the parenchyma of the brain and spinal cord that enhance after IV gadolinium; the spinal cord may be swollen. The development of radiation myelopathy in part depends on the dose of radiation and the time period over which it was adminis- tered. In the acute milder forms, typically pre- senting approximately three months after radiation is applied to the spinal cord, the patient experiences sensations similar to electric shocks in the lower limbs; MRI may show no abnormality. However in severe cases the patient reveals a severe, rapidly progressive myelopathy; in such cases, the spinal cord is swollen, hyperintense on T2-weighted images and enhances following IV contrast injection. Evolution of spinal cord atrophy will occur over time (Fig. 5.48). 366 V. SPINAL EMERGENCIES c Fig. 5.48 - Radiation induced thoracic myelitis/spondylitis three years following radiotherapy. T2-weighted MRI with fat suppression shows hyperintense MRI signal within the thoracic spinal cord and within the bone marrow of several contiguous vertebral bodies, both of which are caused in this case by the preceding radiation therapy. Axial T2*-weighted images demonstrate again the intramedullary location of the pathologic process. No contrast enhancement of the intramedullary process can be identified. Note the postsurgical alterations. [a) sagittal T2-weighted MRI; b) sagittal T1-weighted MRI following IV Gd; c) axial T2*-weighted MRI]. a b REFERENCES 1. Baleriaux DL: Spinal cord tumours. Eur Radiol 9 (7):1252- 1258, 1999. 2. Chen CJ, Chen CM, Lin TK: Enhanced cervical MRI in identifying intracranial dural arteriovenous fistulae with spinal perimedullary venous drainage. Neuroradiology 40: 393-407, 1998. 3. Fortuna A, Ferrante L, Acqui M et al: Spinal cord ischemia diagnosed by MRI. J Neuroradiol 22:115-122, 1995. 4. Karampekios S: Inflammatory, vascular and demyelinating diseases of the spine and spinal cord. Eur Radiol (S1)10:36, 2000. 5. Liou RJ, Chen CY, Chou TY et al: Hypoxic - ischaemic injury of the spinal cord in systemic shock: MRI. Neurora- diology 38:S 181-183, 1996 6. Lyclama à Nijeholt GJ, Uitdehaag BMJ et al: Spinal cord magnetic resonance imaging in suspected multiple sclerosis. Eur Radiol 10:368-376, 2000. 7. Obenberg J, Seidi Z, Plas J: Osteoblastoma in lumbar vertebral body. Neuroradiology 41:279-282, 1999. 8. Rimmelin A, Clouet PL, Salatino S et al: Imaging of thoracic and lumbar spinal extradural arachnoid cysts: report of two cases. Neuroradiology 39:203-206, 1997. 9. Rocca MA, Mastronardo G, Horsfield MA et al: Comparison of three MR sequences for detection of cervical cord lesions in patients with multiple sclerosis. AJNR 20:1710-1716, 1999. 10. Silbergleit R Brunberg JA, Patel SC et al: Imaging of spinal intradural arachnoid cysts: MRI, myelography and CT. Neuroradiology 40:664-668, 1998. 11. Suzuki K, Meguro K, Wada M et al: Anterior spinal artery syndrome associated with severe stenosis of the vertebral artery. AJNR 19:1353-1355, 1998. 12. Wilmink JT: MR imaging of the spine: trauma and degene- rative disease. Eur Radiol 9 (7):1259-1266, 1999. 13. Yamada K, Shrier DA, Tanaka H et al: A case of subacute combined degeneration: MRI finding. Neuroradiology 40: 398-400, 1998. 5.4 EMERGENCY IMAGING OF THE SPINE IN THE NON-TRAUMA PATIENT 367 VI NEUROPAEDIATRIC EMERGENCIES 371 INTRODUCTION This chapter covers the most common emergency situations encountered in neuropaedi- atrics, including cerebrovascular disease, head injuries, infections of the central nervous system (CNS) and intracranial hypertension. CEREBROVASCULAR DISEASE Cerebrovascular disease (15, 32) is rare in infants and newborns and when encountered does not have the same aetiological factors as in adults: the most common causes in the young age group are congenital vascular abnormalities and those secondary to systemic illnesses. Various areas of the brain show significant differences in their sus- ceptibility to cerebral vasculopathy. In addition, there are also important physiological differences in the blood vessels of different areas of the brain. The pathological conditions of cerebrovascular disease are haemorrhage and ischaemia. H AEMORRHAGE NEWBORNS AT TERM AND YOUNG INFANTS In newborns at term, a large number of possible pathological events may result in intracranial haemorrhage: a) trauma: subdural haematoma, epidural haematoma. subarachnoid haemorrhage, intracerebral haemorrhage, intracerebellar haemorrhage, b) clotting disorders: clotting de- fects, thrombocytopenia, c) vascular disorders: aneurysms, arteriovenous malformations, d) metabolic disorders, and e) idiopathic intraparenchymal haemorrhage. The clinical signs of an intracranial haemorrhage lesion in a newborn are often