753CHAPTER 61 Neuroimaging A R 1 L P • Fig 61 21 Acute disseminated encephalomyelitis (ADEM) Axial T2 weightedmagneticresonanceimagingshowssymmetricincreasedsignal intheheadoftheca[.]
CHAPTER 61 Neuroimaging 753 12 seconds on a 3.0 Tesla scanner and 19 seconds on a 1.5 Tesla scanner for the entire head Hence, they not typically require patient sedation Use of this technique offsets the radiation burden of repeated CT scans In the initial evaluation of hydrocephalus, MRI can be helpful in determining the level and Hydrocephalus Hydrocephalus can be congenital or caused by hemorrhage, tumor, and meningitis In the neonatal period, ultrasound is used as a screening tool in evaluating for ventricular enlargement— in particular, associated with GMH Beyond this period, most monitoring of ventricular size and shunts is accomplished with CT Rapidly acquired heavily T2-weighted HASTE MRI sequences have been used in the evaluation of hydrocephalus These sequences can be obtained as individual slices in as little as A R L P • Fig 61.23 Patient with clinical picture of transverse myelitis Sagittal T2- • Fig weighted magnetic resonance imaging of the distal cord shows central T2 hyperintensity within the conus medullaris (arrows) in this case of acute disseminated encephalomyelitis An acute spinal cord infarct also could have this imaging appearance 61.21 Acute disseminated encephalomyelitis (ADEM) Axial T2weighted magnetic resonance imaging shows symmetric increased signal in the head of the caudate nucleus (curved arrows) and anterior lentiform nuclei (straight arrows) associated with ADEM A • Fig 61.22 Multiple B sclerosis in a 16-year-old child (A) Fluid-attenuated inversion recovery magnetic resonance imaging (MRI) shows bilateral white matter lesions (arrows) (B) Diffusion-weighted imaging demonstrates restriction of the left centrum semiovale lesion that was enhanced on postcontrast T1 MRI (not shown), suggesting an acute or active lesion (arrow) 754 S E C T I O N V I Pediatric Critical Care: Neurologic A B • Fig 61.24 Epidural hematoma with skull fracture A computed tomography scan in brain (A) and bone (B) windows shows the typical lentiform configuration of right-sided epidural hematoma (arrows) The bone window reveals an associated fracture (curved arrow) Tumor Cerebral tumors are best imaged with MRI (Fig 61.26) Expedited evaluation of a cerebral mass can be accomplished in the acute setting with CT, which will demonstrate the degree of mass effect and any impending herniation or midline shift Posterior fossa tumors, which are more common in children and occur more often than supratentorial tumors in the 4- to 10-year age group,52 and suspected acute spinal cord abnormalities, possibly associated with tumor, are best evaluated with MRI CT is hampered by beam hardening artifact in the posterior fossa, at the skull base, and within the spinal canal Seizures • Fig 61.25 Diffuse brain edema with herniation T2-weighted magnetic resonance imaging shows diffuse cerebral swelling with effacement of cerebrospinal fluid spaces associated with the ambient (straight arrows) and suprasellar cisterns (curved arrows) possible cause of CSF obstruction (see Fig 61.17) Acute hydrocephalus can be associated with evidence of transependymal CSF flow across the walls of the ventricular system, better appreciated on MRI However, the absence of this appearance does not reliably predict the absence of increased pressure Physiologic/functional evaluation of shunt patency is achieved with nuclear medicine shunt studies, as described previously The CT imaging yield for a single self-limited seizure with no focal neurologic deficit is low, although most children currently will ultimately be scanned with CT or MRI With focal neurologic deficit or prolonged seizure activity, the imaging yield increases As discussed in Chapter 64, after seizures are controlled, MRI is indicated in the absence of a clinically apparent etiology for the seizures Acute abnormalities on MRI, however, may be secondary to rather than reflecting the underlying cause of seizures Prolonged seizures can be associated with transient enhancement due to BBB disruption and cytotoxic edema with hyperintensity on DWI that may be confused with stroke Positron emission tomography can also be used to identify epileptogenic foci by identifying areas of hypermetabolism Conclusion The ultimate selection of imaging modality will depend on clinical question(s), age and condition of the patient, and the locally available imaging technology Consultation