modest and non-specific: apathy or irritability/hyperex- citability without focal neurological signs, seizure, tremors, breathing disorders. Fre- quently acidosis, hypoglycaemia and hypoten- sion are associated with such haemorrhages. a) Labour trauma is the most frequent cause of bleeding in newborns. Subdural haematomas and subarachnoid haemorrhage are the most common types of haemorrhagic lesion. The most frequent site of subdural bleeding is over the cerebral convexity and within the temporal fossa, however haemorrhages can also be encountered adjacent to the falx cerebri, tentorium cerebelli and in the posterior cranial fossa. Intraparenchymal haemorrhages are less frequent and can be associated with subarachnoid and subdural haemorrhage, should the bleeding extend into the ventricles. The prognosis of 6 NEUROPAEDIATRIC EMERGENCIES N. Zamponi, B. Rossi, G. Polonara, U. Salvolini small lesions is good, however serious sequelae are typically observed following larger haemorrhages. Diagnostic imaging should first include CT, which demonstrates the presence, site and ex- tent of the cerebral bleed at an early stage; on the other hand, haemorrhages associated with cerebral infarcts will only become evident some days after the ischaemic event. Ultrasound may not show epidural or subdural haemorrhages localized to the cranial convexity or in the posterior fossa, whereas larger haemorrhages are clearly visible on ultrasound images as hyperechoic areas, and later hypo- anechoic regions. Both ultrasound and CT are capable of doc- umenting and sequentially monitoring the most important sequelae: porencephalic cysts and hydrocephalus. Porencephalic cysts usually form off of the bodies of the lateral ventricles. They typically develop from a haemorrhage that ruptures into the lateral ventricle or the subarachnoid space. Associated posthaemorrhagic hydrocephalus develops in 10-15% of patients with intraventricular haemorrhage. The hydrocephalus halts or improves in most cases; more rarely it pro- gresses and can require surgical ventricular- peritoneal shunt placement. b) Various clotting and platelet disorders can result in intracranial haemorrhage in newborns. The most frequent causes of thrombocytopenia are the use of medicines during pregnancy, ma- ternal infections, immunological disorders and disseminated intravascular coagulation. c) Vascular malformations and intracranial aneurysms may present with intracranial haemorrhages in newborns in rare occasions. Ultrasound may prove useful in diagnosis, especially in infants with aneurysmal dilatation of the vein of Galen. This is a rare congenital disorder wherein abnormal arteriovenous for- mations drain into the deep, dilated vessels of the galenic system. These direct connections with the vein of Galen can be by large fistulae or by multiple smaller arteriovenous connections. The pathogenesis would seem to involve intrauterine vascular thrombosis or absence of formation of the superior sagittal venous sinus. In 90% of cases, signs and symptoms of vasculopathy arise in early infancy: intracranial haemorrhage (intraparenchymal or subarachnoid) and rapidly progressive hydrocephalus are the most frequent presentations. In newborns these complications are frequently associated with cardiac insufficiency, the final pathophysiological result of a preexistent congenital haemodynamic anomaly (e.g., increase in blood flow across an arteriovenous fistula, increase in blood return to the right atrium, right-to-left blood flow through cardiac de- fects). In addition, the large blood flow through the fistula can create a secondary state of cerebral ischaemia. In newborns, the aneurysmal dilatation of the vein of Galen can be simply diagnosed us- ing ultrasound. On colour Doppler images, turbulent flow can usually be seen. On CT without IV contrast medium, the vein of Galen appears as a rounded mass in the region of the tentorial incisura and straight venous sinus; aqueduct compression may cause obstructive hydrocephalus. After IV contrast medium administration, intense enhancement is typically seen within the aneurysmally dilated vessel which is smooth and well defined. In the presence of thrombosis of this structure, variable degrees of non-enhancement will be observed. On MRI the vascular malformation appears hypointense on both T1- and T2-weighted sequences due to the rapid blood flow within the abnormal vessels. The arteries that supply the malformation can be reasonably well shown with MRA. Conventional selective angiography will still better define the arterial feeding vessels and the draining venous structures and may assist in presurgical planning (27, 32, 37). P REMATURE NEWBORNS Subependymal and intraventricular haemorrhages are more frequently encountered in premature newborns than in those born at term (3, 5, 11). Babies with a gestational age of less than 35 weeks or a birth weight of less than 1.5 kg have a higher risk of such haemorrhages, which 372 VI. NEUROPAEDIATRIC EMERGENCIES commonly present during the second or third day of life. The haemorrhage originates from the germinal matrix that surrounds the lateral cerebral ventricles. Small haemorrhages remain confined to the subependymal regions, however, when the bleeding is larger it can extensive- ly involve the cerebral parenchyma or rupture into the ventricular system. Certain factors make haemorrhage in this area more likely. The vessels of the germinal matrix are fragile and contain little connective tissue. This germinal matrix begins to involute at approximately the 35 th week of gestation. Until that time it has a high arterial perfusion with consonantly elevat- ed venous and capillary pressure. Two clinical syndromes have been described in association with subependymal and intraventricular haemorrhage. The catastrophic syndrome has an acute onset and a rapid evolution towards coma; the mortality rate is high. The salt losing syndrome is a disorder of conscious- ness, accompanied with a reduction in spontaneous movements, hypotonia and oculomotor abnormalities; these signs evolve slowly and are often followed by a period of stabilization followed by a second phase of deterioration. The mortality rate is lower for this syndrome than for the catastrophic syndrome. From the standpoint of medical imaging, germinal matrix haemorrhages can be broken down into 4 stages: stage I is characterized by a small germinal matrix haemorrhages together with a small intraventricular haemorrhage; stage II is characterized by germinal matrix haemorrhage accompanied by a large intraventricular haemorrhage; stage III is characterized by a subependymal haemorrhage, intraventricular haemorrhage, and hydrocephalus; and, stage IV indicates the spread of the parenchymal haemorrhage into one or both cerebral hemispheres. The use of ultrasound, which can be performed safely at the bedside, has lead to an increase in the identification and characterization of neonatal subependymal and intraventricular haemorrhages. On ultrasound, stage I germinal matrix subependymal haemorrhage appears as a hyperechoic mass lesion, which is either uni- or bilateral and is primarily located in the head of the caudate nucleus. Generally speaking, in order to be visualized, it must measure 4-5 mm in diameter. A Stage II haemorrhage appears as hyperechoic material within the lateral ventricle(s). A stage III haemorrhage is represented by a dilatation of the ventricular system and the presence of intraventricular hyperechoic blood. The intraparenchymal component of a stage IV haemorrhage appears on ultrasound as an in- tensely hyperechoic lesion located in the deep white matter of the centrum semiovale. Subsequent ultrasound scans will show progressive stages of resolution of the subependymal-intraventricular haemorrhage. An extensive haemorrhage can evolve over 2-3 months towards the formation of porencephalic cysts or the development of cystic encephalomalacia. On CT, acute germinal matrix haemorrhages appear as hyperdense foci, usually adjacent to the lateral ventricle near the head of the caudate nucleus. MRI is also fairly sensitive and specific in demonstrating acute germinal matrix haemorrhage. In premature neonates with the hypoxic-ischaemic syndrome white matter alterations are also frequently detected: periventricular leukomalacia appears on ultrasound as widespread, poorly defined hyperechoic periventricular regions. These are especially prominent in the ventricular trigone regions and adjacent to the foramina of Monroe. The hyperecho findings are due to oedema and petechial haemorrhage. The abnormality is generally bilateral, but is often asymmetric. After 2-3 weeks, small cysts form within the hyperechoic region that coa- lesce to form a multicystic lesion, before col- lapsing, fusing and being replaced by glial scars. In this late phase of glial scarring the ultrasound findings are usually unremarkable. During the acute phase of ischemia, CT can be normal or can show a minor attenuation in the parenchyma of the periventricular regions; during the subacute phase it is only possible to iden- tify medium-sized cysts, whereas chronic glial scarring is not usually visible on CT (Fig. 6.1). MRI is rarely used in the acute phase, however it is the best technique for highlighting chronic periventricular leukomalacia. On T2- weighted scans the residual glial scars localized NEUROPAEDIATRIC EMERGENCIES 373 to the