with radiology colleagues is encouraged, and discussion of the clinical scenario and suspicions yields an appropriately tailored imaging protocol and a more relevant interpretation, which is becoming increasingly important with the ever-increasing complexity of imaging modalities CHAPTER 61 Neuroimaging A B 755 C • Fig 61.26 Posterior fossa medulloblastoma Axial noncontrast computed tomography scan (A) and sagittal T1-weighted magnetic resonance imaging (MRI) with gadolinium (B) show a midline posterior fossa mass that has heterogeneous enhancement on postcontrast T1 and heterogeneous signal on axial T2-weighted MRI (C) Key References Barry M, Hallam DK, Bernard TJ, Amlie-Lefond C What is the role of mechanical thrombectomy in childhood stroke? Pediatr Neurol 2019;95:19-25 Blumfield E, Swenson DW, Iyer RS, Stanescu AL Gadolinium-based contrast agents: review of recent literature on magnetic resonance imaging signal intensity changes and tissue deposits, with emphasis on pediatric patients Pediatr Radiol 2019;49(4):448-457 LaRovere KL, O’Brien NF Transcranial Doppler sonography in pediatric neurocritical care: a review of clinical applications and case illustrations in the pediatric intensive care unit J Ultrasound Med 2015;34(12):2121-2132 Mascalchi M, Filippi M, Floris R, Fonda C, Gasparotti R, Villari N Diffusion-weighted MR of the brain: methodology and clinical application Radiol Med 2005;109(3):155-197 Mendichovszky IA, Marks SD, Simcock CM, Olsen OE Gadolinium and nephrogenic systemic fibrosis: time to tighten practice Pediatr Radiol 2008;38(5):489-496; quiz 602-603 Ment LR, Bada HS, Barnes P, et al Practice parameter: neuroimaging of the neonate: report of the Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society Neurology 2002;58(12):1726-1738 Nickerson JP, Richner B, Santy K, et al Neuroimaging of pediatric intracranial infection—part 1: techniques and bacterial infections J Neuroimaging 2012;22(2):e42-e51 Nickerson JP, Richner B, Santy K, et al Neuroimaging of pediatric intracranial infection—part 2: TORCH, viral, fungal, and parasitic infections J Neuroimaging 2012;22(2):e52-e63 Poussaint TY, Panigrahy A, Huisman TA Pediatric brain tumors Pediatr Radiol 2015;45(suppl 3):S443-S453 Schaefer PW, Grant PE, Gonzalez RG Diffusion-weighted MR imaging of the brain Radiology 2000;217(2):331-345 The full reference list for this chapter is available atExpertConsult.com ee1 References Lowe LH, Bulas DI Transcranial Doppler imaging in children: sickle cell screening and beyond Pediatr Radiol 2005;35(1):54-65 Soetaert AM, Lowe LH, Formen C Pediatric cranial Doppler sonography in children: non-sickle cell applications Curr Probl Diagn Radiol 2009;38(5):218-227 Rasulo FA, De Peri E, Lavinio A Transcranial Doppler ultrasonography in intensive care Eur J Anaesthesiol Suppl 2008;42:167-173 Adams RJ Big strokes in small persons Arch Neurol 2007;64(11): 1567-1574 LaRovere KL, O’Brien NF Transcranial Doppler sonography in pediatric neurocritical care: a review of clinical applications and case illustrations in the pediatric intensive care unit J Ultrasound Med 2015;34(12):2121-2132 Rilinger JF, Smith CM, deRegnier RAO, et al Transcranial Doppler identification of neurologic injury during pediatric extracorporeal membrane oxygenation therapy J Stroke Cerebrovasc Dis 2017;26(10): 2336-2345 Siegel MJ, Ramirez-Giraldo JC Dual-Energy CT in children: imaging algorithms and clinical applications Radiology 2019;291(2):286-297 Kanamalla US, Ibarra RA, Jinkins JR Imaging of cranial meningitis and ventriculitis Neuroimaging Clin N Am 2000;10(2):309-331 Mendichovszky IA, Marks SD, Simcock CM, Olsen OE Gadolinium and nephrogenic systemic fibrosis: time to tighten practice Pediatr Radiol 2008;38(5):489-496; 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Neuroradiology 2007;49(8):651-657 52 Poussaint TY, Panigrahy A, Huisman TA Pediatric brain tumors Pediatr Radiol 2015;45(suppl 3):S443-S453 ... MRI CT is hampered by beam hardening artifact in the posterior fossa, at the skull base, and within the spinal canal Seizures • Fig 61.25 Diffuse brain edema with herniation T2-weighted magnetic... flow across the walls of the ventricular system, better appreciated on MRI However, the absence of this appearance does not reliably predict the absence of increased pressure Physiologic/functional... Diffusion-weighted MR imaging of the brain Radiology 2000;217(2):331-345 The full reference list for this chapter is available atExpertConsult.com ee1 References Lowe LH, Bulas DI Transcranial Doppler