periventricular areas appear hyperintense. These areas generally border the ventricles and typically spread into the adjacent white matter in a flame-shaped configuration. A thin- ning of the posterior body and splenium of the corpus callosum are seen in the chronic phase as a result of degeneration of the transcallosal fibres, ventricular dilatation and atrophy of the hemispheric white matter (Fig. 6.2). I NFANTS Vascular malformations are the most common cause of haemorrhage in infants (15, 32) and can be broken down into four main types: arteriovenous malformations, venous angiomas, capillary telangiectasias and cavernous angiomas. The most common clinical manifestations are headache and seizures rather than haemorrhage; however, if the lat- ter do occur, they may be subarachnoid, intraparenchymal or combined. Arteriovenous malformations (AVM’s) consist of an aggregate of abnormal vessels with thin walls (i.e., nidus) in which there is direct continuity between dilated arteries and veins without the interposition of capillaries. Ap- proximately 90% are superficial and are located within the cerebral hemispheres. AVM’s are responsible for up to 40% of spontaneous intracranial haemorrhages in infants. The mortality rate associated with the rupture of an AVM is approximately 10%. On unenhanced CT, a typical AVM appears as a heterogeneous area with slightly increased density compared to the normal surrounding parenchyma. After IV contrast medium administration, intense enhancement of the malformation and its afferent and efferent vessels is observed. On MRI the fast blood flow within AVM’s creates flow voids on spin echo sequences. The nidus appears as a tangle of tubular shaped black vessels. However, in order to obtain an accurate anatomical map of the vascular malformation, an angiographic examination is re- quired. Typically a tangle of small, irregular blood vessels supplied by dilated and twisted arteries and drained by dilated veins that fill rapidly. In the case of haemorrhage, unenhanced CT details the haemorrhagic spread into the sub- 374 VI. NEUROPAEDIATRIC EMERGENCIES Fig. 6.1 - Hypoxic-ischaemic injury in newborn. a, b) Unenhan- ced CT shows widespread hypodensity of the subcortical and periventricular white matter and enlargement of the cerebral ventricular system. a b arachnoid space, cerebral parenchyma and cerebral ventricles. In severe cases haemorrhage can obscure the underlying vascular malformation. In the acute phase the haematoma appears hyperdense and relatively homoge- neous (Fig. 6.3); in the chronic phase, encephalomalacia, rarely accompanied by calcifi- cations, may result. Cavernous vascular malformations consist of a tangle of dilated vessels that do not possess the characteristics of normal arteries or of veins. With the exception that thrombi can be present, the draining veins and arteries usually have a normal calibre. The malformation may contain small intrinsic areas of neural tissue. Most of these lesions are located in the cerebral parenchyma, and although they are usually iso- lated they can also be multiple and have a fa- milial pattern of expression. The clinical presentation is typically seizures, but more rarely it can be cerebral haemorrhage. In fact, subclini- cal haemorrhages often occur. The diagnosis is currently based on MRI due to the characteris- tic imaging findings, including a mixed signal core surrounded by a hypodense haemosiderin ring on T2-weighted sequences. Venous malformations are often incidentally detected on MR or CT scans. The risk of bleeds is generally low. MRI, which is more sensitive than CT, shows a branching network of small draining veins that unite to form a single, large terminal vein. In the venous phase, conventional angiography shows a collection of abnormal veins (i.e., “Medusa head”) that drain into a single large collecting vein before emptying into a superficial cortical vein or dural venous sinus. Aneurysms are rare in children under the age of ten years; males are more frequently affected than are females. The clinical presentation is typically a subarachnoid haemorrhage, however, some patients present with seizures. Aneurysms in children under 2 years usually originate from the anterior cerebral or the in- ternal carotid arteries. Such aneurysms are usually larger than 1 cm in diameter. CT at presentation shows an acute subarachnoid haemorrhage. If the aneurysm is suf- ficiently large it will demonstrate intense en- NEUROPAEDIATRIC EMERGENCIES 375 Fig.6.2 - Periventricular leukomalacia. A, b) Axial FLAIR MRI shows an increase in the subependymal and periventricular white matter MR signal with sickle shape of the cerebral ventricles. a b [...]... of 35 cases AJNR 11:67 7-6 83, 1990 6 Chabbert V, Ranjeva JP, Sevely A: Diffusion and magnetisation transfer-weighted MRI in childhood moya-moya Neuroradiology 40(4):26 7-7 1, 1998 7 Chanalet S, Chatel M, Grellier P et al.: Symptomatologique clinique et diagnostic radiologique des tumeurs intracraniennes Editions Techiniques Encycl Méd Chir (Paris, France) Neurologie 1 7-2 1 0- A6 0-1 0, 1994 8 Conway PD: Oechler... Neurologie, 1 7-0 35-N -1 0, 8p, 1999 21 Jan M, Aesch B: Traumatismes cranio-encéphaliques Editions Techiniques-Encycl Med Chirurg Paris Neurologie, 15785 A10, 15 p, 1991 22 Jelink J, Smorniotopulos Db, Parisis JE: Lateral Ventricular Neoplasms of the Brain: differential Diagnosis Based on clinical CT and MR Findings AJR 11:56 7-5 74, 1990 23 Jonsson RT: Acute encephalitis Clin Infect Dis 23:21 9-2 26, 1996 24... as a crescent-shaped extracranial soft tissue mass directly adjacent to the outer table of HEAD INJURY slight moderate no x-ray in the absence of CT: skull x-ray + observation no worsening observation at home Diagram 6.1 hospitalisation for brief period severe worsening CT + Neurosurgery 382 VI NEUROPAEDIATRIC EMERGENCIES c a b d Fig.6.7 - Cerebral haematoma a) T 1-, b) T 2-, c) T2 *-, d) T1-weighted MRI... examination performed in emergency situations in these cases The initial findings may be negative, in 390 VI NEUROPAEDIATRIC EMERGENCIES c a d b Fig 6.13 - Herpes encephalitis a, b) CT shows cortical and subcortical temporal-insular hypodensity with signs of associated cerebral swelling Corresponding c) coronal T2-weighted and d) sagittal T2-weighted MRI in the subacute phase part due to the relatively... review of the risks and benefits Can Med Ass, 148:96 1-9 65, 1996 VI NEUROPAEDIATRIC EMERGENCIES 3 Bowerman RA, Donn SM, Di Pietro MA et al: Periventricular leukomalacia in the pretem newborn infant: sonographic and clinical features Radiology 151:38 2-3 88, 1984 4 Bruneel F, Wolff M: Méningites aigues Encycl Méd Chir Elsevier SAS, Paris Neurologie 1 7-1 60-C -1 0, 2000 5 Carson SC, Hertzberg Bs, Bowie JD et al:... vessels 378 VI NEUROPAEDIATRIC EMERGENCIES a c b d Fig.6.5 - Left cerebellar ischaemia a) Unenhanced CT scan shows minor cortical-subcortical hypodensity b, c) Unenhanced T2-weighted MRI demonstrates areas of increased signal in the left cerebellar hemisphere and midbrain-pontine junction d) Enhanced T1weighted MRI reveals breakdown in the blood-brain barrier following IV gadolinium administration NEUROPAEDIATRIC... a frontoorbital or occipital location, often has an intermittent character, and it tends to worsen with the evo- c a b Fig 6.14 - Acute disseminated encephalomyelitis (ADEM) a, b) CT demonstrates areas of hypodensity of the subcortical white matter c-e) axial T2-weighted and d) coronal T2-weighted MRI reveals regions of signal alteration in the subcortical white matter with associated mass effect d... astrocytoma Cancer 67:2772, 1991 9 Crowe W: Aspects of Neuroradiology of head injury Neurusurg Clin North Am 2:321, 1991 10 Dias Ms, Backstrom J, Falk M, Li V: Serial radiography in the infant shaken impact syndrome Pediatr Neurosurg 29 (2):7 7-8 5, 1998 11 Flodmark O, Lupton B et al.: MR imaging of periventricular leukomalcia in childhood AJNR 10: 11 1-1 118, 1989 12 Ganesan V, Savv YL, Chong WK et al: Conventional... carcinomatous characteristics Signs and symptoms can be sec- NEUROPAEDIATRIC EMERGENCIES 399 a c d b Fig.6.17 - Papilloma of the choroid plexus a) CT shows an intraventricular mass lesion associated with obstructive hydrocephalus b) PD-weighted and c) T2-weighted MRI shows an intraventricular mass lesion with inhomogeneous signal on long TR sequences, in part possibly due to intratumoural macroscopic neoplastic... Premature craniosynostosis Neoplasia and space-occupying lesions The manner in which a space-occupying lesion within the cranium produces signs and symptoms is partially linked to the position of the mass and its rapidity of growth Neoplasia is a relatively common cause of hydrocephalus in infancy The location of brain tumours during childhood is somewhat age-dependent: in the first six months of life . progressively hypodense in the chronic phase. Calcification may occur late in the evolutionary process. Another common post-partum posttraumat- ic lesion is so-called caput succedaneum characterized. imaging in suspected multiple sclerosis. Eur Radiol 10: 36 8-3 76, 2000. 7. Obenberg J, Seidi Z, Plas J: Osteoblastoma in lumbar vertebral body. Neuroradiology 41:27 9-2 82, 1999. 8. Rimmelin A, Clouet. thrombosis of this structure, variable degrees of non-enhancement will be observed. On MRI the vascular malformation appears hypointense on both T 1- and T2-weighted sequences due to the rapid